Servlets Faq From Jguru

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Servlets FAQ From jGuru Generated Sep 13, 2005 2:17:14 PM Location: http://www.jguru.com/faq/Servlets Ownership: http://www.jguru.com/misc/user-agree.jsp#ownership. How do I set my CLASSPATH for servlets? Location: http://www.jguru.com/faq/view.jsp?EID=141 Created: Sep 3, 1999 Modified: 2001-05-05 14:19:15.228 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) That depends. For developing servlets, just make sure that the JAR file containing javax.servlet.* is in your CLASSPATH, and use your normal development tools (javac and so forth). • •

For JSDK: JSDK_HOME/lib/jsdk.jar For Tomcat: TOMCAT_HOME/lib/servlet.jar

For running servlets, you need to set the CLASSPATH for your servlet engine. This varies from engine to engine. Each has different rules for how to set the CLASSPATH, which libraries and directories should be included, and which libraries and directories should be excluded. Note: for engines that do dynamic loading of servlets (e.g. JRun, Apache Jserv, Tomcat), the directory containing your servlet class files shoud not be in your CLASSPATH, but should be set in a config file. Otherwise, the servlets may run, but they won't get dynamically reloaded. The Servlets 2.2 spec says that the following should automatically be included by the container, so you shouldn't have to add them to your CLASSPATH manually. (Classloader implementations are notoriously buggy, though, so YMMV.) • •

classes in the webapp/WEB-INF/classes directory JAR files in the webapp/WEB-INF/lib directory

This applies to webapps that are present on the filesystem, and to webapps that have been packaged into a WAR file and placed in the container's "webapps" directory. (e.g. TOMCAT_HOME/webapps/myapp.war) The Complete CLASSPATH Guide for Servlets (http://www.meangene.com/java/classpath.html) by Gene McKenna ([email protected]) has detailed instructions on how to set your CLASSPATH for JavaWebServer and JRun. See also http://www.jguru.com/faq/view.jsp?EID=413601 Comments and alternative answers

Important precision : Under Apache (at least with... Author: Denis BUCHER (http://www.jguru.com/guru/viewbio.jsp?EID=7742), Jan 22, 2000

Important precision : Under Apache (at least with jserv under Linux) you SHOULD NOT put this in any system path, as it won't work. You must put the new path into jserv.properties file, that you located maybe into your apache config dir !!! I've found it simpler to just copy the JAR file to... Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7), Jun 15, 2000 I've found it simpler to just copy the JAR file to the extensions directory of your runtime: jre/lib/ext under your JDK directory, as in: c:\jdk1.3\jre\lib\ext If you are using JRun (atleast with v2.3.3), adding... Author: sharad gupta (http://www.jguru.com/guru/viewbio.jsp?EID=100198), Jul 21, 2000 If you are using JRun (atleast with v2.3.3), adding servlet classes in system path won't work. Instead add the path in jsm.properties file. Unfortunately, Jaz' extension solution doesn't work... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Sep 17, 2000 Unfortunately, Jaz' extension solution doesn't work for some JARs, notably XML parsers. I'm not exactly sure why; perhaps it's package name collision. The webapp solution (WEB-INF/lib) is preferred. I would not hesitate to have a static block in one... Author: Aprameya Paduthonse (http://www.jguru.com/guru/viewbio.jsp?EID=4707), Feb 1, 2001 I would not hesitate to have a static block in one of my early loaded servlets to list the environment parameters static { Properties envProps = System.getProperties(); System.out.println("__________________________ BEGIN JAVA SETTINGS _______________________________"); for (Enumeration e = envProps.propertyNames() ; e.hasMoreElements() ;) { String prop = (String)e.nextElement(); System.out.println(prop + " : " + envProps.getProperty(prop)); } System.out.println("_____________________________END JAVA SETTINGS _______________________________"); }

view this Author: kumar varma (http://www.jguru.com/guru/viewbio.jsp?EID=1225116), Feb 4, 2005 along with classpath explanation can you please give us details about servletapi.jar,tools.jar,etc.? Is it the "servlets" directory or the "servlet" directory? Location: http://www.jguru.com/faq/view.jsp?EID=142 Created: Sep 3, 1999 Modified: 1999-12-22 11:09:48.603 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) For Java Web Server: • •

on the file system, it's "servlets" c:\JavaWebServer1.1\servlets\DateServlet.class in a URL path, it's "servlet" http://www.stinky.com/servlet/DateServlet

Other servlet engines have their own conventions. Usually on the file system it's "servlets" and in a URL it's "/servlet" (which is an alias or virtual path). Comments and alternative answers

It depends on your mapping. Virtual path could be ... Author: Roceller Alvarez (http://www.jguru.com/guru/viewbio.jsp?EID=41828), Apr 28, 2000 It depends on your mapping. Virtual path could be different from the real path. Re: It depends on your mapping. Virtual path could be ... Author: Tim Urberg (http://www.jguru.com/guru/viewbio.jsp?EID=510070), Oct 17, 2001 If you have Tomcat the directory will be: TOMCAT_HOME/webapps/ROOT/WEB-INF/classes If you're running JRun it will be: C:\Program Files\Allaire\JRun\servers\default\default-app\WEB-INF\classes I hope that helps Why doesn't my servlet work inside a tag? Location: http://www.jguru.com/faq/view.jsp?EID=143 Created: Sep 3, 1999 Modified: 2000-05-21 14:36:17.445 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3)

If you use your servlet inside an SSI, you must use res.getOutputStream() and not res.getWriter(). Check the server error logs for more details. Comments and alternative answers

Does anyone here have any experience getting <s... Author: Slim Whitman (http://www.jguru.com/guru/viewbio.jsp?EID=29020), Mar 27, 2000 Does anyone here have any experience getting <servlet> tags to work under Netscape Enterprise Server version 4? (I have service pack 3) I don't get any errors, but it's as if the server never parses the servlet tag. Parse HTML is turned on in the server, without using the exec tag, and for all html files. (instead of shtml) I'm not quite sure about this, but I believe that only... Author: Roceller Alvarez (http://www.jguru.com/guru/viewbio.jsp?EID=41828), Apr 28, 2000 I'm not quite sure about this, but I believe that only works on JRUN. Jason Hunter's Servlet book was a defacto when it was... Author: Matt Woody (http://www.jguru.com/guru/viewbio.jsp?EID=36408), May 12, 2000 Jason Hunter's Servlet book was a defacto when it was released because in 1998. He, under O'Reilly, released the best servlet book to date. Because he used the JavaWebServer in all his examples, he frequently used the <servlet> tag. The <servlet> tag is NOT a part of the Servlet API. It was simply a cool thing that JavaWebServer supported. I would suggest that you look towards JSP if you like that idea of combining HTML and Servlets. Otherwise you could create your own utilities to parse html documents, extract syntax within <servlet> and , write to a different file, compile it, and then somehow tie the compiled code and the html together. Another option would be to parse an html document, inverse the outlying html and the syntax within <servlet>, and then compile that. I have quite often pondered doing this. How do I support both GET and POST protocol from the same Servlet? Location: http://www.jguru.com/faq/view.jsp?EID=144 Created: Sep 3, 1999 Modified: 2000-08-10 10:04:27.869 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) The easy way is, just support POST, then have your doGet method call your doPost method:

public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { doPost(req, res); }

Note that implementing the <mono>service() method is usually not what you want to do, since HttpServlet provides its own implementation of <mono>service() that turns around and calls <mono>doGet(), doPost(), etc. Lee Crocker ([email protected]): "It's probably cleaner not to override <mono>service() when extending HttpServlet. The existing service method just calls <mono>doGet(), <mono>doPost(), etc. as appropriate, so you can certainly override it if you feel like it, but then you wind up not only treating GET and POST identically, but also all other HTTP commands, like HEAD, TRACE, and OPTIONS. If you want GET and POST to do the same thing, just have <mono>doGet() and <mono>doPost() call the same private method that does all the work." See also: • • •

What is the difference between the doGet and doPost methods? How does one choose between overriding the doGet(), doPost(), and service() methods? What is the difference between POST and GET methods? What about PUT, DELETE, TRACE, OPTIONS, and HEAD?

Comments and alternative answers

I created a servlet, from which I usually extend, by... Author: Nicola Ken Barozzi (http://www.jguru.com/guru/viewbio.jsp?EID=39153), Apr 23, 2000 I created a servlet, from which I usually extend, by making a new method that gets called by doGet() and doPost() and handles error handling. Apart from that it is a normal HttpServlet. CODE: /** * Copyright: Copyright (c) 2000 * @author Nicola Ken Barozzi */ import java.io.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; public abstract class WebAppServlet extends HttpServlet { public void init(ServletConfig config) throws ServletException { super.init(config); }

public final void doGet ( HttpServletRequest request, HttpServletResponse response ) throws ServletException, IOException { doSafeGetOrPostWrapper(request, response); } public final void doPost ( HttpServletRequest request, HttpServletResponse response ) throws ServletException, IOException { doSafeGetOrPostWrapper(request, response); } private void doSafeGetOrPostWrapper ( HttpServletRequest request, HttpServletResponse response ) throws ServletException, IOException { HttpSession CurrentSession; try { CurrentSession = request.getSession(/*false*/); doSafeGetOrPost(request, response, CurrentSession);

} catch(Throwable t) { System.out.println("Error caught by doSafeGetOrPostWrapper:\n"+t+"\n"); t.printStackTrace(); System.out.println("Writing to log..."); CurrentSession = request.getSession(); this.getServletContext().log("Error",

t);

System.out.println("...ok."); try { response);

ServletUtils.sendHttpError(t, request, }

{ } }

catch(Throwable tr)

} public abstract void doSafeGetOrPost ( HttpServletRequest request, HttpServletResponse response, HttpSession CurrentSession, ) throws Throwable;

}

Re: I created a servlet, from which I usually extend, by... Author: Nirav Patel (http://www.jguru.com/guru/viewbio.jsp?EID=424727), May 18, 2001 Exactly... The same happens when you use an IDE such as IBM Visual Age for Java. When you create a new Servlet, Visual Age for Java automatically creates the init(), doGet(..), doPost(..), and performTask(..) method. It also invokes the performTask(..) method from within the doGet(..) and doPost(..) methods. So, now when the user invokes either of the doGet() or doPost() method from the HTML Form using GET and POST, the query is automatically redirected to performTask(..) method. Re: I created a servlet, from which I usually extend, by... Author: Ajay P (http://www.jguru.com/guru/viewbio.jsp?EID=1234517), Mar 24, 2005 Hi! When i am trying to compile the code using ApacheTomcat on IE i am getting the entire code as an output display. How am i suppose to run this servlet? Should i be saving the code as WebAppServlet.html? Help me out with this.If i am conceptually wrong then please tell me as what concept is involved with the execution. Thank you. Re[2]: I created a servlet, from which I usually extend, by... Author: Ajay P (http://www.jguru.com/guru/viewbio.jsp?EID=1234517), Mar 24, 2005 Hey i'm sorry.I need to store it in a java file. I don know as where i kept my brain that time. Its fine now. No need for any reply to the previous message. Thank you.

How do I fully shut down the server? Location: http://www.jguru.com/faq/view.jsp?EID=145 Created: Sep 3, 1999 Modified: 1999-12-22 11:10:54.113 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) For JWS, under Windows, pressing control-C doesn't fully shut down the server. You should use the Admin Tool and click "Shut Down". (Or you can hit ctl-alt-del, find "JREW" in the list, and "End Task".) Comments and alternative answers

How do I fully shut down the server? Author: Rajan Kumar (http://www.jguru.com/guru/viewbio.jsp?EID=416254), May 6, 2001 You can shut down the JWS from admin tool; or alternativly by going to NT services and "stop" the "javawebserver" service. My browser says "the server returned an invalid or unrecognized response" -- what gives? Location: http://www.jguru.com/faq/view.jsp?EID=146 Created: Sep 3, 1999 Modified: 1999-12-22 11:11:42.609 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) This is probably due to a NullPointerException being thrown. There's a bug in JWS 1.1 whereby it doesn't correctly log these exceptions. The solution is to put your doPost() method inside a try block and catch NullPointerException. See the debugging question in this FAQ for more details and source code. What is the HelloWorld Servlet? Location: http://www.jguru.com/faq/view.jsp?EID=147 Created: Sep 3, 1999 Modified: 2001-12-29 11:08:03.612 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3)

import javax.servlet.*; import javax.servlet.http.*; import java.io.*; public class HelloHttpServlet extends HttpServlet { public void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException { String name = req.getParameter("name"); if (name == null) name = "Joe"; res.setContentType("text/plain"); ServletOutputStream out = res.getOutputStream(); out.println("Hello, " + name + "!"); }

} This code responds to an invocation of the form http://myserver.foo.com/servlet/HelloHttpServlet?name=Fred Comments and alternative answers

Don't forget to include imports!!!! Author: Sharat N (http://www.jguru.com/guru/viewbio.jsp?EID=502507), Oct 16, 2001 (for new guys)In the above program, include http imports. import javax.servlet.*; import javax.servlet.http.*; import java.io.*; Thanks Sharat function setContentType not found in Tomcat 3.2.1 Author: John Meagher (http://www.jguru.com/guru/viewbio.jsp?EID=813752), Mar 26, 2002 Whenever I javax helloWorld.java, I get this error: function setContentType(java.lang.String) not found in class javax.servlet.http.HttpServletResponse Why would I get this message, if my classpath is ok? How do I get the name of the currently executing script? Location: http://www.jguru.com/faq/view.jsp?EID=148 Created: Sep 3, 1999 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Use req.getRequestURI() or req.getServletPath(). The former returns the path to the script including any extra path information following the name of the servlet; the latter strips the extra path info. For example:

URL http://www.purpletech.com/servlets/HelloEcho/extra/info?height=100&width=200 getRequestURI /servlets/HelloEcho/extra/info getServletPath /servlets/HelloEcho getPathInfo /extra/info getQueryString height=100&width=200 This is useful if your form is self-referential; that is, it generates a form which calls itself again. For example:

out.println(""); (encodeURL adds session information if necessary. See the Sun Servlet Tutorial and this FAQ's Session Tracking question. Note that this method was renamed from "encodeUrl" to the properly-capitalized "encodeURL" somewhere around version 2.1 of the servlet spec.) Note that early versions of Java Web Server and some servlet engines had a bug whereby getRequestURI would also return the GET parameters following the extra path info. Comments and alternative answers

I tried to do this in IBM WAS 3.02 and got the error... Author: Avinash Kachhy (http://www.jguru.com/guru/viewbio.jsp?EID=224947), Oct 9, 2000 I tried to do this in IBM WAS 3.02 and got the error that the method req.getServletPath() was not defined. Is this correct for WAS or did I do something wrong? out.println("Servlet Path = " + req.getServletPath()); Thanks Avinash Use this piece of code to demonstrate the physical... Author: Aprameya Paduthonse (http://www.jguru.com/guru/viewbio.jsp?EID=4707), Feb 1, 2001 Use this piece of code to demonstrate the physical location of the servlet that gets invoked by a virtual path(URI)

out.println(getServletConfig().getServletContext().getRealPath(request.getRequestURI(

How do I ensure that my servlet is thread-safe? Location: http://www.jguru.com/faq/view.jsp?EID=150 Created: Sep 3, 1999 Modified: 2003-01-08 14:30:31.956 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) [See also What is the meaning of calling a method or object "thread-safe?" ] This is actually a very complex issue. A few guidelines:

1. The init() method is guaranteed to be called once per servlet instance, when the servlet is loaded. You don't have to worry about thread safety inside this method, since it is only called by a single thread, and the web server will wait until that thread exits before sending any more threads into your service() method.

2. Every new client request generates (or allocates) a new thread; that thread calls the service() method of your servlet (which may in turn call doPost(), doGet() and so forth). 3. Under most circumstances, there is only one instance of your servlet, no matter how many client requests are in process. That means that at any given moment, there may be many threads running inside the service() method of your solo instance, all sharing the same instance data and potentially stepping on each other's toes. This means that you should be careful to synchronize access to shared data (instance variables) using the synchronized keyword. (Note that the server will also allocate a new instance if you register the servlet with a new name and, e.g., new init parameters.)

4. Note that you need not (and should not) synchronize on local data or parameters. And especially you shouldn't synchronize the service() method! (Or doPost(), doGet() et al.) 5. A simple solution to synchronizing is to always synchronize on the servlet instance itself using "synchronized (this) { ... } ". However, this can lead to performance bottlenecks; you're usually better off synchronizing on the data objects themselves.

6. If you absolutely can't deal with synchronizing, you can declare that your servlet "implements SingleThreadModel". This

empty interface tells the web server to only send one client request at a time into your servlet. From the JavaDoc: "If the target servlet is flagged with this interface, the servlet programmer is guaranteed that no two threads will execute concurrently the service method of that servlet. This guarantee is ensured by maintaining a pool of servlet instances for each such servlet, and dispatching each service call to a free servlet. In essence, if the servlet implements this interface, the servlet will be thread safe." Note that this is not an ideal solution, since performance may suffer (depending on the size of the instance pool), plus it's more difficult to share data across instances than within a single instance. See also What's a better approach for enabling thread-safe servlets and JSPs? SingleThreadModel Interface or Synchronization?

7. To share data across successive or concurrent requests, you can use either instance variables or class-static variables, or use Session Tracking.

8. The destroy() method is not necessarily as clean as the init() method.

The server calls destroy either after all service calls have been completed, or after a certain number of seconds have passed, whichever comes first. This means that other threads might be running service requests at the same time as your destroy() method is called! So be sure to synchronize, and/or wait for the other requests to quit. Sun's Servlet Tutorial has an example of how to do this with reference counting.

9. destroy() can not throw an exception, so if something bad happens, call log() with a helpful message (like the exception). See the

"closing a JDBC connection" example in Sun's Tutorial.

Comments and alternative answers

Point 3: Isn't it one servlet instance per regist... Author: sharma MR (http://www.jguru.com/guru/viewbio.jsp?EID=4939), Mar 15, 2000 Point 3: Isn't it one servlet instance per registered name of the servlet? Point 6: What is the initial size of the pool? Assume there is only one instance of the servlet that implements singlethreadmodel. Does more request imply more instances ( as opposed to more thread when the servlet does not implement SingleThread)? If so, what is the maximum servlet instances? Does it depend on the resource? Point 2: Each client generates a thread which can call... Author: Tony Biag (http://www.jguru.com/guru/viewbio.jsp?EID=27664), Mar 23, 2000 Point 2: Each client generates a thread which can call doGet() (et al) method. Does the thread associated with the client request guaranteed to have the sole access and ownership of HttpServletRequest and HttpServletResponse objects? To put it the other way, do I need to synchronize access to these objects (HttpServletRequest and HttpServletResponse)? 3. Maybe. It probably depends on the engine implem... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Mar 24, 2000 3. Maybe. It probably depends on the engine implementation. It might be good to check the spec and documentation if your logic depends on it. 6. The thread pool size is determined by the engine; there should be a config parameter. Every request that comes in while another request is being processed spawns a new instance, up to a certain number of instances. After that, they stall. Again, the numbers are up to the engine. 2. You definitely always are the only one who has the Request and Response objects, so don't bother synchronizing on them. They're per client request, remember. 2. "Every new client request generates a new ... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Apr 3, 2000 2. "Every new client request generates a new thread" -- actually, the servlet engines are free to implement thread pools, which means there's a chance that two successive doGets will happen on the same actual thread. You shouldn't make any assumptions about this either (in case you're tempted to use ThreadLocal variables or some other bad idea :-).

in case you're tempted to use ThreadLocal variables or some other bad idea :-). Author: Pahl Aakh (http://www.jguru.com/guru/viewbio.jsp?EID=1170988), Apr 16, 2005 Alex, Would you please explain why thie could be a problem? I would think that as long as you assign a new, appropriate, value to ThreadLocal variable before it is used, it will be used properly! A thread will complete the first request-processing before it starts the next one even if reused out of the threadpool, won't it. Thanks Point 3: Reading the "Playing it Smart With Java... Author: Lars Andersson (http://www.jguru.com/guru/viewbio.jsp?EID=40504), Apr 26, 2000 Point 3: Reading the "Playing it Smart With Java Servlets" by Matthew Ferris and Michael Bogovich in Servlet Central March 1999, the authors suggest a solution where a new instance of a transaction class is created for every client request. Calling this instance's doRun() method would create an execution environment similar to what you get when using the SingleThreadModel. The benefit would be that you can maintain common resources such as connection pools in the servlet's doGet() method before calling the transaction instance's doRun() method. The transaction object can be pooled for performance, or associated with the session if further processing is needed in a later request. This setup sounds good to me, but I have not tried it yet. Any comments? How local data in servlet is syncronized Author: Arun Selvaraj (http://www.jguru.com/guru/viewbio.jsp?EID=1105676), Aug 1, 2003 you need not (and should not) synchronize on local data or parameters. And especially you shouldn't synchronize the service() method! (Or doPost(), doGet() et al.) But at any point of time we will have only one instance created for a single servlet.It means that there will be a memory allocation for each and every member of that servlet class only one. So calls to service method will actually use the allocated memory reference. Then how the local variables inside the service will not be allocated at sigle place? And if i declare any other method which is called from service() method in my servlet, will it be thread-safe (or) do i need to syncronize it? Please Clarify. Re: How local data in servlet is syncronized Author: Steve Xu (http://www.jguru.com/guru/viewbio.jsp?EID=1107576), Aug 9, 2003 don't confuse the instance variable with the local variable inside service method. instance variable: allocated at the object level, needs to be synchronized. local variable: allocated on the stack of the calling thread, does not need to be synchronized.

synchronize the read only instance variable Author: Deepesh Rastogi (http://www.jguru.com/guru/viewbio.jsp?EID=1119170), Oct 2, 2003 Do I need to synchronize the instance variable/object, which I am trying to keep for read only purposes? I am using two instnce variable, the first is the property from file and the other is an object on which I need to make a method calls to log/store in the database.I do not think both the variable be synchronized... thanks deepesh whats the difference Author: Prashant Jain (http://www.jguru.com/guru/viewbio.jsp?EID=1251496), Jul 2, 2005 what exactly the difference between synchronizing the service method of the servlet and making the servlet to implement singlethreadmodel ? when there just one instance of a servlet then synchronizing the service method would actually sync' every request (thread) calling the servlet. ??? How do I use Session Tracking? That is, how can I maintain "session scope data" between servlets in the same application? Location: http://www.jguru.com/faq/view.jsp?EID=151 Created: Sep 3, 1999 Modified: 2000-09-10 10:49:31.243 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Session Tracking is one of the most powerful features of Servlets and JSP. Basically, the servlet engine takes care of using Cookies in the right way to preserve state across successive requests by the same user. Your servlet just needs to call a single method (getSession) and it has access to a persistent hashtable of data that's unique to the current user. Way cool. See section 2.3 of the Servlet Essentials tutorial (http://www.novocode.com/doc/servlet-essentials/) . Also see The Session Tracking API (http://webreview.com/wr/pub/1999/01/08/bookshelf/) , excerpted from Java Servlet Programming (http://www.oreilly.com/catalog/jservlet/) by Jason Hunter (http://webreview.com/wr/pub/au/Hunter_Jason). A point I haven't seen emphasized enough is that you should only add objects that are serializable to an <mono>HttpSession. Specifically, a JDBC Connection object is not serializable, so should not be added to the session (despite the example in Jason Hunter's otherwise admirable Java Servlet Programming). If you'd like to associate a connection with a session, then store some arbitrary, unique handle in the session, then use that to key off your own hashtable of connections. (Make sure upon retrieval that the returned connection is not null, and if it is, create a new connection!) The reason is that sessions may, at the whim of the server, be swapped out to disk, in order to save memory or reboot the server. This behavior can be disabled by setting a configuration parameter in your server or servlet engine. (I can't remember offhand what these are -- please email me if you know.) From the spec:

Some servlet engine implementations will persist session data or distribute it amongst multiple network nodes. For an object bound into the session to be distributed or persisted to disk, it must implement the Serializable interface. Comments and alternative answers

Also see the FAQ What servlet code corresponds to... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 21, 2000 Also see the FAQ What servlet code corresponds to the various "scope" values for the <jsp:useBean> tag? . Re: Also see the FAQ What servlet code corresponds to... Author: Aditya Sharma (http://www.jguru.com/guru/viewbio.jsp?EID=1151271), Mar 10, 2004 Sorry i feel it is just an explanation by words.A small illustration of code for session tracking will help Re[2]: Also see the FAQ What servlet code corresponds to... Author: Link Tree (http://www.jguru.com/guru/viewbio.jsp?EID=1212794), Nov 24, 2004 Very simple code - let say that the public void doPost(HttpServletRequest request, HttpServletResponse response){ ... //lets take the session obj HttpSession session = request.getSession(true); //now let us take the user name assosiated with this session String currUserLogin = (String) session.getAttribute("currentUserLogin") ... //now we do the work according to the user name doSomeWork(currUserLogin); ... }

You should do the same thing in the login servlet where you take the user name and use the addAttribute() of the session obj. what about the "jsessionid" added to keep the session ? Author: M. washu (http://www.jguru.com/guru/viewbio.jsp?EID=1217388), Dec 21, 2004 Hi all, Is there a way to include jsessionid in a hidden field (in a form) rather than in the URL (by the URL rewriting mechanism ) ? I saw that HttpSessionContext class was deprecated for security reason, but for security reasons too i would like to know if there is a way to prevent the jessionid from being logged in the HTTP server log files (of course without using cookies) ? Thanks in advance.

How can I detect whether the user accepted my cookie? Location: http://www.jguru.com/faq/view.jsp?EID=152 Created: Sep 3, 1999 Modified: 2000-09-06 16:35:12.955 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Here's a clever trick: use a redirect. Drop a cookie on the HttpServletResponse object, then call response.sendRedirect() to a "phase two" servlet. The "phase two" servlet then tests whether the cookie was sent back to it. If so, that means the user accepted the cookie the first time; if not, it means that either the client rejected the cookie, or the browser doesn't support cookies. Note that this technique only works if the "phase two" servlet is hidden from the user; if the user can jump directly to the test phase, then the servlet can't tell the difference between newly-arrived clients and cookie-unfriendly clients. That means you should send a redirect from the test phase, to make sure the user doesn't have a chance to bookmark the test phase's URL. Alex Chaffee (http://www.stinky.com/alex/, [email protected]) has written a Servlet that demonstrates this technique called CookieDetector (http://www.purpletech.com/code/CookieDetector.html) See also http://www.jguru.com/jguru/faq/view.jsp?EID=138297 How do I integrate HTML design into my Servlet? Location: http://www.jguru.com/faq/view.jsp?EID=153 Created: Sep 3, 1999 Modified: 2001-01-15 07:31:27.091 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) The question can be rephrased, "How can I design a work flow that incorporates HTML designers and programmers to build a dynamically generated web site that will keep expanding and growing over time?" This is a special case of the intractable Content Management Problem of the Web in general. The real problem is to allow HTML designers (that is, humans) to use their favorite HTML editing tools without learning Java, and to allow marketing people (arguably humans) to change the look of the site on a whim, without having to alter the database access code inside the servlet. (And vice versa -- to alter the business logic and data access without altering the user interface.) See my article at Servlet Central (http://www.servletcentral.com/199812/designprocess.dchtml) for an expansion on these themes. There are many, many possibilities... The list below is not complete, but should give you some guidelines. A. Hardcode HTML. You can just put HTML inside of print statements in your Servlet's doGet() or doPost() method. Pro: easy to code, easy to understand for the programmer. Con: difficult to understand for the designer; when a change has to be made, the programmer has to wait for the designer to finish her HTML, then re-hard-code it all back into print statements, then make sure the generated HTML actually does what

the original HTML did. Basically, good for a hello world servlet, not good for a real web site. B. Server Side Includes (SSI). Use the <SERVLET> tag inside your HTML file (and rename it .shtml). The HTML designers will make pretty pages; your servlets will output small pieces of text that get spliced in to the web page by the server. Pro: separates UI (HTML) and code. Con: You have two possible end paths with SSI: either your servlet outputs many tiny bits of text with no HTML tags, or your servlet outputs a big bunch of text with embedded HTML tags. In the first case, your code can't take advantage of its knowledge of the structure of the data -- for example, you can't format an HTML table from a database. In the second case, you're back to hardcoding HTML, thus making it hard to change the look of your pages. C. Presentation Templates. This is a good way to put common navigation elements (button bar, credits, etc) on all of your pages. The technology is built in to the Java Web Server, and implemented by several (though not all) of the servlet engines. Pro: you don't have to enter in the same common HTML for all the countless pages in your web site. Con: your servlet code still has to hardcode HTML if it wants to be powerful (see item B, SSI). D. JSP Java Server Pages. You write files in HTML format, and embed actual Java code inside the HTML. This is kind of like using JavaScript, only it's on the server, and it's real Java. This is directly parallel to Microsoft's ASP. Pro: it's really cool; you only need a single file to do both UI and layout code; you don't have to type "println" so much. Con: if you do anything interesting, then your HTML designers will get really confused looking at the interlaced Java and HTML code -- so make sure to put the complicated code inside a JavaBean where it belongs, not in the JSP page. The new version of the JSP spec has lots of features for integrating with JavaBeans, which is a great way to separate user interface (JSP) from data and business logic (beans). See also the JSP FAQ (see our References section for a link). Halcyon Software has a product called Instant ASP, which allows you to execute Microsft IIS-style ASPs (including code in VBScript, Jscript, Perl, Java, and JavaScript) in any Servlet Engine. Also Live Software has CF_Anywhere, which executes Cold Fusion CFML pages. See the References section for links. E. Write your own page parser. If for some reason you're not happy with the standard mechanisms for doing templates (see B-D above), you can always write your own parser. Seriously. It's not rocket science. F. HTML Object Model Class Libraries e.g. htmlKona, XML. With these class libraries, you write code and build an object model, then let the objects export HTML. This doesn't really work for complicated layouts -- and forget about letting your designer use an HTML editor -- but it can be useful when you have a highly dynamic site generating HTML, and you want to automate the process. Unfortunately, you still have to learn HTML, if only to understand and validate the output. See the References section of this FAQ for a listing of some class libraries that can help.

G. Do it all yourself Develop a database-driven content management system. Think C|Net. It has a lot of standard content, but the database is king. HTML designers have little pieces of the page that they can play with, but ultimately they're just putting content into a database, and the site (servlet) is generating every page request dynamically. This sort of system is very difficult to design and build, but once you've built it, it can really pay off -- but only if you have dozens of writers, editors, designers, and programmers all working on the same site on an ongoing basis. For a brief list of alternate page template systems, see the References section of this FAQ. Comments and alternative answers

Comments on E and F Page parsers have been written.... Author: Brett Knights (http://www.jguru.com/guru/viewbio.jsp?EID=8054), Jan 27, 2000 Comments on E and F Page parsers have been written. Go to http://www.docuverse.com/htmlsdk/index.html and you can download the pieces necessary to parse html files into a dom Document. You can then use dom methods to modify then emit the results. OR if you prefer F you can suck most of an html page into an xsl template tag and insert <xsl: tags to format your dynamic output. It's not great for really dynamic sites but it's an excellent way to have a page designer do a bunch of work then turn it over to you for installing dynamism (dynamicality? :-) Saxon is an excellent engine for this. There's another option: use SSI for Java. It's an SSI... Author: Joe Morse (http://www.jguru.com/guru/viewbio.jsp?EID=91113), Jun 29, 2000 There's another option: use SSI for Java. It's an SSI parser that runs in your VM, and it's open source (GPL). It also includes some cool utility classes (which you can mimic or extend) for creating stateful form elements and other things. There's even an iterator for printing variable-length collections (e.g. db recordsets, etc). Plus, it's portable; it will run on any web server with little or no changes. Check it out at http://www.freecode.com/cgi-bin/viewproduct.pl?8543. XMLC Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Oct 27, 2001 A great new "third way" solution -- with templates on one side, and servlets on the other -- is XMLC. Faced with the problem of separating presentation from code, XMLC takes the radical step of... (drumroll please...) actually separating the presentation from the code! The presentation "layer" is literally an HTML file. The code "layer" is a servlet (or any Java class) that reaches into the HTML file and changes its content, based on "ID" attributes embedded inside the HTML tags. (The way it accomplishes this is by compiling the HTML file into a Java class and data structure, but that's almost beside

the point.) How do I send email from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=154 Created: Sep 3, 1999 Modified: 2000-07-25 12:18:54.284 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) From: James Cooper ([email protected]) GSP and GnuJSP both come with SMTP classes that make sending email very simple. if you are writing your own servlet you could grab one of the many SMTP implementations from www.gamelan.com (search for SMTP and java). All the ones I've seen are pretty much the same -- open a socket on port 25 and drop the mail off. so you have to have a mail server running that will accept mail from the machine JServ is running on. See also the JavaMail FAQ for a good list of Java mail resources, including SMTP and POP classes. Comments and alternative answers

If you want to use the JavaMail API, get it and create... Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7), Jul 24, 2000 If you want to use the JavaMail API, get it and create a program similar to the Hello World program. See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Sep 20, 2001 This thread: Re: Automatically send and get mails using servlet... Some examples Author: Chris Lack (http://www.jguru.com/guru/viewbio.jsp?EID=326717), Sep 21, 2001 I've written an "EMailClient" class for sending e-mails for my guestbook entries. I've also done an "InBox" servlet class that lists e-mails in your pop mail in-box so that you can delete or bounce them before downloading to your PC. Have a look at the code, it might help http://www.chris.lack.org and choose the java option on the professional menu. By the way you'll need JavaMail and Java Activation foundation from Sun if you've not already downloaded them. You don't need your own mail server. Are there any ISPs that will host my servlets? Location: http://www.jguru.com/faq/view.jsp?EID=155

Created: Sep 3, 1999 Modified: 2003-04-04 10:57:05.916 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) The Adrenaline Group maintains a list of over 50 ISP's who host Java Servlets (http://www.adrenalinegroup.com/jwsisp.html) . Another list is at http://www.servlets.com. Those that our gurus (you) have had specific experience with include: • • • • • • • • • • •

Daniel Kehoe ([email protected]) has had "very happy experiences" with Silicon Valley Web Hosting (http://www.svwh.net/) for several clients. Horus Networks - http://www.horus.ch/servlets.shtml (http://www.servlets.net) is an ISP geared towards hosting servlets. http://www.ebpcs.net http://www.mycgiserver.com is free (!) and does EJB too http://www.tricreations.com http://www.webappcabaret.com http://www.cwihosting.com (see comment below) http://scorpions.net/ Rage Media Rimu Hosting

A few ISPs have also said that they can host Java applications: • • •

The Sphere (http://www.thesphere.com/) Centralogic (http://www.centralogic.com/) Electronaut (http://www.electronaut.com/)

Please report any experiences, good or bad, you have with these services to this thread. See also What ISPs provide hosting services which include JSP support? Comments and alternative answers

Horus Networks is very flexible on all services, and... Author: Denis BUCHER (http://www.jguru.com/guru/viewbio.jsp?EID=7742), Jan 22, 2000 Horus Networks is very flexible on all services, and we would be pleased to host servlets... c.f. our own programmation tests under http://www.horus.ch/servlets.shtml http://www.horus-networks.com/servlets.shtml Web Hosting Author: dufunk Eugene Rozum (http://www.jguru.com/guru/viewbio.jsp?EID=1193732), Aug 17, 2004 Prokmu jsp hosting offers the best quality/price JSP/Servlet services! Re: Web Hosting

Author: dufunk Eugene Rozum (http://www.jguru.com/guru/viewbio.jsp?EID=1193732), Sep 6, 2004 http://www.prokmu.com Re[2]: Web Hosting Author: Eugene Rozum (http://www.jguru.com/guru/viewbio.jsp?EID=1254770), Jul 24, 2005 Prokmu Jsp hosting http://www.prokmu.net http://www.ebpcs.net is a very cool one too Author: Steve Nguyen (http://www.jguru.com/guru/viewbio.jsp?EID=39558), Apr 24, 2000 http://www.ebpcs.net is a very cool one too If anyone looking for free Servlet/JSP hosting check... Author: Nilesh Shah (http://www.jguru.com/guru/viewbio.jsp?EID=1810), May 30, 2000 If anyone looking for free Servlet/JSP hosting check this out. http://www.mycgiserver.com http://www.servlets.net http://www.tricreations.co... Author: Melanie Munden (http://www.jguru.com/guru/viewbio.jsp?EID=138305), Aug 30, 2000 http://www.servlets.net http://www.tricreations.com Check out www.wantjava.com They support Tomcat, O... Author: James Ward (http://www.jguru.com/guru/viewbio.jsp?EID=242591), Nov 1, 2000 Check out www.wantjava.com They support Tomcat, Oracle, and mySQL! They also have great customer service! Another good listing of ISPs that support Java Servlets... Author: Bill Day (http://www.jguru.com/guru/viewbio.jsp?EID=135825), Dec 8, 2000 Another good listing of ISPs that support Java Servlets is at: www.servlets.com The listings include contact info and rates. More more more Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 16, 2001 • •

http://www.webappcabaret.com http://www.mycgiserver.com

CWI Hosting (http://www.cwihosting.com) Author: Scott Barstow (http://www.jguru.com/guru/viewbio.jsp?EID=226863), Oct 11, 2001 Do not use these guys. I have had nine kinds of grief with them, and their support is less than adequate. I have had outages of three days, and mail outages of three - four days. Re: CWI Hosting (http://www.cwihosting.com) Author: Joost Schouten (http://www.jguru.com/guru/viewbio.jsp?EID=581960), Jan 24, 2004 I just wanted to say that I use CWI hosting aswell, and do appreciate their service. They have provided me with good support, even on my own code at times. Just wanted to give them a fair chance. Joost re: Webhosting for servlets Author: richard freeman (http://www.jguru.com/guru/viewbio.jsp?EID=752499), Feb 8, 2002 Zetnet.com will host jsp, sql, mysql, etc. with all of their standard hosting packages (Ranging from UK£100 per annum). Drop me a line on 01524 34918 if you are interested in doing so... 4Java.ca - inexpensive and reliable host Author: support 4javaca (http://www.jguru.com/guru/viewbio.jsp?EID=804843), Mar 20, 2002 They host JSP, Servlet, J2EE. Very inexpensive, only USD$8.50/month! http://www.4java.ca MyServletHosting.com Author: Walter Meyer (http://www.jguru.com/guru/viewbio.jsp?EID=23642), Mar 27, 2002 I've been with MyServletHosting.com for over a year. The experience was great at first, but over that last 5 or 6 months, stability has really degraded. When I contact tech support they always apologize and say they're in the middle of moving their clients to more stable servers. Maybe they'll straighten everything out in the future, but for now, I'm looking for a new host.

Re: Scorpions.net Author: John Colucci (http://www.jguru.com/guru/viewbio.jsp?EID=816265), Mar 28, 2002 I am with Scorpions.net for about 8 months now. I have personal and business sites there. They use Tomcat,iPlanet, Java web server. Oracle hosting is super cheap and no set up fees. So far I am happy with them. John. Check out http://www.ragemedia.ca Author: Alex Iljin (http://www.jguru.com/guru/viewbio.jsp?EID=894025), May 27, 2002 Check out http://www.ragemedia.ca They provide J2EE application hosting (including Servlets, JSP and EJB's) based on Tomcat/Jboss platform, plus PostgreSQL database is standard for all plans. Rimu Hosting Author: Peter B (http://www.jguru.com/guru/viewbio.jsp?EID=1071364), Mar 29, 2003 Try http://rimuhosting.com Rimu Hosting provide Virtual Dedicated servers. That includes 128MB of memory, 8GB of disk space, and 30GB of transfers. Accounts come with JBoss and include JDK1.4, JSP, EJB and servlet support. You don't share the Java VM and you get to configure JBoss the way you need it. Other features include SSH root access, Webmin CP, MySQL, PHP, Redhat Linux.

Re: Rimu Hosting Author: Peter B (http://www.jguru.com/guru/viewbio.jsp?EID=1071364), Oct 15, 2003 A customer who just signed up pointed that our plans now come with 4GB of disk. Our Red Hat file systems have been updated to use Java 1.4.2, JBoss 3.2.1 as well a choice of a recent Tomcat or Jetty servlet engine.

RE: Java Hosting Author: Alacarte Java (http://www.jguru.com/guru/viewbio.jsp?EID=1118665), Sep 29, 2003

I am with Alacarte Java Hosting (http://www.alacartejava.com) and we specialize in low cost Java JSP Hosting, Servlet Hosting, and much more. Checkout our Web Site at http://www.alacartejava.com « previous

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What is the difference between URL encoding, URL rewriting, HTML escaping, and entity encoding? Location: http://www.jguru.com/faq/view.jsp?EID=156 Created: Sep 3, 1999 Modified: 2000-09-17 15:25:28.842 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) URL Encoding is a process of transforming user input to a CGI form so it is fit for travel across the network -- basically, stripping spaces and punctuation and replacing with escape characters. URL Decoding is the reverse process. To perform these operations, call java.net.URLEncoder.encode() and java.net.URLDecoder.decode() (the latter was (finally!) added to JDK 1.2, aka Java 2). Example: changing "We're #1!" into "We%27re+%231%21" URL Rewriting is a technique for saving state information on the user's browser between page hits. It's sort of like cookies, only the information gets stored inside the URL, as an additional parameter. The HttpSession API, which is part of the Servlet API, sometimes uses URL Rewriting when cookies are unavailable. Example: changing into (or whatever the actual syntax is; I forget offhand) (Unfortunately, the method in the Servlet API for doing URL rewriting for session management is called encodeURL(). Sigh...) There's also a feature of the Apache web server called URL Rewriting; it is enabled by the mod_rewrite module. It rewrites URLs on their way in to the server, allowing you to do things like automatically add a trailing slash to a directory name, or to map old file names to new file names. This has nothing to do with servlets. For more information, see the Apache FAQ (http://www.apache.org/docs/misc/FAQ.html#rewrite-more-config) . Comments and alternative answers

HTML Escaping, Entity Encoding Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 8, 2003 Yet another form of encoding is called "escaping" or "entity encoding," which involves transforming special characters, like " into their HTML entity replacements, like " or ". HTML entities are a convenient (or sometimes mandatory) way of representing special characters like symbols or international language idiograms.

See http://hotwired.lycos.com/webmonkey/reference/special_characters/ for a list of the standard HTML entities. You must HTML-escape characters in fields that your servlet sends as default values inside form fields, for instance I have written a utility method for transforming Unicode strings into HTML strings with properly escaped entities at Purple Code site. Look for com.purpletech.util.Utils.java, method htmlescape() and htmlunescape().

Re: HTML Escaping, Entity Encoding Author: Christopher Koenigsberg (http://www.jguru.com/guru/viewbio.jsp?EID=722897), Jan 9, 2003 Also in the email world you may run across "quoted-printable" and "base64" as the 2 main "content-transfer-encodings" to protect message content during transmission. The Web standards were developed based on the earlier email standards (e.g. changing a blank space into "%20", in URL encoding, comes originally from the email "quoted-printable" content-transfer-encoding), so it helps to read about both.

How can my applet or application communicate with my servlet? Location: http://www.jguru.com/faq/view.jsp?EID=157 Created: Sep 3, 1999 Modified: 2003-01-09 06:27:13.548 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) It's pretty straightforward. You can use the java.net.URLConnection and java.net.URL classes to open a standard HTTP connection to the web server. The server then passes this information to the servlet in the normal way. Basically, the applet pretends to be a web browser, and the servlet doesn't know the difference. As far as the servlet is concerned, the applet is just another HTTP client. (Of course, you can write a servlet that is meant to be called only by your applet, in which case it *does* know the difference. You can also open a ServerSocket on a custom TCP port, and have your applet open a Socket connection. You must then design and implement a custom socket-level protocol to handle the communication. This is how you could write, e.g., a Chat applet communicating with a servlet. In

general, a custom protocol requires more work than HTTP, but is more flexible. However, custom protocols have a harder time getting through firewalls.) For more detail, you can see the Sun Web Server FAQ (http://www.sun.com/software/jwebserver/faq/faq.html) Questions C8 (http://www.sun.com/software/jwebserver/faq/faq.html#c8) and C9 (http://www.sun.com/software/jwebserver/faq/faq.html#c9) . Also, Chad Darby has an article with source code (http://www.jnine.com/pubs/applet2servlet/index.htm) on the subject. And Netscape DevEdge Online has a similar article - Applet-to-Servlet Communication for Enterprise Applications (http://developer.netscape.com/viewsource/index_frame.html?content=fields_servlet /fields_servlet.html) skip to the "Communication Tactics" section to get to the good part. See also: • • • •

How can I pass an object from an applet to a servlet ? When you communicate with a servlet from an Applet, how can you ensure that the session information is preserved? That is, how do you manage cookies in applet-servlet communication? How can an applet or application pass data to and read output from a CGI script or Servlet? see the section "An Applet That Sends POST Data" here http://archive.coreservlets.com/Chapter17.html

Comments and alternative answers

Beware! Author: tommy Palm (http://www.jguru.com/guru/viewbio.jsp?EID=483108), Aug 24, 2001 There is a typo on the Sun FAQ (http://www.sun.com/software/jwebserver/faq/faq.html#c8). It says " out.println(URLEncoder.encode("key1") + "=" + URLEncoder.encode("value1")); out.println(URLEncoder.encode("&key2") + "=" + URLEncoder.encode("value2"));

The last line of code should be

out.println("&"+URLEncoder.encode("key2") + "=" + URLEncoder.encode("value2"));

Otherwise the parameters is not seperated since the URLEncoder encodes the '&'. How can I debug my servlet? Location: http://www.jguru.com/faq/view.jsp?EID=158 Created: Sep 3, 1999 Modified: 2001-07-19 15:41:41.969 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3)

Hoo boy, that's a tough one. First off, you should always do your own exception handling. An uncaught exception can silently kill your servlet, and if you don't know where to look in the log files, or if your server has a bug in it whereby it silently swallows certain exceptions, you'll have no idea where the trouble is. The following code sets up a catch block that will trap any exception, and print its value to standard error output and to the ServletOutputStream so that the exception shows up on the browser (rather than being swallowed by the log file). Chances are that any error is in your code; the exception shows you what line the problem happened at. (If you see "Compiled Code" instead of line numbers in the exception stack trace, then turn off the JIT in your server.) res.setContentType("text/html"); ServletOutputStream out = res.getOutputStream(); try { // do your thing here ... } catch (Exception e) { StringWriter sw = new StringWriter(); PrintWriter pw = new PrintWriter(sw); e.printStackTrace(pw); out.println(" "); out.print(sw.toString()); out.println(" "); } Lately, I've started catching all Throwables, just in case. I know this is bad form but what are you gonna do? Next, you should make liberal use of the log() method, and you should keep your own log files. Again, don't trust the server to do the right thing. Also, printing the log after every request can help debugging because you can immediately see the output of your servlet without going into the server-side log files. (Another problem this avoids is that some servlet engines forget to flush their logs after each request, so even if you go to the server, you won't see the most recent log messages.) Here's some source code you can add to any HttpServlet that keeps an in-memory log:

StringBuffer logBuffer = new StringBuffer(); public void log(String s) { s = new Date().toString() + ": " + s; System.err.println(s); logBuffer.append(s); logBuffer.append("\n"); super.log(s);

} And here's some code that you can add to the end of your doGet or doPost method that prints out the entire log after each request: out.println("

Error log this session:

"); out.println(logBuffer.toString()); out.println("

"); Both of these should be disabled once you actually ship your servlet, but they can be very useful during development and debugging. You should remember to use servletrunner (renamed "JSDK WebServer" with the JSDK version 2 -- run with the script startserver) to debug your servlet. It's a tool that ships with the JSDK that basically starts up a miniature web server that runs your servlet inside itself. It means you don't have to stop and restart your real web server every time you recompile your servlet. It also affords a more pure environment, so you can make sure your servlet truly conforms to the spec before you try to run it inside a (possibly buggy or nonstandard) servlet engine. (Note that Tomcat does not have a replacement for servletrunner :-(.) A few IDEs support servlet debugging. Symantec Cafe claims to have a fairly robust system for doing visual source-level debugging of servlets (as well as RMI, CORBA, and EJB objects). [If anyone has any experience with Cafe or other IDEs, please email &feedback;.] May Wone ([email protected]) writes: I am debugging servlets running servletRunner inside of IBM's VisualAge for Java. On my first servlet project, I used a ton of log messages for debugging. This is my second servlet project, and this debugging technique has enhanced my productivity many folds. I am able to set code break points, step through each line of code, inspect all the objects visible to this class as well as view the objects in the current stack. I can also view, suspend, resume threads. The setup instructions are at: (http://www.ibm.com/java/education/serverside/server-side.html) jRun also claims to have excellent log file support as well as some debugging facilities. Eric Gilbertson ([email protected]) adds: Another way to debug servlets is to invoke JWS with java_g and then attach to the process using any debugger that is capable of attaching to a running Java process given a debug password. To do this invoke JWS as follows:

java_g.exe -debug -Dserver.name="javawebserver" [extra args...] com.sun.server.ServerProcess jdb password=[password]

This will start the Web server process and echo a password. The password may be then used with jdb to attach to the process. Note that this will start only the Web server, not the admin server. Sun does not advertise this mechanism which in my mind is the only way to debug non-trivial servlets. Comments and alternative answers

Jetty is an open-source HTTP servlet server written... Author: Kent Johnson (http://www.jguru.com/guru/viewbio.jsp?EID=3211), Dec 22, 1999 Jetty is an open-source HTTP servlet server written in Java. It makes an excellent servlet debugging and deployment environment. I build Jetty and my servlets and supporting classes into a single executable that I debug the same as any other application. I am using CodeWarrior on a Macintosh but this technique should work with any development tools that can debug an application. Jetty is available from http://www.mortbay.com. New Atlanta has a free product called ServletExecD... Author: Erik Hanson (http://www.jguru.com/guru/viewbio.jsp?EID=38768), Apr 21, 2000 New Atlanta has a free product called ServletExecDebugger which is a debugging version of their ServletExec product. It consists of a jar file containing some or all of ServletExec and a small source file containing a main() method. You build that with your servlets, and then you can use your debugger on your servlets. It should work with any development environment. See also this question in the JSP FAQ which describes... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 22, 2000 See also this question in the JSP FAQ which describes debugging with VAJ and Tomcat. From the tomcat-user mailing list: From: Vincent... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 22, 2000 From the tomcat-user mailing list: From: Vincent Aumont Organization: Vancouver Software Labs To: [email protected] Subject: Re: I need to debug a serlet: How can I do it?

To debug your servlets, you need to run tomcat itself in the debugger. To do so, you must write your own tomcat main (see code below). Note that you must define the tomcat.home property ( in a properties file or passed on the command line (-Dtomcat. home=[...]/jakarta-tomcat) import org.apache.tomcat.startup.Tomcat; import java.lang.Exception;

import java.util.*; import java.io.*; public class Tomcat { public static void main(String[] args) throws IOException { try { Tomcat.main(new String[] {}); } catch (Exception e) { System.out.println("Can't start Tomcat"); System.out.println(e); System.exit(0); } } }

With Tomcat 4.1.12 and JDeveloper 9.0.3.... From: Vincent... Author: Tommy Skodje (http://www.jguru.com/guru/viewbio.jsp?EID=446264), Nov 18, 2002 ... I used this call: org.apache.catalina.startup.Catalina.main( new String[] { "-config" , "D:\\Programs\\Apache\\Tomcat4.1\\conf\\server.xml" , "-debug" , "start" } .. in place of Tomcat.main(...) call, as well as added each and every jar-file in Tomcat4.1\server\lib\ and Tomcat4.1\common\lib\ in classpath. For Symantec Visual Cafe debugging, see Patrick Ch... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 31, 2000 For Symantec Visual Cafe debugging, see Patrick Chanezon's Debug JSP and Servlets with Visual Cafe using Tomcat howto. You can download the latest version of JBuilder for... Author: Robert Castaneda (http://www.jguru.com/guru/viewbio.jsp?EID=4362), Aug 8, 2000 You can download the latest version of JBuilder for free and use it to debug your servlets using Tomcat, the official Servlet reference implementation. Doing this ensures that you are up-to-date with the standards, as the Servlet engine shipped with JBuilder 2.01 is not the latest. You can view a detailed paper on how to set up you environment at community.borland.com See also Are there any IDE's which will help me debug... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Aug 14, 2000 See also Are there any IDE's which will help me debug JSPs?

This link gives a list of products that use Java P... Author: Aprameya Paduthonse (http://www.jguru.com/guru/viewbio.jsp?EID=4707), Feb 1, 2001 This link gives a list of products that use Java Platform Debugger Architecture (JPDA) and all of them are supposed to support remote debugging. http://java.sun.com/products/jpda/using.html re: debugging servlets Author: Bob Mook (http://www.jguru.com/guru/viewbio.jsp?EID=404742), Apr 17, 2001 Oracle has a nice IDE for debugging servlets - JDeveloper. Its runs in a built-in JSWDK server. bob Re: re: debugging servlets Author: Jo Hh (http://www.jguru.com/guru/viewbio.jsp?EID=961119), Jul 23, 2002 debuging servlets is one thing but is there a way to integrate catalina/tomcat to debug whole sessions like in forte? i couldnt find a way with the actual jdev release. did you? Debugging using IntelliJ Ideas Author: raj subramani (http://www.jguru.com/guru/viewbio.jsp?EID=576334), Mar 6, 2002 I got tomcat working through my Idea's IDE (from Intellij) To acheive this: •

• •

•

Make sure the source code is present in your Tomcat installation dir (hereinafter referred to as TID and the Java Installation directory as JID). If you don't have it, get if from jakarta and install it in the TID. The main class must be set to org.apache.catalina.startup.Bootstrap (you should see this once the source is added to your project path) The VM parameters are set to: o -Djava.endorsed.dirs ="TID\bin;TID\common\lib" o -classpath "JID\lib\tools.jar;TID\bin\bootstrap.jar" o -Dcatalina.base="TID" o -Dcatalina.home="TID" o -Djava.io.tmpdir="TID\temp" Program parameter must contain start

Finally make sure that you do not compile anything by setting the appropriate dirs in the "Compiler" option

Re: Debugging using IntelliJ IDEA Author: Walter Rumsby (http://www.jguru.com/guru/viewbio.jsp?EID=544477), Apr 1, 2002 I'm using IDEA (Ariadana) Build 602 - a preview release of the next version along with Tomcat 3.3a on Windows 2000. You can use IDEA's remote debugging option to debug servlets. 1. In Run/Debug - Remote tab of Project Properties dialog choose to add a new default configuration (with the "+" button). 2. Copy the JVM settings in the dialog box, eg. mine look like the following: Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp: transport=dt_socket,server=y,suspend=n,address=5000 3. Open the bin/tomcat.bat file in your Tomcat directory and go to the :startServer label (Unix open the tomcat.sh file, I guess). A few lines below the label should be the following: %_STARTJAVA% %TOMCAT_OPTS% -Djava. security.policy=="%TOMCAT_HOME%/conf/tomcat.policy" -Dtomcat.home="%TOMCAT_HOME%" %_MAIN% start %2 %3 %4 %5 %6 %7 %8 %9 Add the JVM parameters you copied from IDEA into that line, so you have something like: %_STARTJAVA% %TOMCAT_OPTS% -Djava. security.policy=="%TOMCAT_HOME%/conf/tomcat.policy" -Dtomcat.home="%TOMCAT_HOME%" -Xdebug -Xnoagent -Djava. compiler=NONE -Xrunjdwp: transport=dt_socket,server=y,suspend=n,address=5000 %_MAIN% start %2 %3 %4 %5 %6 %7 %8 %9 4. If Tomcat is running stop it and restart it. Once it is up and running again, set a breakpoint somewhere in your Java source with IDEA and then click on the bug icon, choose debug and you should now be able to use IDEA's debugger to debug your servlet.

Re[2]: Debugging using IntelliJ IDEA Author: Justin Hopper (http://www.jguru.com/guru/viewbio.jsp?EID=855419), Apr 26, 2002 Yes, yes, yes this is a very nice feature of both IntelliJ and Java. However, I have found that while running Tomcat 3.2 and IntelliJ 2.5.2 in this remote debugger, that everytime I hit an exception an "native" access violation would

occur. This would cause Tomcat to shutdown and obviously end the debugging session. In order to get around this I had to include the -classic

to the list of options shown above. Therefore, the resulting option look like this -classic -Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp: transport=dt_socket,server=y,suspend=n,address=5000

Oddly enough, this seemed to speed up the debugger response as well. One other thing that I would like to add is that the TOMCAT_OPTS

variable was put there so the it can be set to the value of all of these additional parameters. So an alternative would be to not modify the "startServer:" portion of the script but rather initialize the TOMCAT_OPTS variable to the list of options specified below. Either way will result in the same behavior, it is just that using the variable will allow you to turn debugging on and off by setting and unsetting the TOMCAT_OPTS variable from some external action (i.e. separate "startup.*" scripts). Thanks for posting this solution. Justin Re: Debugging using IntelliJ Ideas Author: raj subramani (http://www.jguru.com/guru/viewbio.jsp?EID=576334), Apr 2, 2002 PS: In response to the question asked (repeatedly) • •

•

•

I just downloaded the binary version of catalina 4.0.3 and installed it. I then downloaded the src version of the above and just copied in the source code directory into the above installation so that I could then point Idea's to this source (No Compilation of this source was done). Make sure that this source directory is included in the exclusions list of the "Compiler" options otherwise Idea's will attempt to compile this catalina source as well Finally, maybe the remote debugging option below is neater, IMHO

How do I create an image (GIF, JPEG, etc.) on the fly from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=159

Created: Sep 3, 1999 Modified: 2001-12-16 12:47:29.26 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) To create an image or do image processing from Java, there are several packages and classes available. See the Purple Servlet References for a list. Once you have an image file in your servlet, you have two choices:

1. Write the file to disk and provide a link to it. Make sure you write it to a location that's in your web server directory tree (not just anywhere on the server's disk). You can use the Java 2 JPEGCodec class, or Acme Labs' GIFEncoder class, to turn a Java Graphics into an image file or bytestream. (Note that in some servlet engine setups, the servlet directory is not accessible by the web server, only by the servlet engine, which means you won't be able to access it through an http:// URL.) You can either send an IMG tag in the HTML your servlet is outputting, or send an HTTP redirect to make the browser download the image directly (as its own page). (CookieDetector (http://www.purpletech.com/code/CookieDetector.html) has an example, with source code, of sending a redirect.) Pro: the image can be cached by the browser, and successive requests don't need to execute the servlet again, reducing server load. Con: the image files will never be deleted from your disk, so you'll either have to write a script to periodically clean out the images directory, or go in and delete them by hand. (Or buy a bigger hard disk :-) ).

2. Output the image directly from the servlet. You do this by setting the

Content-type header to image/gif (for GIFs), or image/jpeg (for JPEGs). You then open the HttpResponse output stream as a raw stream, not as a PrintStream, and send the bytes directly down this stream using the write() method.

Focus on Java (http://java.miningco.com/library/weekly/aa090299.htm) has a brief article describing the use of the Java 2 JPEGCodec class. You can also use JIMI to read and write images in many formats, including GIF, JPEG, TIFF (TIF), PNG, PICT, Photoshop, BMP, Targa, ICO, CUR, Sunraster, XBM, XPM, and PCX. See also: • • • •

A list of Java Image links is at Purple Technology See also How can I plot data on a graph or chart from a ser... on plotting charts and graphs from a servlet. Is there any way to generate offscreen images without relying on the native graphics support? How can I display tif graphics in my Java applet?

•

Reading TIF file with a servlet, converting it into...

Comments and alternative answers

Remember the IMG tag Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Dec 16, 2001 Remember, to display an image inside an HTML page, you have to use the IMG tag, like

Just writing the data to the servlet response isn't going to work, unless you're writing an entire image/gif or image/jpeg document. code to write imgs on the fly from a jsp Author: kamalesh kam (http://www.jguru.com/guru/viewbio.jsp?EID=1158032), Mar 28, 2004 <%@ page import="javax.servlet.http.*"%> <%@ page import="java.io.*"%> <%@ page import="java.awt.*"%> <%@ page import="java.util.Random"%> <%@ page import="java.awt.Color"%> <%@ page import="java.awt.image.*"%> <%@ page import="Acme.JPM.Encoders.GifEncoder"%> <%@ page import="com.sun.image.codec.jpeg.JPEGCodec"%> <%@ page import="com.sun.image.codec.jpeg.JPEGImageEncoder"%> <%BufferedImage image= new BufferedImage(500,500, BufferedImage.TYPE_INT_RGB); Graphics g=image.getGraphics(); Random r=new Random(); g.fillRect(r,r,r,r); FileOutputStream fos=new FileOutputStream("c:/ewr.jpg"); JPEGImageEncoder encoder= JPEGCodec.createJPEGEncoder(fos); encoder.encode(image); %>

Jake stone adds source code Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Dec 16, 2001 public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { File f = new File(System.getProperty("user.home")+"\\zoewrap.jpg"); JPEGImageDecoder decoder = JPEGCodec.createJPEGDecoder(new FileInputStream(f)); BufferedImage image =decoder.decodeAsBufferedImage() ;

}

// Send back image ServletOutputStream sos = response.getOutputStream(); JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(sos); encoder.encode(image);

Re: Jake stone adds source code Author: Ping Long (http://www.jguru.com/guru/viewbio.jsp?EID=799119), May 15, 2002 Alex, I got cached image problem in my application. I need to update image without changing name. Your idea may fix my problem. I would like to know when I can get those classes such as: JPEGImageDecode, JPEGImageEncoder, JPEGCodec. Thanks in advance. PL Re[2]: Jake stone adds source code Author: jpeg jones (http://www.jguru.com/guru/viewbio.jsp?EID=885462), May 20, 2002 These classes are in the com.sun.image.codec.jpeg. package; they should be in your jdk 1.3 (or whatever) src.jar Re[3]: Jake stone adds source code Author: Ohad Kravchick (http://www.jguru.com/guru/viewbio.jsp?EID=1025885), Nov 14, 2002 I have a problem with that. i made a painter applet, and i need to write the result of the painting to the server (asp). i've created an asp page which gets posted data, from the applet (ACME.GifEncoder), and it still doesnt work. will you please help me, i'm stuck badly. go and take a look at the painter: my Painter send me email for response..... Regarding the cache problem Author: Thomas Isaksen (http://www.jguru.com/guru/viewbio.jsp?EID=1132932), Dec 9, 2003 I think I had the same problem when trying to display an image fetched from a servlet talking to the db. I simply added another parameter to the url which caused the cache problem to go away: First I had: which didn't work, it was cached and showed the same image all the time. So I put this in: and the image caching problem is gone :-) "some_random_number" can be as simple as putting the value of System.currentTimeMillis() or using java.util.Random to come up with a value. Hope this helps. How do I upload a file to my servlet or JSP? Location: http://www.jguru.com/faq/view.jsp?EID=160

Created: Sep 3, 1999 Modified: 2003-01-11 10:39:24.072 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) On the client side, the client's browser must support form-based upload. Most modern browsers do, but there's no guarantee. For example,

Look out

"); out.println ("Sharks ahead"); a good JSP implementation would put all the strings in a char array and write() them, a la: private static final char _chunk_0[] = { '','H','1','>','L','o','o','k', ' ','o','u','t','','/','H','1', '>','\r','\n','S','h','a','r','k', 's',' ','a','h','e','a','d','\r', '\n' }; out.write(_chunk_0); About that "lightweight thread context switch" -- ... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Dec 31, 1999 About that "lightweight thread context switch" -- that's true if you're using a Java Web Server, but most web servers are written in C and must launch a separate process for the Servlet JVM. So the request actually does have to go through a socket and swap in a different (heavyweight) process. Of course, some servlet engines launch the Java VM in-process, but most do not. (I'm not sure which do and which do not. I know Apache mod_jserv launches a separate process.) Note that spawning a separate process can actually improve performance since it allows you to use separate hosts, or multiple hosts, to load-balance servlet execution. How can I download a file (for instance, a Microsoft Word document) from a server using a servlet and an applet? Location: http://www.jguru.com/faq/view.jsp?EID=3696 Created: Dec 29, 1999 Modified: 2001-07-23 09:19:32.296 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Try telling the applet to call

getAppletContext().showDocument("http://foo.com/whatever/bl ah.doc"). That makes the browser responsible for fetching and saving the document (including putting up the "Save As" dialog).

You may also want to check the web server configuration to make sure the approprate MIME-type configuration is set. If your servlet is the one fetching the document (or creating it on the fly), then it must set the MIME-type using response.setContentType("application/ms-word") or equivalent. Comments and alternative answers

Also see this FAQ for more information on downloading... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Feb 5, 2000

Also see this FAQ for more information on downloading files from servlets: http://www.jguru.com/jguru/faq/view.jsp?EID=10646 I've installed the JSWDK and it says I've run out of environment space when I try to start the server. How do I increase the amount of environment space under Windows? Location: http://www.jguru.com/faq/view.jsp?EID=3903 Created: Jan 3, 2000 Modified: 2000-06-03 14:35:40.648 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) The end of your CONFIG.SYS file should include a line like the following: SHELL=C:\COMMAND.COM C:\ /E:4096 /P This assumes your COMMAND.COM file is in your root level C: directory and you wish your shells to start in that directory, too. The 4096 is the new environment size. You can increase this to a larger number if that is still a problem. Comments and alternative answers

I added this setting to my config.sys and I also i... Author: Luc Luong (http://www.jguru.com/guru/viewbio.jsp?EID=29681), Mar 29, 2000 I added this setting to my config.sys and I also increased the environment memory size to 4096 in DosPrompt windows. Nothing helped. Replace 4096 by 5096 or by any larger value. Author: arun puri (http://www.jguru.com/guru/viewbio.jsp?EID=301533), Feb 28, 2001 Replace 4096 by 5096 or by any larger value. I need to communicate from my servlet to another independent process. Can I use the RequestDispatcher instead of opening a socket connection? Location: http://www.jguru.com/faq/view.jsp?EID=4224 Created: Jan 6, 2000 Modified: 2000-06-03 14:36:16.703 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) No. The RequestDispatcher can only send a message to a servlet or JSP running inside the same servlet engine. You either have to open a socket, use native code, or use Runtime.exec() to spawn a process on the web server host. Comments and alternative answers

Does it mean that attributes set with ServletReque... Author: Maxim Senin (http://www.jguru.com/guru/viewbio.jsp?EID=21992), Mar 8, 2000 Does it mean that attributes set with ServletRequest.setAttribute() or any other nonString object available thru ServletRequest CANNOT be sent to servlet or jsp on

another server? I.e. I cannot pass instance of JavaBean to servlet located on Yahoo! website? That's right -- you definitely can't count on variables... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Mar 9, 2000 That's right -- you definitely can't count on variables (session or otherwise) being available in a different JVM, let alone a whole different web site! This broaches another big topic -- persistence of variables across load-balanced servers -- but that deserves a FAQ of its own. 1. Well, engine could try to download requested re... Author: Maxim Senin (http://www.jguru.com/guru/viewbio.jsp?EID=21992), Mar 9, 2000 1. Well, engine could try to download requested resource, instantiate it locally and pass necessary data to it. But I agree, it doesn't make any sense. 2. I understand why RequestDispatcher.forward() can only access resources WITHIN SAME ServletContext. But: a. servlet engine can use it's sendRedirect() method to forward to remote resource even though it cannot pass it's ServletRequest or ServletResponse. b. what if I want to include() some data from Yahoo! website into content that my servlet is returning? There's nothing wrong with that. Anyway: even if servlet engine would not let me include() resource from Yahoo!, I can still just copy content from them by opening URL connection and copying data from URL.getInputStream() to ServletOutputStream. Can a servlet add request parameters into a request object before passing on the request to another servlet or jsp? Location: http://www.jguru.com/faq/view.jsp?EID=4920 Created: Jan 13, 2000 Modified: 2000-06-03 14:37:55.388 Author: Joy Mangaliman (http://www.jguru.com/guru/viewbio.jsp?EID=4919) I am currently doing this - passing a request object to a jsp. However, you need JRun to do so. JRun has some packages included which define classes called JRunServletRequest and JRunServletResponse which are extensions of HttpServletRequest and HttpServletResponse. JRunServletRequest has the method setAttribute which allows the setting of request parameters. JRunServletResponse has the method callPage which allows the JRunServletRequest to be passed to the servlet/jsp. - Joy Mangaliman ([email protected]) Comments and alternative answers

Anil Bhatt ([email protected]) writes: Yes,... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 26, 2000 Anil Bhatt ([email protected]) writes: Yes, I think a new attribute can be added using the setAttribute(String key, Object o) method of the Request Object eg. req.setAttribute("action", "delete");

then the request can be forwarded using the requestdispatcher object. ServletContext sc = getServletContext(); RequestDispatcher rd = sc.getRequestDispatcher(url); rd.forward(req, res);

Where url is the srting containg the url of the destination servlet, req and res are request and response objects respectively. Actually, I think there's a difference between Request... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 30, 2000 Actually, I think there's a difference between Request Parameters and Request Attributes. So the question is still unanswered. Workarounds Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 9, 2003 See http://www.jguru.com/forums/view.jsp?EID=1016603 Construct your own ActionForward Author: Jason Tang (http://www.jguru.com/guru/viewbio.jsp?EID=1231997), Mar 11, 2005 If you use structs and your project didn't allow you use request.setAttribute() to pass the value to next action, just try construct your own ActionForward object and add your parameters into it. Example .... ActionForward forward = mapping.findForward("success"); StringBuffer bf = new StringBuffer(forward.getPath()); bf.append("?id=1");//add parameter here return new ActionForward(bf.toString(),false);

How do I call one servlet from another servlet? Location: http://www.jguru.com/faq/view.jsp?EID=5049 Created: Jan 15, 2000 Modified: 2001-09-26 14:11:21.807 Author: Sameer Tyagi (http://www.jguru.com/guru/viewbio.jsp?EID=4381) [ Short answer: there are several ways to do this, including • • • •

use a RequestDispatcher use a URLConnection or HTTPClient send a redirect call getServletContext().getServlet(name) (deprecated, doesn't work in 2.1+)

- Alex ] It depends on what you mean by "call" and what it is you seek to do and why you seek to do it.

If the end result needed is to invoke the methods then the simplest mechanism would be to treat the servlet like any java object , create an instance and call the mehods. If the idea is to call the service method from the service method of another servlet, AKA forwarding the request, you could use the RequestDispatcher object. If, however, you want to gain access to the instance of the servlet that has been loaded into memory by the servlet engine, you have to know the alias of the servlet. (How it is defined depends on the engine.) For example, to invoke a servlet in JSDK a servlet can be named by the property myname.code=com.sameer.servlets.MyServlet The code below shows how this named servlet can be accessed in the service method of another servlet public void service (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ... MyServlet ms=(MyServlet) getServletConfig().getServletContext().getServlet("myname"); ... } That said, This whole apporach of accessing servlets in another servlets has been deprecated in the 2.1 version of the servlet API due to the security issues. The cleaner and better apporach is to just avoid accessing other servlets directly and use the RequestDispatcher instead. Comments and alternative answers

An easy way is to make an HTTP request from within... Author: Yakov Sirotkin (http://www.jguru.com/guru/viewbio.jsp?EID=6342), Jan 26, 2000 An easy way is to make an HTTP request from within the first servlet. After that, you can read it line by line and do what you want. Like this: try { URL news = new URL("http://myserver/myservlet"); BufferedReader in = new BufferedReader(new InputStreamReader(news.openStream())); String inputLine; while ((inputLine = in.readLine()) != null) { out.println(inputLine); } in.close(); } catch (Exception e){}

Re: An easy way is to make an HTTP request from within...

Author: Delarie Oliver (http://www.jguru.com/guru/viewbio.jsp?EID=388919), Mar 27, 2001 I want to forward the request from servlet1 on one server to the request in servlet2 on another server. Where do I put the HttpServletRequest object in the above code? How to call one servlet from another servlet. I tried... Author: kumar subramanian (http://www.jguru.com/guru/viewbio.jsp?EID=17901), Feb 25, 2000 How to call one servlet from another servlet. I tried the option which you specified here. getting the handle of one servlet within another servlet. How to call a servlet from an application. If called the servlet should not return an html page Istead it should return a set of values which i can use in my application. Kumar: on the client side, you must simply write a... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 17, 2000 Kumar: on the client side, you must simply write a parser to process the InputStream. It's not hard. You can use the StreamTokenizer class to help. See also this FAQ Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 17, 2000 See also this FAQ: How can my applet communicate with my servlet? I want to call a method on an instance of a servlet.... Author: nitin k (http://www.jguru.com/guru/viewbio.jsp?EID=137461), Sep 14, 2000 I want to call a method on an instance of a servlet. for eg. lets say we have a saveState() method in all servlets in a web application which writes to the database(picked up from Jason Hunters book). I need to call this method from another servlet. How do i do it? I cannot treat the servlet as just another class as i want to call the method on a particular instance of the servlet. whats the best way to this, given that getServletNames() and getServlet(String s) are deprecated? Make an object that both servlets can share via ap... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Sep 14, 2000 Make an object that both servlets can share via application (context) properties; put the method there instead. But that object will be accessible from any servlet... Author: nitin k (http://www.jguru.com/guru/viewbio.jsp?EID=137461), Sep 15, 2000 But that object will be accessible from any servlet in the application. Is there any

elegant way by which i can call a method in a servlet from the other servlet? I want to save the state of a servlet, which is done when the saveState() method of the servlet is called. If i place the method in a common object then i will also have to pass all the properties of that servlet to that object. and i wnat to control the savestate() methods of several servlets. this will become extremely tedious. thanks nitin You should probably redesign your app so the "... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Sep 17, 2000 You should probably redesign your app so the "state" you're describing is in a data object that contains all these properties and state. A servlet should really not contain much state; if you find a servlet growing too big then it's probably time to refactor. Think of the servlet as a simple request processor, sitting on top of more complex data storage and business logic objects. As for tedium, it will be just as tedious to locate N servlets and call their saveState() methods as to locate N objects and call their saveState() methods. If you use the URLConnection, and want to preserve... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Nov 7, 2000 If you use the URLConnection, and want to preserve session information, you'll need to add the session cookie to the URLConnection request. See this FAQ for information on how to do that. How can I access or create a file or folder in the current directory from inside a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=5272 Created: Jan 17, 2000 Modified: 2000-06-03 14:39:10.347 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Since there's no telling which directory the servlet engine was launched from, you should always use absolute pathnames from inside a servlet. Usually I pass in the root directory in an InitParameter, and create File objects relative to that directory. Comments and alternative answers

...unless it's part of the WAR Author: William Pietri (http://www.jguru.com/guru/viewbio.jsp?EID=142508), Nov 16, 2001 If the file is part of the web application, you can get the proper path from the ServletContext: String filename = getServletContext().getRealPath("/WEBINF/appconfig.xml");

That avoids making any assumptions about where on the server your files end up.

Re: ...unless it's part of the WAR Author: leo leung (http://www.jguru.com/guru/viewbio.jsp?EID=575344), Dec 6, 2001 I don't think that works if it is inside a WAR file. Base on the J2EE spec. the getRealPath() should return null. :( Re: ...unless it's part of the WAR Author: William Pietri (http://www.jguru.com/guru/viewbio.jsp?EID=142508), Jan 1, 2002 Excellent point! The servlet container I was testing with automatically expands the WARs. Sorry for the confusion. Re[2]: ...unless it's part of the WAR Author: Chris Bailey (http://www.jguru.com/guru/viewbio.jsp?EID=906038), Jun 6, 2002 And, even in servlet containers that expand the WAR, getRealPath may still return null (it does in Tomcat 4.0.3 for example). I'm wondering the same thing. I'd like to be able to write files into a subdirectory in my expanded servlet directory, but I don't see how to do this if the web app is in a WAR file. Re[3]: ...unless it's part of the WAR Author: James Flagg (http://www.jguru.com/guru/viewbio.jsp?EID=1014787), Oct 20, 2002 For reading files within your WAR archive, you could use ServletContext.getResourceAsStream("/myfile.xml"). This may only work if the file you want is in WEB-INF/classes. And this doesn't help at all if you want to write to the file. :( How can I maintain "application scope data" in Servlets or JSPs as ASPs do? Location: http://www.jguru.com/faq/view.jsp?EID=5879 Created: Jan 20, 2000 Modified: 2000-08-25 08:51:32.021 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) In the Servlets 2.1 spec, you can set a Servlet Context Attribute. For example, getServletContext().setAttribute("counter", new foo.Counter()); . You can also access (or initialize) these Attributes as Application Scope Beans in a JSP, using <jsp:useBean scope="application">. Comments and alternative answers

But watch out if you have a multiple-server config... Author: Peter Kobak (http://www.jguru.com/guru/viewbio.jsp?EID=8747), Jan 25, 2000 But watch out if you have a multiple-server configuration. Not all application servers guarantee that application-level attributes will propagate between all servers, or even all JVMs in the same server. (For instance, Netscape Application Server 4.0 only sets

application attributes in the current JVM.) anil chakravarthy ([email protected]) suggests... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 26, 2000 anil chakravarthy ([email protected]) suggests using the System Properties object, using System.getProperties().put(key, foo); and Foo foo = (Foo)System.getProperties.get(key); . However, this is not recommended, since System Properties are global to the entire VM. Use Servlet Attributes instead. Also see the FAQ What servlet code corresponds to... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 21, 2000 Also see the FAQ What servlet code corresponds to the various "scope" values for the <jsp:useBean> tag? . Using the ServletContext object is dependent on the... Author: shivashis bose (http://www.jguru.com/guru/viewbio.jsp?EID=79345), Jul 21, 2000 Using the ServletContext object is dependent on the servlet container implementation of a web server. An alternative way would be to create a class say Class A which would inherit the HttpServlet class. All application level data can be placed in it. All the servlets which need to share the application level data would inherit Class A. This approach would work in all implementations and make maintainability easier. In case data is to be added/removed, changes are necessary only in Class A Re: Using the ServletContext object is dependent on the... Author: Biswajit Ganguly (http://www.jguru.com/guru/viewbio.jsp?EID=1171166), May 17, 2004 A better way to do would be to keep a singleton class which maintains application level data and instialise it from within the init method of any servlet that is marked for loading at startup of the server. I really can't understand how subclassing servlets is going to help to share application level data . I don't see how having all the servlets in the same... Author: Guillaume Barreau (http://www.jguru.com/guru/viewbio.jsp?EID=249459), Nov 9, 2000 I don't see how having all the servlets in the same application inherit from a common ancestor would solve this problem. An object of class Child and an object of class Parent do not actually share any data when Child extends Parent.

What are all the different kinds of servers? (Such as Web Servers, Application Servers, etc) Location: http://www.jguru.com/faq/view.jsp?EID=5917 Created: Jan 20, 2000 Modified: 2000-12-20 10:06:49.031 Author: Paul Danckaert (http://www.jguru.com/guru/viewbio.jsp?EID=5801) The servers involved in handling and processing a user's request break down into a few basic types, each of which may have one or more tasks it solves. This flexibility gives developers a great deal of power over how applications will be created and deployed, but also leads to confusion over what server is able to, or should, perform a specific task. Starting at the basic level, a user is typically submitting a request to a system through a web browser. (We are conveniently ignoring all other types of clients (RMI, CORBA, COM/DCOM, Custom, etc..) for the time being for purposes of clarity.) The web request must be received by a Web Server (otherwise known as an HTTP Server) of some sort. This web server must handle standard HTTP requests and responses, typically returning HTML to the calling user. Code that executes within the server environment may be CGI driven, Servlets, ASP, or some other server-side programming language, but the end result is that the web server will pass back HTML to the user. The web server may need to execute an application in response to the users request. It may be generating a list of news items, or handling a form submission to a guest book. If the server application is written as a Java Servlet, it will need a place to execute, and this place is typically called a Servlet Engine. Depending on the web server, this engine may be internal, external, or a completely different product. This engine is continually running, unlike a traditional CGI environment where a CGI script is started upon each request to the server. This persistance gives a servlet connection and thread pooling, as well as an easy way to maintain state between each HTTP request. JSP pages are usually tied in with the servlet engine, and would execute within the same space/application as the servlets. There are many products that handle the web serving and the servlet engine in different manners. Netscape/iPlanet Enterprise Server builds the servlet engine directly into the web server and runs within the same process space. Apache requires that a servlet engine run in an external process, and will communicate to the engine via TCP/IP sockets. Other servers, such as MS IIS don't officially support servlets, and require add-on products to add that capability. When you move on to Enterprise JavaBeans (and other J2EE components like JMS and CORBA) you move into the application server space. An Application Server is any server that supplies additional functionality related to enterprise computing -- for instance, load balancing, database access classes, transaction processing, messaging, and so on. EJB Application Servers provide an EJB container, which is the environment that beans will execute in, and this container will manage transactions, thread pools, and other issues as necessary. These application servers are usually stand-alone products, and developers would tie their servlets/JSP pages to the EJB components via remote object access APIs. Depending on the application server, programmers

may use CORBA or RMI to talk to their beans, but the baseline standard is to use JNDI to locate and create EJB references as necessary. Now, one thing that confuses the issue is that many application server providers include some or all of these components in their product. If you look at WebLogic (http://www.beasys.com/) you will find that WebLogic contains a web server, servlet engine, JSP processor, JMS facility, as well as an EJB container. Theoretically a product like this could be used to handle all aspects of site development. In practice, you would most likely use this type of product to manage/serve EJB instances, while dedicated web servers handle the specific HTTP requests. See also: What is the difference between an Application Server and a Web Server? Comments and alternative answers

The following link provides a list of all available... Author: Govind Seshadri (http://www.jguru.com/guru/viewbio.jsp?EID=14), Feb 3, 2000 The following link provides a list of all available web servers (HTTP servers). It also offers detailed information regarding the functionality offered by each of them. http://serverwatch.internet.com/webservers.html Here's a great comparison chart listing all the Java... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Apr 12, 2000 Here's a great comparison chart listing all the Java application servers: http://www.flashline.com/Components/appservermatrix.jsp There are three types of servlet engines: 1) StandAlone... Author: Shuchi Agarwal (http://www.jguru.com/guru/viewbio.jsp?EID=30635), May 2, 2000 There are three types of servlet engines: 1) StandAlone Servlet Engine: It is a web server that includes built in support for servlets.For eg Java Web Server etc. 2) Add on Servlet Engine:It functions as a plug-in for an existing server,a server that was not originally designed with servlets in mind.For eg JServ, JRun,IBM WebSphere etc. 3) Embeddable Servlet Engine:It is a lightweight server deployment platform that can be embeddable in another application. That application becomes the true server.For eg JavaServerEngine etc. what are all the different web servers that support... Author: krishna murthy (http://www.jguru.com/guru/viewbio.jsp?EID=274676), Dec 21, 2000 what are all the different web servers that support servlet 2.0 technology ? how to decide up on the which servlet enebled web server to use for developing a web based application ?

Good Response Paul Danckaert ! Author: Jeevie S (http://www.jguru.com/guru/viewbio.jsp?EID=3836), Sep 5, 2001 I came across this response after a long time from it's post date, but it's very good. Should I override the service() method? Location: http://www.jguru.com/faq/view.jsp?EID=8824 Created: Jan 25, 2000 Modified: 2000-01-26 05:55:45.502 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) No. It provides a fair bit of housekeeping that you'd just have to do yourself. If you need to do something regardless of whether the request is e.g., a POST or a GET, create a helper method and call that at the beginning of e.g., doPost() and doGet(). Comments and alternative answers

In some cases it does make sense to override the s... Author: Oliver Burn (http://www.jguru.com/guru/viewbio.jsp?EID=16181), Mar 9, 2000 In some cases it does make sense to override the service() method. For example, on the project I am working on we have a lot of Servlets that need to perform the same checks (for example, is the session authenticated) before processing the request. Rather than having to copy the logic into each Servlet we write, we developed a common base class that extends HttpServlet. The logic inside the service method is effectively: service(...) { common processing logic.... super.service(...); }

What exactly are the housekeeping functions that s... Author: Evan Owens (http://www.jguru.com/guru/viewbio.jsp?EID=123877), Sep 17, 2000 What exactly are the housekeeping functions that service() provides? More reasons not to Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 9, 2003 Michael Dean writes: In other words, your servlet class that extends HttpServlet should not override the service(...) method because: •

•

You can add support for different behaviors for different request types by overriding the appropriate doXXX(...) method. This makes sense since a servlet should not return a "successful" response (i.e. status code in the 200 range) for a DELETE request unless it actually did delete the requested resource. The default service(...) method supports modification dates

(i.e.conditional GET requests) by using the getLastModified(HttpServletRequest) •

method (which you can override

to improve performance). You get automatic support for TRACE, OPTIONS, and HEAD requests (although you can override the doHead(...) method (in servlets 2.3+) to improve performance).

Of course, you could override service directly (to "improve" performance by reducing the number of method calls) and include the appropriate logic to replace the aforementioned functionality, but why re-invent the wheel? (And if performance is really your primary concern, never "micro-optimize" before profiling. Chances are, the code you've written has some bottlenecks that make the performance impact of these extra method calls negligible. As a matter of fact, the code you write to replace the functionality you are losing might just contain some of these bottlenecks. :)

Re: More reasons not to Author: john b (http://www.jguru.com/guru/viewbio.jsp?EID=1059477), Feb 22, 2003 Okay, but what if I wanted to let my servlet decide if it wants to process the request locally or forward it onto another servlet server? Wouldn't it be best to decide that in the service(..) method? What work is happening towards creating Servlet API v2.3? Location: http://www.jguru.com/faq/view.jsp?EID=8876 Created: Jan 26, 2000 Modified: 2000-01-26 05:57:08.695 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Check out: http://java.sun.com/aboutJava/communityprocess/jsr/jsr_053_jspservlet.html What is a servlet development framework? Location: http://www.jguru.com/faq/view.jsp?EID=9092 Created: Jan 26, 2000 Modified: 2000-01-31 09:02:31.121 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) A 'servlet development framework' is a package which helps us create servlet-based solutions more efficiently and effectively. Basically, after you've written a bunch of servlets from scratch, you'll proabably be irked by having to do the same sorts of things over and over again. A good

framework helps to minimize how much of that rot that you have to do. For example, check out: WebMacro Most Application Servers contain their own frameworks. See this question on the FAQ. Is there a mailing list for the discussion of servlets? Location: http://www.jguru.com/faq/view.jsp?EID=9247 Created: Jan 27, 2000 Modified: 2000-01-31 09:41:04.907 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Yes. There is a comprehensive list of mailing lists at The Purple Servlet Resource List. Be sure to check out the Sun's SERVLET-INTEREST mailing list. Subscribe by sending an email to [email protected] with a message body of: subscribe SERVLET-INTEREST Also, check out the archive of the mailing list. Comments and alternative answers

There's also an advanced servlet list, albeit with... Author: Tom Copeland (http://www.jguru.com/guru/viewbio.jsp?EID=1396), Mar 20, 2000 There's also an advanced servlet list, albeit with very low traffic (as of 3/20/00). More info can be found here. [email protected] is a great place for... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jun 21, 2000 [email protected] is a great place for discussion of Tomcat-related servlet/JSP issues. Also, look at [email protected] Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Aug 16, 2000 Also, look at [email protected] How do I open and redirect to a popup window from a servlet? (Under certain circumstances I want my servlet to bust out of the frames and redirect to another servlet or page.) Location: http://www.jguru.com/faq/view.jsp?EID=10507 Created: Jan 31, 2000 Modified: 2002-12-04 16:47:32.187 Author: Brett Knights (http://www.jguru.com/guru/viewbio.jsp?EID=8054) Question

originally posed by David Thompson (http://www.jguru.com/guru/viewbio.jsp?EID=5551 You can't do this directly but it is easy to do indirectly using JavaScript. Essentially you return a page that has as its onLoad event code that opens a page and gets your new data. Your servlet would create or return a page that contains: ... <script language="javascript"> function bustOut(){ var newWin = window.open("the real url", ....); // params and stuff } window.onLoad = bustOut; //this should work but often doesn't. Lack of parens () is correct. Eat at Joe's You could set this up as a static html page to redirect to with "the real url" being encoded in a query string. If you are unclear as to how to read the query string using JavaScript I'd recommend a good JavaScript reference. O'Reilly (who else) publishes two good books that would help with this: Javascript: The Definitive Guide by David Flanagan and Dynamic HTML by Danny Goodman Comments and alternative answers

Another way to open a new browser window is to use... Author: Tom Copeland (http://www.jguru.com/guru/viewbio.jsp?EID=1396), Mar 17, 2000 Another way to open a new browser window is to use the target element, i.e.: Open Slashdot in a new window!

Write the above string to your servlet's output page and it'll provide a way out of the current browser window and into a new one. Re: Another way to open a new browser window is to use...

Author: Irfan Ahmed (http://www.jguru.com/guru/viewbio.jsp?EID=457477), Jul 23, 2001 What should I do to make the resulting browser window without browser's URL bar, forward - backward buttons ? Thanks in advance Irfan Re[2]: Another way to open a new browser window is to use... Author: Peter Wainwright (http://www.jguru.com/guru/viewbio.jsp?EID=578769), Dec 10, 2001 try ... <script language="javascript"> function bustOut(){ var newWin = window.open("the real url", "subWindow","height=500,width=700,resizable=yes,scrollbars=yes"); } window.onLoad = bustOut; //this should work but often doesn't. Lack of parens () is correct. Eat at Joe's

Re[3]: Another way to open a new browser window is to use... Author: chellaganesh K (http://www.jguru.com/guru/viewbio.jsp?EID=985820), Aug 20, 2002 It works fine. But when ever the back or forward button is pressed opens a new window. I dont know how to stop this. Re[4]: Another way to open a new browser window is to use... Author: Peter Wainwright (http://www.jguru.com/guru/viewbio.jsp?EID=578769), Aug 20, 2002 try using an event handerler other that onload(). Re[5]: Another way to open a new browser window is to use... Author: Shalini Tandon (http://www.jguru.com/guru/viewbio.jsp?EID=1181823), Jun 26, 2004 Hi,I am also trying to do something similar that is checking some

thing in database when a page is submitted and give a jsp in popup window when a particular condition is there using window .onload while page is coming back, everything works fine except when I try to use browser back button,I get that popup back and by clicking buttonson that popup, I can redo database transaction, How can I avoid it, any suggestion is highly appreciated Popup window using javascript Author: zhidong zhao (http://www.jguru.com/guru/viewbio.jsp?EID=1049276), Feb 14, 2003 When using javascript function window.open() to popup a new window in jsp, The window opens a new session. In other words, even if the new window is a .jsp page, user objects stored in the main window does not pass to the popup window. Is there any way to keep the session other than using cookie? Parameters can be passed by putting them in query string, but how to transfer objects? Which is the best servlet server or servlet engine (best performance, easiest, etc)? Location: http://www.jguru.com/faq/view.jsp?EID=10629 Created: Feb 1, 2000 Modified: 2000-06-03 14:42:30.024 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Guillem Valls (http://www.jguru.com/guru/viewbio.jsp?EID=5830 It depends :-) There are a lot of products, and each has advantages and disadvantages. For a more-or-less full list of servlet engines and servlet-enabled web servers, see The Purple Tech Servlet Resource List. The most popular servlet engines seem to be JRun and JServ. Both of these work inside the open-source Apache Web Server (easily the most popular HTTP server). Tomcat is the latest-and-greatest open-source servlet/JSP engine using code from Sun, Apache and JServ. ServletExec is reportedly very stable in high-volume sites -but the other servlet engines are being used on some high-volume sites as well. If you have experience with or opinions about any of these products, please add feedback to this FAQ. Comments and alternative answers

The new iPlanet Web Server 4.0 is supposed to offer...

Author: Tom Khamis (http://www.jguru.com/guru/viewbio.jsp?EID=22263), Mar 9, 2000 The new iPlanet Web Server 4.0 is supposed to offer great servlet performance. See www.i-kinetics.com for a white paper JSDK and JSWDK are development environments, intended... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Apr 30, 2000 JSDK and JSWDK are development environments, intended to be compatible with various versions of the servlet spec but not for production use in a high-load environment. They are written in Java and available from Sun. Sun has a fairly comprehensive list of Servlet Engines... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 11, 2000 Sun has a fairly comprehensive list of Servlet Engines (now called "Servlet Containers" I suppose) at http://java.sun.com/products/servlet/industry.html. Why doesn't response.sendRedirect(response.encodeURL(url)) work? Location: http://www.jguru.com/faq/view.jsp?EID=10632 Created: Feb 1, 2000 Modified: 2000-02-01 08:09:31.471 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Raveenthirakumar Rajagopal (http://www.jguru.com/guru/viewbio.jsp?EID=9644 Use response.sendRedirect(response.encodeRedirectURL(url)) instead. It will correctly rewrite the URL for clients that don't support cookies. Comments and alternative answers

It still doesnt answer the question. _Why_ doesnt it... Author: Jan Sundin (http://www.jguru.com/guru/viewbio.jsp?EID=11515), Feb 4, 2000 It still doesnt answer the question. _Why_ doesnt it work? What are the differences between encodeUrl and encodeRedirectUrl. please clarify some web servers which supports url... Author: srikanth narasimhan (http://www.jguru.com/guru/viewbio.jsp?EID=11221), Feb 26, 2000 please clarify some web servers which supports urlrewite, because i had problems with JSWK2.1 and in OAS but it worked fine with JWS2.0 How do I download a (binary, text, executable) file from a servlet or JSP? Location: http://www.jguru.com/faq/view.jsp?EID=10646 Created: Feb 1, 2000 Modified: 2001-11-02 07:54:23.779 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3)

Solution 1: Just use HTTP! This has nothing to do with servlets per se. Make sure the file is on your web server. Then you can either embed a link for your user to click, as Click here to download the Runme app or have your servlet or JSP send a redirect to the file, as response.sendRedirect("http://myserver.com/files/runme.exe"); or get fancy with JavaScript (see this FAQ for inspiration). The point is -- this is still the World Wide Web! HTTP is a file transfer protocol; downloading files what it's for! Solution 2: Open the file from your servlet using java.io classes, and shove the bytes down the response stream. Make sure to set the content type to match the type of file, e.g. response.setContentType("image/gif") or response.setContentType("application/x-msword"). This technique is a little more expensive, but allows you to do things like security checks, or to access files that are on your web server host, but outside the HTTP directory structure. For source code to a servlet that "downloads" (actually it's uploading, and the client is downloading, right?) a text file, see this FAQ answer. Another way to look at it is, there are three directory trees you need to worry about: 1. webapp 2. webapp/WEB-INF 3. the rest of your file system To download a file from within the webapp, you can use plain old or . To download a file from anywhere else -- including the webapp/WEB-INF under WEBINF -- you need to call a servlet that opens the file and spits out the contents as described above. Note that the user your servlet engine is running as must have permission to access that file, or you will get a server error. See also • • • •

Can I force the browser to save a downloaded file with a name I specify, rather than the name of the URL? How do I read and output a text file from a Servle... How do I open and redirect to a popup window from a... Servlets:Files:Downloading subtopic

Comments and alternative answers

Amit Ghaste ([email protected]) writes: Hi, I have to...

Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Feb 18, 2000 Amit Ghaste ([email protected]) writes: Hi, I have to download files from the server to the user, I have code which works just fine in Netscape, but the same is not working in IE. here is the code sample. for a pdf file _________________________ response.setContentType ("application/pdf"); response.setHeader ("Content-Disposition", "attachment; filename=\"syntax.pdf\""); ServletOutputStream op = response.getOutputStream (); while ((in != null) && ((length = in.read(buf)) != -1)) { // the data has already been read into buf System.out.println("Bytes read in: " + Integer.toString(length)); op.write(buf,0,length); } _________________________

I dont want to give direct links to the files itself, if it is the only option left. Re: Amit Ghaste ([email protected]) writes: Hi, I have to... Author: Bill Chatfield (http://www.jguru.com/guru/viewbio.jsp?EID=439189), Jun 14, 2001 I'm using IE5.0 and jswdk-1.0.1. I have to spell "attachment" as "attachement" to get the PDF to load in the browser instead of downloading. If I spell it as "attachment" it always gives me a download dialog box. Re: Amit Ghaste ([email protected]) writes: Hi, I have to... Author: Brien Hodges (http://www.jguru.com/guru/viewbio.jsp?EID=454110), Jul 12, 2001 I am using: <%@ page contentType="application/download" %>

SO that the page will always be saved to the users harddrive. But I have a problem. When I have a link to my download page the first browser window pops up and says "Run from location.." or "Save file as...". But if I say Save it the name displayed is some random characters with a .JSP extension. If I save "Run from current location" it then has another save box pop up where I can then save the file and the correct filename is displayed. Has anyone seen this before and does anyone have a suggestion as to how to fix it? Thanks, Brien Re: Amit Ghaste ([email protected]) writes: Hi, I have to... Author: ali javed (http://www.jguru.com/guru/viewbio.jsp?EID=475292), Aug 13, 2001

Hello, I used the source code you have used but it is not working. The problem is that one file gets downloaded but on the same page when I cilck some other link, it displays error "getOutputStream() has already been called for this response until I refresh that page. It is an illegalstateException." Please, solve my problem. THANX ali javed Solution 2 works great for binary files under netscape,... Author: Matthew Conway (http://www.jguru.com/guru/viewbio.jsp?EID=24615), Mar 15, 2000 Solution 2 works great for binary files under netscape, and under IE 5 it also downloads the file correctly. Unfortunately IE ends up thinking it still is waiting on something, so the hourglass never goes away, and the globe keeps on spinning. Is there any way to prevent this from happening? Re: Solution 2 works great for binary files under netscape,... Author: Benjamin Kallauch (http://www.jguru.com/guru/viewbio.jsp?EID=451966), Jul 9, 2001 maybe it is a solution to give it an out.close(), but I am really not sure. I was setting the Content-disposition header to be... Author: Matthew Conway (http://www.jguru.com/guru/viewbio.jsp?EID=24615), Mar 16, 2000 I was setting the Content-disposition header to be "attachment;filename=foo.zip" in order to provide a suitable default filename for the client's Save As dialog. Setting it instead to be just "filename=foo.zip" got rid of my problem with IE waiting forever. Re: I was setting the Content-disposition header to be... Author: vinay salehithal (http://www.jguru.com/guru/viewbio.jsp?EID=504996), Sep 27, 2001 Hi, I am downloading a csv file from the server. I am too facing the same propblem of IE waiting for ever after finishing the download. As per your suggestion I tried to set the Content-Disposition header to just "filename=myfilename.csv", but after doing this, when i click on my download link the save as or open popup is not being shown, instead leads to opening of the csv file in the browser itself. Please let me know if u have any ideas on this Re: I was setting the Content-disposition header to be... Author: aytac sen (http://www.jguru.com/guru/viewbio.jsp?EID=516073), Oct 10, 2001 Hi, I try to download files from the server also, and the solution that suggests setting Content-Disposition header to just "filename=..." causes the problem you mentioned for some other file types also(like .doc, .mp3). especially when the ContentType is "APPLICATION/OCTET-STREAM" So how to avoid this and have the popup window still ?? If any solution is

reached can you inform please. Thanks. Re: Re: I was setting the Content-disposition header to be... Author: vinay salehithal (http://www.jguru.com/guru/viewbio.jsp?EID=504996), Oct 10, 2001 Hi, In our case, since we were downloading a csv file we have set the content type to 'application/csv'. Apart from this, the problem was occuring with IE browsers and not with Netscape. We were also facing a problem with IE 5.5 in which once a download link was clicked the other links became unoperational. We managed to solve this(rather a workaround) as follows: 1. Detect the browser type. 2. If(IE5.0) { Content-Disposition: attachment; filename=\"myfilename.csv \";" } else { Content-Disposition: anyWord;filename=\"myfilename.csv \";" } I hope this helps. Regards Re: I was setting the Content-disposition header to be... Author: aytac sen (http://www.jguru.com/guru/viewbio.jsp?EID=516073), Oct 11, 2001 I want to explain my situation and what I tried till now: Part p= getTheAppropriatePartSomeHow(); response.setContentType(p.getContentType()); response.setHeader("Content-Disposition", "filename=\"" + p.getFileName() + "\";"); response.setContentLength(p.getSize()); InputStream is = p.getInputStream(); OutputStream oout = response.getOutputStream(); byte[] b = new byte[4 * 1024]; int len = 0; while ((len = is.read(b)) != -1) { oout.write(b, 0, len); } is.close(); out.flush(); oout.close();

The important point is the line: response.setHeader("Content-Disposition", "filename=\"" + p.getFileName() + "\";"); Whatever I try I couldn't get a perfect result from this code…

•

If I leave the code as response.setHeader("Content-Disposition", "filename=\"" + p.getFileName() + "\";"); then: If the file can be shown in the browser, then it is shown: e.g. x.jpg c.bmp a.eml note.txt but not worked for a .doc file and a .mp3 file I couldn't understand why???(Content-Type: APPLICATION/OCTETSTREAM). One more thing: it did it well for c.bmp, whose content-type was also APPLICATION/OCTET-STREAM

•

If I have the code as response.setHeader("Content-Disposition", "attachment; filename=\"" + p.getFileName() + "\";"); then: e.g. for a x.jpg file BR>it opens a "File Download" Dialog Box, with options "Open file" or "Save to disk" if you choose: "Save To Disk" option then it shows the "Save As" dialog with the CORRECT filename, and by pressing OK, it saves the file, but HOURGLASS never goes away(The problem defined before in the thread) to prevent this I tried to follow the answers given here (like just giving the filename in the Content-Disposition, result is explained above.) but if you choose: "Open File From Current Location" then it does nothing, and just the HOURGLASS never goes away

•

If I have the code as response.setHeader("Content-Disposition", "attachment; filename=\"" + p.getFileName() + "\";"); NOTE: The difference is that "Content- Disposition" is written WITH A SPACE in between and not like " ContentDisposition", I saw that in http://www.jguru.com/faq/view.jsp?EID=252010 Re: In my servlet I am trying to let the user download… (By

seema bhatnagar) Then: If the file can be shown in the browser, then it is shown: e.g. x.jpg c.bmp a.eml note.txt but for c.bmp, whose content-type was also APPLICATION/OCTET-STREAM, and for some other files, it opens a "File Download" Dialog Box, with options "Open file" or "Save to disk" if you choose: in both "Save To Disk" and "Open File" options it SHOWS THE FILENAME IN A FALSE way… (Showing the .jsp file's name to be saved) and saves in this format… So the only problem with the last case is that IT CAN`T get the correct filenames to where to save the parts.

***So since you're reading this sentence, then you probably read all the cases that I tried to explain… If you have any suggestions about how to solve the problems for any case, please share with me, thanks***

Re: Re: I was setting the Content-disposition header to be... Author: vinay salehithal (http://www.jguru.com/guru/viewbio.jsp?EID=504996), Oct 11, 2001 Hi, Do you want all those files to be seen in yr browser or to be saved with Download popup? Also which browser/version are you working with? Looking at yr last case have you tried this: response.setHeader("Content-[space]Disposition", "anyword; filename=\"" + p.getFileName() + "\";"); Re: Re: Re: I was setting the Content-disposition header to be... Author: aytac sen (http://www.jguru.com/guru/viewbio.jsp?EID=516073), Oct 11, 2001 Both can be acceptable. If it CAN show the content in the browser then it is ok... (But download Popup will be better for my case)

In brief; • •

download popup for all types of files is better for me in case that it is easier to construct the other way(I mean -files seen in the browser and download when neededbehaviour like "inline"), then it is acceptable also... navigator.appVersion returns 4.0 (compatible; MSIE 5.0; Windows NT; DigExt) and yes I tried the case you suggested, it doesn't work at all... It always opens a download popup, asking whether to "Save" or "Open the document" , and in each case: It responds with the .jsp file's name, so it tries to open/save the content as like a text file...

Thanks for any suggestions.. I`m sure that solving that problem will form a useful documentation for that kind of "Downloading File From Server" issue. Re: Re: I was setting the Content-disposition header to be... Author: Jonathan Downey (http://www.jguru.com/guru/viewbio.jsp?EID=330209), Oct 19, 2001 Hi, I had the same problem. Basically we wanted to always trigger the Download from an InputStream with the correct filename being displayed. This code works perfectly with IE 5.5 and Netscape protected void doGet(HttpServletRequest req, HttpServletResponse resp) { String fileToFind = req.getParameter("file"); if(fileToFind == null)

return;

File fname = new File(fileToFind); System.out.println("Save As: "+fname.getName() ); if(!fname.exists()) return; FileInputStream istr = null; OutputStream ostr = null; resp.setContentType("application/binary"); resp.setHeader("Content-Disposition", "attachment; filename=\"" + fname.getName() + "\";"); try { istr = new FileInputStream(fname); ostr = resp.getOutputStream(); int curByte=-1;

while( (curByte=istr.read()) !

=-1)

ostr.write(curByte); ostr.flush(); } catch(Exception ex){ ex.printStackTrace(System.out); } finally{ try { if(istr!=null) istr.close(); if(ostr!=null) ostr.close(); } catch(Exception ex){ System.out.println("Major Error Releasing Streams: "+ex.toString()); } } try { resp.flushBuffer(); } catch(Exception ex){ System.out.println("Error flushing the Response: "+ex.toString()); } }

This code uses a FileInputStream. But it's easy to adapt to any stream really. I just used a FileInputStream for demonstration purposes. The actual servlet will be getting the InputStream from an FTP class. Anyone know any problems with this code? Jonathan Re: Re: Re: I was setting the Content-disposition header to be... Author: Jonathan Downey (http://www.jguru.com/guru/viewbio.jsp?EID=330209), Oct 19, 2001 Ooops, the try { resp.flushBuffer(); } catch(Exception ex){ System.out.println("Error flushing the Response: "+ex.toString()); }

bit should be left out, it keeps throwing a

Error flushing the Response: java.io.IOException: Response has been close

error. Re: Re: Re: Re: I was setting the Content-disposition header to be...

Author: aytac sen (http://www.jguru.com/guru/viewbio.jsp?EID=516073), Oct 19, 2001 the logic behind the code is right.. the problem is with IE, and with the way they handle the response.setHeader("Content-Disposition", "attachment;filename=\"" + fname + "\";");

so i can't find a solution to "hourglass staying busy" Re: I was setting the Content-disposition header to be... Author: shree m (http://www.jguru.com/guru/viewbio.jsp?EID=714860), Jan 9, 2002 Hi all! I can download csv data to open in excel properly. I'm using only IE 5.0 and above and jrun3.1 server. I'm posting the data (generated on the client side) as follows:

Servlet is as follows:

public void service(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { // Set Content Type res.setContentType("application/ms-excel"); // Init Locals String method = req.getMethod(); OutputStream os = res.getOutputStream(); OutputStreamWriter osw = new OutputStreamWriter(os,

"UTF8");

PrintWriter out

= new PrintWriter(osw);

// Validate Method if(method.compareToIgnoreCase("POST") != 0) { out.println("Error:"); out.close(); return; } try { // Get CSV Data String strCsvData = req.getParameter("csv_data"); // Return CSV Data if(strCsvData != null) { char [] chCsvData = strCsvData.toCharArray(); res.setHeader("Content-Disposition", "attachment;filename=test.csv")

;

res.setIntHeader("Content-length", chCsvData.length); out.write(chCsvData); out.flush(); } else out.println("Error: out.close(); } catch (Exception e)

No CSV Data found!");

{ System.err.println("Caught Exception: " + e.getMessage()); out.println("Error:

Servlet!");

Invalid Data sent to

out.close(); } finally { if(out != null) out.close(); if(osw != null) osw.close(); } }

The above code shows the open/save dialog TWICE (!?) before 'opening' it in excel. This does not happen if I save it on the disk. I tried different combinations of setContentType(), Content-Disposition, content-length, flush so-on without success. What should be the combination so that a user can view it in excel (not in the browser)? Re[2]: I was setting the Content-disposition header to be... Author: Nagaraja Settra (http://www.jguru.com/guru/viewbio.jsp?EID=1211062), Nov 15, 2004 Do this in your code to fix the issue of open/save dialog showing TWICE, res.setContentType("application/download"); res.setHeader("Content-Disposition", "filename=\"locationOutput.csv\"");

Notice the following things here, 1. Content type is set to application/download 2. There is no attachment in the Content-Disposition header. Re[2]: I was setting the Content-disposition header to be... Author: Manu Bhatia (http://www.jguru.com/guru/viewbio.jsp?EID=1227325), Feb 15, 2005 Did you solve this problem? I am having the same problem, but cannot find any solution to it. I am trying to open an XML file. I found that if there were spaces in the filename I...

Author: Tom Copeland (http://www.jguru.com/guru/viewbio.jsp?EID=1396), Mar 16, 2000 I found that if there were spaces in the filename I needed to use something like this: res.setHeader("Content-Disposition", "attachment; filename=\"" + file.getName() + "\"");

RFC 1806 discusses this in excruciating detail. « previous

beginning

next »

Is the threading concurrency problem more pronunced in a multi-processor environment than in a single-processor environment? Location: http://www.jguru.com/faq/view.jsp?EID=11132 Created: Feb 3, 2000 Modified: 2000-06-03 14:43:20.1 Author: Tim Rohaly (http://www.jguru.com/guru/viewbio.jsp?EID=10) Question originally posed by sharma MR (http://www.jguru.com/guru/viewbio.jsp?EID=4939 From the developer's point of view, the "concurrency problem" is simply that if your object is to be accessed from multiple threads, you need to take steps to ensure that your object is thread safe. Otherwise, your object may end up in an invalid state and may not behave as you expected. It makes no difference whether the accessor threads are running on the same processor or different processors; it is the internals of the JVM and the operating system that guarantee consistency of the address space across CPUs. Because servlets by their nature are intended to be used in a multi-client environment, they should always either implement SingleThreadModel or be designed for thread safety. Note that making a servlet thread safe does not imply that the methods need to be declared as synchronized; synchronization is just one of the many techniques that can be used to impose thread safety. See this FAQ for more information. How can I pass an object from an applet to a servlet ? Location: http://www.jguru.com/faq/view.jsp?EID=11409 Created: Feb 4, 2000 Modified: 2000-12-19 19:32:31.159 Author: Sylvain GIBIER (http://www.jguru.com/guru/viewbio.jsp?EID=11408) Question originally posed by claude hussenet (http://www.jguru.com/guru/viewbio.jsp?EID=2828 Look at this article, they explain exactly how to solve your problem through Object Serialization. http://www.j-nine.com/pubs/applet2servlet/Applet2Servlet.html Have fun. See also:

• •

How can my applet communicate with my servlet? When you communicate with a servlet from an Applet, how can you ensure that the session information is preserved? That is, how do you manage cookies in applet-servlet communication?

Comments and alternative answers

See also this FAQ Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Mar 9, 2000 See also this FAQ When I send an object from Applet to Servlet it throws... Author: Ognyan Ivanov (http://www.jguru.com/guru/viewbio.jsp?EID=208864), Feb 7, 2001 When I send an object from Applet to Servlet it throws me an java.io.EOFExeption code expected. I did all with object input/output streams, and from servlet to applet it works fine. Can somebody to give me some tips . 10X in advance. [Without seeing your source code, it's hard to debug. This sort of question should be asked on a mailing list (like advanced-servlets or tomcat-user) instead of a FAQ. Good luck. -Alex] Re: When I send an object from Applet to Servlet it throws... Author: Shahid Pathan (http://www.jguru.com/guru/viewbio.jsp?EID=526649), Oct 22, 2001 Hi ,Ognyan we had faced the similar problem in my last project where we had lots of applet-servlet ,servlet-servlet commincation.It took us 2-3 days to finally land with a solution for above,but couldn't really understand why it did so.Anyway ,remember whenever you go for servlet-applet communication one sided communication works but if you go for applet-servlet communication it has to be 2 way communication i.e send some dummy values from servlet back to applet. I hope it works for you. How do I read and output a text file from a Servlet? Location: http://www.jguru.com/faq/view.jsp?EID=11569 Created: Feb 4, 2000 Modified: 2000-06-17 12:54:15.461 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by aaron tenney (http://www.jguru.com/guru/viewbio.jsp?EID=9147 Try the following:

import javax.servlet.*; import javax.servlet.http.*; import java.io.*; public class MessageServlet extends HttpServlet {

public void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException { // output an HTML page res.setContentType("text/html"); // load a configuration parameter (you must set this yourself) String root = getInitParameter("root"); // print some html ServletOutputStream out = res.getOutputStream(); out. println(""); out.println("Message of the Day"); out.println("

Today's Message:

Active Sessions:

<% out.println( getActiveSessionData( request ) );%>

#	User	Creation Time	Last Access

Servlet Engine: <%= session.getServletContext().getMajorVersion() %>.<%= session.getServletContext().getMinorVersion() %>

JSP Engine: <%= JspFactory.getDefaultFactory().getEngineInfo().getSpecificationVersion()%>

Application Server: <%= application.getServerInfo()%>

How can I get the absolute URL of a servlet/JSP page at runtime ? Location: http://www.jguru.com/faq/view.jsp?EID=35175 Created: Apr 12, 2000 Modified: 2000-06-16 15:23:39.132

Author: Frank Steidinger (http://www.jguru.com/guru/viewbio.jsp?EID=34216) Question originally posed by Jérôme CAHUZAC (http://www.jguru.com/guru/viewbio.jsp?EID=17646 You can get all the necessary information to determine the URL from the request object. To reconstruct the absolute URL from the scheme, server name, port, URI and query string you can use the URL class from java.net. The following code fragment will determine your page's absolute URL: String file = request.getRequestURI(); if (request.getQueryString() != null) { file += '?' + request.getQueryString(); } URL reconstructedURL = new URL(request.getScheme(), request.getServerName(), request.getServerPort(), file); out.println(URL.toString()); Comments and alternative answers

You can also use the following utility class: jav... Author: Craig Deelsnyder (http://www.jguru.com/guru/viewbio.jsp?EID=41424), Apr 27, 2000 You can also use the following utility class: javax.servlet.http.HttpUtils which has a getRequestURL(HttpServletRequest req) method (returns a StringBuffer). It does about the same thing as noted in the original answer. Thanks! We were having some problems in our appli... Author: Al Scherer (http://www.jguru.com/guru/viewbio.jsp?EID=63091), Jun 7, 2000 Thanks! We were having some problems in our application with relative URLs getting mixed up as we traversed between directories. I took your suggestion but sent your "file" through a StringTokenizer to get just the directory path. I then used this path to create our URL. I used this URL as a "BASE HREF" in our JSP, which appears to have cleared up our problem. Isnt the request object inside a jsp page an instance... Author: sadfjh sdkfjhkdshf (http://www.jguru.com/guru/viewbio.jsp?EID=282540), Jan 26, 2001 Isnt the request object inside a jsp page an instance of ServletRequest NOT HttpServletRequest so it doesnt have getRequestURI? I presumed this was a feature as jsp shouldnt know how it is being accessed. Re: Isnt the request object inside a jsp page an instance...

Author: Julison Mendonca (http://www.jguru.com/guru/viewbio.jsp?EID=429254), May 27, 2001 In the first anwser, where can I find the URL class? Can't get the sample to work... Author: Ken Young (http://www.jguru.com/guru/viewbio.jsp?EID=901514), Aug 29, 2002 this is my error: [29/Aug/2002:18:33:23] info ( 353): JSP: JSP1x compiler threw exception org.apache.jasper.JasperException: Unable to compile class for JSP/usr/local/iplanet/servers/httpsw3/config/../ClassCache/_jsps/_it/_helpdesk/_index2_jsp.java:238: Class _jsps._it._helpdesk.TheURL not found. TheURL reconstructedURL = new TheURL(request.getScheme(), ^ Can a Servlet access an SAP database? Location: http://www.jguru.com/faq/view.jsp?EID=35870 Created: Apr 13, 2000 Modified: 2000-06-21 15:39:38.918 Author: Sandeep Prabhu (http://www.jguru.com/guru/viewbio.jsp?EID=32615) Question originally posed by Sanjay Mistry (http://www.jguru.com/guru/viewbio.jsp?EID=17764 Yes you can. SAP has provided classes for its BAPI methods that you can you use in your servlets. Those are available from your SAP front-end CD. Also you will be needing middleware to connect to SAP from your servlets. Comments and alternative answers

I believe the "middleware" comment is mi... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Apr 24, 2000 I believe the "middleware" comment is misleading; the servlets *are* the middleware, since they connect more-or-less directly to SAP via BAPI. Am I mistaken? No Since your servlets will be talking to the Appl... Author: Sandeep Prabhu (http://www.jguru.com/guru/viewbio.jsp?EID=32615), May 1, 2000 No Since your servlets will be talking to the Application server part of SAP (to get the business object like sales order, customers etc.)rather than the Database server, You will be needing middleware like Orbix from IONA tech or VisualEdge for Java from IBM(AccessBuilder component) or HAHT products. Hope this helps Sandeep Re: No Since your servlets will be talking to the Appl... Author: Xavier Martin (http://www.jguru.com/guru/viewbio.jsp?EID=741065), Jan 30, 2002 SAP provides a Java API called JCO (SAP Java Connector) to interface directly to SAP via RFC. You can execute RFCs and BAPIs directly from your servlet/no need for an ORB or anything like that Re[2]: No Since your servlets will be talking to the Appl...

Author: Trex Lim (http://www.jguru.com/guru/viewbio.jsp?EID=525897), Mar 18, 2003 Xavier Martin: Do you mean that by using JCO, I just need the JCO lib in my tomcat and servlets can use the available classes in the JCO? How about JCA?

What is the return type of ServletRequest.getAttribute( "javax.servlet.request.X509Certificate" ), the method of retrieving client certificates in the Servlet 2.2 API? Location: http://www.jguru.com/faq/view.jsp?EID=37556 Created: Apr 18, 2000 Modified: 2000-08-13 16:30:24.769 Author: Len Norton (http://www.jguru.com/guru/viewbio.jsp?EID=37422) According to the Servlet Specification 2.2 (not the generated API documents, which are vague on the matter), the object returned is an array of type java.security.cert.X509Certificate. How can I plot data on a graph or chart from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=37785 Created: Apr 19, 2000 Modified: 2001-08-19 20:55:22.641 Author: Aaron DeLong (http://www.jguru.com/guru/viewbio.jsp?EID=37781) Question originally posed by aidas suhail (http://www.jguru.com/guru/viewbio.jsp?EID=34212 The KavaChart software, a commercial Java based solution for charts and graphs, is the only servlet based solution of which I am aware. Comments and alternative answers

There is some not-quite-ready-for-primetime code at... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Apr 19, 2000 There is some not-quite-ready-for-primetime code at Purple Technology for creating charts and graphs, and saving them as GIFs. Also, see the Purple Servlet Resource List, in the images section. See also this FAQ on drawing images from servlets.... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Apr 20, 2000 See also this FAQ on drawing images from servlets. A free solution is possible: expose graph data as XML,... Author: Nicola Ken Barozzi (http://www.jguru.com/guru/viewbio.jsp?EID=39153), Apr 25, 2000

A free solution is possible: expose graph data as XML, transform with XSL into SVG or VML and send that to the client. Possible practical solutions: • •

•

Currently Microsoft Explorer has VML built in, so you can send VML directly (in the Microsoft site you can find a VML graph example). Another solution is SVG. You can find a hands-on example of XML2SVG transformation with XSL in Transforming XML into SVG . The result can be transformed in PDF with SVG2PDF or in JPG with the IBM SVG viewer or with any other viewer (the CSIRO SVG Viewer is easy to use) and the result is sent to the client. Another possibility is to send SVG data to the client and use a plugin like the ADOBE SVG plugin or an applet with a Java Viewer like the IBM SVG viewer or with any other viewer.

Re: A free solution is possible: expose graph data as XML,... Author: Raj Subramani (http://www.jguru.com/guru/viewbio.jsp?EID=515135), Oct 9, 2001 SVG can now be viewed directly with IEv6.0. For other browsers you need to install an SVG plug-in from adobe. Also Servlet's can direct svg data to a JSP page, which can be configured to display this SVG data. This is neatly explaind by SUN Another option is to use the KLG Software Group JClass... Author: Shuchi Agarwal (http://www.jguru.com/guru/viewbio.jsp?EID=30635), May 1, 2000 Another option is to use the KLG Software Group JClass and Acme Encoder to encode it and sent it back as a GIF. Re: Another option is to use the KLG Software Group JClass... Author: sashidhar Muthyala (http://www.jguru.com/guru/viewbio.jsp?EID=700981), Dec 24, 2001 Hi, I downloaded the JCServerChart evaluation kit from their web site & tried. I have been getting OutOfMemoryError. Even the tomcat demos give the same error. Have you faced this problem? I appreciate your help. Thanks, Sashi. t-chart is another solution; it costs a few hundred... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jun 3, 2000 t-chart is another solution; it costs a few hundred bucks for source code JFreeChart is an open-source class library for gen... Author: David Gilbert (http://www.jguru.com/guru/viewbio.jsp?EID=19371), Jun 25, 2000

JFreeChart is an open-source class library for generating charts in Java. I'm messing around with it at the moment so that it can be used with servlets... http://www.jrefinery.com Re: JFreeChart Author: David Gilbert (http://www.jguru.com/guru/viewbio.jsp?EID=19371), Mar 22, 2002 Just a note that JFreeChart is still under active development and has moved to: http://www.object-refinery.com/jfreechart/index.html Regards, Dave Gilbert www.object-refinery.com Re[2]: JFreeChart Author: Guido Laures (http://www.jguru.com/guru/viewbio.jsp?EID=948147), Jul 13, 2002 Cewolf is a JSP tag library based on JFreeChart. See http://cewolf.sourceforge.net A few others: MonarchCharts Protoview JFCSuite P... Author: Roger Hand (http://www.jguru.com/guru/viewbio.jsp?EID=292314), Jan 3, 2001 A few others: • • •

MonarchCharts Protoview JFCSuite PowerChart ExpressChart

Re: A few others: MonarchCharts Protoview JFCSuite P... Author: andrew watson (http://www.jguru.com/guru/viewbio.jsp?EID=489616), Oct 11, 2001 I am using a software package from Altio. This client-server solution is sending XML data to the client, which converts the XML into tables and charts. Check out: www.altio.com and look at their demos... Re: A few others: MonarchCharts Protoview JFCSuite P... Author: Jaume Ba (http://www.jguru.com/guru/viewbio.jsp?EID=827369), Jul 9, 2002 RChart als works as servlet, it can even generate image maps to have interactive charts: http://www.java4less.com/charts_e.htm

JClass ServerChart from Sitraka Author: Roger Hand (http://www.jguru.com/guru/viewbio.jsp?EID=292314), Oct 11, 2001 I've been using JClass ServerChart from Sitraka (formerly KL Group). It's been working very reliably for us, although our loads have been pretty light. As of early 2000 (when I did my research) it gave you far more control over different chart parameters than the alternatives. Of course, with that control comes complication . . . Re: JClass ServerChart from Sitraka Author: sashidhar Muthyala (http://www.jguru.com/guru/viewbio.jsp?EID=700981), Dec 24, 2001 Roger, Hi, I downloaded the JCServerChart evaluation kit from their web site & tried. I have been getting OutOfMemoryError. Even the tomcat demos give the same error. Have you faced this problem? I appreciate your help. Thanks, Sashi. Professional SVG Charting from Elansoft Author: Praveen Raju (http://www.jguru.com/guru/viewbio.jsp?EID=532537), Nov 6, 2001 If you want world-class charting with drill-downs, chart in a chart, intitutive navigation, drag and drop etc. Elansoft's AgileBlox Chart 1.0 is what you need. Check out http://www.elansoft.com/es2/elansoft/inside/demo.html All the features are possible with writing very few lines of code. Re: Professional SVG Charting from Elansoft Author: Kate Novac (http://www.jguru.com/guru/viewbio.jsp?EID=1095517), Jun 19, 2003 Would Elansoft care to comment on the fraud-charges at: http://www.manero.org/weblog/archives/000083.html ? Why any one pay 13 times more for the SVG Chart product than Flash Chart product FusionCharts? Cost: Agileblox cost US$1,350 verses just US$99 for FusionCharts. Agileblox needs ASV3 (Adobe SVG Viewer 3.0). However, if you call Adobe for any help or bugs, they tell you that it is not a supported product. Also, they refuse to comment about any future plans for ASV or patches, which led many to speculate that ASV would be discontinued. It is installed on about 7% of the computers. On the other hand FusionCharts needs Macromedia's Flash-player, which is installed on well over 99% computers. Can you get an official statement from Adobe that ASV going to be their one-year from now and Adobe would fix bugs or release patches to ensure compatibility with future releases of IE-browsers? How can I invoke a servlet from JavaScript? Location: http://www.jguru.com/faq/view.jsp?EID=39154 Created: Apr 23, 2000 Modified: 2001-02-02 05:06:58.85 Author: Nicola Ken Barozzi (http://www.jguru.com/guru/viewbio.jsp?EID=39153) Question originally posed by Armaity Rupa (http://www.jguru.com/guru/viewbio.jsp?EID=32852

Yes, and it is quite easy. You just have to remember that a servlet is seen by the browser like a normal web page with its URL. Just call it lke you would call a web page. It is also possible to use servlet data in javascript without changing page. For example I am using Microsoft XML data islands that get XML data from a servlet. CODE: <SCRIPT> function display() { data.transformNodeToObject(ss.XMLDocument, resultTree.XMLDocument); document.write(resultTree.xml); } <SCRIPT FOR="window" EVENT="onload"> data.async = false; data.load("../servlet/SQLResult"); ss.async = false; ss.load("MyStyleSheet.xsl"); display(); <XML id="data"> <XML id="ss"> <XML id="resultTree"> Here "../servlet/SQLResult" is a servlet URL. Comments and alternative answers

Javascript + Servlet Author: Ashish Malgi (http://www.jguru.com/guru/viewbio.jsp?EID=768237), Feb 22, 2002 Why are you giving example of XML ? Give normal example of Javascript code using tags like < SCRIPT language="Javascript"> <----- YOur code -----> <-- Servlet invokation --> What is the difference between Java Servlets and Java ServerPages (JSP)? Location: http://www.jguru.com/faq/view.jsp?EID=39696 Created: Apr 24, 2000 Modified: 2000-11-08 21:03:36.084 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Rasto Toscak (http://www.jguru.com/guru/viewbio.jsp?EID=37399 Short answer: a JSP is a Servlet that thinks it's a Web page. Medium answer: Both use server-side Java to dynamically generate web pages. The source code to a JSP looks like HTML, with Java embedded inside funny tags (*); the

source code to a servlet looks like Java, with HTML embedded in out.print(...) statements. Both use the Servlet API to communicate with the web server and the client. In fact, a JSP gets compiled into a servlet, so they're almost identical in terms of expressive power. The choice is, whether you're more comfortable coding your pages in Java or in JSP-style HTML; and since you can call a JSP from a Servlet and vice versa, you don't have to make an either-or decision. Long answer: See the Servlet FAQ and the JSP FAQ for all the information you need about both technologies. (*) "Funny tags:" JSP can contain (a) normal HTML tags, (b) JSP tags like <jsp:include>, (c) custom tags, (d) scriptlets (Java code surrounded with <% and %>). Comments and alternative answers

Though the both are identical, they have different... Author: Rajesh Ankareddy (http://www.jguru.com/guru/viewbio.jsp?EID=66095), Jun 21, 2000 Though the both are identical, they have different roles in the Model View Controller (MVC) architecture. View corresponds to JSP, Controller corresponds to Servlet and Model to BusinessLogic + Database. Servlet used as Views.. Author: Cheju Thomas (http://www.jguru.com/guru/viewbio.jsp?EID=389628), Mar 28, 2001 Why can't servlets be used as views when they can handle content presentation ? Why do they have to be a controller only ? Re: Servlet used as Views.. Author: sachin kulkarni (http://www.jguru.com/guru/viewbio.jsp?EID=1219090), Jan 2, 2005 Now a days we dont use servlets for View because of it's complexities.However, JSP is very simple and after compilation unit, web container implicitly converts to servlets and does the "controller" job in MVC architecture. What is server push? How do I use it from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=39953 Created: Apr 25, 2000 Modified: 2001-11-03 21:07:11.641 Author: Nicola Ken Barozzi (http://www.jguru.com/guru/viewbio.jsp?EID=39153) Question originally posed by ahmed mohammad (http://www.jguru.com/guru/viewbio.jsp?EID=34131 To understand what "server push" means you must remember that the web operates in an event-driven way; the events can come from clients or servers.

• •

In the normal Web client-server scenario, the browser asks the server for the web pages. This is called "pull", because the client "pulls" the data from the server. The events, in this case, come from the client. Sometimes it is necessary to have the server send data to the client; a typical case is that of stock data, which must change constantly on the web page to remain in sync with actual data, even if the client doesn't request it by clicking on a request button. This is called "push", because the server "pushes" the data to the client. The events, in this case, come from the server.

[However, even with so-called server-push, the server cannot actually initiate a TCP connection to the client. Instead, the server leaves the initial connection open; after the first chunk of data (a whole page, or a partial page, or a single image) is sent, the client is then waiting around for the server to send the next piece of information. Note that this means that the server has to keep its sockets open, which can be expensive. Using an HTML Refresh (e.g. <META HTTP-EQUIV="Refresh" CONTENT="4;URL=http://www.example.com">) may be a better solution. -Alex] On Javaworld you can find an explanation on how to implement server push with servlets in Pushlets, Part 1: Send events from servlets to DHTML client browsers. It describes of a pushlet framework.You may visit the pushlet Website through http://www.justobjects.nl/ to see how development is progressing, to run examples, and to download the framework source. Comments and alternative answers

Pushlets Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Dec 4, 2002 See Pushlets. They also have a yahoo group at: http://groups.yahoo.com/group/pushlet/ Can I include a static HTML file in a servlet response using the RequestDispatcher? Location: http://www.jguru.com/faq/view.jsp?EID=39955 Created: Apr 25, 2000 Modified: 2000-06-21 15:41:39.714 Author: Nicola Ken Barozzi (http://www.jguru.com/guru/viewbio.jsp?EID=39153) Question originally posed by Jiger Patel (http://www.jguru.com/guru/viewbio.jsp?EID=30998 Yes. In the following code, pageName is a String containing the URL to include. String encodedPageName = response.encodeUrl(pageName); this.getServletConfig().getServletContext().getRequestDispatcher(enco dedPageName).include(request, response); How do I build Apache with DSO support, to use Tomcat and mod_jserv? Location: http://www.jguru.com/faq/view.jsp?EID=40693 Created: Apr 26, 2000 Modified: 2000-06-21 15:42:24.376 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3)

You have to add the '--enable-module=so' option to your 'configure' call in order to enable DSO, i.e.: ./configure --prefix=/usr/local/apache --enable_rule=SHARED_CORE --enable-module=so (Thanks to Peter Theill from the Tomcat User Mailing List.) Comments and alternative answers

How can I install Tomcat 3.1 without DSO? Can I just... Author: Bryan Green (http://www.jguru.com/guru/viewbio.jsp?EID=124065), Aug 10, 2000 How can I install Tomcat 3.1 without DSO? Can I just build mod_jserv as part of Apache and then install Tomcat? When using sendRedirect, I always get a page returned stating: "Document moved." Is it possible to go directly to the redirected page? Location: http://www.jguru.com/faq/view.jsp?EID=41049 Created: Apr 27, 2000 Modified: 2000-04-30 11:20:25.606 Author: Nicola Ken Barozzi (http://www.jguru.com/guru/viewbio.jsp?EID=39153) Question originally posed by Iain STIRZAKER (http://www.jguru.com/guru/viewbio.jsp?EID=10849 There are two possibilities. Personally I am using the Jigsaw Web Server from the World Wide Web Consortium and I do not encouter the problem: if I send a redirect the new page automatically loads. CODE: PageName is a String containing the redirect URL response.sendRedirect(PageName); Another possibility is to send a META refresh as a response page, so that the browser calls the page you want to redirect to after your response loads. To be sure, put the redirect link on the page, just in case. CODE: PageName is a String containing the redirect URL PrintWriter TempWriter = response.getWriter(); TempWriter.print(""+ "<META HTTP-EQUIV=\"Refresh\" CONTENT=\"5";URL=\""+PageName+"\">"+ "</HEAD>Redirecting to: <A href="+PageName+" \">"+PageName+"</A></BODY></HTML>"); TempWriter.flush(); TempWriter.close(); Comments and alternative answers

Many browsers will apparently display a "document... Author: Erik Hanson (http://www.jguru.com/guru/viewbio.jsp?EID=38768), May 19,

2000 Many browsers will apparently display a "document moved" message when you are redirecting from one page to the same page. The browser thinks you are in a redirect loop and just displays the message instead of redirecting. You can append a phony argument to the end of the URL so the browser doesn't think you're redirecting to the same page: response.sendRedirect( "/myUrl?phony=baloney" );

You should place the response.sendRedirect() at the... Author: david huang (http://www.jguru.com/guru/viewbio.jsp?EID=60385), May 31, 2000 You should place the response.sendRedirect() at the end of your code, that means you can't place any more code after you call response.sendRedirect(). You also have to call sendRedirect before sending any... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 31, 2000 You also have to call sendRedirect before sending any output whatsoever. Don't even tempt yourself by acquiring the output stream. So, structure your logic: if (shouldRedirect) { response.sendRedirect(...) } else { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.print(...) }

Re: You also have to call sendRedirect before sending any... Author: Daniel Ahern (http://www.jguru.com/guru/viewbio.jsp?EID=850273), Apr 22, 2002 response.sendRedirect works but sometimes certain browsers will throw a document moved if the URL is not encoded properly. Internet explorer is more forgiven than netscape. Certain characters will make netscape show the document has moved message; so run parameters through the java.net.encodeURL.encode() method and this'll let the redirect flow smothly. Where do I store image files so my servlet's HTML pages can display them? Location: http://www.jguru.com/faq/view.jsp?EID=41060 Created: Apr 27, 2000 Modified: 2000-06-21 15:44:48.111 Author: Nicola Ken Barozzi (http://www.jguru.com/guru/viewbio.jsp?EID=39153) Question originally posed by viren s (http://www.jguru.com/guru/viewbio.jsp?EID=31692

Anywhere you want [under your server's document root], just remember to use the correct path relative to the one of the servlet. A servlet is seen by the browser just by its URL. Browsers doesn't see the difference between a file, a servlet or a JSP. Servlets are usually grouped in a directory which is mapped to a directory URL. [You must put the image files in a directory off of the document root, which is not where the servlet class files are, but will probably be near JSP and HTML files. -Alex] This is what a browser may see: -root | -servlet | | | *MyServlet | *TestServlet | -images | | | *Duke.gif | *Web.gif | -MyHtmlFiles | *Main.html *Login.html Here the servlet and the MyHtmlFiles directory are in the same position relative to the images directory. This means that you should write the link to the image in the servlet as you would in the html files in the MyHtmlFiles directory.

How do you check for the existence of a cookie? Location: http://www.jguru.com/faq/view.jsp?EID=41198 Created: Apr 27, 2000 Modified: 2000-06-21 15:45:23.834 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) Retrieving cookie data is a little awkward. You cannot ask for the cookie with a specific key. You must ask for all cookies and find the specific one you are interested in. And, it is possible that multiple cookies could have the same name, so just finding the first setting is not always sufficient. The following code finds the setting of a single-valued cookie:

int sum = 0; Cookie theCookie = null; Cookie cookies[] = request.getCookies(); if (cookies != null) {

for(int i=0, n=cookies.length; i < n; i++) { theCookie = cookies[i]; if (theCookie.getName().equals(SUM_KEY)) { try { sum = Integer.parseInt(theCookie.getValue()); } catch (NumberFormatException ignored) { sum = 0; } break; } } } How do I install Apache and Tomcat with SSL / HTTPS support? Location: http://www.jguru.com/faq/view.jsp?EID=41239 Created: Apr 27, 2000 Modified: 2001-02-25 16:45:02.851 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) STeve Punte, from the Tomcat Users List, writes: The web site http://www.ccl.net/cca/software/UNIX/apache/index.shtml was great for me on getting SSL operational. Not for the faint of heart! Also, Jun Inamori has written a great tutorial walkthrough on compiling and installing Apache with Tomcat and JServ at http://www.oop-reserch.com/tomcat_3_1/. Comments and alternative answers

You can add SSL support to a standalone Tomcat (and... Author: Volker Stolz (http://www.jguru.com/guru/viewbio.jsp?EID=24071), Jun 13, 2000 You can add SSL support to a standalone Tomcat (and almost any other server,e.g. IMAP) with OpenSSL and stunnel. Usually './configure; make; make install' is sufficient. I'm having difficulties trouble shooting a problem... Author: emmy Harrison (http://www.jguru.com/guru/viewbio.jsp?EID=348656), Mar 10, 2001 I'm having difficulties trouble shooting a problem we're experiencing with an Apache Tomact configuration??? I'm the developer (not systems admin) trying to determine if the code or configuration needs changing... Symptons:One app server has a certificate on it and is configured to handle all traffic to https://securedomainname.com where secureServlet1, secureServlet2, and secureJsp exist only on this one machine. (1 of 5 app servers handling traffic) secureJSP calls https://securedomainname.com/servlet/secureSErvlet1 calls https://securedomainname.com/servlet/secureSErvlet2 and forwards to secureJSP using getServletConfig().getServletContext().getRequestDispatcher("/jsp/links.jsp").forward(request , response); I thought both these methods, by specifying https URL, and the forward are guaranteed to stay on the secure app server. But it appears as if sometimes ( getting page not found, and leaving secure server errors ) this traffic is going to another app server. Any

clues??? Is there a chat servlet out there? Location: http://www.jguru.com/faq/view.jsp?EID=41395 Created: Apr 27, 2000 Modified: 2000-04-30 12:45:46.798 Author: qqqqqq qqqqqq (http://www.jguru.com/guru/viewbio.jsp?EID=41393) Question originally posed by anurag gupta (http://www.jguru.com/guru/viewbio.jsp?EID=37343 http://apache.wrox.co.uk/projsp/chap05/index.shtml#74 Comments and alternative answers

A servlet chatroom implementation is available at :... Author: Team [JavaZOOM] (http://www.jguru.com/guru/viewbio.jsp?EID=104856), Jul 18, 2000 A servlet chatroom implementation is available at : http://www.javazoom.net/jzservlets/jzchat10/jzchat.html It should work under any servlet engine. SERVLET API 2.0 compliant. Also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Sep 18, 2001 http://www-105.ibm.com/developerworks/education.nsf/dw/java-onlinecourse-bytitle See: Building a Java chat server (thanks to Virgilio Garcia for pointing this one out) And... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Dec 23, 2001 My own MessageServer chat server doesn't have a servlet interface yet, but it'd be great if you'd like to write one... How can my servlet class which subclasses GenericServlet/HttpServlet provide an RMI service? Location: http://www.jguru.com/faq/view.jsp?EID=41803 Created: Apr 28, 2000 Modified: 2000-06-21 15:46:21.555 Author: Mikael Jakobsson (http://www.jguru.com/guru/viewbio.jsp?EID=41777) Question originally posed by John Zukowski PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=7 Instead of letting your service subclass the java.rmi.server.UnicastRemoteObject class it is possible to make a call to the static method in the same class: exportObject(Remote). Thus you should let your class subclass GenericServlet/HttpServlet and implement a Remote interface. In the init(ServletContext) method your instance can export itself. A simple example follows (exception handling omitted) : public class MyServlet extends HttpServlet implements MyRemoteInterface {

public void init(ServletContext ctx) { UnicastRemoteObject.exportObject(this); } // rest of code goes here... } Good luck! Comments and alternative answers

You can also just use delegation -- make a normal ... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Apr 30, 2000 You can also just use delegation -- make a normal Remote Object by extending UnicastRemoteObject in the normal way; then in your servlet's init method, you create an instance of that remote object and register it with the name server. Then other objects can access it using normal RMI calls. As a bonus, you could have your servlet intercept HTTP GET or POST calls to invoke methods on the remote object. I do not understand the above suggestion by Alex. ... Author: erik leedom (http://www.jguru.com/guru/viewbio.jsp?EID=205011), Sep 13, 2000 I do not understand the above suggestion by Alex. If you do this how is the RemoteObject that is containted within the servlet going to access the servlet's data and methods, which is what it would have to do to provide the functionality that the original question requested? You would have to pass the UnicastRemoteObject instance a refrence to the servlet right? Which wouldn't be so bad but I would hazard is not quite as clean as the original response How do I delete a cookie set by a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=42225 Created: Apr 29, 2000 Modified: 2000-08-13 17:11:40.912 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Question originally posed by Armaity Rupa (http://www.jguru.com/guru/viewbio.jsp?EID=32852 Get the cookie from the request object and use setMaxAge(0) and then add the cookie to the response object. See also How can I delete a cookie from within a JSP page? Comments and alternative answers

Thanks a lot. A simple solution as that is highly ... Author: Armaity Rupa (http://www.jguru.com/guru/viewbio.jsp?EID=32852), May 2, 2000 Thanks a lot. A simple solution as that is highly appreciated. Not working Author: alpesh shah (http://www.jguru.com/guru/viewbio.jsp?EID=968357), Jul 29,

2002 I tried to delete cookie by setting MaxAge to 0 but when i again tried to get cookie from the request object on next page it returned same cookie with 0 maxage (got from getMaxAge()) and again on next page i could retrieve same cookie with cookie's getValue() method.I don't want cookie to be retrieved once i delete it.But even after deletion cookie file exist and cookie is always available even after setting MaxAge to 0.Can't I remove cookie file? Re: Not working Author: R Thackston (http://www.jguru.com/guru/viewbio.jsp?EID=1119662), Oct 5, 2003 Try setting the cookie back in the response. In other words, get the cookie, set the max age, then add the cookie to the response: Cookie c = request.getCookies()[i]; c.setMaxAge(0); response.addCookie(c);

Re[2]: Not working Author: David Han (http://www.jguru.com/guru/viewbio.jsp?EID=1184718), Jul 8, 2004 Works for netscape but not IE6. Any idea? Here is the code biCookie = new Cookie("testing", "testing"); biCookie.setMaxAge(0); biCookie.setPath("/"); biCookie.setDomain("whatever my site domain"); response.addCookie(biCookie); response.sendRedirect("What ever URL"); Best Regards When will a servlet engine send the HTTP response header? Is it immediately after getWriter/getOutputStream is called, or is it just before any call to write()? Location: http://www.jguru.com/faq/view.jsp?EID=42232 Created: Apr 29, 2000 Modified: 2000-04-30 12:20:32.071 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Question originally posed by lee yeow leong (http://www.jguru.com/guru/viewbio.jsp?EID=3804

This is an implementation specific detail of the servlet engines. I.e., it depends. Of course, at the very best, once you've flushed content to the client, there's no way back. :-) In the Java Servlet Specification v2.2, section 6.1, support has been added which gives the servlet developer a lot more information and at least some hope of portably being able to control the buffering. How do I set init parameters in the servlet engine? Location: http://www.jguru.com/faq/view.jsp?EID=42541 Created: Apr 30, 2000 Modified: 2001-05-01 08:44:38.616 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Ian Phillips (http://www.jguru.com/guru/viewbio.jsp?EID=38182 It depends on the servlet engine. Each has its own type of config file in which you can set the names and values of init parameters; these get passed to the servlets (or JSPs) via the getInitParameter() call. For Tomcat and JSWDK, edit the conf/web.xml file. See also this FAQ. Please add information about other servlet engines as feedback to this FAQ. See this FAQ for information on passing an init param to a JSP. Comments and alternative answers

Resin: Look for the resin.conf file in your Resin1... Author: John Saccoccio (http://www.jguru.com/guru/viewbio.jsp?EID=97733), Jul 6, 2000 Resin: Look for the resin.conf file in your Resin1.1/conf directory. It's a typical XML based configuration file that has sample of how to set servlet init and application parameters. Java Web Server : We can set the init parameter in... Author: pradeep chonat (http://www.jguru.com/guru/viewbio.jsp?EID=240326), Nov 15, 2000 Java Web Server : We can set the init parameter in JWS by specifying the initArgs property for the concerned servlet in HOME/properties/server/javawebserver/webpageservice directory. Can a servlet act as an HTTP client? Location: http://www.jguru.com/faq/view.jsp?EID=42553 Created: Apr 30, 2000 Modified: 2000-06-21 15:50:24.286 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Sean Shelby (http://www.jguru.com/guru/viewbio.jsp?EID=39297

Yes. Use the standard java.net.URL class, or "roll your own" using java.net.Socket. See the HTTP spec at W3C for more detail. Feedback to this FAQ has additional information about initiating an HTTP connection from Java. Comments and alternative answers

Also bear in mind that servlets (as well as applets,... Author: Nicola Ken Barozzi (http://www.jguru.com/guru/viewbio.jsp?EID=39153), May 2, 2000 Also bear in mind that servlets (as well as applets, JavaBeans, and so on) are also normal Java classes, which means that in them you can do anything as far as Java and its libraries are concerned. Java:API:Servlets:Message Passing Author: Peter Forrest (http://www.jguru.com/guru/viewbio.jsp?EID=717754), Jan 12, 2002 The most straight-forward means of communication by Servlets on separate servers is using HTTP, according to the Java (tm) Tutorial. What are the advantages of using Servlets rather than CGIs? Location: http://www.jguru.com/faq/view.jsp?EID=43542 Created: May 2, 2000 Modified: 2000-05-02 13:11:36.09 Author: Mikael Jakobsson (http://www.jguru.com/guru/viewbio.jsp?EID=41777) Question originally posed by Gilbert Banks (http://www.jguru.com/guru/viewbio.jsp?EID=17542 When a normal CGI script (or program) is executed, it is spawned in a separate process by the web server, and the output of that process becomes the resulting page that is sent back to the client. Each request to the web server will result in a new process beeing started. Starting a process will create some overhead, in performance and in memory usage. In servlets however, only one process is spawned, and that process contains the JVM. Each request will cause the JVM to create a new thread that will be responsible for creating the output that will be the result. Creating a thread requires much less resources to start up, both CPU and memory. This approach can make servlets much more efficient than even an optimized C program acting as a CGI, simply because of the much reduced overhead. However, there are upcoming standards around CGI that use the same approach with threads instead of processes, such as the Perl FastCGI module. So the above holds true for the comparision with a 'normal' CGI, not necessarily with all variants. There are of course other advantages.

•

•

Java is a well structured language suitable for larger systems. Many of the script languages used for CGI are formidable for small scripts and applications, but when larger systems are built, it is not uncommon to find that the code is a horror to maintain. It is probably easier to find a capable Java programmer than a Perl/CSH/PHP3/... programmer. This is a point not to be forgotten if you want someone else to be able to take over and/or understand your code.

Undoubtedly there are other advantages, but I stop here. I just want to add that: Using the correct technology is not as important as using the technology correctly. How can I get the version of the Servlet API that is being used by a servlet/JSP engine? Location: http://www.jguru.com/faq/view.jsp?EID=43716 Created: May 2, 2000 Modified: 2000-06-21 16:01:18.957 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) Question originally posed by Sajeev Anand (http://www.jguru.com/guru/viewbio.jsp?EID=14623 The ServletContext interface includes methods getMajorVersion() and getMinorVersion() to tell you what version of the Servlet API is in use. [Alex Chaffee adds:] So, for example, JSWDK 1.0.1, which supports the Servlets spec 2.1, would return "2" for getMajorVersion() and "1" for getMinorVersion(). From a JSP, you can use the implicit application object to access the ServletContext. For example:

Major: <%=application.getMajorVersion()%> Minor: <%=application.getMinorVersion()%> Jason Hunter's com.oreilly.servlet package has some code for determining this in an allegedly more robust manner. See also How can I determine the name and version number of the servlet or JSP engine that I am using? Comments and alternative answers

So, for example, JSWDK 1.0.1, which supports the S... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 5, 2000 So, for example, JSWDK 1.0.1, which supports the Servlets spec 2.1, would return "2" for getMajorVersion() and "1" for getMinorVersion(). From a JSP, you can use the implicit application object...

Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 5, 2000 From a JSP, you can use the implicit application object to access the ServletContext. For example: Major: <%=application.getMajorVersion()%> Minor: <%=application.getMinorVersion()%>

What servlet engines support clustering -- that is, sharing of session data across multiple load-balanced web servers? Location: http://www.jguru.com/faq/view.jsp?EID=44035 Created: May 3, 2000 Modified: 2001-05-21 16:06:51.894 Author: Chanan Braunstein (http://www.jguru.com/guru/viewbio.jsp?EID=44032) Question originally posed by John Mitchell PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=4 [Short list: • • • •

JRun 3.0 IBM WebSphere BEA WebLogic Enhydra (open-source app server from Lutris)

If you know any more, please submit feedback. -Alex] JRun 3.0 (Right now in RC1) will support clustering with an add-on. check http://www.allaire.com for info. [Prasad Thammineni adds:] In WebSphere Application Server Advanced Edition, you have to enable persistent sessions in order to support session clustering. Also, you have to employ a load balancer like CISCO local director to distribute HTTP requests across multiple web servers/servlet engines. [victor tago ([email protected]) adds: ] The WebSphere Performance Pack also has a load balancer called Secureway Network Dispatcher. [Monte Kluemper:] WebLogic server has supported robust clustering of servlets, EJBs, etc. for over a year! [See also http://www.jguru.com/faq/view.jsp?EID=418461 -Alex] Comments and alternative answers

WebLogic server has supported robust clustering of... Author: Monte Kluemper (http://www.jguru.com/guru/viewbio.jsp?EID=36918), May 8, 2000 WebLogic server has supported robust clustering of servlets, EJBs, etc. for over a year! What does clustering mean in this context? Is it load... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jun 14, 2000 What does clustering mean in this context? Is it load balancing with sharing of session data? In WebSphere Application Server Advanced Edition the... Author: Richard Raszka (http://www.jguru.com/guru/viewbio.jsp?EID=7963), Jul 3, 2000 In WebSphere Application Server Advanced Edition the sessions are shared across multiple machines by storing the information in a Database. This can be DB2 (comes with WebSphere) or other supported databases (Oracle).This imposes a performance hit on the ability to retreive sessions quickly and requires more resources. Has anybody come across a cluster that has been i... Author: nair suraj (http://www.jguru.com/guru/viewbio.jsp?EID=271956), Dec 30, 2000 Has anybody come across a cluster that has been implemented using the iPlanet application server which fundamentally has servlets in a distributed environment? Enhydra also has an JSP/Servlet engine and is capable... Author: Ivo Limmen (http://www.jguru.com/guru/viewbio.jsp?EID=327483), Feb 22, 2001 Enhydra also has an JSP/Servlet engine and is capable of clustering. Enhydra is open source and can be downloaded at www.enhydra.org, they also have an Enterprise Edition. It's a complete Application Server. Tomcat 4 can be configured to support Session Sharing Author: scotty kwok (http://www.jguru.com/guru/viewbio.jsp?EID=451827), Mar 9, 2002 Tomcat 4 has implemented a Persistent Manager over JDBCStore/FileStore.It manage sessions by storing in & loading from a database/directory. By configuring your Tomcat(s) to use Persistent Manager and pointing to the same database/directory, you can actually share your session data across load-balanced servers. For example, I use Tomcat4.0 & mysql, steps are:

1. create table in database for holding sessions: create table tomcat_sessions ( session_id varchar(100) not null primary key, valid_session char(1) not null, max_inactive int not null, last_access bigint not null, session_data mediumblob );

2. Copy the JDBC driver (.jar) into $CATALINA_HOME/server/lib/, so that container can find your Driver

3. Update server.xml, to force Tomcat to use PersistentManger over a JDBCStore ....... <Manager className="org.apache.catalina.session.PersistentManager" debug="10" checkInterval="1" saveOnRestart="true" maxActiveSessions="-1" minIdleSwap="-1" maxIdleSwap="0" maxIdleBackup="0">

<Store className="org.apache.catalina.session.JDBCStore" debug="100" connectionURL="jdbc:mysql://localhost/tomcat?user=abc&password=efg" driverName="org.gjt.mm.mysql.Driver" sessionDataCol="session_data" sessionIdCol="session_id" sessionLastAccessedCol="last_access" sessionMaxInactiveCol="max_inactive" sessionTable="tomcat.tomcat_sessions" sessionValidCol="valid_session"> ....... Note: Because PersistentManager is orginially NOT intended for real-time storage of session. That 's why checkInterval="1", maxIdleSwap="0",

maxIdleBackup="0" are necessary here to force the session to write to database immediately(with 1-2s delay) after it is created/accessed. Hope that future version of Tomcat will have sth. like RealTimePersistentManager. Details refer to: http://jakarta.apache.org/tomcat/tomcat-4.0doc/config/manager.html

Have JSP or Servlets anything similar to ASP's event "Session_OnStart"? Location: http://www.jguru.com/faq/view.jsp?EID=44037 Created: May 3, 2000 Modified: 2000-06-21 16:03:14.016 Author: Chanan Braunstein (http://www.jguru.com/guru/viewbio.jsp?EID=44032) Question originally posed by Guillem Valls (http://www.jguru.com/guru/viewbio.jsp?EID=5830 The JRun product from Allaire adds a global.jsa file with events for session and application. Comments and alternative answers

Or, you could use the following code: public void... Author: Joe Morse (http://www.jguru.com/guru/viewbio.jsp?EID=91113), Jul 3, 2000 Or, you could use the following code: public void doXXX(...) { HttpSession ses = req.getSession(false); if(ses == null) { //session will be new ses = req.getSession(true); } else { //session is not new ... }

Hello, My problem falls on similar lines. I want to... Author: vijay panchal (http://www.jguru.com/guru/viewbio.jsp?EID=335050), Feb 21, 2001 Hello, My problem falls on similar lines. I want to know how I can retrive HttpSession state just before it gets invalidated/timeout. I tried out with HttpSessionBindingListener but When thecontrol goes to "valueUnbound()", session state is already lost. Regards, Vijay Panchal using global.jsa Author: Pankaj Modi (http://www.jguru.com/guru/viewbio.jsp?EID=387091), Apr 2, 2001

Is global.jsa supported by "all jsp supporting web servers" or just "JRun"? Re: using global.jsa Author: neeraja narayanan (http://www.jguru.com/guru/viewbio.jsp?EID=399701), Apr 10, 2001 only JRun support global.jsa Re[2]: using global.jsa Author: guru prasanth (http://www.jguru.com/guru/viewbio.jsp?EID=847725), Dec 17, 2002 but if there any other way i can implement the same using someother server. regards guru What are the advantages and disadvantages of the different forms of session tracking (cookies, session objects, hidden fields, URL rewriting)? Location: http://www.jguru.com/faq/view.jsp?EID=44914 Created: May 5, 2000 Modified: 2000-08-13 16:42:15.757 Author: Simon Wong (http://www.jguru.com/guru/viewbio.jsp?EID=44276) Question originally posed by arun prathap (http://www.jguru.com/guru/viewbio.jsp?EID=43168 Here are the advantages and disadvantages I found with them:

Technique Advantages

Cookies

Hidden Fields

URL

Disadvantages 1. size and number of cookies stored are limited. 2. it stored as plain-text in a 1. simple specific directory, everyone can 2. don't need to send data back to us, view and modify them. Personal browser can participate in this task. information is exposed. 3. it won't work if the security level set too high in browser. 1. the documents needs to embedded the data inside, waste bandwidth. e.g., if you have to conduct a web-based survey with multiple pages using hidden fields. 1. simple You have to embed the result from 2. No effect on security level setting in previous pages in the next page. browsers. 2. Everyone can see the embedded data by viewing the original source code. 3. If the user surfs to a different site, or to a static section of the same site, the state is lost. 1. Every data is appended on the URL => 1. URL is lengthy and the length of

the URL is limited, can't store much information. 2. The URL contains data. If you send this URL to your friends, they might see your information. 3. If the user surfs to a different site, or to a static section of the same site, the state is lost.

Rewriting

easy to debug. 2. Works even if users disable cookies

Session Objects :

Session usually use either cookies or URL rewriting (depends on security setting of browser) to make it function. Each user will have its own unique session ID to identify himself. The session data will be None :-) stored in the server and we can use the session ID to access these data. The session ID will be sent to user either cookies or URL Rewriting. Since the data are stored in server, the size of data is theoretically unlimited.

Comments and alternative answers

disagree. sessions are OK if your JVM don't crash.... Author: leo shikida (http://www.jguru.com/guru/viewbio.jsp?EID=302805), Jan 15, 2001 disagree. sessions are OK if your JVM don't crash. If this happens, everybody currently using sessions loose their sessions at the same time. K. disagree as well Author: Frans Verhoef (http://www.jguru.com/guru/viewbio.jsp?EID=428343), May 25, 2001 sessions are only good as long as you're happy using them in only one context. It doesn't even work everywhere on the same domain. Disadvantage Author: Horatiu Ripa (http://www.jguru.com/guru/viewbio.jsp?EID=752343), Feb 12, 2002 The main disadvantages of session: 1. Often they make your pages statefull, that means that refresh, back, forward buttons can be a problem. Also opening a new window (Ctrl+N or file/new/window) opens a new window in the same session, and there's a lot of mess with that, both browsers are changing the same session. In my experience I had problems even with different instances of the IE on the same machine. You are highly dependent on the correct implementation of the web server. 2. If you want to use server clusters, because you are using session the user is directed to the same server (the sessions are not common for different servers, and you'll have

to use a statefull type), so when a server fails, all the users connected to that server are disconnected. All the other techniques does not require statefull clusters, and if your pages are stateless, they are automatically redirected to another server without any problem for the user. Also the loading is better balanced. But the decision you have to take is depending on the particular app you are developping. How do I pass session information from a JSP to a Applet. Can I pass them as parameters or can I talk back from an Applet to the JSP page? Location: http://www.jguru.com/faq/view.jsp?EID=45661 Created: May 7, 2000 Modified: 2000-08-14 10:15:35.454 Author: Pete Lyons (http://www.jguru.com/guru/viewbio.jsp?EID=41793) Question originally posed by David Sanderson (http://www.jguru.com/guru/viewbio.jsp?EID=44421 The easiest way to pass session info is through the applet parameters. The following example code uses some scriptlet tags to set the parameters of the applet. <% for (x = 0; x < session.fooData.getCount(); x++) { %> <param name="<%= session.fooData.getName(x) %>" value="<%= session.fooData.getValue(x) %>"> <% } %> If you want to have the applet be able to talk back to the server as it runs you can do that too. In this case the applet should not communicate with the JSP that hosted it but rather with a servlet running in the same web application. Both the JSP and the servlet would share the same session info so you have access to the same data. The following example uses serialized object to pass the information back and forth but you could form the requests and responses with plain text or xml or whatever. The applet needs to open a connection to the web application, post a request and listen for the response. public MyResponse

postRequest(MyRequest myRequest) {

try { // Open the connection URL url = new URL(getCodeBase(), "myServlet"); URLConnection uc = url.openConnection(); // Post the request uc.setDoOutput(true); uc.setDoInput(true); uc.setUseCaches(false); uc.setRequestProperty("Content-type", "java-internal/" + myRequest.getClass().getName()); ObjectOutputStream out = new ObjectOutputStream(uc.getOutputStream());

out.writeObject(myRequest); out.flush();

}

// Read the response ObjectInputStream in = new ObjectInputStream(uc.getInputStream()); return (MyResponse) in.readObject(); } catch (Exception e) { e.printStackTrace(); } return null;

The servlet that handles the post would be pretty simple too. It just needs to read the request, figure out what the request was and return the correct data. public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { try { // Read the resquest ObjectInputStream ois = new ObjectInputStream(req.getInputStream()); MyRequest myRequest = (MyRequest) ois.readObject(); // Format the response from the session data HttpSession session = req.getSession(true); MyResponse myResponse = new MyResponse(session.fooData); // Send the response ObjectOutputStream oos = new ObjectOutputStream(res.getOutputStream()); oos.writeObject(myResponse); } catch (Exception e) { e.printStackTrace(); } } Comments and alternative answers

See also When you communicate with a servlet from an... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Aug 14, 2000 See also When you communicate with a servlet from an Applet, how can you ensure that the session information is preserved? That is, how do you manage cookies in applet-servlet communication? Can I have multiple browser windows use different session IDs? Location: http://www.jguru.com/faq/view.jsp?EID=46305 Created: May 8, 2000 Modified: 2000-06-21 16:18:50.91 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Renny Bas (http://www.jguru.com/guru/viewbio.jsp?EID=44238

No. Sessions are referenced using cookies, and cookies are set per-client, not perwindow. However, there's nothing keeping you from writing your own state management code, using URL rewriting, hidden fields, or the like, for use in parallel windows on the same machine. Comments and alternative answers

I believe this depends on if you're using single-s... Author: Rob Dickinson (http://www.jguru.com/guru/viewbio.jsp?EID=47338), May 10, 2000 I believe this depends on if you're using single-session cookies or persistent cookies. Single-session cookies are stored in the browser's memory cache, so two browser instances would see different cookies (and therefore different sessions). Persistent cookies (which reside on the hard disk) are limited to one per client. Please correct me if I'm wrong, since I'm using this technique ! There's a difference between multiple instances of... Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7), May 10, 2000 There's a difference between multiple instances of the browser and multiple browser windows. Multiple browser windows is one instance. All windows share the cookies. Multiple instances would allow one to have separate session IDs as they are separate clients. I believe you have the persistent cookie part correct. Use hidden fields or URL rewriting instead Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 5, 2001 Michael Wax adds: The easiest thing to do is not to worry about the session, but to send a parameter from the client (as a hidden field in a form, or a GET parameter in the URL) each time the client makes a request. This parameter could specify the doctor, so that the servlet would return information on the doctor appropriate to each page. If you are really hooked on having a separate session for each, you will need to use URL rewriting as a means of specifying the session ID on each page. If you try to use a cookie-based system, it will be defeated by users who hit their browsers' forward and back buttons instead of using the navigation tools that you provide.

see Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Feb 2, 2002 see Getting duplicate session id

Consider this.. Author: S M (http://www.jguru.com/guru/viewbio.jsp?EID=1059986), Feb 24, 2003 Refer to the below link. http://developer.java.sun.com/developer/bugParade/bugs/4223650.html In this page, there is a reference to another bug 4109888. Now when I click on the link, am taken to a page about 4109888. But when I do a right-click and "open in new window", I am taken to a login page. Now both windows were created off the same browser instance, so how was the server able to distinguish between the two windows of the same instance? Name some Web sites that make extensive use of Servlets. Location: http://www.jguru.com/faq/view.jsp?EID=46314 Created: May 8, 2000 Modified: 2000-05-11 10:06:07.657 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Snoopy Boy (http://www.jguru.com/guru/viewbio.jsp?EID=43866 jGuru makes use of both Servlets and JSP, naturally. Sun has a small list of "Servlets in the Real World" at http://java.sun.com/products/servlet/industry.html#real. See also this question in the JSP FAQ for a list of JSP-using sites. Please submit other sites you know of as feedback to this question. Comments and alternative answers

WebHelp (running Tomcat; see also this FAQ.) Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 17, 2000 WebHelp (running Tomcat; see also this FAQ.) ya we have developed a site called http://www.su... Author: Kiran Kumar (http://www.jguru.com/guru/viewbio.jsp?EID=18386), Oct 29, 2000 ya we have developed a site called http://www.supportifa.com which is 100% servlets. Check out http://www.pilotpal.com/logbook which uses... Author: Roshan Shrestha (http://www.jguru.com/guru/viewbio.jsp?EID=130068), Feb 27, 2001 Check out http://www.pilotpal.com/logbook which uses servlets with XML/XSL as the presentation method Site uses Servlets, JSP and EJB

Author: Anand Balasubramanian (http://www.jguru.com/guru/viewbio.jsp?EID=56405), Jul 2, 2001 We have developed a site using Servlets, JSP and EJB www.signatureflight.com Why do GenericServlet and HttpServlet implement the Serializable interface? Location: http://www.jguru.com/faq/view.jsp?EID=46477 Created: May 9, 2000 Modified: 2000-05-10 17:45:18.376 Author: Nicola Ken Barozzi (http://www.jguru.com/guru/viewbio.jsp?EID=39153) Question originally posed by Mohan Thomas (http://www.jguru.com/guru/viewbio.jsp?EID=19527 GenericServlet and HttpServlet implement the Serializable interface so that servlet engines can "hybernate" the servlet state when the servlet is not in use and reinstance it when needed or to duplicate servlet instances for better load balancing. I don't know if or how current servlet engines do this, and it could have serious implications, like breaking references to objects gotten in the init() method without the programmer knowing it. Programmers should be aware of this pitfall and implement servlets which are stateless as possible, delegating data store to Session objects or to the ServletContext. In general stateless servlets are better because they scale much better and are cleaner code. How do you manage sessions if the web servers are load balanced onto more than one server? Location: http://www.jguru.com/faq/view.jsp?EID=46481 Created: May 9, 2000 Modified: 2000-05-10 17:11:21.008 Author: Nicola Ken Barozzi (http://www.jguru.com/guru/viewbio.jsp?EID=39153) Question originally posed by Pedro Jr. Urgello (http://www.jguru.com/guru/viewbio.jsp?EID=16961 Session management is automatic if the server supports load-balancing on more machines. The JavaWorld article What's New in Java Servlet API 2.2? clarifies on the subject in the paragraph Distributed Applications. The following is taken from that doc. Distributed Applications A few clarifications were also made in 2.2 with regards to distributed applications, in which application components can be spread across multiple back-end server machines. The specification dictates that, for an application marked as distributable in its deployment descriptor, there will be a single ServletContext instance per JVM. This means the context attributes cannot be used to share global information. Global information in a distributed app needs to be stored externally from the Web server, as is the case in database or EJB component.

An application marked as distributable also has special rules for user sessions. Servers will use session affinity to efficiently manage user state across multiple backend servers. This means that all requests that are part of a single session from a particular user are to be handled by only one JVM at a time. This in turn eliminates the need to constantly replicate session information across all the back-end servers. Responsibility for the session can be moved to another server between user requests, though in practical terms this is unlikely to occur frequently. Still, to enable the moving of a session, all objects placed into a session by servlets in a distributed application must implement Serializable. A Web server can throw an IllegalArgumentException if this condition is not met. Nondistributed apps, of course, can store any objects into the session. Comments and alternative answers

See also http://www.jguru.com/jguru/faq/view.jsp?E... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 6, 2000 See also http://www.jguru.com/jguru/faq/view.jsp?EID=44035 How does one choose between overriding the doGet(), doPost(), and service() methods? Location: http://www.jguru.com/faq/view.jsp?EID=47730 Created: May 11, 2000 Modified: 2000-08-10 10:06:08.528 Author: Nicola Ken Barozzi (http://www.jguru.com/guru/viewbio.jsp?EID=39153) Question originally posed by Amit Srivastava (http://www.jguru.com/guru/viewbio.jsp?EID=46445 The differences between the doGet() and doPost() methods are that they are called in the HttpServlet that your servlet extends by its service() method when it recieves a GET or a POST request from a HTTP protocol request. A GET request is a request to get a resource from the server. This is the case of a browser requesting a web page. It is also possible to specify parameters in the request, but the length of the parameters on the whole is limited. This is the case of a form in a web page declared this way in html:

or . A POST request is a request to post (to send) form data to a resource on the server. This is the case of of a form in a web page declared this way in html: . In this case the size of the parameters can be much greater. The GenericServlet has a service() method that gets called when a client request is made. This means that it gets called by both incoming requests and the HTTP requests are given to the servlet as they are (you must do the parsing yourself). The HttpServlet instead has doGet() and doPost() methods that get called when a client request is GET or POST. This means that the parsing of the request is done by the servlet: you have the appropriate method called and have convenience methods to read the request parameters. NOTE: the doGet() and doPost() methods (as well as other HttpServlet methods) are called by the service() method.

Concluding, if you must respond to GET or POST requests made by a HTTP protocol client (usually a browser) don't hesitate to extend HttpServlet and use its convenience methods. If you must respond to requests made by a client that is not using the HTTP protocol, you must use service(). See also: • • •

How do I support both GET and POST protocol from the same Servlet? What is the difference between the doGet and doPost methods? What is the difference between POST and GET methods? What about PUT, DELETE, TRACE, OPTIONS, and HEAD?

What is the best way of implementing a web application that uses JSP, servlet and EJB technologies all together following a Model View Controller (MVC) architecture? Location: http://www.jguru.com/faq/view.jsp?EID=48001 Created: May 11, 2000 Modified: 2000-06-21 11:05:30.729 Author: Dan Christopherson (http://www.jguru.com/guru/viewbio.jsp?EID=39644) Question originally posed by christophe hillegeer (http://www.jguru.com/guru/viewbio.jsp?EID=43669 [See the Sun J2EE Blueprints for "an integrated set of documentation and examples that describe and illustrate 'best practices' for developing and deploying componentbased enterprise applications using the J2EE platform" including some good architecture whitepapers and source code. -Alex] Hmm, 'Best Way' is a bit rough - there are several 'good' ways, and the usual set of trade-offs between them. (I'm a consultant - I have to start any answer with "It depends...", otherwise they revoke my whiteboard privileges) The main thing you need to keep in mind as you design this sort of a system is that you want the interface into the EJB's to be rather narrow: in any flow, the ideal is to call one EJB method (hopefully on a stateless session bean), and let it make calls to entities on your behalf, then hand back the data you need to display. How you display it depends: you can either embed beans on your JSPs and let the beans make that hopefully-one EJB call, or you can post to a servlet, let that make the call, then forward to the JSP for display. The second of these is more flexible and gives you more leverage to hide, change, and enforce your site's structure. The first, however, will be easier for developers new to this web thing to follow. Essentially, I'm saying that Entity beans are your model, your controller is Session beans (maybe with a bit of help from servlets or beans), and your JSPs, beans and servlets are your View. One thing to note here: this discussion strongly implies that your EJBs are capable of externalizing their state as some number of very simple 'value objects' (not EJBs themselves, just something we can pass back and forth). These value objects are probably tuned tightly to a workflow, and will be produced by that session bean. This

way the traffic between the EJB (server) and the JSP/Servlet (client) is tuned to what the client needs, while the transaction load on the server is minimized. Comments and alternative answers

I have to disagree (somewhat) with the comment that... Author: Shaun Childers (http://www.jguru.com/guru/viewbio.jsp?EID=30243), May 17, 2000 I have to disagree (somewhat) with the comment that "...your controller is Session beans...", because it really "depends" on the architecture of the system. The Session beans will not look up any Entity beans or invoke any methods on an Entity bean without a client invoking a method on the Session bean itself. In other words, the controller could be an independent Java application, or a C++ application using CORBA, or a combination of HTML/WML page with servlets, or another EJB application. The controller really takes on multiple forms depending on the architecture of the system. If I had a simple system constructed of EJB beans, with JSP's providing the interface between the client (web) and the application, then the JSP's (actually servlets compiled from JSP) would be the controller. If I had an RMI application on another server talking directly to the Session beans of my server, then the RMI application is the controller. I am working on a large project using model view a... Author: Vibhu Srinivasan (http://www.jguru.com/guru/viewbio.jsp?EID=60278), May 31, 2000 I am working on a large project using model view architecture. Here goes my two cents worth of an architecture that has produced good results for us The architecure involves a MVC with the controllers being entity and session beans. We are moving away from using entity beans unless there are many transactions involved. These ejbs pass back value objects as specified in the blueprints by sun. We also use bulk accessor session beans which go directly to the database and also call some other session or entity beans. This is the model. Now about the controller and the view: • • •

• •

All the JSP's talk to servlets which are the controllers. The servlets control creation and setting various properties on the java beans. The java beans are broken to two kinds. 1. Data access beans 2. Presentation beans The servlets create the presentation beans which are tied to some screens . The JSPs only read information from the java beans.

Check out the blueprints from sun for some good analysis! Re: I am working on a large project using model view a... Author: Anupam De (http://www.jguru.com/guru/viewbio.jsp?EID=958113), Mar 15, 2003 I have a question - if you are using JSP/Beans combination, then the View model will be tying in the bean hard coding the data to the table with the html codes. How best to separate it out ? One I was thinking was with Hashtables/Array ? But I am looking or complete separation of the presentation layer from any code snippets of Java. I am using Apache Tomcat 4.0.1 J2EE architecture Author: Mindy Couleur (http://www.jguru.com/guru/viewbio.jsp?EID=1175354), Jun 1, 2004 I am new to J2EE and am wondering if you can expand on your answer a bit. I've noticed that much of the logic that I see in Servlets could go in EJB's. I'm wondering just how thin the servlet layer should be. I also would like to confirm some RMI logic flow. As far as I understand..... JSP calls Servlet Remote interface then Servlet call EJB remote interface....reply goes back to servlet then servlet forwards to JSP for display. Is that considered the best way to separate the layers? How do I send a WML page as a response from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=48359 Created: May 12, 2000 Modified: 2000-05-16 16:51:42.795 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) Sending WML is no different than sending back HTML. The only difference is you have to setup the MIME type in the response:

response.setContentType("text/vnd.wap.wml"); Is Tomcat robust enough for production use? Location: http://www.jguru.com/faq/view.jsp?EID=49745 Created: May 16, 2000 Modified: 2000-06-21 16:27:33.755 Author: Matthew Dornquast (http://www.jguru.com/guru/viewbio.jsp?EID=27320) Question originally posed by John Mitchell PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=4 IMHO yes. We are presently running Tomcat (servlet & jsp requests) with Apache (graphics, perl, html) on 9 Solaris/Sparc servers servicing over 10 million servlet/jsp transactions per day. No known issues at this time! The site is Webhelp.com Comments and alternative answers

Can you give any details regarding versions of apache and tomcat your are using? Author: Bronson Silva (http://www.jguru.com/guru/viewbio.jsp?EID=716572), Jan 10, 2002 I need to determine a version of tomcat and apache plus the connector module. I think knowing what you are using will help greatly. Could you let me knw what version of the following you are using? jdk: memory allocated to each jvm? solaris: apache: tomcat: connector module used: mod_webapp, mod_jk, mod_jserver? Are you doing any clustering/failover? Do you have any pointers on documentation, other than the jakarta project docs? Did you use any special configuration that deviated from what any jakarta docs say or reccommend? Thanks, -Bronson Why is my cookie is expiring before the time set using the Cookie.setMaxAge method? Location: http://www.jguru.com/faq/view.jsp?EID=49794 Created: May 16, 2000 Modified: 2000-06-21 16:28:52.895 Author: Matthew Dornquast (http://www.jguru.com/guru/viewbio.jsp?EID=27320) Chances are you have an "=" char in the value of your cookie. Make sure you URL encode the value of your cookie before setting it. How do servlets differ from RMI? What are the advantages and disadvantages of each technology? Location: http://www.jguru.com/faq/view.jsp?EID=49828 Created: May 16, 2000 Modified: 2000-06-21 16:29:19.035 Author: Shaun Childers (http://www.jguru.com/guru/viewbio.jsp?EID=30243)

Question originally posed by mehdi lababidi (http://www.jguru.com/guru/viewbio.jsp?EID=48184 Servlets extend the server-side functionality of a website. Servlets communicate with other application(s) on that server (or any other server) and perform tasks above and beyond the "normal" static HTML document. A servlet can receive a request to get some information through EJB from one or more databases, then convert this data into a static HTML/WML page for the client to see, for example. Even if the servlet talks to many other applications all over the world to get this information, it still looks like it happened at that website. RMI (Remote Method Invocation) is just that - a way to invoke methods on remote machines. It is way for an application to talk to another remote machine and execute different methods, all the while appearing as if the action was being performed on the local machine. Servlets (or JSP) are mainly used for any web-related activity such as online banking, online grocery stores, stock trading, etc. With servlets, you need only to know the web address and the pages displayed to you take care of calling the different servlets (or actions within a servlet) for you. Using RMI, you must bind the RMI server to an IP and port, and the client who wishes to talk to the remote server must know this IP and port, unless of course you used some kind of in-between lookup utility, which you could do with (of all things) servlets. For more detailed information regarding servlets and RMI refer to following sun sites: http://www.java.sun.com/products/servlet/index.html and http://developer.java.sun.com/developer/onlineTraining/rmi/ [(the last link is a tutorial by JGuru!)]. How can I call one servlet from another servlet, where each of them is at a different web server? Location: http://www.jguru.com/faq/view.jsp?EID=50791 Created: May 17, 2000 Modified: 2003-01-08 15:28:50.432 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Venkateswaran Muthuswamy (http://www.jguru.com/guru/viewbio.jsp?EID=47714 You have to use HTTP like everyone else. See How can my applet communicate with my servlet? and How do I call one servlet from another servlet? What are the main differences between Servlets and CGI? Location: http://www.jguru.com/faq/view.jsp?EID=51048 Created: May 18, 2000 Modified: 2000-05-26 16:23:10.589 Author: Simon Brown (http://www.jguru.com/guru/viewbio.jsp?EID=44588) Question originally posed by Harihara Rao Velamala (http://www.jguru.com/guru/viewbio.jsp?EID=30512 Servlets are effectively a Java version of CGI scripts, which are written in Perl, C, C++, UNIX shell scripts, etc. There are however, a few important differences.

When a CGI program (or script) is invoked, what typically happens is that a new process is spawned to handle the request. This process is external to that of the webserver and as such, you have the overhead of creating a new process and context switching, etc. If you have many requests for a CGI script, then you can imagine the consequences! Of course, this is a generalization and there are wrappers for CGI that allow them to run in the same process space as the webserver. I think ISAPI is/was one of these. Java Servlets on the other hand actually run inside the webserver (or Servlet engine). The developer writes the Servlet classes, compiles them and places them somewhere that the server can locate them. The first time a Servlet is requested, it is loaded into memory and cached. From then on, the same Servlet instance is used, with different requests being handled by different threads. Of course, being Java, the compiled Servlet classes can be moved from one Servlet compatible webserver to another very easily. CGI programs or scripts on the other hand may be platform dependent, need to be recompiled or even webserver dependent. Take a look at the Servlet product page for more details about Servlets. Where can I find a method that returns a properly escaped HTML string from a given string of raw HTML? Location: http://www.jguru.com/faq/view.jsp?EID=51171 Created: May 18, 2000 Modified: 2000-05-18 07:48:14.63 Author: Rob Edmondson (http://www.jguru.com/guru/viewbio.jsp?EID=35309) Question originally posed by Sharif Rahman (http://www.jguru.com/guru/viewbio.jsp?EID=47415 You can find that method in java.net.URLEncoder. ie: String Args = URLEncoder.encode("The raw data you want to encode"); [FAQ Manager note: See also How can an applet or application pass parameters to and read output from a CGI script? .] Comments and alternative answers

Is this question about encoding URL GET parameters,... Author: Monty Shaw (http://www.jguru.com/guru/viewbio.jsp?EID=30689), Jun 10, 2000 Is this question about encoding URL GET parameters, i.e. changing spaces to '+', or about encoding data to be displayed on an HTML page that may have '<','>', and '&' in it? You've given the answer for the first, but not the case of of HTML escape encoding. You'd want to do this if you're writing a guestbook (or FAQ entry system) and you don't want the submitter to be able to submit HTML. I ended up writing a small loop

using StringBuffer.replace() to replace '<' with '<', etc. Is there a better way?

Re: Is this question about encoding URL GET parameters,... Author: Alain Renaud (http://www.jguru.com/guru/viewbio.jsp?EID=416804), May 7, 2001 I've used this little gimmick that takes advantage of the HTML classes built-in the J2SE to do the reverse, converting from HTML encoding to text (in the package javax.swing.text.html): HTMLDocument doc = new HTMLDocument(); HTMLEditorKit kit = new HTMLEditorKit(); Reader rd = new StringReader("School - École"); kit.read(rd,doc,0); System.out.println(doc.getProperty(Document.TitleProperty)); So, I guess the reverse of that code should do the trick you need, although I did not test it... HTMLDocument doc = new HTMLDocument(); HTMLEditorKit kit = new HTMLEditorKit(); Writer wr = new StringWriter(); doc.putProperty(Document.TitleProperty, "School - École"); kit.write(wr,doc,0,100); System.out.println(wr.toString()); I rolled my own Author: Greg Wolfe (http://www.jguru.com/guru/viewbio.jsp?EID=426310), May 22, 2001 The encoding/decoding is fairly simple. The character set that HTML encoding uses is ISO-8859-1. Here is a useful table: private static { null, null, null, null, null, null, null, null,

String[] specialCharsTable = null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

"quot", null, null, null, "amp", null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, "lt", null, "gt", null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null,

null, null, null, null, null, null, null, null,

null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, "nbsp", "iexcl", "cent", "pound", "curren", "yen", "brvbar",

"sect",

"uml", "copy", "ordf", "laquo", "not", "shy", "reg", "macr", "deg", "plusmn", "sup2", "sup3", "acute", "micro", "para", "middot", "cedil", "sup1", "ordm", "raquo", "frac14", "frac12", "frac34", "iquest", "Agrave", "Aacute", "Acirc", "Atilde", "Auml", "Aring", "Aelig", "Ccedil", "Egrave", "Eacute", "Ecirc", "Euml", "Igrave", "Iacute", "Icirc", "Iuml", "Eth", "Ntilde", "Ograve", "Oacute", "Ocirc", "Otilde", "Ouml", "times", "Oslash", "Ugrave", "Uacute", "Ucirc", "Uuml", "Yacute", "THORN", "szlig", "agrave", "aacute", "acirc", "atilde", "auml", "aring", "aelig", "ccedil", "egrave", "eacute", "ecirc", "euml", "igrave", "iacute", "icirc", "iuml", "eth", "ntilde", "ograve", "oacute", "ocirc", "otilde", "ouml", "divide", "oslash", "ugrave", "uacute", "ucirc", "uuml", "yacute", "thorn", "yuml", };

-gwolfe Is there a problem with calling Response.sendRedirect() after Response.addCookie() ? Location: http://www.jguru.com/faq/view.jsp?EID=53251 Created: May 21, 2000 Modified: 2000-05-21 13:49:57.176 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Shalabh Nigam (http://www.jguru.com/guru/viewbio.jsp?EID=47481 Yes, there is a bug in Tomcat 3.1 (and possibly other servlet engines). To send a cookie through a redirect, you must set the headers manually. [email protected] suggests: Cookie long_term = new Cookie(LONG_TERM_COOKIE_NAME, user_name); long_term.setMaxAge(60*60*24*4); long_term.setPath("/Blah"); response.addCookie(long_term); response.setStatus(HttpServletResponse.SC_MOVED_TEMPORARILY); response.setHeader("Location",REDIRECT_PAGE); Comments and alternative answers

Your solution works perfectly. Author: Shalabh Nigam (http://www.jguru.com/guru/viewbio.jsp?EID=47481), May 22, 2000 Your solution works perfectly. Re: Your solution works perfectly. Author: Anbuchezhian Chelliah (http://www.jguru.com/guru/viewbio.jsp?EID=1144363), Feb 7, 2004 When a page redirect occurs at the Apache (using ErrorDocument directive in Apache) do you think that cookies from two different browsers could get mixed up? In such a case(cookies getting mixed up)too do you think that setting the headers manually would prevent the problem? Thanks Anbu What servlet code corresponds to the various "scope" values for the <jsp:useBean> tag? Location: http://www.jguru.com/faq/view.jsp?EID=53309 Created: May 21, 2000 Modified: 2002-10-30 23:00:49.748 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) The jsp:useBean tag is very powerful. It allows you to declare a variable using a single syntax, but produces code that (a) either initializes the variable, or locates it if it's already been initialized, and (b) stores it in one of a number of locations, depending on its scope. In order to share variables between JSPs and Servlets, you need to know how to create and to access variables from inside your servlet code. Following are examples which should help you understand how to do this. ----------------------------------------------------------------------

<jsp:useBean class="foo.Counter" scope="application" /> In this example, when the Counter bean is instantiated, it is placed within the servlet context, and can be accessed by any JSP or servlet that belongs to the application (i.e. belongs to the same servlet context). The servlet equivalent of the above useBean action is:

foo.Counter counter = (foo.Counter)getServletContext().getAttribute("counter"); if (counter == null) {

counter = new foo.Counter(); getServletContext().setAttribute("counter", counter); } ----------------------------------------------------------------------

<jsp:useBean id="counter" class="foo.Counter" scope="session" /> In this example, when the Counter bean is instantiated, it is placed within the current session, and can be accessed by any JSP or servlet during a subsequent request by the current user. The servlet equivalent of the above useBean action is:

HttpSession session = request.getSession(true); foo.Counter counter = (foo.Counter)session.getValue("counter"); if (counter == null) { counter = new foo.Counter(); session.putValue("counter", counter); } ----------------------------------------------------------------------

<jsp:useBean id="counter" class="foo.Counter" scope="request" /> In this example, when the Counter bean is instantiated, it is placed within the current request object, and can be accessed by any JSP or servlet during a the same request; e.g., if a RequestDispatcher is used, or if <jsp:include> or <jsp:forward> sends the request to another servlet or JSP. The servlet equivalent of the above useBean action is:

foo.Counter counter = (foo.Counter)request.getAttribute("counter"); if (counter == null) { counter = new foo.Counter(); request.setAttribute("counter", counter); } ----------------------------------------------------------------------

<jsp:useBean id="counter" class="foo.Counter" scope="page" /> In this example the Counter bean is instantiated as a local variable inside the JSP method. It is impossible to share a page scope variable with another JSP or Servlet.

The servlet equivalent of the above useBean action is:

foo.Counter counter = new foo.Counter(); Comments and alternative answers

superb! crystal clear!! Author: Rosdi Kasim (http://www.jguru.com/guru/viewbio.jsp?EID=479028), Aug 17, 2001 Superb!.. the explanation is crystal clear!! I am looking for this info all over.., and this page explain it all. Thanks god for the Internet! ...and the author of the answer too.. :-) Re: superb! crystal clear!! Author: Rotti Sowmindra (http://www.jguru.com/guru/viewbio.jsp?EID=487648), Dec 30, 2001 Yes Really superb but what one can do is go and check the temporary java files generated by the web server while compiling the JSP page.We can get answers to all our questions Regards Sowmindra What servlet code corresponds to the various "scope" values for the <jsp:useBean> tag? Author: Sridhar kancharlapalli (http://www.jguru.com/guru/viewbio.jsp?EID=479357), Aug 19, 2001 This is what I was looking for.. got more than I expected.I would like to thank the author for his explanation in such detail.

Re: What servlet code corresponds to the various "scope" values for the <jsp:useBean> tag? Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Aug 20, 2001 Aw, shucks. You're welcome. :-) For jsp page script, more info about page scope. Author: Roger Hand (http://www.jguru.com/guru/viewbio.jsp?EID=292314), Oct 1, 2001 If you're using script in a jsp page, as opposed to just jsp bean tags as shown above, you can use the following form to put an already instantiated object into the page context so it can be used via Bean tags. <% foo.Counter counter = new foo.Counter(); //use counter object in scriptlet . . . //now let's set it up so we can use it with jsp bean tag . . . pageContext.setAttribute("counter", MyPhoneNumberBean); %>

Hello, World! Counter value is <jsp:getProperty name="counter" property="counterValue"/>

Re: For jsp page script, more info about page scope. Author: Roger Hand (http://www.jguru.com/guru/viewbio.jsp?EID=292314), Oct 2, 2001 Oops! Instead of pageContext.setAttribute("counter", MyPhoneNumberBean);

it should've been . . . pageContext.setAttribute("counter", counter);

(That's what I get for copy and pasting ...) For older APIs... Author: Josh Marquart (http://www.jguru.com/guru/viewbio.jsp?EID=30693), Aug 9, 2002 it should've been . . . pageContext.setAttribute("counter", counter); Do note for those of you using the older servlet/jsp APIs that you need to use pageContext.setAttribute("counter", counter, PageContext.SESSION_SCOPE); pageContext.getAttribute("counter", PageContext.SESSION_SCOPE); for session scoped Objects. You can also substitute PageContext.APPLICATION_SCOPE PageContext.REQUEST_SCOPE and PageContext.PAGE_SCOPE in place of "PageContext.SESSION_SCOPE" depending on the scope you want to deal with. Help!! With setAttribute Author: Jennifer Johnson (http://www.jguru.com/guru/viewbio.jsp?EID=531401), Oct 26, 2001 I am trying to pass a variable to a bean that has a parametarized constructor. I only want the constructor to be initiallized once. Below is the code I am using to call the bean: <%String ttree1 = new String("fins.tb_reports"); BotLevBean1 botlev1 = (BotLevBean1)getServletContext().getAttribute("botlev1"); if (botlev1 == null) { botlev1 = new BotLevBean1(ttree1); getServletContext.setAttribute("botlev1", botlev1); }

I am getting this error: /u01/sdk/jsp_scratch/jsp/_treejsp2/_arvartree_bud_2ejsp.java:109: Undefined variable or class name: getServletContext getServletContext.setAttribute("botlev1", botlev1); Please Help!!! What am I doing wrong? Thanks!!! %> Re: Help!! With setAttribute Author: oleg morenkov (http://www.jguru.com/guru/viewbio.jsp?EID=579913), Dec 11, 2001 getServletContext() good but i still get error Author: priyadarshi upadhyaya (http://www.jguru.com/guru/viewbio.jsp?EID=325951), Jan 4, 2002 Hi i m using <jsp:useBean id="t" class="testbean" /> <% t.var11=11 %> <% // here var11 is int type variable and is defined in testbean.testbean is initialized by a servlet.But when i run this JSP page ,I get error saying variable t is not initialized.but if i initialize testbean in JSP , i lose my data which is set by servlet please help me out Re: good but i still get error Author: sreenivas ananthakrishna (http://www.jguru.com/guru/viewbio.jsp?EID=752289), Feb 8, 2002 Priya, Hope your question has been answered by now. If now, make sure that the scope of the bean in the jsp:useBean tag is same as the scope in which it was created. for ex: in the servlet if you are storing the bean in ServletContext , you need to specify <jsp:useBean id="t" class="testbean" scope="application" /> like wise, for request: servlet : request.setAttribute("t",t); JSP: request.getAttribute("t"); for session : servlet : request.getSession(true).putValue("t",t); jsp: <jsp:useBean id="t" class="testbean" scope="session" /> hope this works, if not please let me know how you are creating and storing the bean in the servlet thanks, sreeni Re[2]: good but i still get error Author: priyadarshi upadhyaya (http://www.jguru.com/guru/viewbio.jsp?EID=325951), Feb 9, 2002 thnx anath I appreciate your reply..anyway i tried it out and it worked out. u can view my site at www.mycgiserver.com/~priyadarshi786/ its totally in JSP and i took lots of help from jguru FAQs ..Jguru realy helps..thnx jguru priyadarshi

extremely useful Author: jay denis (http://www.jguru.com/guru/viewbio.jsp?EID=792493), Apr 9, 2002 Thanks! I have been puzzled by this question for a long time. Thanks for giving such clear a n answer. Question Author: mark faine (http://www.jguru.com/guru/viewbio.jsp?EID=1122412), Oct 18, 2003 In your example for request scope: <jsp:useBean id="counter" class="foo.Counter" scope="request" />

The servlet equivalent of the above useBean action is: foo.Counter counter = (foo.Counter)request.getAttribute("counter"); if (counter == null) { counter = new foo.Counter(); request.setAttribute("counter", counter); }

Is there really any need to check for the existence of the bean in the request scope? In other words, wouldn't any subsequent access to the servlet be a new reqeust? I'm just imagining the requestdispatcher being used to forward to a JSP/servlet, now unless that JSP/servlet immediately forwards back to the servlet there would't be a need to check the request context for the counter bean? -Mark Re: What servlet code corresponds to the various "scope" values for the jsp:useBean tag? Author: Steven Hines (http://www.jguru.com/guru/viewbio.jsp?EID=1131441), Dec 2, 2003 You, my friend, are an absolute hero! its simply the best help Author: jai prakash (http://www.jguru.com/guru/viewbio.jsp?EID=1189709), Jul 30, 2004 i got what i looking for. thanks How can I support HTTPS (SSL) in a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=53931 Created: May 22, 2000 Modified: 2000-08-24 19:10:45.933 Author: Jim Garrett (http://www.jguru.com/guru/viewbio.jsp?EID=53862) Question originally posed by Al Buk (http://www.jguru.com/guru/viewbio.jsp?EID=47884

The servlet technology by design already supports https (SSL). However, the way this works is not through the servlet technology but through the Web Server. The web server controls whether information is done securely (https) versus non-securely (http). One way to force servlets to go down the https path is to define your web server to only allow secure connections when accessing servlets. In IIS this can be accomplished through the definition if ISAPI filters. The ISAPI filter can instruct the web server to route all requests that end with a pre-defined prefix to the servlet engine. The trick is to then define files, with the predefined extension, in the web servers directory. For example, if the servlet's name is MyServlet a file with the name MyServlet.xxx would be placed on the web server. All calls to this file would be routed to the servlet engine. And IIS would be used to force all calls to the MyServlet.xxx file to go through https. The JRun servlet engine has examples of how to do this documented on their web page. Comments and alternative answers

Tomcat supports SSL, either through Apache, or on its... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jun 21, 2000 Tomcat supports SSL, either through Apache, or on its own (currently in an unstable state, though it should work in time for the next major release). Does anybody know how to do that for Apache/JServ ?... Author: Victor Stratan (http://www.jguru.com/guru/viewbio.jsp?EID=134872), Oct 26, 2000 Does anybody know how to do that for Apache/JServ ? [Yes, see the Tomcat documentation web site. -A] Can the security context be passed between a web container (servlets/jsp) and an EJB container ? When the servlet calls an EJB I want its identity to be that of the original web client authenticated with a certificate. Location: http://www.jguru.com/faq/view.jsp?EID=53955 Created: May 22, 2000 Modified: 2000-08-13 16:38:04.872 Author: Siva Visveswaran (http://www.jguru.com/guru/viewbio.jsp?EID=46210) Question originally posed by Daniel Weimer (http://www.jguru.com/guru/viewbio.jsp?EID=25540 The whole issue of propagation of authentication context from client to the EJB server is still evolving - both in terms of the specification as well as vendor offerings. According to the current Java 2 specification (page 224): "the container is the authentication boundary between callers and components hosted by the caller. For inbound calls it is the container's responsibility to make an authentic representation of the caller identity available to the component". The JAAS 1.0 specification extends the types of principals and credentials that can be associated with the client but it is also evolving. Thus given the container implementation that is required to drive this whole thing, the answer depends on your app vendor - some like Weblogic (WLE), Websphere

provide security plug-ins/SDKs that can enable the propagation. Other vendors are close behind. Check your vendor plug-in. Comments and alternative answers

Some vendors, like Pramati, provide a facility where... Author: Asit Padhi (http://www.jguru.com/guru/viewbio.jsp?EID=61648), Jul 18, 2000 Some vendors, like Pramati, provide a facility where the security credentials of the web client are first authenticated by the web container and when the Servlet calls the EJB components the same security context is passed on to the EJB container. Re: Some vendors, like Pramati, provide a facility where... Author: Nilesh Shah (http://www.jguru.com/guru/viewbio.jsp?EID=1810), Sep 19, 2002 Is this still true?. We are want to use Resin servlet engine at web layer and weblogic 7.0 at EJB layer. Can we pass security context from resin to weblogic?. Can JAAS help use here?. If we use weblogic at both layer that it passes the context.

How can I cache the results of my servlet, so the next request doesn't have to go through all the calculation / database access / other time-consuming stuff all over again? Location: http://www.jguru.com/faq/view.jsp?EID=54322 Created: May 23, 2000 Modified: 2000-05-26 17:01:45.921 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Jason Hunter, author of the O'Reilly Servlets book, has written a nice little class called CacheHttpServlet. If your servlet subclasses CacheHttpServlet and overrides one method, the superclass takes care of caching the last response. Note that as written, it only caches one version; if you have multiple possible pages based on request parameters, it won't be as effective. Someone should probably extend this class to handle multiple pages. How can we use a servlet as a proxy for communications between two applets? Location: http://www.jguru.com/faq/view.jsp?EID=56017 Created: May 24, 2000 Modified: 2000-09-18 13:13:36.54 Author: Jim Garrett (http://www.jguru.com/guru/viewbio.jsp?EID=53862) Question originally posed by kavala mallikarjun (http://www.jguru.com/guru/viewbio.jsp?EID=44978 Jim Garrett writes:

One way to accomplish this is to have the applets communicate via TCP/IP sockets to the servlet. The servlet would then use a custom protocol to receive and push information between applets. However, this solution does have firewall problems if the system is to be used over and Internet verses an Intranet. Alex Chaffee adds: You could also have the applets use HTTP to communicate with the servlet, using the standard URLConnection classes as described in How can my applet communicate with my servlet?. This is more likely to get through the firewall, but it means that the second (receiver) applet must continually poll the servlet to check for new information. Jim Garrett continues: One other solution which works with simple data is to combine Java Applet technology with Java Scripts. Since an applet can communicate with Java Script, and Java Script can communicate with applets, it is possible to create an environment where JavaScript is used to pass information between applets. This solution works when the data being sent between applets is text data. [ Douglas E Miller had given some source code examples. It has been pointed out to me that this code is actually from the Java Tutorial; you can look at the KnockKnock example at http://java.sun.com/docs/books/tutorial/networking/sockets/clientServer.html. Of course, the KnockKnockServer isn't actually a servlet, which is kind of important for the sake of the example, but you can probably figure it out from here. In this architecture, the servlet must spawn a thread (probably in its init() method) that opens and listens on a socket. This does not use HTTP at all, though you can extend the doGet() method to provide a status page. That means it's still sensitive to firewalls. -Alex ] What is the difference between POST and GET methods? What about PUT, DELETE, TRACE, OPTIONS, and HEAD? Location: http://www.jguru.com/faq/view.jsp?EID=56472 Created: May 25, 2000 Modified: 2000-08-10 10:06:51.465 Author: Simon Brown (http://www.jguru.com/guru/viewbio.jsp?EID=44588) Question originally posed by Amisha Patel (http://www.jguru.com/guru/viewbio.jsp?EID=52054 GET and POST basically allow information to be sent back to the webserver from a browser (or other HTTP client for that matter). Imagine that you have a form on a HTML page and clicking the "submit" button sends the data in the form back to the server, as "name=value" pairs. Choosing GET as the "method" will append all of the data to the URL and it will show up in the URL bar of your browser. The amount of information you can send back using a GET is restricted as URLs can only be 1024 characters. A POST on the other hand will (typically) send the information through a socket back to the webserver and it won't show up in the URL bar. You can send much more information to the server this way - and it's not restricted to textual data either. It is possible to send files and even binary data such as serialized Java objects! A PUT allows you to "put" (upload) a resource (file) on to a webserver so that it be found under a specified URI. DELETE allows you to delete a resource (file). These are

both additions to HTTP/1.1 and are not usually used. HEAD returns just the HTTP headers for a resource. TRACE and OPTIONS are also HTTP/1.1 additions and also rarely used. The Servlet spec allows you to implement separate Java methods implementing each HTTP method in your subclass of HttpServlet. Override the doGet() and/or doPost() method to provide normal servlet functionality. Override doPut() or doDelete() if you want to implement these methods. There's no need to override doOptions() or doTrace(). And the superclass handles the HEAD method all on its own. The full specs for HTTP are available (if you're interested) can be found on the w3c.org site. See also the JavaDoc for HttpServlet. [Edited/enhanced by Alex] See also: • • •

How do I support both GET and POST protocol from the same Servlet? What is the difference between the doGet and doPost methods? How does one choose between overriding the doGet(), doPost(), and service() methods?

How can I design my servlet/JSP so that query results get displayed on several pages, like the results of a search engine? Each page should display, say, 10 records each and when the next link is clicked, I should see the next/previous 10 records and so on. Location: http://www.jguru.com/faq/view.jsp?EID=60818 Created: May 31, 2000 Modified: 2000-10-03 10:16:08.397 Author: Richard Raszka (http://www.jguru.com/guru/viewbio.jsp?EID=7963) Question originally posed by arun prathap (http://www.jguru.com/guru/viewbio.jsp?EID=43168 Use a Java Bean to store the entire result of the search that you have found. The servlet will then set a pointer to the first line to be displayed in the page and the number of lines to display, and force a display of the page. The Action in the form would point back to the servlet in the JSP page which would determine whether a next or previous button has been pressed and reset the pointer to previous pointer + number of lines and redisplay the page. The JSP page would have a scriplet to display data from the Java Bean from the start pointer set to the maximum number of lines with buttons to allow previous or next pages to be selected. These buttons would be displayed based on the page number (i.e. if first then don't display previous button). Joe Sam Shirah adds: There are many of methods to accomplish this. One way is to use the Pager Tag Library, recently discussed at Implementing Page Scrolling on the servlet mailing list. You may also want to look through the list Archives for other ideas. Comments and alternative answers

The problem with the ResultSet object in the JDBC1.2.2... Author: Alexandros Kotsiras (http://www.jguru.com/guru/viewbio.jsp?EID=64209), Jun 3, 2000 The problem with the ResultSet object in the JDBC1.2.2 version is that it is not scrollable. It is scrollable in the latest JDBC2.0 version which only the latest versions of the RDBMS support. Note that you can still use a JDBC2.0 Type 4 driver (eg. classes12.zip for Oracle) with an RDBMS that does not support JDBC2.0 features (like Oracle 8.1.5) but you won't be able to use the new JDBC2.0 functionality. The new features can only be used if the RDBMS supports them by itself like Oracle 8.1.6. I found very useful the CachedRowSet API from Sun which is an extension to java.sql. After you create your ResultSet object you wrap it arround a CachedRowSet object which is disconnected and scrollable. It's like putting all you result records in a Collection object but the CachedRowSet does this job for you plus it offers all the methods that you need to scroll like : next(), previous(), relative(numberOfRows), getRow(rowPosition), size() (to determine the number of records in your ResultSet) etc. Then you just need to put it in the users session, retrieve from the next page, scroll to the appropriate position and display a range of records. The above approach might not be the appropriate one if you have a very large ResultSet since the CachedRowSet object that you will store in the session will take a lot of memory. For ResultSets of some hundrends of records you should be fine. It can be downloaded from the Sun/JDBC page at http://java.sun.com/products/jdbc/ The approaches discussed above are good for a few ... Author: jeyabalan sethuraman (http://www.jguru.com/guru/viewbio.jsp?EID=120328), Aug 5, 2000 The approaches discussed above are good for a few hundreds of records as mentioned above. What is the best approach when the result set is huge ( for example, more than 10000 records ) ? As noted above, there are many ways to do this, but... Author: yogesh tk (http://www.jguru.com/guru/viewbio.jsp?EID=200141), Oct 6, 2000 As noted above, there are many ways to do this, but all basically involve storing a variable in order to know which set of records is to be shown next. Following are three methods of storing the count: 1. Keep the count in the session. 2. Keep a hidden field in the page. 3. Place this count in the URL as a part of the QueryString. The servlet then uses the count in its logic to determine the next set of records to

display. Having had the same problem I found that in PostgreSQL... Author: Tarmo Kallas (http://www.jguru.com/guru/viewbio.jsp?EID=227773), Oct 13, 2000 Having had the same problem I found that in PostgreSQL database one can make SQL-queries so that resultSet returns only records from certain record to certain record (e.g. records 5->10) In SELECT statement one needs only add LIMIT and OFFSET atributes (e.g. 'SELECT * FROM table_name ORDER BY one_field_name LIMIT 5 OFFSET 5' this statement should return the records from 5 to 10 in table_name table when sorted by one_field_name field). See the LIMIT CLAUSE documentation in the PostgreSQL documentation for additional information. I have never been able to figure out if there is any... Author: martin smith (http://www.jguru.com/guru/viewbio.jsp?EID=260406), Dec 31, 2000 I have never been able to figure out if there is any way to have the DBMS retain a scrollable cursor/resultset and feed only parts of it to the client or mid-tier. This is NOT the same as re-executing the query and somehow restricting the number of values returned to a page-full. I actually want the resultset retained on the server side, since it seems this would be MUCH more efficient for complex ad-hoc multi-table join queries on large tables (which is what we do.) Is this implementable within Oracle? Re: I have never been able to figure out if there is any... Author: Prasoon Kumar Choudhary (http://www.jguru.com/guru/viewbio.jsp?EID=588711), Dec 18, 2001 There are many solutions to this problem. I agree that if the result set is a too large, storing 1000 of record in session will not be a good idea. Better solution will be to get record from database for each page. If you are working with mysql there is a limit key work that will help you the featch for the particular page. On oracle there is no such keyword but there is a query throught which you can select record form middle of the total selected record for your search condition. say you are fetching emp name from emp table and you want names from 20th to 30th record for a search criteria say in emp in city newyork. The query will be select x.emp_name from (select rownum y, emp_name from emp where city='newyork')x where x.y between 20 and 30;

I have used this many time in my projects

Re[2]: I have never been able to figure out if there is any... Author: Ajay Sharma (http://www.jguru.com/guru/viewbio.jsp?EID=746666), Feb 4, 2002 Hi Prasoon , U are absolutely right , but the this is possible only in MYSQL .But if U see Oracle , it isn't possible. I feel there are a number of ways U can do this and it all depends upon the application requirements. Ajay Sharma Re[3]: I have never been able to figure out if there is any... Author: Prasoon Choudhary (http://www.jguru.com/guru/viewbio.jsp?EID=264897), Feb 5, 2002 The query you see above works with oracle. Rownum ect is part of oracle sql implementation. On Mysql you do not have rownum if you are working with mySql use Limit keword Re[4]: I have never been able to figure out if there is any... Author: Robert Williams (http://www.jguru.com/guru/viewbio.jsp?EID=1080681), Apr 30, 2003 How about for Microsoft SQL Server? Is there any keyword like rownum or limit? Re[2]: I have never been able to figure out if there is any... Author: E L (http://www.jguru.com/guru/viewbio.jsp?EID=819637), Apr 1, 2002 this sounds like a good idea but how can i retrieve the total number of records even after I set the rownum range? eg. select rownum y, emp_name from emp where city='newyork' the total number of employees. I need to retrieve the total number so that I can determine the number of pages needed to display all the records. (with PageCount=RecordSize/PageSize) where PageSize is the rownum range. Pls help.. Re[3]: I have never been able to figure out if there is any... Author: Prasoon Choudhary (http://www.jguru.com/guru/viewbio.jsp?EID=264897), Apr 1, 2002 You will have you fire a select count(*) from emp where city='newyork' before that. you can store this count in session so that you dont have to do this for every page. This will work well for most of the cases where count will not change very frequently i,e there is not much insert or delete taking place on the table. "select x.emp_name from (select rownum y, emp_name from emp where city='newyork')x where x.y between 20 and 30;"

Author: X F (http://www.jguru.com/guru/viewbio.jsp?EID=887397), May 28, 2002 select emp_name from emp where city = 'newyork' and rownum < 31 MINUS select emp_name from emp where city = 'newyork' and rownum < 20 this clause will perform better, i think so but no test. Re: "select x.emp_name from (select rownum y, emp_name from emp where city='newyork')x where x.y between 20 and 30;" Author: segmoti segmoti (http://www.jguru.com/guru/viewbio.jsp?EID=415596), Jun 15, 2002 One of the issues I find (in the query you have given with a minus clause) is inability to sort by using 'order by' clause. For a query like 'select emp_name from emp where city = 'newyork' and rownum < 20 order by emp_name' 'Rownum' is executed before the order by clause. So if I put both rownum and order by in a query, then oracle first gets the set of rows as evaluated using rownum and then sorts it. Whereas behaivor I require is that sort the records first and then use rownum to limit the rows. Any idea how to get past it? Regards Mohit Good Sql,but can not execute under ODBC for access Author: Jeason Zhao (http://www.jguru.com/guru/viewbio.jsp?EID=1037417), Dec 13, 2002 Good Sql,but can not execute under ODBC for access Re[2]: I have never been able to figure out if there is any... Author: HAKAN YILDIZ (http://www.jguru.com/guru/viewbio.jsp?EID=1175989), Jun 3, 2004 what about if I have a query containing a group by clause in it. My query is : select /*+ ALL_ROWS +*/ policeno pno,bitistarih bittar,Sum(primfark) prim,sum(komisyonfark) komisyon from police where statu='E' and baslangictarih=to_date('01/05/2005','dd/MM/yyyy') group by policeno,bitistarih order by policeno )pol this query gets about 2 million rows and I go through these rows for calculating something,and my compiler(jdk 1.3.1) gives an outofmemory exception in the middle. I dont want to increase heap size of jvm . I want to get rows in three or more parts like the example you gave. but as I mentioned I have a group by clause in my query and I am forced to put rownum into groupby. if I do that I got wrong data from query ! has anybody suggestion about this. thanks lot. See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Feb 13, 2002 •

How can I cache the results of my servlet, so the next request doesn't have to

go through all the calculation / database access / other time-consuming stuff all over again?

Search Reasult Author: Birendar Waldiya (http://www.jguru.com/guru/viewbio.jsp?EID=1131260), Dec 1, 2003 One more way to acheive the result, in a page wise display of page r is by using Scrollable ResultSet every time you want to get the next page shift the cursor to that particular point in ResultSet.absolute(int) method. How do I upload a file using a Java client (not a browser) and HTTP POST? Many of the examples show how a HTML page can be constructed to select the file and do the POST, but I need to do it from a java client. Location: http://www.jguru.com/faq/view.jsp?EID=62798 Created: Jun 2, 2000 Modified: 2001-07-23 10:27:35.199 Author: Richard Raszka (http://www.jguru.com/guru/viewbio.jsp?EID=7963) Question originally posed by Sean Woodhouse (http://www.jguru.com/guru/viewbio.jsp?EID=14628 [Note: the following example works, but it does not encode the POSTed file in the multipart/* format expected by servlets as described in How do I upload a file to my servlet?. Perhaps another Guru could submit some feedback ...? -Alex] Use the URLConnection class to upload a file to a web site and a servlet that understands how to read that file. At the client level import java.net.*; import java.io.*; public class HTTP_post { static URL u; public static void main(String args[]) { String s=URLEncoder.encode("A Test string to send to a servlet"); try {

HTTP_post post = new HTTP_post(); post.u = new URL("http://myhost/servlet"); // Open the connection and prepare to POST URLConnection uc = u.openConnection(); uc.setDoOutput(true); uc.setDoInput(true);

uc.setAllowUserInteraction(false); DataOutputStream dstream = new DataOutputStream(uc.getOutputStream()); // The POST line dstream.writeBytes(s); dstream.close(); // Read Response InputStream in = uc.getInputStream(); int x; while ( (x = in.read()) != -1) { System.out.write(x); } in.close(); BufferedReader r = new BufferedReader(new InputStreamReader(in)); StringBuffer buf = new StringBuffer(); String line; while ((line = r.readLine())!=null) { buf.append(line); } } catch (IOException e) { e.printStackTrace(); handling } } }

// should do real exception

At Servlet end Perform a getInputStream to read the input and send the data to a file. Example: InputStream in = request.getInputStream(); BufferedReader r = new BufferedReader(new InputStreamReader(in)); StringBuffer buf = new StringBuffer(); String line; while ((line = r.readLine())!=null) { buf.append(line); } String s = buf.toString(); Comments and alternative answers

I agree with Alex, the approach I have taken is to... Author: Richard Raszka (http://www.jguru.com/guru/viewbio.jsp?EID=7963), Jun 3,

2000 I agree with Alex, the approach I have taken is to provide a simple method to demonstrate how to upload a file to a servlet If a full HTTP Client is required. Then I would recommend HTTP_Client Version 0.32 written by Ronald Tschalär. This provides a reasonably complete client with multipart/* format if that is required. Documentation is sufficient to write clients with the standard JavaDoc supplied, and combined with the servlet found in How do I upload a file to my servlet? should provide a solution to most situations.

Re: I agree with Alex, the approach I have taken is to... Author: Priya Selva (http://www.jguru.com/guru/viewbio.jsp?EID=1109586), Aug 19, 2003 Hi All, I'm using com.oreilly.servlet package for uploading file through html. I want to use the same package for file upload through Java client. Can anyone help me to write the java client ? Thanks in advance --Selva File Uplod Servlet: Java Client for com.oreilly.servlet package Author: Priya Selva (http://www.jguru.com/guru/viewbio.jsp?EID=1109586), Aug 20, 2003 I figured it through a web forum. Here is the code for the Java Client import java.io.*; import java.net.*; public class ServletCom

{

public static void main(String[] args) throws Exception { HttpURLConnection conn = null; BufferedReader br = null; DataOutputStream dos = null; DataInputStream inStream = null; InputStream is = null; OutputStream os = null; boolean ret = false; String StrMessage = ""; String exsistingFileName = "C:\\account.xls";

String lineEnd = "\r\n"; String twoHyphens = "--"; String boundary = "*****"; int bytesRead, bytesAvailable, bufferSize; byte[] buffer; int maxBufferSize = 1*1024*1024; String responseFromServer = ""; String urlString = "http://localhost:8080/FileUpload/requestupload"; try { //------------------ CLIENT REQUEST FileInputStream fileInputStream = new FileInputStream( new File(exsistingFileName) ); // open a URL connection to the Servlet URL url = new URL(urlString); // Open a HTTP connection to the URL conn = (HttpURLConnection) url.openConnection(); // Allow Inputs conn.setDoInput(true); // Allow Outputs conn.setDoOutput(true); // Don't use a cached copy. conn.setUseCaches(false); // Use a post method. conn.setRequestMethod("POST"); conn.setRequestProperty("Connection", "Keep-Alive"); conn.setRequestProperty("Content-Type", "multipart/formdata;boundary="+boundary); dos = new DataOutputStream( conn.getOutputStream() ); dos.writeBytes(twoHyphens + boundary + lineEnd); dos.writeBytes("Content-Disposition: form-data; name=\"upload\";"

+ " filename=\"" + exsistingFileName +"\"" + lineEnd); dos.writeBytes(lineEnd);

// create a buffer of maximum size bytesAvailable = fileInputStream.available(); bufferSize = Math.min(bytesAvailable, maxBufferSize); buffer = new byte[bufferSize]; // read file and write it into form... bytesRead = fileInputStream.read(buffer, 0, bufferSize); while (bytesRead > 0) { dos.write(buffer, 0, bufferSize); bytesAvailable = fileInputStream.available(); bufferSize = Math.min(bytesAvailable, maxBufferSize); bytesRead = fileInputStream.read(buffer, 0, bufferSize); } // send multipart form data necesssary after file data... dos.writeBytes(lineEnd); dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd); // close streams fileInputStream.close(); dos.flush(); dos.close(); } catch (MalformedURLException ex) { System.out.println("From ServletCom CLIENT REQUEST:"+ex); } catch (IOException ioe) { System.out.println("From ServletCom CLIENT REQUEST:"+ioe); } //------------------ read the SERVER RESPONSE try { inStream = new DataInputStream ( conn.getInputStream() ); String str; while (( str = inStream.readLine()) != null)

{

System.out.println("Server response is: "+str); System.out.println("");

} inStream.close();

} catch (IOException ioex) { System.out.println("From (ServerResponse): "+ioex); } } }

Thanks Selva How to realize streaming proxy Author: Mirko Geilert (http://www.jguru.com/guru/viewbio.jsp?EID=1147488), Feb 19, 2004 Hi, i'm trying to make a http proxy (with some additional features) which is able to forward multipart/form-data requests. I tried your code and it works fine. There's only one drawback: files which come with the request are fully written to the forwarding request before it is sent. How do i get the request to be processed by the server while writing the files content at the client (streaming behaviour)? Are there any other client implementations able to do this? Thanx a lot Mirko Re: File Uplod Servlet: Help Required Author: Kumar Uttam (http://www.jguru.com/guru/viewbio.jsp?EID=1149406), Feb 26, 2004 I am using the same file provided by you.It compiles and connection is made when server is running.But still the file is not uploaded in the folder mentioned.Can u pls provide a solution to this.I have to upload an XML file I am using jakarta tomcat as webserver. Thanks in advance. Can mail me at [email protected] import java.io.*; import java.net.*; public class ServletCom { public static void main(String[] args) throws Exception { HttpURLConnection conn = null; BufferedReader br = null; DataOutputStream dos = null; DataInputStream inStream = null; InputStream is = null; OutputStream os = null; boolean ret = false; String StrMessage = ""; String exsistingFileName ="C:\\TimeSheet.xml"; String lineEnd = "\r\n"; String twoHyphens = "--"; String boundary = "*****"; int

bytesRead, bytesAvailable, bufferSize; byte[] buffer; int maxBufferSize = 1*1024*1024; String responseFromServer = ""; //String urlString = "http://192.168.221.63:80"; // String urlString = "http://localhost:8080/FileUpload/requestupload"; String urlString = "http://localhost:8080/examples/jsp"; //"http://localhost:8080/examples/jsp/Timeperiod/Timeperiod.xml" try { //------------------ CLIENT REQUEST FileInputStream fileInputStream = new FileInputStream( new File(exsistingFileName) ); // open a URL connection to the Servlet URL url = new URL(urlString); System.out.println("URL::::::::::"+url); // Open a HTTP connection to the URL conn = (HttpURLConnection) url.openConnection(); conn.setAllowUserInteraction(true); // Allow Inputs conn.setDoInput(true); // Allow Outputs conn.setDoOutput(true); // Don't use a cached copy. conn.setUseCaches(false); // Use a post method. conn.setRequestMethod("POST"); conn.setRequestProperty("Connection", "Keep-Alive"); conn.setRequestProperty("Content-Type", "multipart/formdata"); // conn.getResponseCode() ; dos = new DataOutputStream(conn.getOutputStream()); conn.getResponseMessage(); dos.writeBytes(twoHyphens + boundary + lineEnd); dos.writeBytes(exsistingFileName); dos.writeBytes(lineEnd); // create a buffer of maximum size bytesAvailable = fileInputStream.available(); bufferSize = Math.min(bytesAvailable, maxBufferSize); buffer = new byte[bufferSize]; // read file and write it into form... bytesRead = fileInputStream.read(buffer, 0, bufferSize); while (bytesRead > 0) { dos.write(buffer, 0, bufferSize); bytesAvailable = fileInputStream.available(); bufferSize = Math.min(bytesAvailable, maxBufferSize); bytesRead = fileInputStream.read(buffer, 0, bufferSize); } // send multipart form data necesssary after file data... dos.writeBytes(lineEnd); dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd); // close streams fileInputStream.close(); dos.flush(); dos.close(); } catch (MalformedURLException ex) { System.out.println("From ServletCom CLIENT REQUEST:"+ex); } catch (IOException ioe) { System.out.println("From ServletCom CLIENT REQUEST:"+ioe); } //------------------ read the SERVER RESPONSE try { inStream = new DataInputStream ( conn.getInputStream() ); String str; while (( str = inStream.readLine()) != null) { System.out.println("Server response is: "+str); System.out.println(""); } inStream.close(); } catch (IOException ioex) { System.out.println("From (ServerResponse): "+ioex); } catch (Exception e) { System.out.println("From ServletCom CLIENT REQUEST:"+e); } } } When you use readLine() to read data over a socket... Author: Tim Rohaly (http://www.jguru.com/guru/viewbio.jsp?EID=10), Oct 26, 2000 When you use readLine() to read data over a socket at the servlet end, you're

making the very bad assumption that the data is text, not binary. Don't do this. Similarly, if you use println() to write data over a socket, you're assuming the data is text and that the protocol uses the same line terminator as your client. You leave yourself open to nasty problems if you do this.

I have been using HTTPClient to make posts from Java... Author: Jim Coker (http://www.jguru.com/guru/viewbio.jsp?EID=2), Oct 26, 2000 I have been using HTTPClient to make posts from Java programs and it has worked well so far, and is very easy to use. It also handles cookies smoothly, and is LGPL. I plan to use it to build testing programs for jGuru. Re: I have been using HTTPClient to make posts from Java... Author: hari prasad (http://www.jguru.com/guru/viewbio.jsp?EID=1059077), Feb 21, 2003 hai can u help me i have seen the code to send the text string to servlet and servlet reads it can u help me to have a example to send a xml file to servlet and servlet send back the xml file to the client please its urgent what about connecting to a J2EE app server? Author: John Nilson (http://www.jguru.com/guru/viewbio.jsp?EID=27129), Dec 31, 2001 Will this work when/if the client gets a form based authentication response, that is the JSEE login page with a , j_security_check etc. How do you handle this case and then set the username and password back, which I imagine have to be encrypted as well? John What version of the Servlets or JSP specification is supported by my favorite servlet product? (JSDK, JSWDK, Tomcat, J2EE, etc.) Location: http://www.jguru.com/faq/view.jsp?EID=64205 Created: Jun 3, 2000 Modified: 2000-08-13 14:39:09.242 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Related FAQs: •

What's the difference between the JSDK and the JSWDK? And what's the current version?

The following table summarizes the confusion.

Product Tomcat

Product Version Servlet spec JSP spec 3.1

2.2

1.1

Tomcat

3.0

2.2

1.1

Sun J2EE Reference Implementation beta

2.2

?

Sun JSWDK

1.0.1

2.1

1.0.1

Sun JSDK

2.1

2.1

none

Sun JSDK

2.0

2.0

none

Allaire JRun

3.0

2.2

1.1

Sun Java Web Server

2.0

2.1

-

Sun Java Web Server

1.1

2.0

-

Sun/Netscape iPlanet Web Server

4.1

2.2

?

Please add information for other servlet engines as feedback to this FAQ; I'll incorporate it into the table. Comments and alternative answers

JRun 3.0 -- Servlet 2.2, JSP 1.1 Author: Larry Kim (http://www.jguru.com/guru/viewbio.jsp?EID=71699), Jun 10, 2000 JRun 3.0 -- Servlet 2.2, JSP 1.1 Enhydra 3.0 -- Servlet 2.2, JSP 1.1 Author: Klaus Krull (http://www.jguru.com/guru/viewbio.jsp?EID=136930), Aug 28, 2000 Enhydra 3.0 -- Servlet 2.2, JSP 1.1 Oracle JVM rel 3 supports Servlet 2.2 and JSP 1.1 Author: Kuassi Mensah (http://www.jguru.com/guru/viewbio.jsp?EID=267862), Dec 2, 2000 Oracle JVM rel 3 supports Servlet 2.2 and JSP 1.1 jo! 1.0b3 Author: Roger Chung-Wee (http://www.jguru.com/guru/viewbio.jsp?EID=448003), Jun 30, 2001 Supports Servlet 2.2 and JSP 1.1. Available from tagtraum.com.

Tomcat 4.0 Author: sachin walia (http://www.jguru.com/guru/viewbio.jsp?EID=472972), Sep 19, 2001 Tomcat 4.0 supports fully Servlet 2.3 (servlet filters) and JSP 1.2 including inbuilt support for J2EE API's like javax.transaction.*, jndi, javax.sql.* thereby making all

the web applications hosted on it fully compatible with any major application servers. When should one use applets and when should one use servlets? Location: http://www.jguru.com/faq/view.jsp?EID=64403 Created: Jun 3, 2000 Modified: 2000-06-03 22:44:09.3 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by swati m (http://www.jguru.com/guru/viewbio.jsp?EID=64343 Applets run inside browsers, and servlets run inside servers. So broadly speaking, use applets when you need dynamism on the client side, and use servlets when you need dynamism on the server side. Servlets can produce any HTML (or indeed, any file type), and therefore are much more versatile than applets. Servlets can tailor the HTML they produce based on the browser type (as specified in the "User-Agent" header), and thus can produce output that will work in virtually any client, including WAP browsers or the like. Applets are notoriously poorly supported, and even in browsers that ostensibly have Java support, don't work consistently. Servlets can also produce HTML with embedded JavaScript, which allows a fair amount of dynamic behavior on browsers which support it. However, due to the infuriating limitations and bugs in JavaScript, sometimes you've just got to have an applet to get the client-side behavior you want. In these cases, take comfort in the fact that you can generate HTML containing APPLET tags from inside a servlet. What is the best way to convert HTML to XML, separating the content(data) from presentation in HTML? Are there any Java API's that we can make use of? Location: http://www.jguru.com/faq/view.jsp?EID=66681 Created: Jun 6, 2000 Modified: 2000-10-11 09:33:33.868 Author: Brill Pappin (http://www.jguru.com/guru/viewbio.jsp?EID=60239) Question originally posed by Praveen Paranjay (http://www.jguru.com/guru/viewbio.jsp?EID=40359 Try Cocoon and ECS, or JetSpeed from the Apache group (java.apache.org). Thijs Stalenhoef adds: There aren't really any APIs specifically for doing this. What do you want to do with the HTML-data after it has been converted to XML? If all you want to do is display it again using different style-sheets you should consider converting the HTML to XHTML. XHTML is simply an XML compliant form of HTML If you want to convert the HTML to XML compliant with a DTD or schema of your own making then doing it can pose many problems. It all depends on the HTML. Do all the HTML-files use the same "template"? Then it is possible to write a program to convert it. If they are all different it is probably easy to do it by hand.

Comments and alternative answers

convert HTML to XML Author: amit shukla (http://www.jguru.com/guru/viewbio.jsp?EID=870149), May 7, 2002 Hope this can help : public org.w3c.dom.Document executeXML(org.w3c.dom.Document request) { return _execute(request) ; } public org.w3c.dom.Document execute(HTTPServletRequest iRequest) { org.w3c.dom.Document request = iRequest.getRequestDoc(); return _execute(request) ; } public org.w3c.dom.Document _execute(org.w3c.dom.Document request) { String xml = this.execute(request); org.w3c.dom.Document response = parser.parse(xml); xml = null; return response; } if objective is for parsing HTML, JTIDY or JDK's HTML parser can be considered Author: Avani Shah (http://www.jguru.com/guru/viewbio.jsp?EID=28330), Jul 23, 2003 JTIDY is an open source and HTML parser is available in JDK1.4 (swing parser) The answer is JEDI Author: Daniel Matyas (http://www.jguru.com/guru/viewbio.jsp?EID=445610), Jan 20, 2005 JEDI - the most complex project solving this problem. http://www.ipsi.fraunhofer.de/oasys/projects/jedi/ Good luck Is there a way to run Tomcat under JView (Microsoft's Java VM)? Location: http://www.jguru.com/faq/view.jsp?EID=66180 Created: Jun 8, 2000 Modified: 2000-08-24 19:02:13.343 Author: Nicola Ken Barozzi (http://www.jguru.com/guru/viewbio.jsp?EID=39153) Question originally posed by Pramod Thuse (http://www.jguru.com/guru/viewbio.jsp?EID=44250 I found this answer at the Tomcat FAQ. Can Jakarta use Microsoft's JVM? ealtman Last Mod: 2000-03-27 01:55:47.0 Out of the box -- probably not unless MS started shipping the RMI classes. There's a little bit of RMI used in the admin of Tomcat. Other than that, it should run just fine. IBM has apparently packaged up the RMI classes missing from the Microsoft JVM and is distributing them at http://www.alphaworks.ibm.com/formula/RMI. Other options would be to get the RMI classes from Microsoft (although it is not clear they can be redistributed), or to download the JDK from Sun and manually grab just the RMI class, or just don't use the online administration tools that require RMI. How do I deal with multi-valued parameters in a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=71968 Created: Jun 10, 2000 Modified: 2000-06-17 17:12:16.352 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) Question

originally posed by stephen marshall (http://www.jguru.com/guru/viewbio.jsp?EID=53636 Instead of using getParameter() with the ServletRequest, as you would with singlevalued parameters, use the getParameterValues() method. This returns a String array (or null) containing all the values of the parameter requested. Comments and alternative answers

You can separate each value by a '|' inside a single... Author: Nexus6 Free (http://www.jguru.com/guru/viewbio.jsp?EID=12709), Jun 17, 2000 You can separate each value by a '|' inside a single input value tag !

You can split this value by a '|' ... How can I pass data retrieved from a database by a servlet to a JSP page? Location: http://www.jguru.com/faq/view.jsp?EID=73439 Created: Jun 12, 2000 Modified: 2000-08-14 11:16:49.756 Author: Govind Seshadri (http://www.jguru.com/guru/viewbio.jsp?EID=14) Question originally posed by senthil kumar (http://www.jguru.com/guru/viewbio.jsp?EID=57182 One of the better approaches for passing data retrieved from a servlet to a JSP is to use the Model 2 architecture as shown below:

Basically, you need to first design a bean which can act as a wrapper for storing the resultset returned by the database query within the servlet. Once the bean has been instantiated and initialized by invoking its setter methods by the servlet, it can be placed within the request object and forwarded to a display JSP page as follows: com.foo.dbBean bean = new com.foo.dbBean(); //call setters to initialize bean req.setAttribute("dbBean", bean); url="..."; //relative url for display jsp page ServletContext sc = getServletContext(); RequestDispatcher rd = sc.getRequestDispatcher(url); rd.forward(req, res); The bean can then be accessed within the JSP page via the useBean tag as: <jsp:useBean id="dbBean" class="com.foo.dbBean" scope="request"/> ... <% //iterate through the rows within dbBean and //access the values using a scriptlet %>

Also, it is best to design your application such that you avoid placing beans into the session unless absolutely necessary. Placing large objects within the session imposes a heavy burden on the performance of the servlet engine. Of course, there may be additional design considerations to take care of - especially if your servlets are running under a clustered or fault-tolerant architecture. Comments and alternative answers

We currently are not allowed to use beans at our site.... Author: Doug Weems (http://www.jguru.com/guru/viewbio.jsp?EID=69536), Jun 13, 2000 We currently are not allowed to use beans at our site. To communicate with servlets, we use something similiar to above code w/o the bean stuff. We pass information back and forth with the session object. It's clunky, but it works. If a servlet which does some significant task gets hit with enough concurrent users, it will eventually throw a java.lang.OutOfMemory exception. Is there a graceful way to handle/avoid this? Location: http://www.jguru.com/faq/view.jsp?EID=64889 Created: Jun 13, 2000 Modified: 2000-06-17 13:01:57.72 Author: Simon Wong (http://www.jguru.com/guru/viewbio.jsp?EID=44276) Question originally posed by J Majik (http://www.jguru.com/guru/viewbio.jsp?EID=61152 Because the initial memory occupied by the JVM is only 2Mb, you can assign more memory for the JVM such that the OutOfMemory Error won't occur. There is a non-standard parameter -Xmsn for the java launcher, where n is the multiple of 1024 greater than 2Mb. See http://java.sun.com/j2se/1.3/docs/tooldocs/win32/java.html for more about this option. Comments and alternative answers

Yes, but there is a limit that will be reached given... Author: J Majik (http://www.jguru.com/guru/viewbio.jsp?EID=61152), Jun 17, 2000 Yes, but there is a limit that will be reached given enough concurrent users, reguardless of what you set the max heap to (especially with something like XML parsing where a 150K document requires 7 MEGS of heap to process!). In that case, an OutOfMemory error occurs and potentially screws up many people's sessions. Would you have to catch the OutOfMemory error throughout your code? I'd like to think there's a more elegant solution... You can theoretically put try { ... } catch (OutO... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jun 17, 2000 You can theoretically put try { ... }

catch (OutOfMemoryError e) { // print appropriate error message, like "the server // is experiencing a lot of requests, please try // again later" }

in your doGet() routine. I don't see why an OOM would screw up other sessions, assuming the garbage collector works... You may also try calling System.gc() explicitly, which used to help back in JDK 1.0 days. How can I use a servlet to generate a site using frames? Location: http://www.jguru.com/faq/view.jsp?EID=69191 Created: Jun 14, 2000 Modified: 2000-06-14 23:14:45.768 Author: Vincent Cirel (http://www.jguru.com/guru/viewbio.jsp?EID=69061) Question originally posed by Susan P (http://www.jguru.com/guru/viewbio.jsp?EID=63595 In general, look at each frame as a unique document capable of sending its own requests and receiving its own responses. You can create a top servlet (say, FrameServlet) that upon invocation creates the frame layout you desire and sets the SRC parameters for the frame tags to be another servlet, a static page or any other legal value for SRC. ---------------------- SAMPLE ---------------------public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

response.setContentType("text/html"); PrintWriter out = new PrintWriter (response.getWriter()); out.println(""); out.println("Your Title"); // // // //

definingthe three rows of Frames for the main page top : frm_1 middle : frm_2 bottom : frm_3

out.println(""); out.println(""); out.println(""); out.println(""); out.println(""); out.println(""); out.println(""); out.close(); -------------------------- END -----------------------------------------Where MenuServlet and DummyServlet provide content and behavior for the frames generated by FrameServlet.

Hope this helps. Comments and alternative answers

See http://www.coolservlets.com/developer/tips/tip... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jun 14, 2000 See http://www.coolservlets.com/developer/tips/tip02.html But see Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 23, 2001 But see Why do Frames suck? for the reasons not to. From a servlet running in IIS under Windows, is it possible to kick off an rsh command to run a script on a remote UNIX machine? Location: http://www.jguru.com/faq/view.jsp?EID=69592 Created: Jun 14, 2000 Modified: 2000-06-14 13:41:34.172 Author: Vincent Cirel (http://www.jguru.com/guru/viewbio.jsp?EID=69061) Question originally posed by Augustine Wan (http://www.jguru.com/guru/viewbio.jsp?EID=28441 Just off the top of my head, the following (pseudo code) is how I'd stab at it; should point in the right direction anyway. If you want a response you'll need to create the corresponding DataInputStream.

import java.net.* //create a Socket object connected to port 514 (shell/cmd port used by rsh) Socket mySock = new Socket("destination host",514); //get the output stream for the socket DataOutputStream outStream; outStream = new DataOutputStream(mySock.getOutputStream()); //construct the command string String rshStr = "whatever command you want to send" //send it on its way outStream.writeBytes(rshStr); outStream.write(13);

outStream.write(10); outStream.flush(); This assumes you have rsh set up on the host and you send an appropriate username with the command if required. Hope this helps. Vincent Is there a way I can capture the output of a servlet, without immediately sending it to the client response stream? Location: http://www.jguru.com/faq/view.jsp?EID=75971 Created: Jun 14, 2000 Modified: 2000-10-16 13:10:44.361 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by stanley santiago (http://www.jguru.com/guru/viewbio.jsp?EID=70999 [In other words, I want to override/specify the response.getServletOutputStream(). To be even more specific, why is there not something like response.setServletOutputStream()?] The original design of servlets was rather simplistic; it conceived of a single request and a single response stream. As it evolved, it has added bits and pieces (like the RequestDispatcher) to allow more servlet-to-servlet communication, including, and forwarding, but it is still mostly inadequate to do things like filtering or capturing the output of another Servlet. Rumor has it that the next version of the Servlet specification will have explicit support for this, but until then, there are a number of solutions. The simplest solution is to use the URL class to initiate an HTTP connection from your servlet. Specify the URL of the target servlet, and capture the result from the URL's InputStream. See How can I include content from a URL, not from a local file? and How can I download files from a URL using HTTP?. Jason Hunter's CacheHttpServlet contains a class called CacheHttpResponse (and a corresponding CacheServletOutputStream) that saves all its output to a buffer. In theory, you can create one of these, and pass it into a RequestDispatcher's forward() or include() methods, then read the buffer when it's complete. You may have to massage some fields so they match the caller's ServletResponse. If anybody tries this, please let me know (submit a feedback)! Also, Resin has a feature called Servlet Filtering that may do what you want. See also • •

How can I daisy chain servlets together such that the output of one servlet serves as the input to the next? How do I capture a request and dispatch the exact request (with all the parameters received) to another URL?

Comments and alternative answers

HttpServletResponseWrapper Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 21, 2003 As of Servlet 2.3 spec, you can theoretically use HttpServletResponseWrapper and override it to capture data written to its output stream. I'd love to see source code demonstrating this, though. Do any commerical or free servlet containers currently support the retrieval of client and server certificates? Location: http://www.jguru.com/faq/view.jsp?EID=71670 Created: Jun 16, 2000 Modified: 2000-12-12 19:37:04.466 Author: Prasad Thammineni (http://www.jguru.com/guru/viewbio.jsp?EID=36479) Question originally posed by Len Norton (http://www.jguru.com/guru/viewbio.jsp?EID=37422 [The Servlet 2.2 spec seems to address this, mentioning that calling ServletRequest.getAttribute(String) with the attribute value javax.servlet.request.X509Certificate will return the client certificate. I presume it will be an instance of a subclass of java.security.cert.X509Certificate. Now what about the server certificate?] WebSphere Application Server 3.0+ supports retrieval of client certificates. Refer to http://www4.ibm.com/software/webservers/appserv/doc/v30/ae/web/doc/howto/itaccssl.html. Comments and alternative answers

Client authentication Author: Flavio Cesar (http://www.jguru.com/guru/viewbio.jsp?EID=488065), Aug 31, 2001 Do you have a sample source code doing client authentication through SSL ? What servlet engine have you tried ? Can you send me those examples to [email protected] ? Thanks Are there benchmarks available for the various servlet engines? Which one shows better performance on my favorite platform? Location: http://www.jguru.com/faq/view.jsp?EID=71682 Created: Jun 17, 2000 Modified: 2000-06-17 12:18:32.59 Author: Prasad Thammineni (http://www.jguru.com/guru/viewbio.jsp?EID=36479) Question originally posed by max headroom (http://www.jguru.com/guru/viewbio.jsp?EID=54255

Attached are two benchmarks. Use these benchmarks for informational purposes only and not for product selection. The list of servlet engines is not complete. You will see that WebSphere is notably missing from the benchmark. http://www.objexcel.com/workingjava.htm#Servlet Engine Performance http://www.mortbay.com/software/iX.html Comments and alternative answers

More current benchmarks Author: Marcel Offermans (http://www.jguru.com/guru/viewbio.jsp?EID=5070), Nov 21, 2001 Has anybody found any more recent benchmarks? The servlet engines mentioned have all been replaced by newer versions or products. Surely, somebody must still be doing benchmarks before deciding on a specific platform.

How to configure Nescape Enterprise Server to use a Resource Bundle (file.properties)? Location: http://www.jguru.com/faq/view.jsp?EID=71716 Created: Jun 17, 2000 Modified: 2000-06-17 12:19:36.854 Author: Prasad Thammineni (http://www.jguru.com/guru/viewbio.jsp?EID=36479) Question originally posed by sakesan k. (http://www.jguru.com/guru/viewbio.jsp?EID=50946 The file.properties file should be present in the same directory as the class file loading the properties. How can I specify which kind of cookies (single-session cookies or persistent cookies) I want to use ? Location: http://www.jguru.com/faq/view.jsp?EID=75969 Created: Jun 17, 2000 Modified: 2000-08-11 13:23:50.836 Author: Vincent Cirel (http://www.jguru.com/guru/viewbio.jsp?EID=69061) Question originally posed by Leonid Blokh (http://www.jguru.com/guru/viewbio.jsp?EID=64684 Refer to Sun's Servlet API Reference at http://java.sun.com/products/servlet/2.2/javadoc/ and take a look at Cookie class constructor and methods. In general: // create the cookie Cookie c = new Cookie("stringname","stringvalue"); // set Age c.setMaxAge((int)iAge);

// send it back with the HTTP response response.addCookie(c); • • •

Setting iAge < 0 indicates the default behavior of "death to the cookie upon browser exit" Setting iAge = 0 indicates that the browser should delete the cookie immediately. Setting iAge > 0 specifies the max age of the cookie before expiration (in seconds) = iAge

You could also use :

response.setHeader("Set-Cookie","name=value; expires=date"); where date = Wdy, DD-Mon-YYYY HH:MM:SS GMT (ie. Monday, 12-Jun-2000 17:24:00 GMT).

One reason I can think of where you might want to use the setHeader method is if you need to set an expiration date > 68.1 years future. The largest +(int) value allowed is 2147483647 or about 68.1 years. Note that in either case cookies are sent back using HTTP headers. Therefore, you should add them to the response BEFORE you send any content back to the browser. See also How do I setup a cookie to expire after a certain time? What is HTTP tunneling viz. RMI? Location: http://www.jguru.com/faq/view.jsp?EID=77164 Created: Jun 17, 2000 Modified: 2000-06-21 13:59:18.491 Author: Suja Rao (http://www.jguru.com/guru/viewbio.jsp?EID=62310) Question originally posed by Nagaraj Sivashanmugam (http://www.jguru.com/guru/viewbio.jsp?EID=11016 HTTP tunneling is a method that RMI uses to make calls through a local firewall. To get across firewalls, which disallow regular outbound TCP connections but permit HTTP through a proxy server, RMI makes use of HTTP tunneling by encapsulating the RMI calls within an HTTP POST request. The reply too is sent back as HTTPencapsulated data. Comments and alternative answers

How is this done ? Author: Klearhos Klearhou (http://www.jguru.com/guru/viewbio.jsp?EID=540399), Jul 7, 2002 How somebody could implement that ? Assuming he already has an HTTP server (that is probably needed). What is HTTP tunneling, in the general sense? Location: http://www.jguru.com/faq/view.jsp?EID=74588

Created: Jun 17, 2000 Modified: 2000-06-21 14:00:02.888 Author: Prasad Thammineni (http://www.jguru.com/guru/viewbio.jsp?EID=36479) Question originally posed by Nagaraj Sivashanmugam (http://www.jguru.com/guru/viewbio.jsp?EID=11016 HTTP tunneling is a general technique whereby arbitrary data may be sent via an HTTP connection to and from CGI scripts or Java Servlets on a Web server. This is done by serializing the data to be transmitted into a stream of bytes, and sending an HTTP message with content type "application/octet-stream". HTTP tunneling is also referred to as Firewall tunneling. Refer to: • •

"HTTP Tunneling" for an illustrated example in Java. "Firewall Tunneling" for an example of a Java Client connecting to a Java server through a firewall/proxy.

See also this question in the RMI FAQ. Comments and alternative answers

See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jun 23, 2001 See also: Re: What is HTTP Tunneling?Why servlets are a bett... RE: What is HTTP tunneling, in the general sense? Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985), Jun 24, 2001 Hello, Suppose your computer is behind a firewall but HTTP connection is allowed and is made through a proxy server. This is a common scenario, isn't that? You can use the HTTP Tunneling to connect outside the firewall thru the proxy. Example: why you are able to connect with you browser to http://www.somehost.com:8080 if just HTTP port (80) is allowed by the firewall? It's done thru HTTP tunelling: your browser sends to the proxy an HTTP connection request like this: CONNECT www.somehost.com:8080 HTTP/1.0 User-agent: Mozilla/1.1N

then the proxy tunnels the request via HTTP protocol to port 8080 of www.somehost.com and enstablishes the connection. The proxy can response something like: HTTP/1.0 200 Connection established Proxy-agent: Netscape-Proxy/1.1

200 is the code saying "ok"; if it's <> 200 the connection is not enstablished. This works just fine for other ports and protocols.

Regards, Luigi. How do I start with servlets using Microsoft IIS and Windows NT? Location: http://www.jguru.com/faq/view.jsp?EID=74589 Created: Jun 17, 2000 Modified: 2000-08-24 19:00:58.142 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Emilian Luca (http://www.jguru.com/guru/viewbio.jsp?EID=68127 Many servlet engines exist as plugins to IIS. Tomcat and JRun seem to be the most popular. See • •

How do I use the DLLs from Tomcat to Servlet-enable IIS? Can I use Tomcat or JavaWebServer as a service on NT?

Comments and alternative answers

Also refer to the recently published article at Use... Author: Prasad Thammineni (http://www.jguru.com/guru/viewbio.jsp?EID=36479), Jun 21, 2000 Also refer to the recently published article at Use Microsoft's Internet Information Server as a Java servlet engine Re: Also refer to the recently published article at Use... Author: warrell HARRIES (http://www.jguru.com/guru/viewbio.jsp?EID=318121), Apr 4, 2001 Where is this article!!!! I have followed the instructions to the letter and can't get it working!!! Since the HttpSession object is stored in VM heap memory, is there a limit to number or size of the HttpSession objects on the server? Location: http://www.jguru.com/faq/view.jsp?EID=75823 Created: Jun 17, 2000 Modified: 2000-06-17 16:43:23.495 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Amit Singh (http://www.jguru.com/guru/viewbio.jsp?EID=68394 Yes, obviously, since session objects are stored in RAM, they are dependent on the amount of RAM installed on your server machine, and the RAM allocated to the servlet engine VM. See this FAQ for more information on avoiding OutOfMemory errors. How do I "load balance" my application? That is, I want to redirect the user to another server if the number of users is over a threshold. Location: http://www.jguru.com/faq/view.jsp?EID=74630

Created: Jun 17, 2000 Modified: 2000-09-28 19:42:11.599 Author: Prasad Thammineni (http://www.jguru.com/guru/viewbio.jsp?EID=36479) Question originally posed by Anand Naik (http://www.jguru.com/guru/viewbio.jsp?EID=44857 To implement the basic HTTP request load balancing you would need a load balancer like CISCO Director (hardware based) or IBM WebSphere Network Dispatcher(software based). Implementing a load balancer would allow you to spray HTTP requests across multiple Web Server/Servlet Engines (node) within a cluster. If using Servlet Sessions make sure that you configure the load balancer for stickiness. Stickiness guarantees that all requests from a client are delivered to the same Servlet Engine. Also, if you want to guarantee that your session data survives node failures you have to persistent your session state to a shared database and reconstruct it in case of failure. Advanced Servlet Engines like IBM WebSphere Application Server Adv. Edition support persistent sessions out of the box, whereas Java Web Server does not. See also http://www.jguru.com/jguru/faq/view.jsp?EID=44035 and http://www.jguru.com/jguru/faq/view.jsp?EID=46481 How can I do load balancing using Java Web Server? Location: http://www.jguru.com/faq/view.jsp?EID=74624 Created: Jun 17, 2000 Modified: 2000-06-17 16:48:55.052 Author: Prasad Thammineni (http://www.jguru.com/guru/viewbio.jsp?EID=36479) Question originally posed by Anand Naik (http://www.jguru.com/guru/viewbio.jsp?EID=44857 Beyond simple HTTP request load balancing you cannot implement advanced load balancing capabilities with Java Web Server. See How do I "load balance" my application? for more information. How do I pick up the attachment from the client's machine, in a web-based email system? Location: http://www.jguru.com/faq/view.jsp?EID=81033 Created: Jun 20, 2000 Modified: 2001-07-23 10:50:29.979 Author: Andrea Pompili (http://www.jguru.com/guru/viewbio.jsp?EID=51802) Question originally posed by John Zukowski PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=7 You can do it using an HTML form, a Servlet and the class MultipartRequest of the O'Reilly package avaiable at http://www.servlets.com/resources/com.oreilly.servlet/. In this zip file (named cos.zip) you can found all the information you need to upload a file using a browser and a servlet. Remember that the file you upload is stored in the server filesystem, so remember to remove it after sending your E-mail. I tried also another way that worked perfectly, but is more complicated. I wrote three classes :

• • •

A mine DataSource for handling a stream of byte with a filename and a content type An ExtendedMultipartRequest class that extracts the parts from the stream of the Servlet (similar to the one provided by O'Reilly) A MultipartInputStream for reading the InputStream of the servlet line by line

For creating a message I passed each data (bytes), content-type, and filename parsed by my ExtendedMultipartRequest class to my DataSource. Then I built a DataHandler using this DS and a Message using this as Content... It worked perfectly!!! Comments and alternative answers

See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 23, 2001 See also How do I upload a file to my servlet? and the topic Servlets:Files:Uploading How do I handle FORMs with multiple form elements (e.g. radio buttons) using the same name? Location: http://www.jguru.com/faq/view.jsp?EID=82970 Created: Jun 21, 2000 Modified: 2000-07-06 12:33:06.353 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Morgan Sheets (http://www.jguru.com/guru/viewbio.jsp?EID=51204 For radio buttons, the HTML spec assumes that a given group of buttons will have the same NAME and different VALUEs; the browser makes sure that only one button per group name will be selected (at most). So you can just call request.getParameter("groupname").

Cheese Pepperoni Anchovies If the user selects "Pepperoni" then request.getParameter("topping") will return the string "pepperoni". For lists using the <select multiple> FORM tag, multiple values can be returned for the same parameter name. When that can happen, use request.getParameterValues("param") which returns a String[] you can iterate through. It's bad form (so to speak), but you can also duplicate other element types, like

Name 1: Name 2: These also get returned in an array by request.getParameterValues(). See http://hotwired.lycos.com/webmonkey/99/30/index4a.html for a good tutorial on HTML FORMs. How can I take advantage of introspection and have a servlet process the entire form like I can using the JSP directive <jsp:setProperty name="formHandler" property="*"/> ? Location: http://www.jguru.com/faq/view.jsp?EID=86920 Created: Jun 25, 2000 Modified: 2000-06-25 14:30:23.972 Author: Govind Seshadri (http://www.jguru.com/guru/viewbio.jsp?EID=14) You can make use of the HttpUtils class to gain similar introspective functionality within servlets. It may not be as elegant as the introspection feature provided by the servlet engine when using JSPs, but still, it works fine. For example, let's assume that you've created your form as: Value1 Value2 Value3 You can automagically create a Hashtable object from the parsed key-value pairs of the POSTed data within doPost() of the servlet via the following snippet:

Hashtable h = HttpUtils.parsePostData(request.getContentLength(),request.getInputStre am()); String[] one = (String[])h.get("one"); String[] two = (String[])h.get("two"); String[] three = (String[])h.get("three"); //print out the value of 1st input element pw.println("

One: "+one[0]+"

"); //print out the value of 2nd input element pw.println("

Two: "+two[0]+"

"); //print out the value of 3rd input element

pw.println("

Three: "+three[0]+"

"); Comments and alternative answers

Great for early servlets Author: John Hollingsworth (http://www.jguru.com/guru/viewbio.jsp?EID=487396), Aug 30, 2001 ...but how do I use this with J2EE 1.3 without getting a deprication warning? HttpUtils is a depricated object now.... Re: Great for early servlets Author: Gundluri Manjula (http://www.jguru.com/guru/viewbio.jsp?EID=1047986), Jan 22, 2003 We can use request.getParameterNames() which will return Enumeration of element names in the page for example we have created the form Page1.jsp page2.jsp

The result of this form will be the values entered in the previous form How do I separate presentation (HTML) from business logic (Java) when using servlets? Location: http://www.jguru.com/faq/view.jsp?EID=91180 Created: Jun 29, 2000 Modified: 2001-01-15 08:28:54.918 Author: Joe Morse (http://www.jguru.com/guru/viewbio.jsp?EID=91113) Almost anybody who has ever written a servlet can identify with this one. We all know it's bad for to embed HTML code in our java source; it's lame to have to recompile and re-deploy every time you want an HTML element to look a bit different. But what are our choices here? There are two basic options; 1. Use JSP: Java Server Pages allows you to embed Java code or the results of a servlet into your HTML. You could, for instance, define a servlet that gives a stock quote, then use the <servlet> tag in a JSP page to embed the output. But then, this brings up the same problem; without discipline, your content/presentation and program logic are again meshed. I think the ideal here is to completely separate the two. 2. Use a templating/parsing system: Hmm...I know you're about to rant about re-inventing the wheel, but it's not that bad (see below). Plus, it really does pay to take this approach; you can have a group of programmers working on the Java code, and a group of HTML producers maintaining the interface. So now you probably want to know how to do it...so read on. Use SSI! Remember SSI? It hasn't gotten much attention in recent years because of embeddable scripting languages like ASP and JSP, but it still remains a viable option. To leverage it in the servlet world, I believe the best way is to use an API called SSI for Java from Areane. This API will let you emulate SSI commands from a templating system, and much more. It will let you execute any command on any system, including executing java classes! It also comes with several utility classes for creating stateful HTML form elements, tables for use with iteration, and much more. It's also open source, so it's free and you can tweak it to your heart's content! You can read the SSI for Java documentation for detailed info, but the following is an example of its use. Here's the servlet: import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import java.util.*; import com.areane.www.ssi.*; public class SSITemplatingServlet extends HttpServlet { private String templateFilesDirectory = "d:\\projects\\idemo\\templates\\"; //Holds path to template files /**Handles GET requests; defers every request to the POST processor*/ public void doGet(HttpServletRequest req, HttpServletResponse res)

throws ServletException, IOException, FileNotFoundException {doPost(req, res);} /**Handles all requests. Processes the request, *saves the values, parses the file, then feeds the file to the out stream*/ public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException, FileNotFoundException { HttpSession ses = req.getSession(true); Properties context = null; if((context = (Properties)ses.getValue("user.context")) == null) { //if properties doesn't already exist, create it. context = new Properties(); } //Write parameters to Properties object Enumeration paramNames = req.getParameterNames(); String curName, curVal; while(paramNames.hasMoreElements()) { curName = (String)paramNames.nextElement(); curVal = req.getParameter(curName); context.setProperty(curName, curVal); } //Save the values to the session ses.putValue("user.context", context); //Parse the page and stream to the client String templateName = req.getParameter("template"); // Get the file name of the template to use res.setContentType("text/html"); SsiPage page = SsiParser.parse(this.templateFilesDirectory + templateName); //Parsing occurs here page.write(res.getWriter(), context); //Stream to the client }

page = null; //clean up

} Now, just create a template file, pass the servlet the template file name, and have at it! Comments and alternative answers

Don't be afraid of using ONLY servlets! If you want... Author: Yakov Sirotkin (http://www.jguru.com/guru/viewbio.jsp?EID=6342), Jul 6, 2000 Don't be afraid of using ONLY servlets! If you want to separate html-code and logic you can just put them in different classes.

But in my opinion this solution is reasonable only if different people are working on html-code and logic. But even if one man is doing all the job html-code generation and logic MUST be separated in different procedures. I have found a good article about this subject in ... Author: Ze'ev B (http://www.jguru.com/guru/viewbio.jsp?EID=2224), Dec 2, 2000 I have found a good article about this subject in JavaWorld called "Solve your servletbased presentation problems" at http://www.javaworld.com/javaworld/jw-11-2000/jw1103-presentation.html We have been using webmacro, wich is a free templa... Author: ido ido (http://www.jguru.com/guru/viewbio.jsp?EID=291815), Jan 3, 2001 We have been using webmacro, wich is a free templating/parsing system. It works realy well. All of your html files are seperate from the servlet. The home page is www.webmacro.org. Hope this helps. A great new "third way" solution -- with... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 15, 2001 A great new "third way" solution -- with templates on one side, and servlets on the other -- is XMLC. Faced with the problem of separating presentation from code, XMLC takes the radical step of... (drumroll please...) actually separating the presentation from the code! The presentation "layer" is literally an HTML file. The code "layer" is a servlet (or any Java class) that reaches into the HTML file and changes its content, based on "ID" attributes embedded inside the HTML tags. (The way it accomplishes this is by compiling the HTML file into a Java class and data structure, but that's almost beside the point.) Use XML ... Author: Angus McDonald (http://www.jguru.com/guru/viewbio.jsp?EID=476304), Aug 14, 2001 The simplest way we have found to do just this is to use XML/XSLT. The servlet creates XML documents - only. Your business logic specifies what these XML documents look like (essentially the changing business data on a page). Associate this XML document with an XSLT (XSL Transformation language) file. Have an XML parser apply the XSLT stylesheet to the file and produce an XHTML file. This is served to the browser as HTML. You place all static image tags, text and table constructs in the XSLT file (it takes a little learning but you can easily create dynamic tables with this). Visit www.xml.com for some ideas about how to do this.

Re: Use XML ... Author: Tripp Lilley (http://www.jguru.com/guru/viewbio.jsp?EID=1743), Jun 10, 2004 The purist in my likes this solution, but the pragmatist in me points out that part of the reason for the proliferation of "raw HTML"-based templating systems is the fact that designers just plain like working in what they're used to: HTML. XMLC, which Alex mentions above, sounds fantastic, inasmuch as it lets designers work in tools that only know HTML (but know it well,) so long as those tools can assign id attributes (which they dang well better be able to!) Besides, there's no reason your app can't spit out XML then run it through XMLC, so that you have the best of both worlds. You have pure, clean XML on tap for when you want to do some transformation (XSL-FO, anyone?,) but your basic, bread-and-butter HTML templating is about as native as you can get.

For an HTML FORM with multiple SUBMIT buttons, how can a servlet respond differently for each button? Location: http://www.jguru.com/faq/view.jsp?EID=87441 Created: Jun 29, 2000 Modified: 2000-06-29 16:54:48.087 Author: Richard Raszka (http://www.jguru.com/guru/viewbio.jsp?EID=7963) Question originally posed by Shubham Mehta (http://www.jguru.com/guru/viewbio.jsp?EID=85149 The servlet will respond differently for each button based on the html that you have placed in the HTML page. Let's explain. For a submit button the HTML looks like . A servlet could extract the value of this submit by using the getParameter("Left") from the HttpRequest object. It follows then that if you have HTML within a FORM that appears as:
type=submit type=submit type=submit type=submit

name="Direction" name="Direction" name="Direction" name="Direction"

value="left">
value="right">
value="up">
value="down">

Then the getParameter("Direction") from the HttpRequest would extract the value pressed by the user, either "left", "right", "up" or "down". A simple comparision in the servlet with the these values could occur and processing based on the submit button would be performed. Similiarly,for submit buttons with different names on a page, each of these values could be extracted using the getParameter() call and acted on. However, in a situation where there are multiple buttons, common practice would be to use one name and multiple values to identify the button pressed.

Comments and alternative answers

Doesn't work with images Author: Rob Ellis (http://www.jguru.com/guru/viewbio.jsp?EID=532765), Jan 6, 2002 This doesn't seem to work for submissions using type=image. The only way I have found of doing this is to use plain old images with onClick events firing javascript which will amend the submission URL with a parameter indicating the different image clicked. Plain the backside, but it works. Re: Doesn't work with images Author: Damon Anderson (http://www.jguru.com/guru/viewbio.jsp?EID=775042), Feb 27, 2002 It still works with TYPE=IMAGE, just a little bit differently. Given:

The browser submits foo.x=_x and foo.y=_y, (_x,_y) being the coordinates in the image where the mouse click occurred. This does mean that you can't have multiple TYPE=IMAGE buttons and branch on the VALUE=, so what I do is assign a different NAME= to each button and parse it. Example:
TYPE=IMAGE TYPE=IMAGE TYPE=IMAGE TYPE=IMAGE

NAME="_go_left" SRC="left.gif"> NAME="_go_right" SRC="right.gif"> NAME="_go_up" SRC="up.gif"> NAME="_go_down" SRC="down.gif">

... Enumeration params = request.getParameterNames(); while (params.hasMoreElements()) { String param = (String)params.nextElement(); if (param.startsWith("_go_")) { String direction = param.substring("_go_".length()); }

// ...

}

(Untested, this is just off the top of my head.)

Re[2]: Doesn't work with images

Author: Damon Anderson (http://www.jguru.com/guru/viewbio.jsp?EID=775042), Feb 27, 2002 Sorry, you also need to check for the ".x" and ".y" suffix and remove/ignore it, obviously. With that addition, this technique has worked pretty well for me. I use it for servlet dispatching, and it works with both TYPE=SUBMIT and TYPE=IMAGE without any backend changes. (It also avoids having to change any Java code when the HTML designer decides to change VALUE="Submit" to VALUE="Save".) Re: Doesn't work with images Author: Harsh Sugandhi (http://www.jguru.com/guru/viewbio.jsp?EID=401509), May 2, 2002 Well you can do it by javascript. What you have to do for this is write a Javascript like this: <script Language="JavaScript"> function changeAction(aForm,aButtonName) { if(aButtonName == "A") aForm.action = A.html else if(aButtonName == "B") aForm.action = B.html else aForm.action = C.html }

Enjoy. Harsh. Is it possible to use the method ServletContext.getRequestDispatcher() to ascertain the presence or the absence of a server resource? Location: http://www.jguru.com/faq/view.jsp?EID=92548 Created: Jul 3, 2000 Modified: 2000-07-03 14:47:26.801 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) Some examples of servlets in the community literature seem to suggest that ServletContext.getRequestDispatcher() could be used to determine the presence or the absence of a server resource. But the truth of the matter is that it cannot.

In what follows, I will first mention an example that is posted at a tutorial at the Java Developer Connection that could potentially create this wrong impression about the return value of ServletContext.getRequestDispatcher(). I'll then show a simple servlet that someone just beginning with servlets could find useful for testing this method. The otherwise very instructive servlet code for the Duke's BooksStore example at Java Developer Connection has the following code fragment for BookStoreServlet.java:

RequestDispatcher dispatcher = getServletContext().getRequestDispatcher( ....some server resource ...); if (dispatcher == null) { System.out.println("There was no dispatcher"); // No dispatcher means the html file could not be found. response.sendError(response.SC_NO_CONTENT); } else { System.out.println("There is a dispatcher"); HttpSession session = request.getSession(); dispatcher.forward(request, response); } The manner in which the value of dispatcher is tested and the comment that follows definitely create the impression that the return value of ServletContext.getRequestDispatcher() could be used to determine whether the server resource supplied as the argument to the method is actually present at its specified location. You can use the following servlet to verify that the return value of ServletContext.getRequestDispatcher() is non-null regardless of the presence or the absence of the html file that is mentioned as the argument to the method. In either case, the message "There is a dispatcher" will be printed out in the window in which the servlet engine is running.

import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class CheckDispatcherServlet extends HttpServlet { public void service (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { RequestDispatcher dispatcher = getServletContext().getRequestDispatcher( "/servlets/nonExistentFile.html"); // for Tomcat3.1

// Tomcat3.1 // jsdk2.1

"/servlets/welcome.html");

// for

"/WEB-INF/servlets/nonExistentFile.html");

// for

System.out.println( "" + dispatcher ); if (dispatcher == null) { System.out.println("There was no dispatcher"); response.sendError(response.SC_NO_CONTENT); } else { System.out.println("There is a dispatcher"); dispatcher.forward(request, response); }

} }

The lines that are commented out are for verifying that the servlet does indeed work for a file that is actually present at the specified location. If you are just starting out with servlets, the following additional comments might be helpful. (These comments apply specifically to a Windows NT environment.) • • • •

For Tomcat3.1, I have placed this servlet in the following directory C:\tomcat\webapps\avi-servlets\WEB-INF\classes\

where avi-servlets is a directory that I created for some servlets. • • • • • • • •

For jsdk2.1, I put this servlet in C:\jsdk2.1\avi-servlets\WEB-INF\servlets\ Since Tomcat3.1 is not allowed to serve any files under WEB-INF, the "welcome.html" resource file in the commented out line in the code sits in the directory C:\tomcat\webapps\avi-servlets\servlets\

whereas for jsdk2.1, it can sit in the same directory as the servlet. What is "hot deployment" in WebLogic? Location: http://www.jguru.com/faq/view.jsp?EID=97622 Created: Jul 6, 2000 Modified: 2000-07-06 12:37:25.632 Author: Keith Schwartz (http://www.jguru.com/guru/viewbio.jsp?EID=27189) Question originally posed by rajasekhar pokuri (http://www.jguru.com/guru/viewbio.jsp?EID=81912

"Hot Deployment" in weblogic is the act of deploying, re-depolying, and un-deploying EJBs while the server is still running (you don't have to shutdown the server to deploy an EJB). see: http://www.weblogic.com/docs51/classdocs/API_ejb/EJB_deployover.html#1054622 Comments and alternative answers

Also, the beans that are "Hot Deployed" are... Author: Anoop Sehdev (http://www.jguru.com/guru/viewbio.jsp?EID=208040), Sep 17, 2000 Also, the beans that are "Hot Deployed" are not retained when the server is restarted. To retain the bean, it's entry has to be made in the weblogic.properties file. Regards Anoop Sehdev What is meant by the term "business logic"? Location: http://www.jguru.com/faq/view.jsp?EID=97696 Created: Jul 6, 2000 Modified: 2000-07-06 13:17:00.956 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Ramkumar Krishnamurthy (http://www.jguru.com/guru/viewbio.jsp?EID=89709 "Business logic" is just a fancy way of saying "code." :-) More precisely, in a three-tier architecture, business logic is any code that is not specifically related to storing and retrieving data (that's "data storage code"), or to formatting data for display to the user (that's "presentation logic"). It makes sense, for many reasons, to store this business logic in separate objects; the middle tier comprises these objects. However, the divisions between the three layers are often blurry, and business logic is more of an ideal than a reality in most programs. The main point of the term is, you want somewhere to store the logic and "business rules" (another buzzword) of your application, while keeping the division between tiers clear and clean. Can an EJB handle (RMI remote reference) be stored in an HttpSession? Location: http://www.jguru.com/faq/view.jsp?EID=97963 Created: Jul 7, 2000 Modified: 2000-07-09 06:39:45.243 Author: David Garcia (http://www.jguru.com/guru/viewbio.jsp?EID=17915) Question originally posed by David Garcia (http://www.jguru.com/guru/viewbio.jsp?EID=17915 [Note: My HttpSessions are persistent (disk swap), so if the handle is not serializable I will have troubles when the HttpSession is restored. ] Test result: I have used the handle for locating local and remote EJB. I have no problem about storing the handle inside the HttpSession and swapping the HttpSession. However if

some problem arise about the swap of the HttpSession, you may could keep the HttpSession in memory. Test conditions: BEA Weblogic 4.5.1 (uses EJB 1.0 and allow keep HttpSessions in memory). Windows NT 4.0 Observations: I'm a little surprised about the test since I keep in mind that handles could only be used for locating local EJB's not remote ones (wrong?). Comments and alternative answers

You can refer to the url below for more info and a... Author: kishore_k_v k (http://www.jguru.com/guru/viewbio.jsp?EID=202022), Sep 11, 2000 You can refer to the url below for more info and a clear picture on this topic although i think you know the answers. http://www.weblogic.com/docs51/classdocs/API_ejb/EJB_design.html#1022000 To offer printing from an applet in order to print on the client computer, is the only good solution to have a print servlet and upload the print file from the applet to the servlet and then download the print file back to the client browser? Location: http://www.jguru.com/faq/view.jsp?EID=98857 Created: Jul 9, 2000 Modified: 2000-07-13 08:33:35.487 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by ananda bagley (http://www.jguru.com/guru/viewbio.jsp?EID=75027 Yes!

:-)

That reminds me of a riddle: Q: Did the chicken cross the road to get to the other side? A: Yes. (Feel free to submit feedback containing code and advice for how to do this printing thing properly.) Comments and alternative answers

A few other possibilities that come to mind are: Set... Author: Andre van Dalen (http://www.jguru.com/guru/viewbio.jsp?EID=7570), Jul 17, 2000 A few other possibilities that come to mind are:

•

• •

Set the MAYSCRIPT parameter in your applet tag and call a JavaScript subroutine with the data you want to get printed / shown. The javascript subroutine can then write that data into a frame to get it printed. See this FAQ for a code example. Copy the data onto the clipboard and have the user or some JavaScript paste it before printing it. Have a servlet generate the document based on parameters posted by the applet

Another option is print from the applet using the ... Author: delfim martins (http://www.jguru.com/guru/viewbio.jsp?EID=9614), Jul 21, 2000 Another option is print from the applet using the PrintJob. The only disadvantage is that you will have to sign the applet and the user will have to trust you. However, with this method you have full control of what is going to the printer. How do I get the Duke's Bookstore servlet example at the Java Developer Connection to work under Servlet API version 2.2 (and Tomcat 3.1)? Location: http://www.jguru.com/faq/view.jsp?EID=98986 Created: Jul 9, 2000 Modified: 2000-07-10 12:39:58.58 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) The Duke's Bookstore example at the Java Developer Connection is indeed very instructive. As currently posted, this example works for JSDK 2.1. To get it to work under Tomcat 3.1, which uses the Servlet API 2.2, you'd need to make the following changes: In the override definitions of the doGet(HttpServletRequest, HttpServletResponse) method in the files CatalogServlet.java, ShowCartServlet.java, Cashier.servlet, BookDetailServlet.java, and in the override definition of the doPost(HttpServletRequest, HttpServletResponse) method in the file ReceiptServlet.java, replace the invocation

ShoppingCart cart = (ShoppingCart)session.getValue(session.getId()); by ShoppingCart cart = (ShoppingCart)session.getAttribute(session.getId()); and the invocation session.putValue(session.getId(), cart);

by session.setAttribute(session.getId(), cart); The methods getValue(String) and putValue(String, Object) declared for the HttpSession interface have been deprecated in the Servlet2.2 API and replaced by the getAttribute(String) and setAttribute(String, Object) methods. Some of the other changes you'd need to make depend on how and where you install the code in Tomcat3.1. For example, I have installed the code in a directory called bookstore under C:\tomcat\webapps\. I put all the servlets and the support classes in C:\tomcat\webapps\bookstore\WEB-INF\classes\ and the html page bookstore.html in C:\tomcat\webapps\bookstore\servlets\. The resulting pathnames to the servlets and the html page would need to be reflected in the code. Is there any way to get a session object when knowing the session id? Location: http://www.jguru.com/faq/view.jsp?EID=99348 Created: Jul 10, 2000 Modified: 2001-02-25 17:06:26.808 Author: David Garcia (http://www.jguru.com/guru/viewbio.jsp?EID=17915) Question originally posed by Herve Devos (http://www.jguru.com/guru/viewbio.jsp?EID=88981 This would be useful for reattaching a user to a preexisting session. [Unfortunately, this behavior has been deemed dangerous. The code below used to work, but has been deprecated as of Servlet API version 2.1. (The method HttpSessionContext.getSession(String sessionid) has been deprecated.) There may be a way to make it work under certain servlet engines, but no portable/standard way that I know of. -Alex] Code sample: // first, store the target HttpSession id, no problems about this cause the id is a Serializable String object HttpSession oldSesion=request.getSession(false); String id=oldSesion.getId(); database.storeID(id); // next, maybe in another servlet or object // recover target ID String idOldSesion=database.recoverID(); // recover target HttpSession HttpSession currentSesion=request.getSession(false); HttpSessionContext sCtx=currentSesion.getSessionContext(); HttpSession recoveredOldSesion=sCtx.getSession(idOldSesion); Test conditions: BEA Weblogic 4.5.1 (uses httpServlet Specification 2.1 ). Windows NT 4.0

How can I explicitly unload a servlet or call the destroy method? Location: http://www.jguru.com/faq/view.jsp?EID=99949 Created: Jul 11, 2000 Modified: 2000-07-11 14:56:23.115 Author: Oliver Springauf (http://www.jguru.com/guru/viewbio.jsp?EID=32379) Question originally posed by Shardul Joshi (http://www.jguru.com/guru/viewbio.jsp?EID=13401 In general, you can't. The Servlet API does not specify when a servlet is unloaded or how the destroy method is called. Your servlet engine (ie the implementation of the interfaces in the JSDK) might provide a way to do this, probably through its administration interface/tool (like Webshpere or JWS). Most servlet engines will also destroy and reload your servlet if they see that the class file(s) have been modified. Can JRun be configured so that it converts GET or POST parameters encoded in UTF-8 correctly into Unicode for use in the Java servlet? Location: http://www.jguru.com/faq/view.jsp?EID=100767 Created: Jul 12, 2000 Modified: 2000-07-18 02:55:27.27 Author: Andy Malakov (http://www.jguru.com/guru/viewbio.jsp?EID=89102) Question originally posed by Frank Renftle (http://www.jguru.com/guru/viewbio.jsp?EID=94444 Try to add

-Dfile.encoding=UTF8

to Java arguments in JRun administrator. [Are you sure this works? It does set a system property, but there's no a priori guarantee JRun will be smart enough to use it to change its interpretation of UTF-8 parameters. Furthermore, as I understand it, there's a definite ambiguity or flaw in the HTTP spec, and extended character sets are not necessarily legal as CGI parameters. HTML-escaped values are, so you must use { format. But some browsers do send raw non-ASCII characters, so it's a serious problem. -Alex] How can I generate special responses for WebTV users from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=102571 Created: Jul 14, 2000 Modified: 2000-07-15 08:39:19.212 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) If getHeader("User-Agent") returns "WebTV", then your client is using a WebTV browser and you can customize the display accordingly. Can I use Basic HTTP Authentication using Apache+JServ? Location: http://www.jguru.com/faq/view.jsp?EID=103759 Created: Jul 17, 2000 Modified: 2000-07-21 19:19:08.246 Author: Joshua Lynch (http://www.jguru.com/guru/viewbio.jsp?EID=103303) Question originally posed by Mike Reedy (http://www.jguru.com/guru/viewbio.jsp?EID=98127 I recently did this with Apache and Tomcat. Using Basic HTTP Authentication is an Apache function, so this method should work with Apache and any servlet engine. Different web servers will, of course, work differently.

If you haven't already done so, read the Apache FAQ about authentication (section G) at apache.org, especially QA G.2. Also read the Apache Week article referenced there (http://www.apacheweek.com/issues/96-10-18#userauth). These resources will give you a good idea about how Apache can be configured to restrict access to URL's. Neither one explicitly tells you how to use authentication with servlets, so I'll spell it out here. Use the directive to indicate to Apache that your specific servlet URL or servlet URL prefix (for multiple servlets) can be accessed only by authenticated users. The following template should be added to one of the Apache configuration files (such as http.conf) with appropriate substitutions for your system:

AuthName "your realm" AuthType Basic AuthUserFile /your/user/file require valid-user This directive tells Apache to restrict access to the specified URL, so don't use the filesystem path to your servlet. Use the servlet's URL. You will also need to create a user file with htpasswd. See the Apache Week article for details. Comments and alternative answers

See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 16, 2001 How do I assign basic authentication on Tomcat + A... Can I call a CGI script from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=104987 Created: Jul 18, 2000 Modified: 2000-07-19 20:31:41.242 Author: Shirish Bathe (http://www.jguru.com/guru/viewbio.jsp?EID=88588) Question originally posed by anshu shah (http://www.jguru.com/guru/viewbio.jsp?EID=88223 [The following example works if the script is located behind a web server (either remote, or running on the same machine). But if you're using a standalone Java web server, and want to run (e.g.) a Perl CGI, is there any way to use System.exec() to invoke the script with the correct parameters? -Alex] Yes, you can call CGI Script from a servlet. You can write your servlet as if it is sending data from browser. (Either using POST/ GET Method) public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { response.setContentType("text/html");

PrintWriter out = response.getWriter(); try{ // Put you URL/CGI here !!! URL url = new URL("http://localhost:8080/CgiRedir"); URLConnection connection = url.openConnection(); connection.setDoOutput(true); PrintStream outStream = new PrintStream(connection.getOutputStream()); //Sending parameter to URL/CGI outStream.println("dataname=" + URLEncoder.encode("Shirish")+"&datavalue=" + URLEncoder.encode("Bathe")); //outStream.println("dataname=Shirish&datavalue=Bathe"); outStream.flush(); outStream.close(); // reading from URL DataInputStream inStream; String inputLine; inStream = new DataInputStream(connection.getInputStream()); while (null != (inputLine = inStream.readLine())) { //System.out.println(inputLine); out.println(inputLine); } inStream.close(); } catch (MalformedURLException me) { System.err.println("MalformedURLException: " + me); } catch (IOException ioe) { System.err.println("IOException: " + ioe); } For detail please visit : http://java.sun.com/docs/books/tutorial/networking/urls/readingWriting.html. Hope this will solve your problem. Comments and alternative answers

What if the call from the servlet to the CGI is not... Author: Pat Hong (http://www.jguru.com/guru/viewbio.jsp?EID=222295), Oct 4, 2000 What if the call from the servlet to the CGI is not a simple URL call, but a call to a perl module (in CGI)? And vise versa? Here's a servlet wrapper that makes it easy. Author: Roger Hand (http://www.jguru.com/guru/viewbio.jsp?EID=292314), Jun 14, 2001 Some of the code provided above has been deprecated. Here's a more up-to-date (servlet spec 2.2) example that I have made into a servlet for easy use (see useage example at top). I have used this servlet to successfully pass html form values to a legacy cgi (via POST) along with additional values from the Java app. Since you're basically intercepting the

request you can do whatever you want with the parameters, and the user will never see the parameters you add since they never hit his browser, not even as hidden fields. BTW, I haven't tested the functionality to add headers much, but believe it should work. It just takes a few lines of code to use this servlet. Hope this saves somebody some time . . . and please let me know if you see ways it could be improved! package com.ragingnet.util; import import import import import

javax.servlet.*; javax.servlet.http.*; java.io.*; java.util.*; java.net.*;

/** Called by another servlet or jsp page to pass post parameters - both from the original request, * and new ones added to it - on to another page, such as a CGI script. * This is probably not of any use in a pure Servlet/JSP environment, but useful for passing * requests along to existing CGI scripts, etc. * * Useage: First call the following: * setUrlForward(url) [required] * setPassExistingParams(boolean) [optional - default is TRUE] * setParam(paramName, paramValue) [multiple times if desired] * setHeader(headerName, headerValue) [multiple times if desired] * * Then call Go(request, response) * * @author Roger Hand * @date April 2, 2001 * */ public class PassPostRequestServlet extends HttpServlet { private String urlForward = null; private Vector vectParams = new Vector(); private Vector vectHeaders = new Vector(); /* by default, we pass existing params from the originating page, but this can be suppressed if desired. */ private boolean passExistingParams = true; /**Initialize global private static final private static final private static final private static final private static final private static final

variables*/ String CONTENT_TYPE = "text/html"; int ARRAY_POS_PARAMNAME = 0; int ARRAY_POS_PARAMVALUE = 1; int ARRAY_POS_HEADERNAME = 0; int ARRAY_POS_HEADERVALUE = 1; boolean debug = true;

public void init(ServletConfig config) throws ServletException { super.init(config); }

public void setParam(String paramName, String paramValue) { String[] arrayParamName_Value = {paramName, URLEncoder.encode(paramValue)}; vectParams.add(arrayParamName_Value); } public void setParam(String paramName, int paramValue) { setParam(paramName, Integer.toString(paramValue)); } public void setHeader(String headerName, String headerValue) { String[] arrayHeaderName_Value = {headerName, headerValue}; vectHeaders.add(arrayHeaderName_Value); } public void Go(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { boolean debug = false; response.setContentType(CONTENT_TYPE); PrintWriter out = response.getWriter(); try{ /** * First we SEND the request to the web server */ URL url = new URL(urlForward); URLConnection connection = url.openConnection(); connection.setDoOutput(true); if (debug) System.out.println("Opened connection to " + urlForward); /* ADD our NEW HEADERS here */ /* We don't pass on any existing headers It could be we may want to pick and choose a few to send on */ for (int iHeader = 0;iHeader < vectHeaders.size(); iHeader++) { String[] arrayHeaderName_Value = (String[])vectHeaders.get(iHeader); connection.setRequestProperty(arrayHeaderName_Value[ARRAY_POS_HE ADERNAME], arrayHeaderName_Value[ARRAY_POS_HEADERVALUE]); if (debug) System.out.println("Added header " + arrayHeaderName_Value[ARRAY_POS_HEADERNAME] + " with value " + arrayHeaderName_Value[ARRAY_POS_HEADERVALUE]); } //next header PrintStream outStream = new PrintStream(connection.getOutputStream()); /* Pass on EXISTING PARAMS here (if desired) These are parameters set in the original form from the browser. It seems we should just be able to pass them on, but I haven't

found a way, so we've gotta recreate them here. */ String paramString = ""; if (passExistingParams) { Enumeration enumPNames = request.getParameterNames(); while(enumPNames.hasMoreElements()) { String paramName = (String)enumPNames.nextElement(); String[] arrayParam = request.getParameterValues(paramName); if (arrayParam != null) { for(int iParam=0; iParam < arrayParam.length; iParam++) { paramString += paramName + "=" + arrayParam[iParam] + "&"; } }

} } //if (passExistingParams) {

/* ADD our NEW PARAMS here */ for (int iParam = 0;iParam < vectParams.size(); iParam++) { String[] arrayParamName_Value = (String[])vectParams.get(iParam); paramString += arrayParamName_Value[ARRAY_POS_PARAMNAME] + "=" + arrayParamName_Value[ARRAY_POS_PARAMVALUE] + "&"; } //next parameter

1);

/* get rid of last '&' */ if (paramString.endsWith("&")) { paramString = paramString.substring(0, paramString.length() } if (debug) System.out.println("paramString is " + paramString); //Sending parameter to URL/CGI outStream.println(paramString); outStream.flush(); outStream.close();

/** * Now we RECEIVE response from web server and pass it back to browser client */ String inputLine; BufferedReader inStream = new BufferedReader( new InputStreamReader(connection.getInputStream())); /* this was in example, but is deprecated usage */ //inStream = new DataInputStream(connection.getInputStream()); while (null != (inputLine = inStream.readLine())) { out.println(inputLine);

} inStream.close(); } catch (MalformedURLException me) { System.err.println("MalformedURLException: " + me); } catch (IOException ioe) { System.err.println("IOException: " + ioe); } vectParams.clear(); } /**Clean up resources*/ public void destroy() { } public void setUrlForward(String newUrlForward) { urlForward = newUrlForward; } public void setPassExistingParams(boolean newPassExistingParams) { passExistingParams = newPassExistingParams; } }

How can I load a resource file from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=106003 Created: Jul 19, 2000 Modified: 2001-07-17 09:54:31.996 Author: Shirish Bathe (http://www.jguru.com/guru/viewbio.jsp?EID=88588) Question originally posed by Anh Le (http://www.jguru.com/guru/viewbio.jsp?EID=9885 [The below example leaves out a cruicial step: where to put the .properties files. Fortunately, Java looks for properties files using the same method with which it looks for class files. So just put the .properties files in the appropriate package directory, either under WEB-INF/classes or in a JAR file in WEB-INF/lib/ -Alex] Please try with following code. Compile and deploy servlet files in resp. directories. Create 3 different resource files. Start Servlet engine and access servlet using following url 1. For franch message http://172.22.67.23:8080/examples/servlet/ResourceServlet?MyLanguage=0 2. For german message http://172.22.67.23:8080/examples/servlet/ResourceServlet?MyLanguage=1 3. For english message http://172.22.67.23:8080/examples/servlet/ResourceServlet?MyLanguage=2 -------------------- ResourceServlet -----------------------------------import java.io.*; import java.math.*; import java.text.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; public class ResourceServlet extends HttpServlet {

ResourceBundle rb = null; public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); HttpSession session = request.getSession(true); int localeSelected = 2; String strTemp = request.getParameter("MyLanguage"); if (null != strTemp) localeSelected = (new BigDecimal(strTemp)).intValue(); switch (localeSelected){ case 0 : System.out.println("User Requested French Page"); rb = ResourceBundle.getBundle("LocaleStrings", Locale.FRENCH); System.out.println(rb.toString()); break; case 1 : System.out.println("User Requested German Page"); rb = ResourceBundle.getBundle("LocaleStrings", Locale.GERMAN); break; case 2 : default: System.out.println("User Requested Default/English Page"); rb = ResourceBundle.getBundle("LocaleStrings", Locale.ENGLISH); } out.println(""); out.println(""); out.println(""); String title = rb.getString("title"); out.println("" + title + ""); out.println(""); out.println(""); out.println(rb.getString("Question")); out.println(""); out.println(""); out.println(""); out.println(""); } public void doPost(HttpServletRequest request,

HttpServletResponse response) throws IOException, ServletException { doGet(request, response); } }

------------------- LocaleStrings.properties --------------------Question=How are you? title=This page is in english ------------------- LocaleStrings_fr.properties --------------------Question=Comment allez-vous? title=This page is in Franch ------------------- LocaleStrings_de.properties --------------------Question=Wie geht es Ihnen? title=This page is in German Hope it is solution you required? Have a nice day...

Shirish ([email protected]) Comments and alternative answers

I used a different method to get user's language within... Author: Stefano Bussolon (http://www.jguru.com/guru/viewbio.jsp?EID=132699), Sep 21, 2000 I used a different method to get user's language within a servlet: Locale loc = Locale.ENGLISH; // the default String language = request.getHeader("Accept-Language"); if (language == null) return loc; if (language.equalsIgnoreCase ("en")) { loc = Locale.ENGLISH; } if (language.equalsIgnoreCase ("it")) { loc = Locale.ITALIAN;

} if (language.equalsIgnoreCase ("de")) { loc = Locale.GERMAN; } // and so on for fr, es .... return loc; Stefano Stefano's comment is accurate as long as the browser... Author: Jean-Baptiste Quenot (http://www.jguru.com/guru/viewbio.jsp?EID=214329), Jan 23, 2001 Stefano's comment is accurate as long as the browser accepts only one language. If this is not the case, its code will fail. Instead, one has to split the header according to ';'s and trim the extra space. What is a servlet bean? Location: http://www.jguru.com/faq/view.jsp?EID=107022 Created: Jul 20, 2000 Modified: 2000-07-20 18:57:40.945 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) Question originally posed by shiva vithal (http://www.jguru.com/guru/viewbio.jsp?EID=55743 A servlet bean is a serializable servlet that follows the JavaBeans component architecture, basically offering getter/setter methods. As long as you subclass GenericServlet/HttpServlet, you are automatically Serializable. If your web server supports them, when you install the servlet in the web server, you can configure it through a property sheet-like interface. Why do we need to call super.init(config) in the init method of a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=108815 Created: Jul 23, 2000 Modified: 2000-07-24 19:44:53.011 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Sridhar Nama (http://www.jguru.com/guru/viewbio.jsp?EID=100882 Just do as you're told and you won't get hurt! :-) Because if you don't, then the config object will get lost. Just extend HttpServlet, use init() (no parameters) and it'll all work ok. From the Javadoc: init() - A convenience method which can be overridden so that there's no need to call super.init(config). Comments and alternative answers

since the Servlet interface defines a method called... Author: Arindam Chattopadhya (http://www.jguru.com/guru/viewbio.jsp?EID=340736), Feb 28, 2001 since the Servlet interface defines a method called getServletConfig(),you should either save the servletconfig object and implement the getServletConfig()method yourself or pass the object to the parent class using super.init(). However this is done for backward compatibility(before version 2.1).In version 2.1 you don't require to call that super.init() Re: since the Servlet interface defines a method called... Author: Igor Zelfon (http://www.jguru.com/guru/viewbio.jsp?EID=517887), Oct 11, 2001 Where do you set the parameters for the config objects in Visual Cafe4? Thanks, Igor. Please reply by e-mail to [email protected] Can I pass the value of variable from a servlet to ASP? Or vice versa? Location: http://www.jguru.com/faq/view.jsp?EID=109106 Created: Jul 23, 2000 Modified: 2000-09-17 21:55:35.809 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) Question originally posed by Deepak Kalra (http://www.jguru.com/guru/viewbio.jsp?EID=99188 The only means of communicating between a Servlet to ASP is via standard GET/POST mechanisms, like by submitting a FORM. Either adding information to the URL or passing in the request header. You can simulate the FORM submittal yourself, or just have it be the ACTION of the FORM. Comments and alternative answers

You can also pass data via HTTP GET using a browser... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Sep 17, 2000 You can also pass data via HTTP GET using a browser redirect. E.g.

response.sendRedirect("http://evil.satan.org/damnation.asp?home=hell&parent=beelzebub

How can I use JUnit to ensure that my servlets/JSP are producing valid HTML? Location: http://www.jguru.com/faq/view.jsp?EID=110644 Created: Jul 25, 2000 Modified: 2000-07-26 15:34:48.697 Author: Tom Copeland (http://www.jguru.com/guru/viewbio.jsp?EID=1396) There's the traditional, brute force way - write a JUnit test case that opens a HttpURLConnection to your servlet, reads the content, and does various String.indexOf() and String.subString() operations until you're satisfied that all is well (or you're tired of hacking together String operations). A slightly more elegant method is to use an XML parser. You can open the connection, read the contents, feed it into your XML parser, get back a document,

and walk the DOM tree checking for elements which should be there. Better, but still clunky. A better way is to use HttpUnit. HttpUnit allows the test case to be written using the same "words" as used in web pages - forms, tables, etc. You can write test cases like this (this is from the example code): public void testWelcomePage() throws Exception { WebConversation conversation = new WebConversation(); WebRequest request = new GetMethodWebRequest( "http://www.meterware.com/servlet/TopSecret" ); WebResponse response = conversation.getResponse( request ); WebForm forms[] = response.getForms(); assertEquals( 1, forms.length ); assertEquals( 1, forms[0].getParameterNames().length ); assertEquals( "name", forms[0].getParameterNames()[0] );

} With a little training, test cases of this sort can be written by an HTML developer and run against the user interface on a regular basis. Comments and alternative answers

XPath Author: Johannes Brodwall (http://www.jguru.com/guru/viewbio.jsp?EID=87292), May 4, 2001 HttpUnit is indeed powerful. An easy way of checking the structure without mocking too much around with text strings is to combine it with XPath. Using Xalan from Apache you can do this: import org.apache.xpath.XPathAPI; import org.w3.dom.*; Node responseRoot = response.getDOM().getDocumentElement(); NodeList tableRows = XPathAPI.selectNodeList(responseRoot, "//table[@id='mytable']/tr"); assertEquals(10, tableRows.getLength());

This will test if the table in the response with the id attribute 'mytable' contains 10 rows.

What is a servlet engine? Location: http://www.jguru.com/faq/view.jsp?EID=112410 Created: Jul 27, 2000 Modified: 2000-07-27 06:47:04.632 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by karuppanan rameshkumar (http://www.jguru.com/guru/viewbio.jsp?EID=102591

A "servlet engine" is a program that plugs in to a web server and runs servlets. The term is obsolete; the preferred term now is "servlet container" since that applies both to plug-in engines and to stand-alone web servers that support the Servlet API. For more detail, see What are all the different kinds of servers? in this FAQ. Which is the most efficient (i.e. processing speed) way to create a server application that accesses a database: A Servlet using JDBC; a JSP page using a JavaBean to carry out the db access; or JSP combined with a Servlet? Are these my only choices? Location: http://www.jguru.com/faq/view.jsp?EID=112424 Created: Jul 27, 2000 Modified: 2000-08-14 11:24:54.884 Author: Alfonso Garcia-Patiño (http://www.jguru.com/guru/viewbio.jsp?EID=111459) Question originally posed by Kaia Cornell (http://www.jguru.com/guru/viewbio.jsp?EID=72359 Your question really should be broken in two. 1-What is the most efficient way of serving pages from a Java object?. There you have a clear winner in the Servlet. Althought if you are going to change the static content of the page often is going to be a pain because you'll have to change Java code. The second place in speed is for JSP pages. But, depending on your application, the difference in speed between JSP pages and raw servlets can be so small that is not worth the extra work of servlet programming. 2-What is the most efficient way of accessing a database from Java?. If JDBC is the way you want to go the I'd suggest to pick as many drivers as you can (II,III,IV or wathever) and benchmark them. Type I uses a JDBC/ODBC bridge and usually has lousy performance. Again, go for the simplest (usually type IV driver) solution if that meets you performance needs. For database applications, the performance bottleneck is usually the database, not the web server/engine. In this case, the use of a package that access JDBC with connection pooling at the application level used from JSP pages (with or withouth beans as middleware) is the usual choice. Of course, your applications requirements may vary. How can I change the port of my Java Web Server from 8080 to something else? Location: http://www.jguru.com/faq/view.jsp?EID=112570 Created: Jul 27, 2000 Modified: 2000-07-29 05:23:10.902 Author: Shirish Bathe (http://www.jguru.com/guru/viewbio.jsp?EID=88588) Question originally posed by Raviraj D (http://www.jguru.com/guru/viewbio.jsp?EID=57509 Hi Raviraj, It is very simple. JAVA WEB SERVER comes with remote Web administration tool. You can access this with a web browser.

Administration tool is located on port 9090 on your web server. To change port address for web server: 1. Access tool (http://hostname:9090) 2. Enter User Id/Password (by default it is admin/admin) 3. Select service (Web service) 4. Click on "manage" button. You will get a popup screen with all settings. 5. Click on network tree node, On right hand side you will get text box for entering port no. 6. Change port number with desire one. 7. click on restart button. Hope this is solution for the problem. In case If you want more info please contact me on [email protected] Thanks Shirish I have created a remote reference to an EJB in FirstServlet. Can I put the reference in a servlet session and use that in SecondServlet? Location: http://www.jguru.com/faq/view.jsp?EID=114024 Created: Jul 29, 2000 Modified: 2000-07-29 05:59:08.95 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Nagaraj shyagale (http://www.jguru.com/guru/viewbio.jsp?EID=29160 Yes. The EJB client (in this case your servlet) acquires a remote reference to an EJB from the Home Interface; that reference is serializable and can be passed from servlet to servlet. If it is a session bean, then the EJB server will consider your web client's servlet session to correspond to a single EJB session, which is usually (but not always) what you want. How can I set a cookie that is persisted only for the duration of the client's session? Location: http://www.jguru.com/faq/view.jsp?EID=114132 Created: Jul 29, 2000 Modified: 2000-07-29 12:15:32.021 Author: Govind Seshadri (http://www.jguru.com/guru/viewbio.jsp?EID=14) Question originally posed by Basawaraj Pagade (http://www.jguru.com/guru/viewbio.jsp?EID=105646 You can create and set a cookie in the usual way. For example, if you are using a scriptlet, you can specify: <% Cookie aCookie = new Cookie("aName","aValue"); aCookie.addCookie(); %>

If you do not explicitly set a lifetime for the cookie using cookie.setMaxAge(), the cookie is automatically deleted when the user closes his browser. Can I send multiple responses for a single request? Location: http://www.jguru.com/faq/view.jsp?EID=114957 Created: Jul 31, 2000 Modified: 2000-07-31 05:02:36.133 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Deepak Kulkarni (http://www.jguru.com/guru/viewbio.jsp?EID=84086 No. That doesn't even make sense :-) You can, however, send a "redirect", which tells the user's browser to send another request, possibly to the same servlet with different parameters. Search this FAQ on "redirect" to learn more. What is FORM based login and how do I use it? Also, what servlet containers support it? Location: http://www.jguru.com/faq/view.jsp?EID=115231 Created: Jul 31, 2000 Modified: 2001-01-19 14:41:27.417 Author: Dieter Wimberger (http://www.jguru.com/guru/viewbio.jsp?EID=25708) Question originally posed by Alex Chaffee PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=3 Form based login is one of the four known web based login mechanisms. For completeness I list all of them with a description of their nature:

1. HTTP Basic Authentication An authentication protocol defined within the HTTP protocol (and based on headers). It indicates the HTTP realm for which access is being negotiated and sends passwords with base64 encoding, therefore it is not very secure. (See RFC2068 for more information.)

2. HTTP Digest Authentication Like HTTP Basic Authentication, but with the password transmitted in an encrypted form. It is more secure than Basic, but less then HTTPS Authentication which uses private keys. Yet it is not currently in widespread use.

3. HTTPS Authentication (SSL Mutual Authentication) This security mechanism provides end user authentication using HTTPS (HTTP over SSL). It performs mutual (client & server) certificate based authentication with a set of different cipher suites.

4. Form Based Login

A standard HTML form (static, Servlet/JSP or script generated) for logging in. It can be associated with protection or user domains, and is used to authenticate previously unauthenticated users. The major advantage is that the look and feel of the login screen can be controlled (in comparison to the HTTP browsers' built in mechanisms). To support 1., 3., and 4. of these authentication mechanisms is a requirement of the J2EE Specification (as of v1.2, 3.4.1.3 Required Login Mechanisms). (HTTP Digest Authentication is not a requirement, but containers are encouraged to support it.) You can also see section 3.3.11.1 of the J2EE Specs. (User Authentication, Web Client) for more detailed descriptions of the mechanisms. Thus any Servlet container that conforms to the J2EE Platform specification should support form based login. To be more specific, the Servlet 2.2 Specification describes/specifies the same mechanisms in 11.5 including form based login in 11.5.3. This section (11.5.3) describes in depth the nature, the requirements and the naming conventions of form based login and I suggest to take a look at it. Here is a sample of a conforming HTML login form: Known Servlet containers that support FORM-based login are: • •

iPlanet Application Server Tomcat (the reference implementation of the Java Servlet API)

URL Pointers:

1. Java Servlet API Specification 2.2 2. J2EE Platform Specification Comments and alternative answers

The above form is incorrect. The parameter should read... Author: Robert Castaneda (http://www.jguru.com/guru/viewbio.jsp?EID=4362), Jan 17, 2001 The above form is incorrect. The parameter should read j_username, not j_user_name. This feature is also supported in WebLogic 5.1 (I tested with sp8) and 6.0 [OK, I've fixed it above. -Alex]

See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Oct 19, 2001 See also form based authentication With regard to automatic servlet reloading in Tomcat 3.1, what happens if one servlet makes references to other servlets in the same webapp? Will automatic reloading get enabled for all such servlets? Location: http://www.jguru.com/faq/view.jsp?EID=115575 Created: Jul 31, 2000 Modified: 2000-08-03 21:04:55.078 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) The short answer to the question is: No. Let's say that a webapp for which automatic reload has been enabled consists of a group of mutually referencing servlets. Let's also say that you have modified and recompiled all the servlets. When you hit the reload button on the browser, only one servlet -- the servlet that the browser is pointing to -- will be automatically reloaded by the container. Hitting the reload button on the browser for the other servlets will not cause their reload into the container and you will only see their older versions. If you want the newer versions of the other servlets to be reloaded into the container, in general you'd need to shutdown and restart the servlet container. This behavior of Tomcat 3.1 is in keeping with the following statement that appears in Tomcat 3.1 release notes: "...... changes to classes other than the servlet you are requesting do not trigger class reloads -- you will need to restart Tomcat to reflect changes in those classes." In the rest of this posting, I will explain this property of Tomcat 3.1 with the help an example. The reader is also referred to a posting by Costin Manolache on this aspect of automatic class reloading in Tomcat 3.1. To demonstrate this behavior of Tomcat 3.1, I have constructed the following example that consists of two simple mutually referencing servlets called TestServlet_1 and TestServlet_2. In my Tomcat 3.1 container, both these servlets are in a webapp called test-suite and reside in the directory TOMCAT_HOME/webapps/test-suite/WEB-INF/classes. In accordance with the jGuru FAQ posting, I have enabled automatic reloading for this webapp by including the following element in the server.xml file in the TOMCAT_HOME/conf directory: Let's say that after starting the servlet container, you point your browser to the following URL: http://localhost:8080/test-suite/servlet/TestServlet_1 the servlet container will load TestServlet_1 into the container, which will cause the browser to display a "Hello..." message. If you click inside this message where

indicated, the browser will make a request for TestServlet_2 and it will be loaded into the container. Now suppose you make changes to both the servlets by altering, say, the value of "Revision number: ". If your browser is pointing to TestServlet_1 and you hit reload button, the servlet container will automatically reload TestServlet_1. But the container will NOT reload TestServlet_2 even if you hit the reload button on the browser when the browser is pointing to TestServlet_2. To see the newer version of TestServlet_2, you have two choices: 1) Recompile the classes and this time start out by pointing your browser to TestServlet_2. Or, 2) Shutdown and restart the servlet container. Here is the code for the two servlets:

//////////

file: TestServlet_1.java

//////////

import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class TestServlet_1 extends HttpServlet { public void init() throws ServletException { System.out.println("TestServlet_1 being loaded into the container"); } public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType( "text/html" ); PrintWriter out = response.getWriter(); out.println( "" + " TestServlet_1 " + "Hello there from TestServlet_1 ------+ "To see the hello message from TestServlet_2," + " click here ------ " +

"

"Revision number: 17" + "" ); } }

//////////

file:

TestServlet_2.java

//////////

import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class TestServlet_2 extends HttpServlet { public void init() throws ServletException { System.out.println("TestServlet_2 being loaded into the container"); } public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType( "text/html" ); PrintWriter out = response.getWriter(); out.println( "" + " TestServlet_2 " + "TestServlet_2 saying hello ------"To see the hello message from TestServlet_1," + " click here ------ " + "Revision number: 17" + "" ); } }

" +

How do I capture a request and dispatch the exact request (with all the parameters received) to another URL? Location: http://www.jguru.com/faq/view.jsp?EID=116711 Created: Aug 2, 2000 Modified: 2000-08-04 04:57:49.317

Author: David Garcia (http://www.jguru.com/guru/viewbio.jsp?EID=17915) Question originally posed by lakshmi prabha (http://www.jguru.com/guru/viewbio.jsp?EID=49600 As far as i know it depends on the location of the next target url. • • • • • •

• • • • • • • • • • • • • • • • •

If the next servlet url is in the same host, then you can use the forward method. Here is an example code about using forward: RequestDispatcher rd = null; String targetURL = "target_servlet_name"; ServletContext ctx = this.getServletContext(); rd = ctx.getRequestDispatcher(targetURL); rd.forward(request, response);

The other possibility is that the target servlet location is in a different host. Then you will need to use Streams,Sockets... and the code could be something like this: URL url=null; URLConnection conn=null; try{ url = new URL (protocol,host,port,"/"+servlet+"?"+requestParams); // the requestParam contains all the attributes (name=value pairs) you want to send taken from the incomming request conn = url.openConnection(); conn.setUseCaches(false); conn.setDoOutput(false); } catch(MalformedURLException e) { // whatever you want } BufferedReader inStream=new BufferedReader(new InputStreamReader(conn.getInputStream())); String respuesta=inStream.readLine(); inStream.close();

You can read more about the first approach in the Java Developer Journal (Number of May 2000 page 102). Test Conditions I have test this approach over webLogic 451 with the Service Pack 8 or higher. I can asure you that with Service Pack 7 or lower, the forward approach doesn't work. [That's all well and good, but you've dodged an important part of the answer: How do we grab the values of the parameters? I have source code that does this, but unfortunately my hard drive just crashed -- can someone else fill this in? -Alex] Comments and alternative answers

The second alternative holds good only for GET request... Author: Shailesh Dangi (http://www.jguru.com/guru/viewbio.jsp?EID=97397), Jan 12, 2001 The second alternative holds good only for GET request where the parameters are encoded in the query String in the URL. How do you deal with POST? [See http://www.jguru.com/jguru/faq/view.jsp?EID=231318 for the answer. -A] Wrapper to make it easy . . . Author: Roger Hand (http://www.jguru.com/guru/viewbio.jsp?EID=292314), Jun 18, 2001 See my alternative answer about a servlet wrapper I wrote to make this easy, at: http://jguru.com/faq/view.jsp?EID=104987 Re: Wrapper to make it easy . . . Author: Tommy Skodje (http://www.jguru.com/guru/viewbio.jsp?EID=446264), Jul 10, 2001 I used Roger's code, with some modifications needed to pass on sessionid. Just thought that someone else might need to do the same, here it is: package com.ragingnet.util; import java.io.*; import java.util.*; import java.net.*; import javax.servlet.*; import javax.servlet.http.*; /** Called by another servlet or jsp page to pass post parameters * - both from the original request, and new ones added to it * on to another page, such as a CGI script. * This is probably not of any use in a pure Servlet/JSP environment, * but useful for passing requests along to existing CGI scripts, etc. * * Useage: First call the following: * setUrlForward(url) [required] * setPassExistingParams(boolean) [optional - default is TRUE] * setPassExistingHeaders(boolean) [optional - default is TRUE] * setParam(paramName, paramValue) [multiple times if desired] * setHeader(headerName, headerValue) [multiple times if desired] * * Then call Go(request, stream): response is written to stream

* * @author Roger Hand, Tommy Skodje * @date June 27, 2001 * Downloaded from jguru. */ public class PassPostRequestServlet { // extends HttpServlet { private String urlForward = null; private Vector vectParams = new Vector(); private Vector vectHeaders = new Vector(); /* by default, we pass existing params from the originating page, but this can be suppressed if desired. */ private boolean passExistingParams = true; private boolean passExistingHeaders = true; /**Initialize global private static final private static final private static final private static final private static final private static final

variables*/ String CONTENT_TYPE = "text/html"; int ARRAY_POS_PARAMNAME = 0; int ARRAY_POS_PARAMVALUE = 1; int ARRAY_POS_HEADERNAME = 0; int ARRAY_POS_HEADERVALUE = 1; boolean debug = false; // true;

public void init(ServletConfig config) throws ServletException { super.init(config); }

//

public void setParam(String paramName, String paramValue) { String[] arrayParamName_Value = {paramName, URLEncoder.encode(paramValue)}; vectParams.add(arrayParamName_Value); } public void setParam(String paramName, int paramValue) { setParam(paramName, Integer.toString(paramValue)); } public void setHeader(String headerName, String headerValue) { String[] arrayHeaderName_Value = {headerName, headerValue}; vectHeaders.add(arrayHeaderName_Value); } /** Should pass on request to desired url, and return result in outBuf */ public void Go(HttpServletRequest request , OutputStream outBuf ) { try{ PrintWriter out = new PrintWriter( outBuf ); // First we SEND the request to the web server URL url = new URL(urlForward); URLConnection connection = url.openConnection(); connection.setDoOutput(true); if (debug) System.out.println("Opened connection to " + urlForward);

// Pass on EXISTING HEADERS here (if desired) if (passExistingHeaders) { Enumeration enumHNames = request.getHeaderNames(); while(enumHNames.hasMoreElements()) { String headerName = (String)enumHNames.nextElement(); Enumeration enumHeaders = request.getHeaders( headerName ); while ( enumHeaders.hasMoreElements() ) setHeader( headerName, (String) enumHeaders.nextElement() ); } } //if (passExistingHeaders) { // ADD our NEW HEADERS here for (int iHeader = 0;iHeader < vectHeaders.size(); iHeader++) { String[] arrayHeaderName_Value = (String[])vectHeaders.get(iHeader); connection.setRequestProperty( arrayHeaderName_Value[ARRAY_POS_HEADERNAME] , arrayHeaderName_Value[ARRAY_POS_HEADERVALUE] ); if (debug) System.out.println("Added header " + arrayHeaderName_Value[ARRAY_POS_HEADERNAME] + " with value " + arrayHeaderName_Value[ARRAY_POS_HEADERVALUE]); } //next header PrintStream outStream = new PrintStream(connection.getOutputStream()); /* Pass on EXISTING PARAMS here (if desired) These are parameters set in the original form from the browser.

It seems we should just be able to pass them on, but I haven't found a way, so we've gotta recreate them here. */ String paramString = ""; if (passExistingParams) { Enumeration enumPNames = request.getParameterNames(); while(enumPNames.hasMoreElements()) { String paramName = (String)enumPNames.nextElement(); String[] arrayParam = request.getParameterValues(paramName);

iParam++) {

if (arrayParam != null) { for(int iParam=0; iParam < arrayParam.length;

paramString += paramName + "=" + arrayParam[iParam] + "&"; } }

} } //if (passExistingParams) {

{

// ADD our NEW PARAMS here for (int iParam = 0;iParam < vectParams.size(); iParam++)

String[] arrayParamName_Value = (String[])vectParams.get(iParam); paramString += arrayParamName_Value[ARRAY_POS_PARAMNAME] + "=" + arrayParamName_Value[ARRAY_POS_PARAMVALUE] + "&" ; } //next parameter /* get rid of last '&' */ if (paramString.endsWith("&")) { paramString = paramString.substring(0, paramString.length() - 1); } if (debug) System.out.println("paramString is " + paramString); //Sending parameter to URL/CGI outStream.println(paramString); outStream.flush(); outStream.close(); // RECEIVE response from web server and pass it back String inputLine; BufferedReader inStream = new BufferedReader( new InputStreamReader(connection.getInputStream())); // this was in example, but is deprecated usage //inStream = new DataInputStream(connection.getInputStream()); while (null != (inputLine = inStream.readLine())) { out.println(inputLine); } inStream.close(); out.flush(); out.close(); } catch (MalformedURLException me) { System.out.println("MalformedURLException: " + me); } catch (IOException ioe) { System.out.println("IOException: " + ioe); } catch (Throwable t) { System.out.println("Exception: " + t.toString() ); } vectParams.clear(); vectHeaders.clear(); } // Go

/** Clean up resources */ public void destroy() { } public void setUrlForward(String newUrlForward) { urlForward = newUrlForward; } public void setPassExistingParams( boolean newPassExistingParams ) { passExistingParams = newPassExistingParams; } public void setPassExistingHeaders( boolean newPassExistingHeaders ) { passExistingHeaders = newPassExistingHeaders; } }

// class

I cant get the first example to work Author: Michael O Connor (http://www.jguru.com/guru/viewbio.jsp?EID=412596), Jun 22, 2001 I'm using tomcat 3.2 , and have changed the HelloWorldExample servlet supplied to include the forward lines RequestDispatcher rd = null; String targetURL = "/examples/servlet/teststartpage3"; ServletContext ctx = this.getServletContext(); rd = ctx.getRequestDispatcher(targetURL); rd.forward(request,response); And still all i get is a blank page on helloworldexample when i run it Re: I cant get the first example to work Author: mike cunneen (http://www.jguru.com/guru/viewbio.jsp?EID=455381), Jul 25, 2001 try changing the url from: /examples/servlet/teststartpage3

to:

/textstartpage3

Is there any way to tell Tomcat (or any servlet engine) never to use cookies for session management? Location: http://www.jguru.com/faq/view.jsp?EID=116712 Created: Aug 2, 2000 Modified: 2000-08-03 21:18:39.455 Author: David Garcia (http://www.jguru.com/guru/viewbio.jsp?EID=17915) Question originally posed by Graham Lea (http://www.jguru.com/guru/viewbio.jsp?EID=101834 I'm not sure about Tomcat but in WebLogic (from 4.0.2 to 5.1 versions) there is parameter in the weblogic.properties file which can enable (or disable) cookies.

The parameter line is: weblogic.httpd.session.cookies.enable=true or weblogic.httpd.session.cookies.enable=false Comments and alternative answers

disabling use of cookies for sessions in tomcat Author: Bob Rudis (http://www.jguru.com/guru/viewbio.jsp?EID=494420), Nov 28, 2001 in server.xml, you need to create a Context entry for your web app and add: cookies="false"

in order for it to not use cookies by default. Re: disabling use of cookies for sessions in tomcat Author: Vipul Garg (http://www.jguru.com/guru/viewbio.jsp?EID=799638), May 8, 2002 I tried to set cookie="false" for my context entry but when I restart my server after making changes the servet.xml file is reloaded and the changes made are lost. More clues regarding this will be helpful. Let me know if there is any setting to be done to not change the server.xml file on restarting of the server. regds, vipul What about jsessionid ? Author: M. washu (http://www.jguru.com/guru/viewbio.jsp?EID=1217388), Dec 21, 2004 Hi all, Is there a way to include jsessionid in a hidden field (in a form) rather than in the URL (by the URL rewriting mechanism ) ? I saw that HttpSessionContext class was deprecated for security reason, but for security reasons too i would like to know if there is a way to prevent the jessionid from being logged in the HTTP server log files (of course without using cookies) ? Thanks in advance. Re: What about jsessionid ? Author: Minh NGO (http://www.jguru.com/guru/viewbio.jsp?EID=1224287), Jan 31, 2005 Since the tag uses response.encodeURL(), it will append the jsessionId value in the action attribute of the form if cookies are disabled When using JavaMail with the Java WebServer, I get an AccessControlException. How do I disable the security checks to permit this? Location: http://www.jguru.com/faq/view.jsp?EID=117574

Created: Aug 2, 2000 Modified: 2000-08-13 16:29:50.283 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) Assuming you really want to disable the security checks for ALL your servlets, you need to edit the server.properties file and set server.security=false. We are using Apache/Tomcat for our site. Our servlets stream data rather than send it in one big chunk, but unfortunately it seems that Apache is buffering the servlet output stream, so results get to the user's browser only when the servlet closes the stream. Is there any way to control this? Location: http://www.jguru.com/faq/view.jsp?EID=118608 Created: Aug 3, 2000 Modified: 2000-08-04 04:18:58.516 Author: joe w (http://www.jguru.com/guru/viewbio.jsp?EID=112713) Question originally posed by Ofer Shaked (http://www.jguru.com/guru/viewbio.jsp?EID=62619 Have you tried calling flush() on the ServletOutputStream? Comments and alternative answers

We've tried things like setting the buffer size in... Author: Ofer Shaked (http://www.jguru.com/guru/viewbio.jsp?EID=62619), Aug 4, 2000 We've tried things like setting the buffer size in Tomcat and calling flush(). In fact, when using Tomcat alone, it works fine. The thing is that when using it in combination with Apache and the JServ module it looks as if apache insists on buffering anyway. Re: We've tried things like setting the buffer size in... Author: Neil Smyth (http://www.jguru.com/guru/viewbio.jsp?EID=392931), Apr 2, 2001 I've the same problem: I am trying to keep open a connection to the client and periodically write some data to it. I am using Apache with Tomcat 3.2 and mod_jk for the connector, and running on NT. Any thoughts? What I'm doing works fine under PWS/JRun combination, so I think it is a problem with the apache/tomcat combination. The sympton of the problem is that we are getting some strange buffering effects: it seems to buffer up to 256 bytes initially for the first connectionand thereafter pass along the data immediately. However for the second and subsequent connections it always buffers... Any thoughts appreciated!! Regards, Neil Re: Re: We've tried things like setting the buffer size in... Author: Howard Meadows (http://www.jguru.com/guru/viewbio.jsp?EID=411680), Apr 28, 2001 I think the buffering problem originates in the apache source code rather than anything in Tomcat. If you look at request handlers in http_request.c you'll find there is no support for chunk data. JRun probably contains its own buffering because it was not designed specifically to run on Apache.

Re: Re: Re: We've tried things like setting the buffer size in... Author: Timothy Bendfelt (http://www.jguru.com/guru/viewbio.jsp?EID=454480), Jul 13, 2001 From the jdk1.3.1 release notes: J2SDK 1.3.0 introduced a HTTP/1.1 client implementation. Web servers such as Apache return chunked encoded response to HTTP 1.1 clients, but the chunked encoding handling of J2SDK 1.3.0 and 1.3.1 don't stream the chunked response from the server. In practice, this means that methods such as java.net.URLConnection.getInputStream don't return until the server's response is finished. This problem is described in bug 4333920. Workaround: For Apache, the workaround is to put the following in following in httpd.conf BrowserMatch "Java1\.3\..[0-1]" downgrade-1.0

How do I upload a file from an applet to a servlet, i.e. emulate the browser's 'multipart/form' ability to upload files? Location: http://www.jguru.com/faq/view.jsp?EID=119521 Created: Aug 4, 2000 Modified: 2002-03-31 15:20:15.035 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) Question originally posed by alex black (http://www.jguru.com/guru/viewbio.jsp?EID=51517 The HTTPClient offering makes this possible from its mpFormDataEncode method. Keep in mind the security restrictions of an applet accessing the local client's file system. Basically, untrusted applets can't. Comments and alternative answers

Is there an alternate solution to this Author: Anuj Murarka (http://www.jguru.com/guru/viewbio.jsp?EID=558146), Apr 3, 2002 The solutions works fine. But when this package is integrated with my applet the size goes up drastically and my applet takes ages while downloading to the browser. Is there any other short alternative of doing the upload. Some means where file data stream can be posted to my servlet that handles the upload job. In some of the Servlet2.2 API, eg. getSession(boolean create), it says that "you must call this method before the response is committed". What does it mean by "committing" the response? Location: http://www.jguru.com/faq/view.jsp?EID=119666 Created: Aug 4, 2000 Modified: 2000-08-08 01:10:35.882 Author: Prasad Thammineni (http://www.jguru.com/guru/viewbio.jsp?EID=36479) Question originally posed by jon c (http://www.jguru.com/guru/viewbio.jsp?EID=109673

In Servlet 2.2 API, a servlet container is allowed to buffer the response in order to improve performance. The output and header information that is written to the response object is buffered and usually flushed or committed when the doPost(), doGet() or service() method returns. You can also flush the buffer programmatically. Once the buffer is flushed or committed, any headers you set will be ignored by the container. That is what the specification is referring to when it says that certain methods should be called before the response is committed. Where do I specify JVM system properties for a servlet container? For an application, I would say "java -Dfoo=bar ..." [Note: this will have many answers, for the many engines] Location: http://www.jguru.com/faq/view.jsp?EID=119671 Created: Aug 4, 2000 Modified: 2000-08-08 00:50:05.851 Author: Prasad Thammineni (http://www.jguru.com/guru/viewbio.jsp?EID=36479) Question originally posed by Amol Kher (http://www.jguru.com/guru/viewbio.jsp?EID=91021 In WebSphere Application Server, you specify the command line arguments for the JVM in which the Servlet Engine resides using the command line arguments property of the Application Server. This can be set from the Administrative Console. [OK, one down, a dozen to go... Who wants to answer for a different engine? -Alex] How do I get the "Posting and Processing HTML Forms" example at the Java Developer Connection to work under Servlet API version 2.2 (and Tomcat 3.1)? Location: http://www.jguru.com/faq/view.jsp?EID=119718 Created: Aug 4, 2000 Modified: 2000-08-08 00:46:57.202 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) The Java Developer Connection tutorial on servlets contains a very instructive example that shows how servlet can be used for processing HTML forms. This example was written for JSDK 2.1. To get this example to work with Tomcat 3.1, which uses the Servlets 2.2 API, you need to make the following changes: The most significant change you have to make concerns the use of DataInputStream.readLine() method. The readLine() method of the DataInputStream class has been deprecated because, as mentioned in the Java 2 SDK API, it "does not properly convert bytes to characters." Java 2 SDK API further states that "as of JDK 1.1, the preferred way to read lines of text is via the BufferedReader.readLine() method." Therefore, in the servlet class files FormDisplayServlet.java and FormProcessingServlet.java, replace the invocation

DataInputStream disStructure = new DataInputStream( fisStructure ); by

BufferedReader disStructure = new BufferedReader( new InputStreamReader( fisStructure )); and, in the servlet class file FormDisplayServlet.java, replace the invocation DataInputStream disData = new DataInputStream( fisData ); by BufferedReader disData = new BufferedReader( new InputStreamReader( fisData ) ); Changing over to BufferedReader for reading the structure and the data files also makes it necessary to change the test condition in the while loop for reading the files. For illustration, the test condition in the while loop for reading the structure file struct.dat needs to be changed from while ( 0 != disStructure.available() ) { //.... } to while ( ( inputLine = disStructure.readLine() ) != null ) { //.... } since the method available() is not defined for BufferedReader. The other changes you need to make depend on where you store the the files for this example in the Tomcat 3.1 directory structure. In my case, in the TOMCAT_HOME/webapps directory, I created a new webapp for this example and called it form-processing. I deposited the servlet files in the

TOMCAT_HOME/webapps/form-processing/WEB-INF/classes directory, and I deposited the files struct.dat and data.dat in the directory TOMCAT_HOME/webapps/form-processing/servlets/ This placement of the files dictated the following additional changes to the example code:

1. In the FormDisplayServlet.java file, change the statement 2. 3.

fisData = new FileInputStream( "c:\\JavaWebServer1.1\\servlets\\" + paramDataFile );

4. to

fisData = new FileInputStream( "C:/tomcat/webapps/formprocessing/servlets/" + paramDataFile );

5. In the FormDisplayServlet.java file, change the statement 6. 7. 8.

out.println( "

" );

to

out.println( "" );

9. In the FormProcessingServlet.java file, change the statement 10. 11.

isStructure = context.getResourceAsStream( paramStructureFile[0]);

12.

to

isStructure = context.getResourceAsStream( "/servlets/" + paramStructureFile[0]);

How can the data within an HTML form be refreshed automatically whenever there is a change in the database? Location: http://www.jguru.com/faq/view.jsp?EID=121817 Created: Aug 8, 2000 Modified: 2000-08-09 11:36:47.578 Author: David Garcia (http://www.jguru.com/guru/viewbio.jsp?EID=17915) Question originally posed by nitesh ambastha (http://www.jguru.com/guru/viewbio.jsp?EID=120716 JSP is intended for dynamically generating pages. The generated pages can include wml, html, dhtml or whatever you want... When you have a generated page, JSP has already made its work. From this moment you have a page. If you want automatic refreshing, then this should be acomplished by the technology included in the generated page (JSP will tell only what to include in the page). The browser can not be loaded by extern factors. The browser is the one who fetches url's since the http protocol is request-response based. If a server can reload a browser without its allow, it implies that we could be receiving pages which we haven't asked for from servers.

May you could use applets and a ServerSocket for receiving incoming signals from the server for changed data in the DB. This way you can load new information inside the applet or try to force a page reload. [That's a nice idea -- it could use the showDocument() call to reload the current page. It could also use HTTP polling instead of maintaining an expensive socket connection. -Alex] Perhaps (if possible), could be simpler using an automatic JavaScript refreshing function that force page reload after a specified time interval. [Search the FAQ on "redirect" for more information on this technique. -Alex] Comments and alternative answers

You might like to check out PUSHLETS on www.justob... Author: Christopher Morrison (http://www.jguru.com/guru/viewbio.jsp?EID=97335), Aug 9, 2000 You might like to check out PUSHLETS on www.justobjects.nl When the case is servlets? Author: the mask (http://www.jguru.com/guru/viewbio.jsp?EID=426947), Jun 5, 2001 JSP has already done its work by virtue of its own properties, but what can one do when the same page is generated using a servlet where the output is a static HTML page with a couple of applets showing the information? Is there any way to generate offscreen images without relying on the native graphics support? I'd like to create an image without an X server running, or create an image with more colors than the current video mode. Location: http://www.jguru.com/faq/view.jsp?EID=121936 Created: Aug 8, 2000 Modified: 2000-09-18 09:31:11.489 Author: Scott Stanchfield (http://www.jguru.com/guru/viewbio.jsp?EID=11) Question originally posed by David Noel (http://www.jguru.com/guru/viewbio.jsp?EID=119574 You must have a graphical environment installed on your server to work with Java image routines in AWT, even though the image will only be displayed on the client's machine. The AWT image manipulation routines use the native platform's graphics primitives and "grab" the resulting image to send to the client. Comments and alternative answers

You can get a little tool called xvfb: http://www.... Author: Steven Newton (http://www.jguru.com/guru/viewbio.jsp?EID=44606), Aug 8, 2000

You can get a little tool called xvfb: http://www.sunworld.com/sunworldonline/swol03-2000/swol-03-xvfb.html I found the answer on my own. You can use a virtual... Author: David Noel (http://www.jguru.com/guru/viewbio.jsp?EID=119574), Aug 8, 2000 I found the answer on my own. You can use a virtual frame buffer server that comes with Xwindows. The program is caled Xvfb. Another solution is to replace the AWT package with a 100% Java version that implements the native graphic functions. An AWT replacement can be found at www.eteks.com. Using either one of these solutions will allow you to run a headless server. I have written a class called PureImage which does... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Aug 24, 2000 I have written a class called PureImage which does this. It creates an offscreen image in a buffer, and uses another class called PureGraphics to draw to it. No Toolkit required. These classes are available at the Purple Technology web site. In addition to allowing a graphics servlet to run on a Unix box without an X server running, this also solves the problem of an NT box whose graphics card is running in black-and-white or a low-bit mode, where images end up dithered or otherwise uglified. Unfortunately, PureGraphics hasn't been completely implemented. Its drawImage() method works, but drawLine() only works for non-diagonal lines (where either x1=x2 or y1=y2), and most other drawing methods haven't been implemented. Anyone with a copy of a Computer Graphics 101 textbook want to help? This option will be available in JDK1.4 code-named... Author: Davanum Srinivas (http://www.jguru.com/guru/viewbio.jsp?EID=2011), Aug 25, 2000 This option will be available in JDK1.4 code-named merlin. Look at http://developer.java.sun.com/developer/bugParade/bugs/4281163.html at javasoft for more details. You can also look at the public review draft of Merlin at http://java.sun.com/aboutJava/communityprocess/review/jsr059/merlin.pdf. Search for "Headless" as the technical term they use for this mode of operation is named "Headless java". Another VFB program Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 5, 2001 Alessandro A. Garbagnati reports: There is a better package than XVFB that has better results. It's called PJA and it can be found at www.eteks.com. I've started using it about 6 months ago and it works

great. Re: Another VFB program Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 15, 2001 However, see Does anyone have solved the "no default font" error in the "pja" package? for a strange issue with PJA. Re: Another VFB program Author: BRACCHI CABANNES Christophe (http://www.jguru.com/guru/viewbio.jsp?EID=513801), Oct 8, 2001 Need for assistance! On the level localhost/windows JPA goes very well but I have a problem on UNIX: _X11TransSocketINETConnect: Can't connect: errno = 111 java.awt.AWTError: Graphics2D can't be instantiated at com.eteks.java2d.PJAGraphicsEnvironment.createGraphics(PJAGraphicsEnv ironment.java:110) at com.eteks.java2d.PJABufferedImage.createGraphics(PJABufferedImage.jav a:112) etc....

Would somebody have it an idea? Thank. Re[2]: Another VFB program Author: Stephen Oostenbrink (http://www.jguru.com/guru/viewbio.jsp?EID=1018151), Oct 28, 2002 Hi, Did you ever solve this problem? - Stephen See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 2, 2001 See also What causes the error "Can't connect to X11 w... Here's a thread Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Sep 26, 2001 Here's a thread that took place on a different question. I've moved it here for organization's sake. J.P. Jarolim, Apr 18, 2001 You'll find a very usefull replacement of the awt-classes for non x-win enviroments under http://www.eteks.com/pja/en Sharmila Kannangara, Jun 1, 2001 [4] You can load up the XFree86 package from your Linux installation CDs. This has a executable called Xvfb which runs a virtual X server. Set you DISPLAY environment variable to localhost:1.0 Then invoke Xvfb thusly : Xvfb :1 -screen 0 1600x1200x8 &

I've used this on Linux and Solaris 8 successfully. Herold Knauf, Aug 13, 2001 [1] I have downloaded xvfb from ftp.xfree86.org but it won't install! I have downloaded the wright version 4.1 for solaris. but when I run the "sh xinstall.sh -check" script I'll get a "No SunOS/Solaris binaries available for this architecture" message. Sharmila Kannangara, Sep 2, 2001 You may have to get the source code and recompile the binaries. I had to do this in order to install under Solaris. paul carver, Sep 2, 2001 [1] If using Tomcat, how do you associate the Xvfb and screen with the Tomcat daemon at boot time? Sharmila Kannangara, Sep 2, 2001 I didn't have to do anything special for the Tomcat configuration. Setting your DISPLAY variable as I mentioned should take of it. I realize that invoking setMaxAge(0) for a cookie causes the cookie to be deleted. But since such deletions obviously cannot be instantaneous, is it possible for a server to retrieve such a cookie during its next interaction with the client? Location: http://www.jguru.com/faq/view.jsp?EID=123363 Created: Aug 9, 2000 Modified: 2000-08-10 08:46:06.8 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) The answer is yes. My answer is based on the following interesting observation I made concerning the lifespan of a cookie for which the server has invoked the setMaxAge method with zero argument: Let's say your browser is pointing to a servlet that creates and deposits on the client side a cookie whose maximum age was set to zero by the server. The cookie will still be available for a short length of time after the server has processed the original browser request from the client. This can be checked by hitting the reload button on the client browser. The practical implications of this observation are that there can be a measurable latency associated with the demise of a cookie for which the server has invoked setMaxAge(0). During this latency, the cookie is still available to the server for the next request from the client. As my test example reveals, this latency is not caused by server-client propagation delays. This latency is between the moment a client receives notification that the cookie is to be deleted and the moment the client actually deletes the cookie. I have tested this observation under the following conditions:

1. A Solaris machine running Tomcat 3.1 as a stand-alone server and a Windows NT machine as a client on which the Netscape browser pointed to http://rvl2.ecn.purdue.edu:8080/test-suite/servlet/TestZeroLifespan

2. On a Windows NT machine with the browser pointing to http://localhost:8080/test-suite/servlet/TestZeroLifespan If you hit the reload button on the browser repeatedly, when the server successfully retrieves the cookie the client browser will show the following information output by the servlet: Cookie Information status retrieved and, when the server is not able to retrieve the cookie, you'll see just Cookie Information Also, you'll see the following messages in the Tomcat window on the server side as you hit the reload button repeatedly on the client browser. Whether you see a 0 or a 1 for the number of cookies returned depends on whether or not the cookie is retrieved by the server. Number Number Number Number Number Number Number Number Number .... ....

of of of of of of of of of

cookies cookies cookies cookies cookies cookies cookies cookies cookies

retrieved: retrieved: retrieved: retrieved: retrieved: retrieved: retrieved: retrieved: retrieved:

0 1 1 0 0 0 1 1 1

This output on the server side is a sampling from a particular run. The number of times 0's and 1's show up would vary from run to run. Here is the code for the servlet:

import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class TestZeroLifespan extends HttpServlet { public void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { Cookie cookie = new Cookie( "status", "retrieved" ); cookie.setMaxAge( 0 ); response.setContentType("text/html");

response.addCookie( cookie ); Cookie cookies[] = request.getCookies(); System.out.println( "Number of cookies retrieved: " + cookies.length ); PrintWriter out = response.getWriter(); out.println("" + "Cookie Information" + "" + "

Cookie Information

"); if (cookies != null) { for(int i=0, n=cookies.length; i < n; i++) { out.println (""); out.println (""); } } out.println("

" + cookies[i].getName() + "

" + cookies[i].getValue() + "

"); out.close(); } } Comments and alternative answers

Interesting. Sounds like a bug in Netscape. What v... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Aug 10, 2000 Interesting. Sounds like a bug in Netscape. What version of Netscape are you using? [Avi says: 4.73 for Windows NT] Does anyone get this behavior with Internet Explorer or other browsers? If the lifespan of a cookie is left unspecified by not invoking the Cookie.setMaxAge( int ) method, how long will such a cookie be retrievable by the server? Location: http://www.jguru.com/faq/view.jsp?EID=124357 Created: Aug 10, 2000 Modified: 2000-08-11 13:27:52.961 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) A cookie whose age is left unspecified has the same storage property as a cookie for which setMaxAge is invoked with a negative argument. In both cases, the cookie is available only for the duration of the current session with the server. In both cases, the cookie is deleted by the client when the current session expires. I have shown below the code for a simple servlet, TestCookieLifetime, that can be used to verify my answer to the question. The servlet creates five cookies, with the

first four being given different maximum ages, and the last with the age left unspecified. Of the first two cookies, cookie1 is given a maximum age of 1000 secs; and cookie2 of 10 secs. The third cookie, cookie3, is given a maximum age of 0 secs. This cookie will be deleted almost immediately after it is created. The fourth cookie, cookie4, is given a negative value for its age; this cookie will be deleted when the client browser exits. Finally, by not invoking setMaxAge on cookie5, we leave its age unspecified. If you point a client browser to this servlet and hit the reload button on the browser repeatedly, you will notice that the browser will display the following pattern initially

name1 name2 name4 name5

value1 value2 value4 value5

If you wait for more than 10 seconds between reloads, the browser will display name1 value1 name4 value4 name5 value5 and eventually name1 name4 name5 name2

value1 value4 value5 value2

If you reload in very quick succession, occasionally you will also see the following displayed by the browser: name1 name4 name5 name2 name3

value1 value4 value5 value2 value3

The reason for why you may also see the line name3 value3, which corresponds to cookie3 whose age was set to zero, is explained in another posting. The bottom line is that the lines name4 value4 and name5 value5, the former corresponding to a negative number for the age and the latter to age left unspecified, will alway appear together. If you shut down the browser and restart it again, both these lines will fail to appear in the client browser.

Here is the code for the servlet:

import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class TestCookieLifespan extends HttpServlet { public void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { Cookie cookie1 = new Cookie( "name1:", "value1" ); Cookie cookie2 = new Cookie( "name2:", "value2" ); Cookie cookie3 = new Cookie( "name3:", "value3" ); Cookie cookie4 = new Cookie( "name4:", "value4" ); Cookie cookie5 = new Cookie( "name5:", "value5" ); cookie1.setMaxAge( cookie2.setMaxAge( cookie3.setMaxAge( cookie4.setMaxAge(

10000 ); 10 ); 0 ); -10 );

response.setContentType("text/html"); response.addCookie( response.addCookie( response.addCookie( response.addCookie( response.addCookie(

cookie1 cookie2 cookie3 cookie4 cookie5

); ); ); ); );

Cookie cookies[] = request.getCookies(); System.out.println( "Number of cookies retrieved: " + cookies.length );

} }

PrintWriter out = response.getWriter(); out.println("" + "Cookie Information" + "" + "

Cookie Information

"); if (cookies != null) { for(int i=0, n=cookies.length; i < n; i++) { out.println (""); out.println (""); } } out.println("

" + cookies[i].getName() + "

" + cookies[i].getValue() + "

"); out.close();

See also How do I setup a cookie to expire after a certain time? I am using WebSphere. Where exactly should I place my HTML files and servlet class files and how do I access these files from the browser? Location: http://www.jguru.com/faq/view.jsp?EID=124400 Created: Aug 10, 2000 Modified: 2000-08-11 12:46:51.413 Author: Taylor Goetz (http://www.jguru.com/guru/viewbio.jsp?EID=123153) Question originally posed by Yogesh Beri (http://www.jguru.com/guru/viewbio.jsp?EID=99548 Websphere (at least version 1.x-2.x) works as a plug-in for a webserver such as Apache or IIS. You will have an installation directory for both WebSphere and the HTTP server. The location and names of these directories depends on the server platform. Your HTML and JSP pages will be placed in the root folder of the web server (or virtual server), or one of its subdirectories: Apache: /htdocs IIS: <some path>\wwwroot (If you are using virtual servers under IIS, you should realize that each virtual server must be configured to use WebSphere individually) Your compiled servlet classes typically go in the "servlets" subdirectory of the WebSphere installation directory. It is important to point out that this directory is "reloadable", meaning any classes in this directory may be dynamically reloaded if they are modified. The alternative is to place your classes in the "classes" subdirectory, or within the system classpath. In this case, your classes are not subject to dynamic reloading, and the servlet engine must be restarted for any changes to take effect. How can I specify the age of the cookie (single-session or persistent) set by the Servlets session tracking APIs? Location: http://www.jguru.com/faq/view.jsp?EID=125053 Created: Aug 11, 2000 Modified: 2000-08-11 14:29:32.18 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by sharad gupta (http://www.jguru.com/guru/viewbio.jsp?EID=100198 The current specs (2.2 and 2.3) allow the app developer to set the "session timeout" in minutes in the <session-config><session-timeout> element. However, as far as I can tell, there is no standard way to specify the age of the cookie the servlet container uses to drop the session ID on the browser.

One reason this could be useful is to set the cookie age to -1, guaranteeing that a session never lasts longer than the current browser session, regardless of its longevity inside the server. Comments and alternative answers

how can I remove a cookie set by servlet Author: Jan Kester (http://www.jguru.com/guru/viewbio.jsp?EID=410702), Apr 26, 2001 I tried to remove the cookie set by the servlet for sessionid by setting it's time to live to 0 or by trying to overwrite it by another cookie with the same name. But still, any next session call seems to see this cookie as the cookie that contains the session. How can I get rid of this cookie? I want to start session by receiving session by URL, then write my own cookie JSESSIONID with this URL received sessionid and then continue with normal cookie session control. Re: how can I remove a cookie set by servlet Author: Ketan Kakkad (http://www.jguru.com/guru/viewbio.jsp?EID=439788), Jun 15, 2001 We are experiencing similar problem and don't have an answer! Per my understanding, there is no standard way of removing (or even modifying) a JSESSIONID cookie set by the session. Is there any GURU out there who knows some way of accomplishing this?? Re: Re: how can I remove a cookie set by servlet Author: Jan Kester (http://www.jguru.com/guru/viewbio.jsp?EID=410702), Jun 15, 2001 Managed to do it. Have some code to put cookie to null or date to 0. However, you must add context path and server-name to Cookie to make it work. Send me mail if you still need it ([email protected]). Jan Modifying/Removing JSESSIONID cookie. Author: Ketan Kakkad (http://www.jguru.com/guru/viewbio.jsp?EID=439788), Jun 15, 2001 First to define the problem ... Most servlet engines set a JSESSIONID cookies as per-session cookie (browser memory only cookies) instead of persistent cookie (write to disk). This is okay for most part but let's say that you want to modify the JSESSIONID (or whatever cookie name) cookie set by the servlet engine. Most people will try retrieving the cookie set by the servlet engine, setMaxAge to 0 (to delete it) and create a new cookie with same cookie name/value and modified behavior. However, this doesn't seem to work!! Now you have two cookies with same name -- that's not what you want right? You want to REMOVE the previous cookie but it does not get removed!

Until now, you have been trying cookie.setMaxAge(0) to remove a cookie but it does not work because while removing a JSESSIONID cookie, you are also trying to create a new cookie with same name. Now, try 'response.setHeader("SetCookie","name=JSESSIONID; expires=date");' to remove the cookie set by the servlet engine? Per my understanding, servlet engine uses a Hashtable for storing all cookies you provide (either for remove or add new) and uses cookie name as a key in the hashtable entry. So, the moment you create a new cookie, it will overwrite your previous instruction of removing a cookie with the same name (because hashtable caanot accomodate two records with same key). Disclaimer: I haven't tried this myself, but almost sure that it will solve your problem. Good luck! Can I use the PageContext.forward() or RequestDispatcher.forward() method to forward to a specific anchor (something like "mypage.html#intro")? Location: http://www.jguru.com/faq/view.jsp?EID=125063 Created: Aug 11, 2000 Modified: 2000-08-11 14:42:06.484 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Royer Kerwin (http://www.jguru.com/guru/viewbio.jsp?EID=115906 No, you can't. It doesn't make sense, since the server has to generate the entire page, and can't tell the browser to jump to a specific anchor inside the page. Send a redirect instead, using Response.sendRedirect(). Comments and alternative answers

The *browser* is what "goes to" an anchor... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Aug 13, 2000 The *browser* is what "goes to" an anchor inside a fully-generated page. Inside a request, the browser has already asked the server to generate an entire page; the "forward" or "include" results in the server generating such an entire page. In returning such an entire page, the servlet engine can't also tell the browser to scroll to a specific anchor inside the generated page. Another way of thinking of it is, everything after the "#" gets stripped by the browser before it makes a request; it has literally no meaning inside the web server. Every time I start Tomcat and do a ps -awx there appears to be around 35 different instances of Tomcat in memory at the same time. Is this normal? Does it interfere with performance? Location: http://www.jguru.com/faq/view.jsp?EID=125066 Created: Aug 11, 2000 Modified: 2000-08-11 14:43:39.01 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question

originally posed by Jaymes Sorbel (http://www.jguru.com/guru/viewbio.jsp?EID=116271 This is normal, and represents Linux's concept of threads. A thread in Linux is implemented as a process. Even though it says each is using X amount of memory, in reality, they're all sharing the same heap, so it's not taking up extra memory. What is a three-tier architecture? Location: http://www.jguru.com/faq/view.jsp?EID=125072 Created: Aug 11, 2000 Modified: 2000-08-11 14:55:10.431 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by joy choudhury (http://www.jguru.com/guru/viewbio.jsp?EID=104345 A three-tier architecture is any system which enforces a general separation between the following three parts:

1. Client Tier or user interface 2. Middle Tier or business logic 3. Data Storage Tier Applied to web applications and distributed programming, the three logical tiers usually correspond to the physical separation between three types of devices or hosts:

1. Browser or GUI Application 2. Web Server or Application Server 3. Database Server (often an RDBMS or Relational Database) However, inside of the application server, there is a further division of program code into three logical tiers. This is kind of fractal: the part (app server object design) resembles the whole (physical system architecture). In a classic JSP/Servlet system, these objects are usually implemented as:

1. JSPs or Servlets responsible for creating HTML or WML user interface pages 2. Servlets or JavaBeans responsible for business logic 3. Servlets, JavaBeans, or Java classes responsible for data access. These objects usually use JDBC to query the database. In an EJB system, the three logical tiers are usually implemented somewhat differently:

1. JSPs, Servlets, or Java client applications responsible for user interface 2. Session Beans or Entity Beans whose methods implement business logic and business rules

3. Entity Beans whose fields represent data; these fields are "persisted" (stored and retrieved) either by the EJB server (for container-managed persistence) or by the Entity Beans themselves (for bean-managed persistence)

As you can see, the precise definition of "tiers" can vary widely depending on the particular needs and choices of an application designer. However, they all maintain the general division of client-logic-storage. If the architecture contains more than three logical tiers -- for instance, multiple data feeds, multiple transactional data sources, multiple client applications -- then it is typically called an "N-tier" or "Distributed" architecture. See also: • • • • •

What seperates one tier from another in the context of n-tiered architecture? In distributed architecture (typical three tier consisting of thin client, middleware & database) which type of JDBC driver should be used and why? What is meant by the term "business logic"? Are the following schemes 3 tiered architecture? What is the recommended, "best" architecture for JSP applications?

Comments and alternative answers

NEED SOME HELP WITH THE FOLLOWING QUESTIONS Author: hapz happy (http://www.jguru.com/guru/viewbio.jsp?EID=1239371), Apr 18, 2005 hi, just need some answers to some questions about XML coz i dont hav a clue. 1) how to identify a website that is using XML? 2) in which way can you identify a website is using XML and not xhtml? 3) what is server-side XML, what is client-side XML? 4) how to identify a website that is using a Three-Tier Architecture Re: NEED SOME HELP WITH THE FOLLOWING QUESTIONS Author: hapz happy (http://www.jguru.com/guru/viewbio.jsp?EID=1239371), Apr 18, 2005 reply to [email protected] thanx Re[2]: NEED SOME HELP WITH THE FOLLOWING QUESTIONS Author: Felix Zhu (http://www.jguru.com/guru/viewbio.jsp?EID=1241528), Apr 28, 2005 You should think twice about your post on this website. There are many other methods of gaining knowledge. See me in class. I can help. Re[2]: NEED SOME HELP WITH THE FOLLOWING QUESTIONS Author: Leonardo DaVinci (http://www.jguru.com/guru/viewbio.jsp?EID=1245556), May 24, 2005 Meow :) How do I configure IPlanet 4.0 (web server) to work with Tomcat? Location: http://www.jguru.com/faq/view.jsp?EID=125278 Created: Aug 12, 2000 Modified: 2000-08-13 14:42:29.761

Author: Roger Sergeant (http://www.jguru.com/guru/viewbio.jsp?EID=125277) Question originally posed by archana sahu (http://www.jguru.com/guru/viewbio.jsp?EID=112286 Why would you want to do this? Is there a reason for you needing to run 2 servletenabled webservers together. Just run with one or the other. They will both do the same job! We have just moved from tomcat to iPlanet 4.1 for our prod environment and now do not use TC at all. Roger Sergeant. BAE SYSTEMS. [Well, one reason might be that Tomcat may support a more recent version of the spec, or that iPlanet may have bugs that Tomcat does not... But at the moment, they both allegedly support version 2.2 of the Servlet spec. See What version of the Servlets or JSP specification is supported by my favorite servlet product? -Alex] Comments and alternative answers

iPlanet does not support the whole 2.2 spec. Spec... Author: Glen Stampoultzis (http://www.jguru.com/guru/viewbio.jsp?EID=234390), Feb 15, 2001 iPlanet does not support the whole 2.2 spec. Specificaly it does not support web applications. Tomcat and iPlanet Author: Jerry Birchler (http://www.jguru.com/guru/viewbio.jsp?EID=414720), May 3, 2001 Ok, Yet another reason to do this is that some application software does not work with the iPlanet servlet engine. Take Vignette 5.6.1, for example, you can enable the servlet engine in iPlanet, and it does work, but in order to enable JSP V/5 commands, you must use the Tomcat servlet engine. So, this is a completely valid question that I hope someone can answer, as I am having the same problem. Re: Tomcat and iPlanet Author: Frank O'Connell (http://www.jguru.com/guru/viewbio.jsp?EID=425184), May 20, 2001 did you ever get your answer? We are faced with the same problem. DigiChat httptunneling servlet has only been tested on Tomcat. I would also like to configure Netscape to use tomcat as the servlet engine. Re: Re: Tomcat and iPlanet Author: Jerry Birchler (http://www.jguru.com/guru/viewbio.jsp?EID=414720), May 20, 2001 In my case, it was not so much a matter of configuring Tomcat with iPlanet as

it was a matter of configuring Tomcat for Vignette on an iPlanet web server. I was able to do this on a Windows 2000 Server platform. My biggest hurdle was getting the right thin JDBC driver to work for my Oracle database running on a Solaris Intel box. That required a special membership relationship with Oracle to do the appropriate download. Even then, I had to keep guessing until I got the right driver. Also, I had to hack the registry to keep iPlanet from running out of pages for virtual memory and causing the blue screen of death. So, in your case, I suppose you just want to replace the iPlanet Servlet engine with Tomcat? I'm sure that has to be possible, but I haven't had a specific need to do that just yet. I'd look into making changes to the files under c:\netscape\server4\conf. You can configure things there like Classpath, JVM and JRE library settings. Also, I'm running Tomcat as an NT service. This is very convenient if you ever need to reboot the machine. You'll have to play around with Tomcat *.properties files and download a couple of things to make that happen. Eventually, I'll get around to replacing the iPlanet servlet engine, if for no other reason but to prove it can be done. Until then, good luck to you, and if you beat me to the solution, please let me know what you did. Re: Tomcat and iPlanet Author: Kristian Rickert (http://www.jguru.com/guru/viewbio.jsp?EID=432617), Jun 1, 2001 Another reason: There are some configuration issues with iPlanet which are very annoying. 1) If I want a new JAR file in Tomcat, I just add it to a directory and bounce the server - can't do that with iPlanet 2) If I want to configure the JVM, it's much easier with tomcat - because you can see what tomcat does to run the JVM and change it's attributes. 3) iPlanet's servlet enguine does not display the error message unless you do a println() command. I want to use tomcat because it's better documented than iPlanet. Yet iPlanet is kick ass at serving static HTML, and Tomcat is terrible at it. SO YES!! THERE IS A REASON. Re: Re: Tomcat and iPlanet Author: sharon leibel (http://www.jguru.com/guru/viewbio.jsp?EID=447088), Jun 28, 2001 Another reason has to do with iPlanet's memory limitation to the JVM (500 MB) Re[3]: Tomcat and iPlanet Author: Adam boyet (http://www.jguru.com/guru/viewbio.jsp?EID=870968), May 10, 2002 Have you been able to replace the iPlanet servlet engine with Tomcat? SSL is another reason Author: Stewart Elkin (http://www.jguru.com/guru/viewbio.jsp?EID=912723), Jun 14, 2002

Another reason iPlanet to Tomcat upgrades are hampered are that Tomcat uses a JSSE keystore for it's server-SSL implementation, whereas iPlanet uses the proprietary (now open source) NSS format. There is no satisfactory upgrade path for iPlanet customers who have invested in SSL certs installed in iPlanet, and none at all where they require client-auth as well. So, running Tomcat within iPlanet resolves the cert upgrade problem. Re: SSL is another reason Author: Jerry Birchler (http://www.jguru.com/guru/viewbio.jsp?EID=978843), Aug 7, 2002 Ultimately, I would like to see JBOSS and Tomcat 4.03 integrated with iPlanet on both Linux and Solaris. I was able to integrate Tomcat 4.04 with Apache on Linux using mod_jk. Unfortunately, I have been unsuccessful integrating iplanet. However, I am making progress. In a nutshell, you have to download the tomcat connectors source and run a make on the nsapi_redirector.so for iplanet to use a connector called apj13. There are some changes, of course, to tomcat's server.xml, and iplanet's obj.conf. I've been playing with this quite a bit and have yet to make it work. I am able to create the redirector and validate that it at least is being loaded and does not crash. I am also able to validate that the Java classes involved for the connector are being invoked. Check out these links: 1. http://www.mail-archive.com/[email protected]/maillist.html 2. http://www.mail-archive.com/tomcat-user%40jakarta.apache.org/ I document what I've done, so far, there. If this is possible, I'm going to do it, but I'm going to need some help. Please send me any updates to [email protected]. I am planning on doing this on both my Linux and Solaris sandboxes.

What is the difference between JServ and Tomcat? And what's up with mod_jserv and mod_jk? Location: http://www.jguru.com/faq/view.jsp?EID=125676 Created: Aug 13, 2000 Modified: 2000-11-07 08:21:41.353

Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Mark Evertz (http://www.jguru.com/guru/viewbio.jsp?EID=117316 JServ was one of the very first servlet engines. It is now an open source project, consisting of two parts: a pure-java servlet engine, compliant with the Servlet spec version 2.0, and an Apache module written in C called mod_jserv that allows Apache to send servlet requests to the JServ JVM. Tomcat is a completely separate product, originally written by Sun, that is now also open-source and administered by Apache. It supports the Servlet spec version 2.2, and the JSP spec version 1.1. It also contains a pure Java servlet engine, and a number of connectors for several commercial web servers. Here's the confusing part: originally, when it was time to write a connector from Apache to Tomcat, they started with the code base of mod_jserv. Although it has been rewritten and revised to the point where it is no longer compatible with the mod_jserv that comes with JServ, unfortunately, it is still called mod_jserv. This means that if you have the JServ mod_jserv installed, it will not work with Tomcat, and vice versa. Fortunately, the latest version of Tomcat comes with a new connector for Apache, called mod_jk. This connector supports Tomcat but not JServ. It is also more advanced, in that it supports Tomcat-style load balancing, and also supports SSL authentication (though this latter functionality is still a bit rough and may have bugs in actually *reporting* that the connection is secure). So if you just use mod_jk and Tomcat, you should have no problems (at least as far as this connector issue is concerned). Comments and alternative answers

Where, at the jakarta-tomcat site, are the mod_jk... Author: Michael Bourdon (http://www.jguru.com/guru/viewbio.jsp?EID=260421), Nov 22, 2000 Where, at the jakarta-tomcat site, are the mod_jk files located? Can I use mod_jk + Tomcat and mod_jserv + JServ with... Author: Marco Becchio (http://www.jguru.com/guru/viewbio.jsp?EID=278835), Dec 15, 2000 Can I use mod_jk + Tomcat and mod_jserv + JServ with the same Apache server? A compiled mod_jk for linux can be found at http:/... Author: Hans Gerwitz (http://www.jguru.com/guru/viewbio.jsp?EID=100248), Jan 30, 2001 A compiled mod_jk for linux can be found at http://jakarta.apache.org/builds/jakartatomcat/release/v3.2.1/bin/linux/i386/ , documentation at http://jakarta.apache.org/tomcat/jakarta-tomcat/src/doc/mod_jk-howto.html

No, mod_jk and mod_jserv are not compatible (cannot be installed in the same instance of Apache). When transitioning, I've used mod_jserv for both Tomcat and JServ instances with different ports. REALLY? Author: Ravi Luthra (http://www.jguru.com/guru/viewbio.jsp?EID=463147), Jul 26, 2001 Where can I find information about bugs in mod_jk while using mod_ssl? Should I use mod_jserv instead when using Apache+mod_ssl? NOW WHAT? Author: matt scholz (http://www.jguru.com/guru/viewbio.jsp?EID=994323), Sep 4, 2002 I'm not patient enough to try banging my head against this wall any more, if I can avoid it... I have a perfectly functional (more or less) install of Tomcat-4.0.4 on Redhat 7.3. (YAY). I followed the steps I found at http://www.johnturner.com/howto/apache-tomcat-howto.html which got a compiled mod_jk.so installed in libexec/(along with several edits of configuration files, which obviously didn't work). According to the documentation, I should be able to see the same things from http://localhost:8080/examples and http://localhost/examples -but I can't The question, I suppose is now that I have mod_jk.so in the apache/libexec folder, what do I do to convince apache to use it? Thanks in advance, Matt Re: NOW WHAT? Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727), Sep 5, 2002 Hi, Maybe you can look at the AJP documentation Re: NOW WHAT? Author: James Bond (http://www.jguru.com/guru/viewbio.jsp?EID=1063566), Mar 5, 2003 matt, thanks for providing the johnhunter link, it works like a charm on windows xp. How do I set a cookie from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=125813 Created: Aug 13, 2000 Modified: 2000-08-14 06:48:52.921 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) This is answered at How do I set a cookie within a JSP page?. See also • •

How do I access a cookie from a servlet? How do I setup a cookie to expire after a certain time?

• • •

How can I delete a cookie from within a JSP page? How do you check for the existence of a cookie? and all questions in the topic Java:API:Servlets:Cookies, Sessions, and State Management

How do I end (invalidate) a session? Location: http://www.jguru.com/faq/view.jsp?EID=126094 Created: Aug 14, 2000 Modified: 2000-09-07 15:23:55.799 Author: Richard Raszka (http://www.jguru.com/guru/viewbio.jsp?EID=7963) Question originally posed by Ramsey Nasr (http://www.jguru.com/guru/viewbio.jsp?EID=4383 Sessions can be invalidated by calling the invalidate() method on the HttpSession Object. In a Servlet this can be performed using the following code:

import import import import

java.io.*; java.util.*; javax.servlet.*; javax.servlet.http.*;

public class InvalidateSession extends HttpServlet { public void doGet( HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { res.setContentType("text/html"); PrintWriter out = res.getWriter(); // Get the current session HttpSession session = req.getSession(true); // Invalidate it for a particular reason if (....) { session.invalidate(); } // Continue processing // - May need a session to be created to continue processing } } Invalidating a session could be done on an explicit logout of a user from the Web Site or after a period of inactivity that you have defined in the application.

Comments and alternative answers

How do I end (invalidate) a session? - comments Author: Allen S (http://www.jguru.com/guru/viewbio.jsp?EID=50829), May 3, 2001 Don't you think you need to obtain the session even before getting the PrintWriter object? How do I access a cookie from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=126109 Created: Aug 14, 2000 Modified: 2000-08-14 06:44:26.796 Author: Richard Raszka (http://www.jguru.com/guru/viewbio.jsp?EID=7963) Question originally posed by Alex Chaffee PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=3 Cookies can be accessed from a servlet usingthe HttpRequest class and the method getCookies. Sample code is included below:

import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class PrintCookies extends HttpServlet { public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { res.setContentType("text/html"); PrintWriter out = res.getWriter(); // Get the Cookies Cookie[] cookies = req.getCookies(); out.println("<TITLE>COOKIE Values<TITLE>"); out.println("

Cookies in Session

"); // Process the cookies for (int i = 0; i "); } [So, to be clear, if you want to access cookie "foo", replace the "out.println" statements with

if (name.equals("foo")) { out.println(name + " = " + value); // or whatever } Unfortunately, there's no "getCookieByName()" method. -Alex] How do I send a redirect from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=126245 Created: Aug 14, 2000 Modified: 2000-08-25 08:58:41.776 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) First, a definition. "redirect" means sending a response from your servlet to the browser that tells the browser to go to (make a brand new request for) another URL or page. This should not be confused with "forward" which operates inside the servlet engine, without informing the browser of the "new" content. For this function, you can use the RequestDispatcher and/or the JSP <jsp:forward> tag. The standard HttpResponse object has a method, response.sendRedirect(String), that does the right thing with HTTP headers to send an HTTP redirect to the browser. Check the JavaDoc for more details. One important note: you must call sendRedirect() before (or better: instead of) writing any data to the response output stream. You can do the same thing yourself with response.setHeader("Location", "http://foo.com/"); but sendRedirect() is preferred. If you want more control -- for instance, to display a custom page to the user for a few seconds before going to the new page -- you can use META HTTP-EQUIV, e.g.:

Page Has Moved <meta http-equiv="Refresh" content="1; url=http://foo.com/index.html"> You should be transferred automatically to the new page. If not please click this link.

The "1" in the "content" section is the number of seconds the browser should wait. "0" here should produce an almost instantaneous jump, but in that case, you might as well use sendRedirect(). See also How do I perform browser redirection from a JSP page? Comments and alternative answers

Comment: 0-Second Redirection Author: Josh B (http://www.jguru.com/guru/viewbio.jsp?EID=547221), Nov 14, 2001 True. There's not much of a point in specifying a zero-second wait for redirection for the average user. However, the browser I use (Opera) allows me to turn redirection off... so if a page is loaded that gives me a choice of continuing on, it's welcome. FYI... some people get tired of programmers redirecting us willy-nilly on their sites. =) Re: Comment: 0-Second Redirection Author: Kumar Nagarajan (http://www.jguru.com/guru/viewbio.jsp?EID=1166919), Apr 29, 2004 Forward the request from the servlet to a JSP page and have all the parameters you want to send as hidden parameters. In the JSP page, in the on-load event, submit the form to the other servlet (in the other application). Hope this helps. Thanks. Kumar. How do you put a hidden parameter in the response.redirect()? Author: Dave Lu (http://www.jguru.com/guru/viewbio.jsp?EID=585267), Mar 27, 2002 I'm trying to forward or redirect my servlet to another servlet from another application. I want to send some parameters (or attributes) along with the redirection, but the parameters needs to be hidden. What is the solution. Re: How do you put a hidden parameter in the response.redirect()? Author: Jay kumar (http://www.jguru.com/guru/viewbio.jsp?EID=716541), Jun 9, 2002 Dave, I also have some similar requirement. I need to call a servlet on a different server and need to pass some parameter. Are you able to solve your problem, please let me know. It would be very helpful for me. Re[2]: How do you put a hidden parameter in the response.redirect()? Author: Dave Lu (http://www.jguru.com/guru/viewbio.jsp?EID=585267), Jun 17, 2002 Hi Jay, Because my application was web base, my temporary solution was to create a html which auto-forward to the other servlet. What I basically do is, retreive the values from the request and create a small html (with the hidden parameters) which re-submit to the other servlet when onload. If I find a better solution I will let you know ;0)

Re[2]: How do you put a hidden parameter in the response.redirect()? Author: peter eisert (http://www.jguru.com/guru/viewbio.jsp?EID=953342), Jul 18, 2002 I have the same problems. I want to redirect a html page with method=post and informations in hidden fields. response.setStatus(307); response.setHeader("Location", url); It works fine with MSIE. But with the Netscape Navigator the body is always empty. Is there any change to tell the Navigator to do what I want? Best regards peter Re[3]: How do you put a hidden parameter in the response.redirect()? Author: Ken Young (http://www.jguru.com/guru/viewbio.jsp?EID=901514), Oct 12, 2002 Did you try putting the form tag around your hidden varibles? IE works without the form tag, but Netscape doesn't like it when you have form objects without the form tags around it. How can I invoke an EJB from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=126254 Created: Aug 14, 2000 Modified: 2000-08-14 08:57:21.382 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by prakash patel (http://www.jguru.com/guru/viewbio.jsp?EID=102421 You invoke an EJB from a servlet or JSP the same way you invoke one from any other Java code. Just read the EJB docs and FAQ and have fun! Comments and alternative answers

first create the home object, then using home, access... Author: raghavendra ghorpade (http://www.jguru.com/guru/viewbio.jsp?EID=344479), Mar 5, 2001 first create the home object, then using home, access the method. for example:

try { Context c=new InitialContext(); Object o=c.lookup("gor"); first.ABCHome home=(first.ABCHome)PortableRemoteObject.narrow(o,first.ABCHome.class); abc=home.create(); (abc.yourmethod(with paramaters) } catch(Exception ex) { ex.printStackTrace(); }

Re: first create the home object, then using home, access... Author: J C (http://www.jguru.com/guru/viewbio.jsp?EID=756527), Feb 12, 2002 This seems to be lots of details missing. When you run J2EE client with Sun's J2EE reference implementation server, you use runclient command which sets a number of properties. How do you set these within servlet/JSP? I guess that you have to set these properties when starting web server (e.g., servlet), right? Why do I get a "java.net.BindException:Address in use" error? Location: http://www.jguru.com/faq/view.jsp?EID=126267 Created: Aug 14, 2000 Modified: 2001-09-07 09:37:42.354 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by anupama bapat (http://www.jguru.com/guru/viewbio.jsp?EID=124529 Probably because the address is in use :-) You're already running an instance of your servlet engine, or another service is running on its port. Make sure the other service is fully stopped before launching another one. See also • • •

How do I fully shut down the server? Why doesn't Tomcat shut down when I run shutdown.bat (or shutdown.sh)? How do you shut down JServ safely if you've started it (manual mode), such that the destroy() methods of the existing servlet classes are invoked?

Comments and alternative answers

This happens when you stop Tomcat and then restart... Author: d petersen (http://www.jguru.com/guru/viewbio.jsp?EID=140879), Sep 2, 2000 This happens when you stop Tomcat and then restart it... what you have to do is 'ps -a' to find the pid for 'Java' and the 'kill -9 pid' to stop the process. Then you can start Tomcat. Address in use error when starting Tomcat Author: Dan Desch (http://www.jguru.com/guru/viewbio.jsp?EID=827173), Apr 5, 2002 I had the same problem with Tomcat 4.0.3. I tried a dozen different port numbers in server.xml to no avail--still got the same address already in use message except in each case referencing the new port number I was trying. It turns out that when I installed Tomcat, either I inadvertently elected to have Tomcat run as a service (in my case Win2000) or Tomcat decided for itself that it should be a service and start itself up when my machine boots. Invoking the shutdown.bat function did not solve the problem. Evidently, shutdown.bat is unable to stop Tomcat

running as a service--stopping a serice has to be accomplished via the service manager. Now, I would have thought that changing the port number in server.xml would have allowed a 2nd instance of Tomcat to run alongside the instance that is running as a service, each instance listening to its own port, but evidently not. Why use EJB when we can do the same thing with servlets? Location: http://www.jguru.com/faq/view.jsp?EID=126400 Created: Aug 14, 2000 Modified: 2001-11-09 06:08:03.377 Author: Dan Christopherson (http://www.jguru.com/guru/viewbio.jsp?EID=39644) Question originally posed by sreenivasulu kadirimangalam (http://www.jguru.com/guru/viewbio.jsp?EID=123964 Actually, servlets/JSPs and EJB are complementary, not competing technologies: Servlets provide support for writing web based applications whereas EJBs provide support for writing transactional objects. In larger web systems that require scalability, servlet and JSP or XML/XSL technologies provide support for the front end (UI, client) code, where EJB provides support for the back end (database connection pooling, declaritive transactions, declaritive security, standardized parameterization...) The most significant difference between a web application using only servlets and one using servlets with EJBs is that the EJB model mandates a separation between display and business logic. This is generally considered a Good Thing in non-trivial applications because it allows for internal reuse, allows flexibility by providing a separation of concerns, gives a logical separation for work, and allows the business logic to be tested separately from the UI (among others). Some of the hings that servlets and JSPs can do that EJBs cannot are: • • •

Respond to http/https protocol requests. (With JSP) provide an easy way to format HTML output. Easily associate a web user with session information

Some of the things that EJBs enable you to do that servlets/JSPs do not are: •

•

Declaritively manage transactions. In EJB, you merely specify whether a bean's methods require, disallow, or can be used in the context of a transaction. The EJB container will manage your transaction boundaries appropriately. In a purely servlet architecture, you'll have to write code to manage the transaction, which is difficult if a logical transaction must access multiple datasources. Declaritively manage security. The EJB model allows you to indicate a security role that the user must be assigned to in order to invoke a method on a bean. In Servlets/JSPs you must write code to do this. Note, however that the security model in EJB is sufficient for only 90% to 95% of application code -

there are always security scenarios that require reference to values of an entity, etc. How close is the actual session timeout period to the specified timeout period? Location: http://www.jguru.com/faq/view.jsp?EID=127074 Created: Aug 15, 2000 Modified: 2000-08-16 00:21:20.052 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) During some development work recently, I became curious as to how close the actual session timeout period was to the specified timeout period. Much to my surprise, I discovered a wide discrepancy between the two for the case when the specified timeout periods are short. I have not done experiments for the case when the specified timeout periods are long. I'd expect that for the case of long timeout periods, the two -- the specified and the actual -- would be in fairly close agreement. I show below some empirical data obtained for four different values of the specified timeout periods: 10, 20, 60, and 120 seconds. For each case, I ran five trials. Each trial consisted of hitting the reload button of the client browser after the session had already timed out from the previous reload.

all times are in seconds Specified Actual session timeout period Actual session timeout period session timeout for the server running on a for the server running on a period Windows NT machine Solaris 5.6 machine 10 24 32 53 53 53 47 44 48 45 50 20 54 39 44 51 45 40 25 22 49 52 60 105 93 97 114 100 110 113 109 101 110 120 131 161 170 146

169 165 147

135 137 146

These results were obtained with Tomcat 3.1 as a stand-alone web server for both Windows NT and Solaris. The browser used was Netscape 4.73. Shown below is a servlet, TestSessionTimeout, that I used for measuring the actual session timeout periods. For those new to servlets, the following comments should prove useful for understanding this servlet: • • • •

Assuming that a session was not previously created, the method HttpSession session =

HttpServletRequest.getSession( true );

creates a new session between a client and a server. • • • •

The timeout period of this session can be specified by invoking session.setMaxInactiveInterval( int interval );

The timeout period of a session is the maximum permissible time in seconds between successive client accesses. If a client request is not received within the specified timeout period, the session is invalidated and objects bound to it are unbound. •

If an object wishes to receive notification of when it is bound to or unbound from a session, the object must implement the HttpSessionBindingListener interface.

The servlet shown below uses a SessionTimer class that implements the HttpSessionBindingListener interface. When a session times out, the SessionTimer object, timer, is notified of that fact. It then proceeds to calculate the time difference between the creation time instant of the session and the time when the session becomes invalidated. import import import import

java.io.*; java.util.*; javax.servlet.*; javax.servlet.http.*;

public class TestSessionTimeout extends HttpServlet { private static final String TIMER_KEY = "session.timer"; public void doGet (HttpServletRequest request, HttpServletResponse response)

{

throws ServletException, IOException

);

HttpSession session = request.getSession(true); session.setMaxInactiveInterval( 120 ); SessionTimer timer = (SessionTimer) session.getAttribute( TIMER_KEY if ( timer == null ) { timer = new SessionTimer( session.getCreationTime() ); session.setAttribute( TIMER_KEY, timer ); }

// Generate Output response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("" + "Session Information" + "" + "

Session Information

"); out.println (""); out.println (""); out.println (""); out.println (""); out.println (""); out.println (""); out.println (""); out.println (""); Enumeration names = session.getAttributeNames(); while ( names.hasMoreElements() ) { String name = (String) names.nextElement(); out.println (""); out.println (""); } out.println("

Identifier	" + session.getId() + "
Created	" + new Date(session.getCreationTime()) + "
Last Accessed	" + new Date(session.getLastAccessedTime()) + "
New Session?	" + session.isNew() + "
" + name + "	" + session.getAttribute(name) + "

"); out.close(); } }

class SessionTimer implements HttpSessionBindingListener { private long createTime; public SessionTimer( long ctime ) { createTime = ctime; } public void valueBound( HttpSessionBindingEvent event ) {} public void valueUnbound( HttpSessionBindingEvent event ) { try {

long diffTimeInSecs = ( System.currentTimeMillis() - createTime ) / 1000; System.out.println( "The session duration in seconds: " + diffTimeInSecs ); } catch( SecurityException e ) {} } } Comments and alternative answers

Why you don't use the method "isNew" to ... Author: Juan Ignacio (http://www.jguru.com/guru/viewbio.jsp?EID=324997), Feb 16, 2001 Why you don't use the method "isNew" to verify if the session was created. Is it possible with Tomcat running in a standalone mode to obtain the usual httpd logs (with the remote address, date/time of connection, pages, etc.?) Location: http://www.jguru.com/faq/view.jsp?EID=127155 Created: Aug 15, 2000 Modified: 2001-07-19 15:47:30.626 Author: Ignacio J. Ortega (http://www.jguru.com/guru/viewbio.jsp?EID=98626) Question originally posed by Daniel Le Berre (http://www.jguru.com/guru/viewbio.jsp?EID=60379 At the time of writing Tomcat 3.2 Beta nor Tomcat 3.3 Dev have an access log comparable to the ones you can found in Apache,IIS or IPlanet, but in a near future this will be solved. Comments and alternative answers

I use the following code in my jsp pages to obtain... Author: Daniel Le Berre (http://www.jguru.com/guru/viewbio.jsp?EID=60379), Aug 17, 2000 I use the following code in my jsp pages to obtain a similar behaviour: <% application.log(request.getRemoteHost()+" "+(new java.util.Date())+" "+request.getHeader("Referer")); %>

Here is a class that will do the trick. Author: matt paduano (http://www.jguru.com/guru/viewbio.jsp?EID=491036), Sep 5, 2001 I got a class file off the web that provided access logging as a plug in for tomcat. It didn't work quite right, so I ran it through a decompiler and made a hack. It seems to work now. If I could attach it via this interface, I would. But I can't. So drop me a line and let me know where to send it and I'll send it to you with the server.xml config info. [email protected] How do I "make" mod_jserv with Borland C++? (I have make but not nmake.) Location: http://www.jguru.com/faq/view.jsp?EID=128573 Created: Aug 16, 2000 Modified: 2000-08-16 21:18:01.374

Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) Question originally posed by Rafael Coutinho (http://www.jguru.com/guru/viewbio.jsp?EID=115513 If nmake would do the job, it is available as a self-extracting .exe for download from ftp.microsoft.com/Softlib/MSLFILES/nmake15.exe [Does this work? Please submit feedback if so (or if not)... -Alex] Comments and alternative answers

Well i need only the servlet operations so i think... Author: Rafael Coutinho (http://www.jguru.com/guru/viewbio.jsp?EID=115513), Aug 17, 2000 Well i need only the servlet operations so i think that or its was already had compiled or that is only used for JSC. But i appreciate your attention Thanx! Using Tomcat, how can I log each and every call to the servlet engine (something like apache-access.log) ? Location: http://www.jguru.com/faq/view.jsp?EID=128735 Created: Aug 16, 2000 Modified: 2001-07-19 16:09:35.37 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Ofer Shaked (http://www.jguru.com/guru/viewbio.jsp?EID=62619 As of version 3.2, the standalone version of Tomcat does not provide an access log. It depends on the containing web server (e.g. Apache) for that function. If you feel like it, it would be straightforward to write an Interceptor that does this. Subscribe to [email protected], check out the latest CVS tree, and have fun! That's the beauty of open source. (Make sure you support the W3C standard log format, and see the Catalina source for inspiration; there's code in there for formatting access log entries.) What is a web application (or "webapp")? Location: http://www.jguru.com/faq/view.jsp?EID=129328 Created: Aug 17, 2000 Modified: 2000-08-18 19:25:56.836 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) A Web Application (or "webapp") is a concept that was introduced in the Servlet Specification version 2.2. [2.1?] You should definitely read the spec for the full story. From the spec (chapter 9): A web application is a collection of servlets, html pages, classes, and other resources that can be bundled and run on multiple containers from multiple vendors. A web application is rooted at a specific path within a web server. For example, a catalog application could be located at http:// www.mycorp.com/catalog. All requests that start with this prefix will be routed to the ServletContext which represents the catalog application.

A servlet container can also establish rules for automatic generation of web applications. For example a ~user/ mapping could be used to map to a web application based at /home/user/ public_html/. [...] A web application exists as a structured hierarchy of directories. The root of this hierarchy serves as a document root for serving files that are part of this context. For example, for a web application located at /catalog in a web server, the index.html file located at the base of the web application hierarchy can be served to satisfy a request to /catalog/index.html. A special directory exists within the application hierarchy named "WEB-INF". This directory contains all things related to the application that aren't in the document root of the application. It is important to note that the WEB-INF node is not part of the public document tree of the application. No file contained in the WEB-INF directory may be served directly to a client. The contents of the WEB-INF directory are: • • •

/WEB-INF/web.xml deployment descriptor /WEB-INF/classes/* directory for servlet and utility classes. The classes in this directory are used by the application class loader to load classes from. /WEB-INF/lib/*.jar area for Java ARchive files which contain servlets, beans, and other utility classes useful to the web application. All such archive files are used by the web application class loader to load classes from.

Sample Web Application Directory Structure

Illustrated here is a listing of all the files in a sample web application:

/index.html /howto.jsp /feedback.jsp /images/banner.gif /images/jumping.gif /WEB-INF/web.xml /WEB-INF/lib/jspbean.jar /WEB-INF/classes/com/mycorp/servlets/MyServlet.class /WEB-INF/classes/com/mycorp/util/MyUtils.class Comments and alternative answers

JAVABEAN Author: SANJAY DESHPANDE (http://www.jguru.com/guru/viewbio.jsp?EID=452552), Apr 4, 2002 In this dir structure where to store JavaBeans? i ve them in \WEB-INF\Classes but it s not working for me Re: JAVABEAN

Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727), Apr 4, 2002 Hi, Java is a case sensitive language. "Classes" is different from "classes". Accessing images and HTML files within a web app Author: Thomas Sasala (http://www.jguru.com/guru/viewbio.jsp?EID=876089), Dec 5, 2002 Our general policy is to access all images and HTML files using absolute paths. Thus, when the JSP or HTML file is moved to a different directory, the linked resource will still work (assuming it has not been moved). How does one accomplish this with a web app? The web application can be deployed to any context by the site administrator, so there is no way to know before hand what the absolute path would be during the coding phase. Does that mean images (and HTML files) have to be accessed using relative paths? I suppose you could map a servlet to /image and use the servlet to return the correct image, but that's not very efficient. -Tom Re: Accessing images and HTML files within a web app Author: Rama Sarma (http://www.jguru.com/guru/viewbio.jsp?EID=1222294), Jan 20, 2005 Can you help me out with the following problem. It is, if I have to map images in a JSP or HTML from a remote location dynamically, how should i proceed further. I think i should go with a servlet in between. Can you explain the procedure of the same. Hope, you got my question. Thanks n Regards, Ram What is a WAR file and how do I create one? Location: http://www.jguru.com/faq/view.jsp?EID=129333 Created: Aug 17, 2000 Modified: 2000-08-18 19:27:43.733 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) A WAR (or "web archive") file is simply a packaged webapp directory. It is created using the standard Java jar tool. For example:

cd /home/alex/webapps/mywebapp jar cf ../mywebapp.war * See also What is a web application (or "webapp")? How are initialization parameters passed to a servlet under Servlet API version 2.2? Location: http://www.jguru.com/faq/view.jsp?EID=129378 Created: Aug 17, 2000 Modified: 2000-08-18 19:29:39.156 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410)

Through the webapp deployment descriptor, which is the web.xml file in the directory WEB-INF. Note that there are two different types of web.xml files in Tomcat 3.x: There is a web.xml that sits in the top-level configuration directory TOMCAT_HOME/conf and then there can be a separate web.xml for each webapp in the directory WEB-INF for that webapp. You would want to keep webapp specific deployment information, such as initialization parameters and their values, in the web.xml specific to that webapp. The best on-line example that illustrates servlet initialization through a webapp's deployment descriptor is, I believe, the ServletParam servlet in the test webapp in your Tomcat software package. This servlet can be called with two different canonical names, as for example in http://localhost:8080/test/servlet/servletParam1 and http://localhost:8080/test/servlet/servletParam2 The deployment descriptor maps the canonical names servletParam1 and servletParam2 to the actual servlet ServletParam but with different values of the initialization parameters. When the servlet ServletParam is called with the name servletParam1, the initialization parameter-value pairs are param1 value1 param2 value2 and when the same servlet is called with the name servletParam2, the parametervalue pairs are param3 value3 param4 value4 The following constitutes a sufficient deployment descriptor for this example:

<web-app> <servlet> <servlet-name> servletParam1 <servlet-class> ServletParam <param-name>param1 <param-value>value1

<param-name>param2 <param-value>value2 <servlet> <servlet-name> servletParam2 <servlet-class> ServletParam <param-name>param3 <param-value>value3 <param-name>param4 <param-value>value5000 The first half of the web.xml file associates the servlet ServletParam with the name servletParam1 and then goes on to declare its parameter-value pairs. The second half does the same for the name servletParam2. Comments and alternative answers

Cannot get init-params to work Author: Jeffrey Blaze (http://www.jguru.com/guru/viewbio.jsp?EID=529107), Oct 24, 2001 I tried exactly what was detailed in "How are initialization parameters passed to a servlet under Servlet API version 2.2?" I got a 404 when trying to load ...../ServletParam1 or ServletParam2. That's one problem. I then added:; <servlet> <servlet-name> servletParam; ; <servlet-class>; ServletParam; ; ; <param-name>parama; <param-value>valuea; ; ;

<param-name>paramb; <param-value>valueb; ; ; to the web.xml file. Told browser to load ServerParam. It did, but no init-params were displayed. Is there some higher-level setting somewhere, perhaps a security switch, that determines whether init-params can be accessed? also, how exactly does the <server-name> / <server-class> mapping work? The implication in the main topic is that the <server-name> entry specifies an alias for the <server-class>, but this did not work for me. Re: Cannot get init-params to work Author: juan carbajal (http://www.jguru.com/guru/viewbio.jsp?EID=1227809), Feb 17, 2005 I have the same problem were you able to get through it? How can I call a servlet from a JSP page? How can I pass variables from the JSP that the servlet can access? Location: http://www.jguru.com/faq/view.jsp?EID=129506 Created: Aug 17, 2000 Modified: 2000-08-18 20:03:16.052 Author: Priya Venkatesan (http://www.jguru.com/guru/viewbio.jsp?EID=129496) Question originally posed by prasad musunuru (http://www.jguru.com/guru/viewbio.jsp?EID=121993 You can use <jsp:forward page="/relativepath/YourServlet" /> or response.sendRedirect("http://path/YourServlet"). Variables can be sent as: <jsp:forward page=/relativepath/YourServlet> <jsp:param name="name1" value="value1" /> <jsp:param name="name2" value="value2" /> You may also pass parameters to your servlet by specifying response.sendRedirect("http://path/YourServlet?param1=val1"). See also: •

What servlet code corresponds to the various "scope" values for the <jsp:useBean> tag?

Comments and alternative answers

I follow this, but how can I use those parameters once... Author: Jeff Sajor (http://www.jguru.com/guru/viewbio.jsp?EID=62983), Aug 18, 2000

I follow this, but how can I use those parameters once I get to the servlet? In ther words, the first part is solved -- passing parameters from the JSP to the servlet. The part I need to know is when I get inside my servlet, how do I retrieve the parameters that I passed with the JSP? You can also set variables in the request, session,... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Aug 18, 2000 You can also set variables in the request, session, or application; see above link for details. To get the parameter(s) that are passed from JSP page, ... Author: Shankar Narayana (http://www.jguru.com/guru/viewbio.jsp?EID=82031), Aug 19, 2000 To get the parameter(s) that are passed from JSP page, you can use the following snippet of code within your servlet: String somename = request.getParameter("parametername");

You can access them using String varisble1 = req... Author: Rahul kumar Gupta (http://www.jguru.com/guru/viewbio.jsp?EID=4809), Aug 20, 2000 You can access them using

String varisble1 = request.getParameterValues("ParameterName")[0];

or String variable1 =

request.getParameter("ParameterName");

or if you're sending an array

String []variable1 = request.getParameterValues("ParameterName")[0];

The best way is to use Enumeration en = reques... Author: manoj Tripathy (http://www.jguru.com/guru/viewbio.jsp?EID=133823), Aug 24, 2000 The best way is to use Enumeration en = request.getParameterNames();

then loop thru the enumeration to get all the parameters/arguments that you passed Passing Boolean Variables to an Included JSP? Author: Ryan Bales (http://www.jguru.com/guru/viewbio.jsp?EID=922699), Jun 21, 2002 I am passing this boolean variable to the jsp below. How do I access in on the sidebar.jsp this code gives me errors: boolean ridgidbliptag = request.getParmeterValues("ridgidbliptag");

Please help. Thanks Ryan ridgidbliptag = true; <jsp:include page="includes/menu/sidebar.jsp" flush="true"> <jsp:param name="BackGroundImage" value="bg_A.gif"/> <jsp:param name="BackGroundColor" value="#663300"/> <jsp:param name="LogoImage" value="logoA.gif"/> <jsp:param name="ridgidbliptag" value="<%=ridgidbliptag%>" /> Can there be more than one instance of a servlet at one time ? Location: http://www.jguru.com/faq/view.jsp?EID=129558 Created: Aug 17, 2000 Modified: 2000-08-18 20:32:59.181 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) Question originally posed by francois lascelles (http://www.jguru.com/guru/viewbio.jsp?EID=115425 The answer to this question is on page 20 of the Java Servlet API Specification Version 2.2: It is important to note that there can be more than one instance of a given Servlet class in the servlet container. For example, this can occur where there was more than one servlet definition that utilized a specific servlet class with different initialization parameters. This can also occur when a servlet implements the SingleThreadModel interface and the container creates a pool of servlet instances to use. How can I implement HTTP keep-alive on the connection between my applet and servlet? Location: http://www.jguru.com/faq/view.jsp?EID=130219 Created: Aug 18, 2000 Modified: 2000-08-24 10:56:58.625 Author: Rajah Kalipatnapu (http://www.jguru.com/guru/viewbio.jsp?EID=116593) Question originally posed by Venkatesan Lakshmi Narayanan (http://www.jguru.com/guru/viewbio.jsp?EID=29154 You can use public void setRequestProperty(String key, String value) method on URLConnection. Description of the method from Java API: Sets the general request property. Parameters: key - the keyword by which the request is known (e.g., "accept"). value - the value associated with it. Example: This example uses the above method to set "connection" property to "Keep-Alive" and invokes the so called "RequestHeaderExample" servlet and prints the response. part of the output is given after the code.

While the example is an application, the same works in an applet. public class TestConnectionKeepAlive { public static void main(String[] args) { try { java.net.URL url = new java.net.URL ("http://my.host.com/examples/servlet/Example"); java.net.URLConnection uc = url.openConnection(); uc.setRequestProperty("connection","Keep-Alive"); uc.connect(); java.io.BufferedReader br = new java.io.BufferedReader( new java.io.InputStreamReader(uc.getInputStream())); String str = null; while( true ) { str = br.readLine(); if( str == null) break; System.out.println(str); } }catch(Exception e) { e.printStackTrace(); } } } Output:

accept host connection user-agent

text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2 my.host.com Keep-Alive Java1.3.0rc3

Comments and alternative answers

You can find the RFC for HTTP 1.1, which supports ... Author: Yasar Qureshi (http://www.jguru.com/guru/viewbio.jsp?EID=48204), Aug 24, 2000 You can find the RFC for HTTP 1.1, which supports Keep-Alive, at http://www.faqs.org/rfcs/rfc2068.html. Bugtraq has had reports that Tomcat has vulnerabilities that allow remote users to get paths and to compromise root if Tomcat is run as root. Are these true? Location: http://www.jguru.com/faq/view.jsp?EID=131224 Created: Aug 21, 2000 Modified: 2000-08-21 19:02:58.72 Author: Ignacio J. Ortega (http://www.jguru.com/guru/viewbio.jsp?EID=98626)

Question originally posed by zeno godofnothin (http://www.jguru.com/guru/viewbio.jsp?EID=117406 Yes, for Tomcat 3.1. No, for Tomcat 3.2 Beta. But is very easy to secure Tomcat 3.1: • • • • •

Stop Tomcat delete the contents of %TOMCAT_HOME%/work Delete the file: admin.war from %TOMCAT_HOME%/webapps Delete de directory %TOMCAT_HOME%/webapps/admin Start tomcat

Is there any way to retrieve all of the active session ids on a server? The HttpSessionContext interface used to provide methods to do this, but has since been deprecated in the 2.1 API. Location: http://www.jguru.com/faq/view.jsp?EID=131912 Created: Aug 22, 2000 Modified: 2000-08-24 16:33:53.993 Author: Rahul kumar Gupta (http://www.jguru.com/guru/viewbio.jsp?EID=4809) Question originally posed by Anne Goyarts (http://www.jguru.com/guru/viewbio.jsp?EID=127284 There is no way to get the all session ids apart from HttpSessionContext. But you can implement it yourself with a collection. Make a class that is using hash map or hash table object which is global to the application. Whenever a user logs in make an entry into hashmap or hash table and remove it when he/she logs out. At any point you can retrieves keys and their values from that class that coresponds to user identification and session object. for example if you are using JSP look at this code-

... <jsp:useBean id="allsessions" scope="application" class="java.util.HashTable"/> ... <% allsessions.put(userid,session); String user=null; Enumeration users= allsessions.keys(); while(users.hasMoreElements()) { user = users.nextElement(); out.println("Userid ="+user);

out.println("session = "+allsessions.get ((String)user)); } %> [This code doesn't quite work -- where is "userid" acquired? How do you capture logout? But it's a nice hack anyway... -Alex] Comments and alternative answers

Maybe under Tomcat 3.1, but not Tomcat 3.2 Author: Roger Hand (http://www.jguru.com/guru/viewbio.jsp?EID=292314), May 8, 2001 I hacked a version of the above code that I was actually getting to work under Tomcat 3.1, but it doesn't work with Tomcat 3.2, which does some trickery with sessions when you attempt to reference them from outside the request . . . rather than storing an org.apache.tomcat.session.StandardSession as Tomcat 3.1 does, Tomcat 3.2 stores an org.apache.tomcat.facade.HttpSessionFacade, which appears to act as a security shield for the real session, and only returns dummy values. The only way out seems to be the "official" way, whereby you make an object a session listener. Hiding "jsessionid" Author: M. washu (http://www.jguru.com/guru/viewbio.jsp?EID=1217388), Dec 21, 2004 Hi all, Is there a way to include jsessionid in a hidden field (in a form) rather than in the URL (by the URL rewriting mechanism ) ? I saw that HttpSessionContext class was deprecated for security reason, but for security reasons too i would like to know if there is a way to prevent the jessionid from being logged in the HTTP server log files (of course without using cookies) ? Thanks in advance. We are trying to access a large volume of data from a remote database, but the time it takes to get the data from the database is more than the maximum timeout for the web server, so the webpage is not getting displayed. How can we solve this problem? Location: http://www.jguru.com/faq/view.jsp?EID=132065 Created: Aug 22, 2000 Modified: 2000-08-25 20:14:51.715 Author: Nicholas Whitehead (http://www.jguru.com/guru/viewbio.jsp?EID=1260) Question originally posed by Geetha Santhanam (http://www.jguru.com/guru/viewbio.jsp?EID=63150 JDBC is not usually the root cause of the delay, so I'll make the obvious suggestions first: •

Extend the maximum timeout for the web page.

• • • • •

Optimize the query to return the data faster. Reduce the amount of data you return. Increase the bandwidth to the database. Tune the transport protocol to carry more data per packet. Last and most importantly for remote access across a slow line: denormalize the query. One query returning many rows will have a far faster throughput than many queries returning a small number of rows. Differently put, the submission and processing of a query itself can easily longer than the actual retrieval of the rows.

Joe Sam Shirah adds: jGuru received several answers to this question on the JDBC side, most of which emphasized narrowing the query to take less time. This is excellent advice, but not always possible. Additionally, other tasks may bring up the same issues with servlets. During January, 2000, there was an exchange of messages on Sun's servlet mailing list which discussed the issue and provided a more general answer. Essentially, the advice is to start a new thread in the servlet to do the work and then, using refresh in the header, repeatedly send a status message until the long running task is done. See the series Timing out of response data. Interestingly, probably the one that outlines the process best is http://archives.java.sun.com/cgibin/wa?A2=ind0001&L=servlet-interest&D=0&P=80267 by one Nicholas Whitehead. Swarraj "sk or raj" Kulkarni and Kesav Kumar Kolla also contributed to this answer. Comments and alternative answers

Preventing browser HTTP connection timeout Author: Abu Daniel (http://www.jguru.com/guru/viewbio.jsp?EID=50542), Mar 5, 2003 You can send dummy tags to the browser, just to keep the connection alive. A patchcode which I wrote for my JSPs was: <% ///// dummy tags to the browser so that connection is maintained ///////// final java.util.Vector vec = new java.util.Vector(); final java.io.PrintWriter writer = response.getWriter(); Runnable runnable = new Runnable() { public void run() { int count = 0; while(vec.size() == 0) { try { Thread.sleep(5000); } catch (InterruptedException e) { e.printStackTrace(); } try { writer.write("\r\n"); writer.flush();

}

} catch (Exception e) { e.printStackTrace(); }

}

}; Thread transectionThread = new Thread(runnable); transectionThread.start(); ///////////// End New Code to send dummy tags to browser so connection is maintained ///////// %>

After the last line of your bean call (or processing) write the following line: <% vec.addElement("test"); %>

How can I tell if a connection to my servlet is via a secure channel (i.e., HTTPS instead of HTTP)? Location: http://www.jguru.com/faq/view.jsp?EID=134132 Created: Aug 24, 2000 Modified: 2000-08-24 16:05:55.974 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Use the servlet request's isSecure() or getAuthType() methods. Where can I find the API documentation for Servlets? Location: http://www.jguru.com/faq/view.jsp?EID=134133 Created: Aug 24, 2000 Modified: 2000-08-24 16:06:41.865 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) It's available from Sun's J2EE API documentation page. How do I use servlet aliasing, so the URL "http://foo.com/mywebapp/servlet/a.b.c.MyServlet" can become "http://foo.com/mywebapp/Thingy"? Location: http://www.jguru.com/faq/view.jsp?EID=134402 Created: Aug 24, 2000 Modified: 2000-08-24 19:08:46.694 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Alex Chaffee PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=3 According to the Servlet 2.2 spec, you can set a servlet alias in the WEBINF/web.xml deployment descriptor for your webapp. The <servlet-name> element defines the "canonical name" for the servlet. This name is used to refer to the servlet elsewhere in the file. The <servlet-mapping> element defines a mapping from a URL pattern to a servlet. This element contains two sub-elements, <servlet-name> and . For example:

<servlet> <servlet-name>hello <servlet-class>com.stinky.HelloWorld <servlet-mapping> <servlet-name>hello hi in the webapp "examples" would map the URL http://www.stinky.com/examples/hi to the servlet com.stinky.HelloWorld. The url-pattern can contain the wildcard character "*". For instance, Tomcat maps all JSPs to the JspServlet using

<servlet> <servlet-name>jsp <servletclass>org.apache.jasper.runtime.JspServlet <servlet-mapping> <servlet-name>jsp *.jsp The url-pattern can also map entire paths to a single servlet; the url-pattern "/catalog/*" would match a URL like "http://www.stinky.com/examples/catalog/furniture/couches/futon". The servlet can access the extra path info (past "catalog/") via the Request object using the getPathInfo() method. If your server does not support the Servlet 2.2 API, then it usually provides an alternate method. Please submit feedback to tell how your favorite servlet engine does it! Comments and alternative answers

I guess in this answer, the dir "com\stinky&q... Author: neal ravindran (http://www.jguru.com/guru/viewbio.jsp?EID=17737), Nov 5, 2000 I guess in this answer, the dir "com\stinky" is inside "WEB-INF\classes" dir (under that particular webapp...servers\default\somewebApp\WEB-INF\classes) and contains the "Helloworld.class"...is that right? [Yes. -Alex] How can I do this aliasing in IBM Websphere? Author: Farhat Kathawala (http://www.jguru.com/guru/viewbio.jsp?EID=238431), Dec 18, 2000 How can I do this aliasing in IBM Websphere?

This works with jserv but what about mod_jk? Author: javier Beringola (http://www.jguru.com/guru/viewbio.jsp?EID=345612), Jun 14, 2001 How do you do aliasing with mod_jk? How can I map to http://foo.com/Thingy? Author: Yeatts Jones (http://www.jguru.com/guru/viewbio.jsp?EID=541424), Nov 8, 2001 Can you map to somewhere outside the mywebapp directory? servlet-name & url-pattern not working Author: aftab mehmood (http://www.jguru.com/guru/viewbio.jsp?EID=737958), Jan 28, 2002 hello ! in my web application both tags are not working? i am using tomcat 4.0? what else can be done, in addition to adding tags in web.xml here is my code <servlet> <servlet-name>H17 <servlet-class>Servlet17 <servlet-mapping> <servlet-name>H17 /Go my web application is=web now, a )http://localhost:8080/web/Go b )http://localhost:8080/web/servlet/H17 c )http://localhost:8080/web/servlet/Servlet17 only " c " is working ok thank you Re: servlet-name & url-pattern not working Author: aftab mehmood (http://www.jguru.com/guru/viewbio.jsp?EID=737958), Jan 28, 2002 examples provided in web application of tomcat related to mapping (e.g examples) are working fine Servlet Mapping on a Sun Cobalt Server? Author: Kit Reynolds (http://www.jguru.com/guru/viewbio.jsp?EID=821894), Apr 2, 2002 My question relates to servlet mapping on a Sun Cobalt server. I've successfully deployed WAR files to the server and everything works fine, with a new context created etc. However I haven't been able to successfully map files such as *.frm or even *.htm across to servlets, the server just reports file not found. Everything maps

fine on my local Tomcat 3.2 and 4.0 setups. Any suggestions? or thoughts gratefully received. (I'm working with an ISP's shared Sun Cobalt Server with JDK 1.3 installed which provides Tomcat as a plug in to the web server.) What'll happen to a servlet request (including the transactions that have already been carried out) when: a) client's browser has been closed. b) client's connection has been disconnected. c) client presses the stop button. Location: http://www.jguru.com/faq/view.jsp?EID=134657 Created: Aug 25, 2000 Modified: 2000-08-25 08:48:29.763 Author: Stuart Woodward (http://www.jguru.com/guru/viewbio.jsp?EID=129604) Question originally posed by Richard Goh Muk Ling (http://www.jguru.com/guru/viewbio.jsp?EID=18858 All of the above result in a "java.net.SocketException: Connection reset by peer: socket write error" when you close() the PrintWriter in the response. If it is important that the client see's the message then ideally you would want to catch the Exception and rollback the transaction you were working on. In practice, with JSDK 2.0 it doesn't seem possible to trap this Exception. It seems like it is trapped at a lower level and a Stacktrace printed to the console which results in lots of garbage in the server logs. (Any corrections or advice about avoiding this is highly welcome). As a result you really have no choice but to just process the result of a GET/POST to your Servlet regardless of whether the client actually recieves the response. Sometimes an apparently cancelled request is the result of the client double clicking on a link so you may have to take precautions that this doesn't result in say two identical transactions being made. Comments and alternative answers

Right, you have no choice in JSDK 2.0 but with JSDK... Author: Thomas Nagel (http://www.jguru.com/guru/viewbio.jsp?EID=68546), Sep 21, 2000 Right, you have no choice in JSDK 2.0 but with JSDK 2.2 you have a response.flushBuffer method which could be used for the following work around: Example: ... Some Code ... try{ for( int i=0; i<10000; i++ ){ out.println( "test\n" );

Thread.sleep( 2 ); response.flushBuffer(); } } catch( Exception e ){ log( "---> Exception " + e.toString() ); } ... Some Code ...

Hitting the STOP Button in the browser results in something like this: 2000-09-21 02:10:16 - path="/testArea" :TestServlet: ---> Exception java.io.IOException: Datenübergabe unterbrochen (broken pipe)

Hope this helps :-) Bye Thomas Re: Right, you have no choice in JSDK 2.0 but with JSDK... Author: Sung Hyuk Jang (http://www.jguru.com/guru/viewbio.jsp?EID=1022540), Nov 7, 2002 Hi. I tested the problem. (Servlet can't detect browser stopped.) I tested with tomcat 4.0.3 and tomcat 3.2. I catched ioexception in tomcat3.2. but I can't catch any exception in tomcat4.0.3. Why did it happen? Please Guru, tell me. my code is below. <%@ page import="java.net.*,java.util.*,java.text.*,java.io.*" contentType="text/html"%> <% try { while ( true ) { out.println("I am in loop " ); out.flush(); response.flushBuffer(); System.out.println("I'm alive : " + new Date()); Thread.sleep(1000); } } catch (Exception e) { System.out.println("I'm in Exception : " + new Date()); } %> exception Author: david nierop (http://www.jguru.com/guru/viewbio.jsp?EID=418198), May 9, 2001 If you don't use sockets but http, printwriter does not throw any exceptions. Instead you should call the checkerror() routine of printwriter to check it out. But the error flags of printwriter are only set if the webserver is configured to do so. I read this in a book form oreilly. Does anybody know how to configure your (Apache) server? How can I parse an HTML page to capture a URL returned from, e.g., a search engine? Location: http://www.jguru.com/faq/view.jsp?EID=134999 Created: Aug 25, 2000 Modified: 2001-08-18 17:59:34.98 Author: Davanum Srinivas (http://www.jguru.com/guru/viewbio.jsp?EID=2011)

Question originally posed by Sharriff Aina (http://www.jguru.com/guru/viewbio.jsp?EID=122696 Sun has an good article (with sources) at: Writing a Web Crawler in the Java Programming Language Comments and alternative answers

Also, before you start to parse a possibly messy HTML... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Oct 9, 2000 Also, before you start to parse a possibly messy HTML file, you may want to clean it up. HTMLTidy would help. Unfortunately, Andy decided not to keep maintaining the Java version. See http://www3.sympatico.ca/ac.quick/ If I send an encoded URL to a servlet, do I have to decode it before using the getParameter() method or is it automatically decoded by the service() method of the servlet? Location: http://www.jguru.com/faq/view.jsp?EID=135073 Created: Aug 25, 2000 Modified: 2000-08-25 20:34:46.982 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Richard Pilon (http://www.jguru.com/guru/viewbio.jsp?EID=130873 It's decoded for you. The string you get from getParameter is the actual value the user entered, after having been encoded by the browser and decoded by the servlet engine. This can cause some confusion when going back and forth from servlet to HTML to servlet again, since it means that the number of encodes does not match the number of decodes you have to write. See also What is the difference between URL encoding, URL rewriting, and HTML escaping? How can I get access to the properties of my running WebLogic server that have been set inside the weblogic.properties file? In particular I am after the document root of my server. Location: http://www.jguru.com/faq/view.jsp?EID=135221 Created: Aug 25, 2000 Modified: 2000-09-16 16:45:43.949 Author: Robert Castaneda (http://www.jguru.com/guru/viewbio.jsp?EID=4362) Question originally posed by Nagendra V Prasad (http://www.jguru.com/guru/viewbio.jsp?EID=108708 In WebLogic 5.1, to gain access to the weblogic properties, you can use the ConfigServicesDef interface which is accessible from the T3Client. The particular property that you are after is : •

weblogic.httpd.documentRoot

You may need to pre-pend the following properties to get the full path • •

weblogic.system.home weblogic.system.name

The following is some sample code that should get you going import weblogic.common.*; public class SimpleT3Client { public static void main(String[] argv) throws Exception { T3Client t3 = new T3Client("t3://localhost:7001"); t3.connect(); String prop = t3.services.config() .getProperty("weblogic.httpd.documentRoot"); t3.disconnect(); } } Comments and alternative answers

Question Author: sandhya sandhya (http://www.jguru.com/guru/viewbio.jsp?EID=455310), Jul 15, 2001 How can i get access to the properties of my running weblogic server 6.0? Re: Question Author: Radha Krishna Guduru (http://www.jguru.com/guru/viewbio.jsp?EID=769952), Feb 25, 2002

Weblogic 6.0 doesn't have weblogic.properties like in weblogic5.1. There is a config.xml in the mydomain folder under bea/wlserver6.0/cofig/mydomain. To get the configuration details you should need to use JMX API. Here i have given a sample program which will make uses of the JMX API. import import import import import

javax.naming.*; weblogic.jndi.Environment; weblogic.management.MBeanHome; weblogic.management.configuration.DomainMBean; weblogic.management.configuration.ServerMBean;

public class AccessMBeanForJGuru { public AccessMBeanForJGuru() { }

public static void main(String args[]) { String s = "t3://" + args[0] + ":" + args[1]; String s1 = "system"; try { Object obj = new InitialContext(); Environment environment = new Environment(); environment.setProviderUrl(s); environment.setSecurityPrincipal(s1); environment.setSecurityCredentials(args[2]); obj = environment.getInitialContext(); MBeanHome mbeanhome = (MBeanHome)((Context) (obj)).lookup("weblogic.management.adminhome"); DomainMBean domainmbean = mbeanhome.getActiveDomain(); System.out.println("The root directory for the admin home of weblogic is"+domainmbean.getRootDirectory()); //using this domain bean object you //can get and set attributes of //config.xml at runtime. since domainbean extends configuarationmbean //.......................................... //................................ ServerMBean aservermbean[] = domainmbean.getServers(); System.out.println("No of servers in the domain " + mbeanhome.getDomainName() + " " + aservermbean.length); for(int i = 0; i < aservermbean.length; i++) { System.out.println("The Server "+i+" in domain is"+aservermbean[i].getName()); } ((Context) (obj)).close(); } catch(AuthenticationException authenticationexception) { System.out.println("Authentication Exception: " + authenticationexception); } catch(CommunicationException communicationexception) { System.out.println("Communication Exception: " + communicationexception); } catch(NamingException namingexception) { System.out.println("Naming Exception: " + namingexception); } } }

Re[2]: Question

Author: Ben Macdonald (http://www.jguru.com/guru/viewbio.jsp?EID=895571), May 28, 2002 If I define an attribute in the weblogic.xml file like: <weblogic-web-app> ..snip.. <session-descriptor> <session-param> <param-name>TimeoutSecs <param-value>3600 ..snip.. Then using the code above, how would I reference this attribute "TimeoutSecs"? I am not sure of the naming convention. domainmbean.getAttribute("??.??.TimeoutSecs") Re: Question Author: madan kawle (http://www.jguru.com/guru/viewbio.jsp?EID=978499), Aug 7, 2002 How to access user defined property file from Weblogic 6.x ? I want the servlet container to load one or more servlets when the container is first fired up, as opposed to when a client issues a request for the servlets. How do I do that under Servlet 2.2 API? Location: http://www.jguru.com/faq/view.jsp?EID=135396 Created: Aug 26, 2000 Modified: 2000-08-30 12:52:03.497 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) Through the load-on-startup element of the webapp deployment descriptor file web.xml. Suppose you have two servlets, TestServlet_1 and TestServlet_2, that you'd like to get automatically loaded in when the servlet container is first fired up. And let's say that you want TestServlet_2 to be loaded before TestServlet_1. The following web.xml file placed in the WEB-INF directory of the relevant webapp would do the job.

<web-app>

<servlet> <servlet-class> TestServlet_1 5 <servlet> <servlet-class> TestServlet_2 1 The optional content of the load-on-startup element, the positive integer 5 for TestServlet_1 and 1 for TestServlet_2, controls the order in which such servlets would be loaded into the container at startup. The smaller the value of the integer, which must be positive (even 0 is not allowed) to enable automatic loading at startup, the earlier the servlet would be loaded. If no value is specified or if the value specified is not a positive integer, the Tomcat 3.1 container will load the servlet only when a request is received for the servlet. Getting a servlet container to load a servlet at startup can be very useful in certain applications, as for example pointed out by Alex Chaffee in a servlet FAQ posting. Comments and alternative answers

RE: at web.xml of Servlet 2.2 API Author: simon ru (http://www.jguru.com/guru/viewbio.jsp?EID=400431), Apr 10, 2001 What if I am not using Servlet and web container but only the ejb container? Does the app server provide something like that? I am using Borland App Server 4.5. See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 2, 2001 How can I set a servlet to load on startup of the ... See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 15, 2001 Startup class in TOMCAT

How do I designate a servlet to serve as a default servlet for a given webapp under Servlet 2.2 API? Location: http://www.jguru.com/faq/view.jsp?EID=135638 Created: Aug 26, 2000 Modified: 2000-09-06 15:31:03.151 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) Through the servlet-mapping element of the webapp deployment descriptor file web.xml. The url-pattern sub-element of the servlet-mapping element must be set to '/'. If made available, a default servlet is executed by the server whenever the client browser points to the URL

http://foo.com/mywebapp/ or to the URL http://foo.com/mywebapp/nonExistentServlet For example, for a webapp named test-suite, the deployment descriptor shown below permits my server to execute the DefaultHelloServlet for the following URLs: http://localhost:8080/test-suite/ http://localhost:8080/test-suite/NonExistentServlet for any pathname substituted for NonExistentServlet provided it does not begin with /servlet/. Here is the deployment descriptor (web.xml) for this example that sits in the WEBINF directory of my test-suite webapp:

<web-app> <servlet> <servlet-name> hello <servlet-class> DefaultHelloServlet <servlet-mapping>

<servlet-name> hello / See also Alex Chaffee's Servlet FAQ entry dealing with servlet aliasing. Comments and alternative answers

Are there any known problems with Tomcat 3.2.1 and default servlets? Author: Carmine Greco (http://www.jguru.com/guru/viewbio.jsp?EID=414482), May 3, 2001 I have tried to make a servlet the default servlet, as described above, but it's not working. Are there any things to be careful about? I'm using Tomcat 3.2.1 on Linux. Re: Are there any known problems with Tomcat 3.2.1 and default servlets? Author: Carmine Greco (http://www.jguru.com/guru/viewbio.jsp?EID=414482), May 3, 2001 I forgot to mention that I get a directory listing instead of the output of the servlet I want to execute. Tried it - but it seems to catch other requests as well Author: Amos Shapira (http://www.jguru.com/guru/viewbio.jsp?EID=4346), Aug 30, 2001 I tried adding the following to my web.xml file: <servlet> <servlet-name> start <servlet-class> StartController <servlet-mapping> <servlet-name> start /

All that the StartController servlet does is to redirect the client to the right URL. It seems to do its job (using standalone Tomcat 3.2.1, Sun JDK 1.2.2_005, Windows

2000 Professional) but all my images are now missing. If I understand the Servlet 2.2. spec correctly, then what happens is that Tomcat doesn't find any servlet which matches URL paths like "images/image.gif" and so directs the request to the default servlet. I do have the standard mime-mapping in the web.xml file. Can I do anything about this? Thanks, --Amos Use welcome-file and get over with it Author: Amos Shapira (http://www.jguru.com/guru/viewbio.jsp?EID=4346), Aug 30, 2001 I just got around the problem: instead of the Servlet stuff I created an index.jsp file which reads like: <% response.sendRedirect("login"); %>

And added the following to my web.xml file: <welcome-file-list> <welcome-file> index.jsp

And now it works like a charm. What is the difference between response.sendRedirect(), RequestDispatcher.forward(), and PageContext.forward()? Location: http://www.jguru.com/faq/view.jsp?EID=136035 Created: Aug 27, 2000 Modified: 2002-12-30 09:08:31.581 Author: Serge Knystautas (http://www.jguru.com/guru/viewbio.jsp?EID=100012) Question originally posed by Priya Venkatesan (http://www.jguru.com/guru/viewbio.jsp?EID=129496 In a nutshell, RequestDispatcher.forward() works on the server and response.sendRedirect() works on the browser. When you invoke RequestDispatcher.forward(), the servlet engine transfers control of this HTTP request internally from your current servlet or JSP to another servlet or JSP or static file. When you invoke response.sendRedirect(), this sends an HTTP response to the browser to make another request at a different URL. RequestDispatcher.forward() and PageContext.forward() are effectively the same. PageContext.forward is a helper method that calls the RequestDispatcher method. See also:

• • •

How do I send a redirect from a servlet? What are the different cases for using sendRedirect() vs. getRequestDispatcher()? What is the difference between response.sendRedirect(), RequestDispatcher.forward(), and PageContext.forward()?

Comments and alternative answers

Hi Priya, I put up the same question in http://th... Author: Kiran Sarvepalli (http://www.jguru.com/guru/viewbio.jsp?EID=17055), Oct 9, 2000 Hi Priya, I put up the same question in http://theserverside.com and I got the following answer: Well basically both method calls redirect you to new resource/page/servlet. The difference between the two is that sendRedirect always sends a header back to the client/browser. this header then contains the resource(page/servlet) which you wanted to be redirected. the browser uses this header to make another fresh request. thus sendRedirect has a overhead as to the extra remort trip being incurred. it's like any other Http request being generated by your browser. the advantage is that you can point to any resource(whether on the same domain or some other domain). for eg if sendRedirect was called at www.mydomain.com then it can also be used to redirect a call to a resource on www.theserverside.com. In the case of forward() call, the above is not true. resources from the server, where the fwd. call was made, can only be requested for. But the major diff between the two is that forward just routes the request to the new resources which you specify in your forward call. that means this route is made by the servlet engine at the server level only. no headers are sent to the browser which makes this very efficient. also the request and response objects remain the same both from where the forward call was made and the resource which was called. I don't know about PageContext.forward(). Thanks, Kiran Is there a significant difference in handle time? Author: Joost Schouten (http://www.jguru.com/guru/viewbio.jsp?EID=581960), Jun 30, 2003 All requests made to my app go through my controller servlet. Since I often use long query strings I choose to use the response.sendRedirect("myJSPfile"), so the address bar would always look clean. My servlet -> JSP's communication goes through the session beans of the container.

But by the sound of things this is not the fastest option. I was just wondering if anybody knows if this delay of the headers traveling to and from the client one more time is significant? And is it worth to use the requestDispatcher.forward()? Kind regards, Joost Schouten How can I measure the file downloading time using servlets? Location: http://www.jguru.com/faq/view.jsp?EID=136390 Created: Aug 28, 2000 Modified: 2001-07-23 09:16:32.622 Author: Serge Knystautas (http://www.jguru.com/guru/viewbio.jsp?EID=100012) Question originally posed by JayaRam Raja Sekar (http://www.jguru.com/guru/viewbio.jsp?EID=94956 [Note: this could mean servlet-as-client or servlet-as-server; we assume this is the servlet-as-server interpretation] First start by creating a FileServlet... a servlet that takes a dir/filename as a parameter (either query string, post parameters, or extra path info). Get a File object handle to the data you want to download. Before you start writing data, capture the current time in a long primitive. Then write all data out, and at the end, get the current time again. Take the difference, and that was your transfer time. Here's some mockup code. note: do not implement this as it gives read access to your entire web root (including source of JSPs... figure out where you want to serve files from and change accordingly. ServletOutputStream out = response.getOutputStream(); String filename = getServletContext().getRealPath(request.getQueryString()); FileInputStream fin = new FileInputStream(filename); long start = System.currentTimeMillis(); byte data[] = new byte[1024]; int len = 0; while ((len = fin.read(data)) > 0) { out.write(data, 0, len); } out.flush(); long stop = System.currentTimeMills(); log("took " + (stop - start) + "ms to download " + filename); [N.B.: the above approach may not give the results you're looking for. It measures the amount of time spent on the server; however, many other factors can determine the perceived time spent by the client, including net lag and buffering. A more accurate approach would use JavaScript to do the following: 1. 2. 3. 4.

Store the current time in a JavaScript variable Output random data of a known size At the end of that block, mark the time again and subtract as above Divide by data size to get transfer rate

Check out MSN's Bandwidth Speed Test for inspiration.

-Alex] How do I install Tomcat as servlet manager of Domino 5.x? Location: http://www.jguru.com/faq/view.jsp?EID=136393 Created: Aug 28, 2000 Modified: 2000-08-30 12:54:10.19 Author: Serge Knystautas (http://www.jguru.com/guru/viewbio.jsp?EID=100012) Question originally posed by Pablo Rodriguez (http://www.jguru.com/guru/viewbio.jsp?EID=101122 The Tomcat architecture allows for various front-ends or "connectors" to its servlet engine. In Tomcat 3.1, there are connectors for HTTP (to function as a stand-alone web server), IIS, and Netscape. There is no connector for Lotus Domino (either finished or in progress), although you're more than welcome to write one and submit it to the repository. :) Comments and alternative answers

Oh yes there are... Author: Andy Armstrong (http://www.jguru.com/guru/viewbio.jsp?EID=141392), May 29, 2001 We've just released a Domino/Tomcat connector. Find it at http://free.tagish.net/domino-tomcat/index.jsp. Architecturally speaking, under what circumstances must I consider adding EJB into the mix when building web-based applications using servlets and JSP? Location: http://www.jguru.com/faq/view.jsp?EID=137169 Created: Aug 28, 2000 Modified: 2000-08-28 21:39:26.129 Author: Govind Seshadri (http://www.jguru.com/guru/viewbio.jsp?EID=14) The following thread within the Server-side discussion forum at Javaworld offers some concrete guidelines as to when to add EJB into the mix when designing large web-based applications. How can I read GET or POST parameters that were encoded in an international character set? Also, when a user fills in an HTML Form using a custom Input Method Editor for, say, Japanese, how can my servlet/JSP know which encoding was used? Location: http://www.jguru.com/faq/view.jsp?EID=137281 Created: Aug 28, 2000 Modified: 2001-01-06 06:48:12.443 Author: Jan Borchers (http://www.jguru.com/guru/viewbio.jsp?EID=48743) Question originally posed by RAM SAM (http://www.jguru.com/guru/viewbio.jsp?EID=127269 The HttpServletRequest object from 2.0 on provides a method for retrieving the client's character encoding. The follwing sample gets the parameter mytext and converts it to a java Unicode string.

public String getText(HttpServletRequest request) {

String value = request.getParameter("mytext"); try{ value = new String(value.getBytes(), request.getCharacterEncoding()); }catch(java.io.UnsupportedEncodingException ex){ System.err.println(ex); } return value; } See also • •

Can JRun be configured so that it converts GET or POST parameters encoded in UTF-8 correctly into Unicode for use in the Java servlet? If my servlet or JSP contains international characters (like "Ýðüö"), how do I ensure they are displayed correctly?

Comments and alternative answers

But does this assume that there is some information... Author: RAM SAM (http://www.jguru.com/guru/viewbio.jsp?EID=127269), Oct 2, 2000 But does this assume that there is some information about the charset is coming in from the browser? I tried it but I always obtained ISO-8859-1 as the answer even though I used shift-jis to input the characters. I tried it on a machine that has a traditional chinese... Author: Roop Goyal (http://www.jguru.com/guru/viewbio.jsp?EID=287466), Dec 27, 2000 I tried it on a machine that has a traditional chinese operating system. The value returned by request.getCharacterEncoding() is null, although the html page that contains the From has the following line in its HEAD. <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=UTF-8">.

The value of a chinese character entered in the INPUT text in the Form is read by servlet and displayed as a %uh3h2h1h0, in IE5. In Netscape 4.7, the value is reads as %h3h2%h1h0. Whereas, IE referes to a hexadecimal number. The values obtained using java.net.URLDecoder.decode() method are senseless in the cases of both the browsers. Any ideas why? This doesn't work, anyone know how to make it work? Author: Haitao Jiang (http://www.jguru.com/guru/viewbio.jsp?EID=414121), May 2, 2001 request.getCharacterEncoding() simply can not get the charset set by the client. Anyone know how to set it in the JSP so that the servlet can get the encoding info?

Thanks [email protected] Re: This doesn't work, anyone know how to make it work? Author: maria baldassarri (http://www.jguru.com/guru/viewbio.jsp?EID=435002), Jun 7, 2001 with tomcat 3 this workaround works: value=new String(request.getParameter("Input").getBytes("ISO8859_1"), "UTF8") with tomcat 4 read the following article about a new method in the Java servlet API 2.3 and Tomcat 4 http://developer.java.sun.com/developer/technicalArticles/Servlets/servletapi2.3 request.setCharacterEncoding can be used to tell the server the charset to use to correctly parse the parameters and POST data. You have to call this before you call getParameter. Re: Re: This doesn't work, anyone know how to make it work? Author: Hartmut Bernecker (http://www.jguru.com/guru/viewbio.jsp?EID=424953), Jun 27, 2001 Hi, Would it not be possible to tell the servlet-container how to decode POSTed Requests? Concretely: Who knows if it is possible to use the web.xml in Tomcat 3.2.2 to state that each POST Request will be UTF-8 for example? If it would be possible, how can it be done and is that feasibility provided by other Servlet-Container as JRun for example?

This works for me. Author: Andrew Young (http://www.jguru.com/guru/viewbio.jsp?EID=879849), May 15, 2002 Here's what I did to make this work correctly. I'm entering Japanese in Win2k and it's being encoded as UTF-8. getCharacterEncoding() returned null, so I assume it's UTF8. If it returns anything else I assume that it's whatever was returned. String text = request.getParameter("text"); String encoding = request.getCharacterEncoding(); if (encoding == null) { encoding = "UTF-8"; } try { text = new String(textParam.getBytes(), encoding);

} catch(Exception ex) { System.err.println(ex); ex.printStackTrace(); }

I'd like to see a Servlet 2.2 API version of Alex Chaffee's CookieDetector servlet. Location: http://www.jguru.com/faq/view.jsp?EID=138297 Created: Aug 30, 2000 Modified: 2000-09-06 13:34:19.675 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) To create a Servlet 2.2 API version of Alex Chaffee's CookieDetector servlet, replace the statement String self = req.getScheme() + "://" + req.getServerName() + (port == 80 ? "" : ":"+port) + req.getServletPath(); by the following statements: String webapp = null; String realPath = getServletContext().getRealPath( req.getServletPath() ); String fileSeparator = System.getProperty( "file.separator" ); StringTokenizer st = new StringTokenizer( realPath, fileSeparator ); while ( st.hasMoreTokens() ) { if ( st.nextToken().equals( "webapps" ) ) { webapp = st.nextToken(); break; } } String self = req.getScheme() + "://" + req.getServerName() + (port == 80 ? "" : ":"+port) + "/" + webapp + req.getServletPath(); This change in the code is needed to reflect the directory structure for a typical webapp for Servlet 2.2 and the fact that the URL for accessing a servlet usually includes the name of the webapp. For illustration, I have a webapp named testsuite. The servlets for this webapp are in the directory TOMCAT_HOME/webapps/test-suite/WEB-INF/classes/ and the URL I'd use to access, say, a HelloServlet in this webapp would be http://RVL2.ecn.purdue.edu:8080/test-suite/servlet/HelloServlet

All that the replacement code does is to extract the name of the webapp from the pathname string returned by the getRealPath method. [Thanks Avi! Now I guess I'll have to go integrate these changes... -Alex] How can I JSP under Apache JServ? Location: http://www.jguru.com/faq/view.jsp?EID=139446 Created: Aug 31, 2000 Modified: 2000-09-04 19:18:19.025 Author: Serge Knystautas (http://www.jguru.com/guru/viewbio.jsp?EID=100012) Question originally posed by sreenivasa rao gaddam (http://www.jguru.com/guru/viewbio.jsp?EID=136249 Apache JServ is a servlet 2.0 compliant servlet engine, so the best you can do is the JSP 1.0 spec (you can't use JSP 1.1 as it requires servlet 2.2). You can however add GNUJSP at http://klomp.org/gnujsp/. It supports JSP 1.1 on servlet 2.0 or 2.1 engines. In fact, in many ways it's a nicer environment to develop than Tomcat or JRun or other current JSP systems (good debugging and configurability). Unfortunately, the Servlet 2.2 features were too compelling and we had to move away from JServ and GNUJSP. Comments and alternative answers

Use tomcat3.1. It's the best solution to servlet and... Author: luca valenti (http://www.jguru.com/guru/viewbio.jsp?EID=36876), Sep 5, 2000 Use tomcat3.1. It's the best solution to servlet and jsp, IMO, and it supports JSP 1.1 and servlets 2.2. See http://jakarta.apache.org for details. What is inter-servlet communication? Location: http://www.jguru.com/faq/view.jsp?EID=139489 Created: Aug 31, 2000 Modified: 2000-09-06 13:45:54.498 Author: shilpa Tiwari (http://www.jguru.com/guru/viewbio.jsp?EID=138841) Question originally posed by joy choudhury (http://www.jguru.com/guru/viewbio.jsp?EID=104345 As the name says it, it is communication between servlets. Servlets talking to each other. [There are many ways to communicate between servlets, including • • • • • • •

Request Dispatching HTTP Redirect Servlet Chaining HTTP request (using sockets or the URLConnection class) Shared session, request, or application objects (beans) Direct method invocation (deprecated) Shared static or instance variables (deprecated)

Search the FAQ, especially topic Message Passing (including Request Dispatching) for information on each of these techniques. -Alex]

Basically interServlet communication is acheived through servlet chaining. Which is a process in which you pass the output of one servlet as the input to other. These servlets should be running in the same server. e.g. ServletContext.getRequestDispatcher(HttpRequest, HttpResponse).forward("NextServlet") ; You can pass in the current request and response object from the latest form submission to the next servlet/JSP. You can modify these objects and pass them so that the next servlet/JSP can use the results of this servlet. There are some Servlet engine specific configurations for servlet chaining. Servlets can also call public functions of other servlets running in the same server. This can be done by obtaining a handle to the desired servlet through the ServletContext Object by passing it the servlet name ( this object can return any servlets running in the server). And then calling the function on the returned Servlet object. e.g. TestServlet test= (TestServlet)getServletConfig().getServletContext().getServlet("OtherServlet"); otherServletDetails= Test.getServletDetails(); You must be careful when you call another servlet's methods. If the servlet that you want to call implements the SingleThreadModel interface, your call could conflict with the servlet's single threaded nature. (The server cannot intervene and make sure your call happens when the servlet is not interacting with another client.) In this case, your servlet should make an HTTP request to the other servlet instead of direct calls. Servlets could also invoke other servlets programmatically by sending an HTTP request. This could be done by opening a URL connection to the desired Servlet. Comments and alternative answers

interservlet communication between two dofferent web sevrs Author: dhanasekar dhandapani (http://www.jguru.com/guru/viewbio.jsp?EID=392865), Apr 30, 2001 Well u mentioned the different ways that servlets can communicate to generate a respons, provided the servlets are running in the same server. how can two servlets running in different server can communication? . The server may be running in the same network (or) . different networks please answer my question Re: interservlet communication between two dofferent web sevrs Author: Gaurav Shukla (http://www.jguru.com/guru/viewbio.jsp?EID=932052), Jul 16, 2002 When two different Servlets are residing on two different servers, there servlet contexts are different. This would require careful consideration while playing with the request dispatcher object. J2EE spec says that different Context communication is not achievable.

How do I make servlet aliasing work with Apache+Tomcat? Location: http://www.jguru.com/faq/view.jsp?EID=140877 Created: Sep 2, 2000 Modified: 2000-09-06 13:40:32.764 Author: Ken Kress (http://www.jguru.com/guru/viewbio.jsp?EID=43931) [See How do I use servlet aliasing? for background.] Chapter 13 of the Java Servlet Specification v2.2, gives an example of using a "deployment descriptor" to add a new path to a servlet. The problem is the technique shown fails when you integrate Tomcat with Apache. When you use Tomcat standalone as your web server, you can modify the web.xml in $TOMCAT_HOME/webapps/myApp/WEB-INF to add a url-pattern: <web-app> <servlet> <servlet-name> myServlet <servlet-class> myServlet <servlet-mapping> <servlet-name> myServlet /jsp-bin/* This will let you use: http://webserver:8080/myApp/jsp-bin/stuff.html instead of: http://webserver:8080/myApp/servlet/myServlet/stuff.html But it won't work on port 80 if you've integrated Tomcat with Apache. Graeme Wallace provided this trick to remedy the situation. Add the following to your tomcat-apache.conf (or to a static version of it, since tomcat re-generates the conf file every time it starts): SetHandler jserv-servlet This lets Apache turn over handling of the url pattern to your servlet. Comments and alternative answers

Using mod_jk Author: Kyle Tippetts (http://www.jguru.com/guru/viewbio.jsp?EID=131600), Mar 28, 2001 Does this work if you are using mod_jk? I have exactly the problem described here, but I'm using mod_jk, not mod_jserv.

Re: Using mod_jk Author: Donna Varnell (http://www.jguru.com/guru/viewbio.jsp?EID=400951), Apr 11, 2001 I was able to get this to work by adding the following to httpd.conf (after the include of the mod_jk.conf_auto): JkMount /myApp/jsp-bin/* ajp12. This told Apache to send anything that matched that url pattern to Tomcat. Re[2]: Using mod_jk Author: Mike Konikoff (http://www.jguru.com/guru/viewbio.jsp?EID=700186), Dec 23, 2001 I tried this as well with no luck. Is there any alternative? mod_jk doesn't read web.xml, does it? Author: javier Beringola (http://www.jguru.com/guru/viewbio.jsp?EID=345612), Jun 14, 2001 so, how?...........and what about if my servlets are in this way: dsds.gdfg.ere.fdffd.myServlet? Is there any way to determine the number of concurrent connections my servlet engine can handle? Location: http://www.jguru.com/faq/view.jsp?EID=142244 Created: Sep 5, 2000 Modified: 2000-09-06 16:16:54.581 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) Question originally posed by Manoj Tripathi (http://www.jguru.com/guru/viewbio.jsp?EID=122726 Depends on whether or not your servlet container uses thread pooling. If you do not use a thread pool, the number of concurrent connections accepted by Tomcat 3.1, for example, is 10. This you can see for yourself by testing a servlet with the Apache JMeter tool. However, if your servlet container uses a thread pool, you can specify the number of concurrent connections to be accepted by the container. For Tomcat 3.1, the information on how to do so is supplied with the documentation in the TOMCAT_HOME/doc/uguide directory. Comments and alternative answers

Here's a different, related, question: What is the... Author: Roy Wilson (http://www.jguru.com/guru/viewbio.jsp?EID=53232), Sep 6, 2000 Here's a different, related, question: What is the maximum number of connections that my servlet engine can accept and also meet service level agreements (like reaction time, response time, throughput, not refusing more than a certain percentage of connections attempted)? The answer to that, of course, depends on (at least) the rate at which connections are requested and the resource demand per request.

I have a problem using HttpServletResponse.sendRedirect() with microbrowsers (WML/HDML). Those browsers don't seem to understand this and return an error. How do I send a redirect to a WAP device? Location: http://www.jguru.com/faq/view.jsp?EID=201403 Created: Sep 8, 2000 Modified: 2000-09-11 09:22:40.326 Author: Matt Small (http://www.jguru.com/guru/viewbio.jsp?EID=92190) Question originally posed by francois lascelles (http://www.jguru.com/guru/viewbio.jsp?EID=115425 I had this problem myself. I found that I had to use a full HTTP URL in the redirect. Relative paths do not work. [Many WAP browsers do not understand redirects. Anyone with experience with specific clients, please post a feedback. Thanks! -Alex] Comments and alternative answers

In JSP you can use <jsp:forward> instead. This... Author: Artur de Sousa Rocha (http://www.jguru.com/guru/viewbio.jsp?EID=70489), Jan 5, 2001 In JSP you can use <jsp:forward> instead. This does the redirection server-side. Drawback: browser-side the URL doesn't change. To do it from a "normal" servlet you would have to call the other servlet and stream its response back to browser - not very practical. How do I set up Servlets on Linux? Location: http://www.jguru.com/faq/view.jsp?EID=202543 Created: Sep 11, 2000 Modified: 2000-09-11 10:57:32.629 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by vivek tawde (http://www.jguru.com/guru/viewbio.jsp?EID=133324 There are many products which support servlets on Linux. Most of them operate either in a standalone mode (acting as both web server and servlet engine) or as a back-end servlet engine plugging in to an existing web server (like Apache). The most popular products seem to be: • • • •

Tomcat from Apache Jakarta JServ from Apache Resin from Caucho JRun from Allaire

See the individual products' web sites and README files for installation instructions. Comments and alternative answers

Another good, free all-Java Web server and servlet...

Author: Nathan Meyers (http://www.jguru.com/guru/viewbio.jsp?EID=138686), Sep 15, 2000 Another good, free all-Java Web server and servlet engine is Jetty from Mort Bay Consulting. How do I use Tomcat with Netscape Server? Location: http://www.jguru.com/faq/view.jsp?EID=206207 Created: Sep 14, 2000 Modified: 2000-09-14 19:17:00.746 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) Look at the Tomcat Netscape How to file located at the address : http://jakarta.apache.org/tomcat/jakarta-tomcat/src/doc/tomcat-netscapehowto.html. What is a request dispatcher and how does it work? Location: http://www.jguru.com/faq/view.jsp?EID=206736 Created: Sep 14, 2000 Modified: 2000-09-17 14:16:11.941 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) Question originally posed by Alex Chaffee PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=3 A RequestDispatcher object can forward a client's request to a resource or include the resource itself in the response back to the client. A resource can be another servlet, or an HTML file, or a JSP file, etc. You can also think of a RequestDispatcher object as a wrapper for the resource located at a given path that is supplied as an argument to the getRequestDispatcher method. For constructing a RequestDispatcher object, you can use either the ServletRequest.getRequestDispatcher() method or the ServletContext.getRequestDispatcher() method. They both do the same thing, but impose slightly different constraints on the argument path. For the former, it looks for the resource in the same webapp to which the invoking servlet belongs and the pathname specified can be relative to invoking servlet. For the latter, the pathname must begin with '/' and is interpreted relative to the root of the webapp. To illustrate, suppose you want Servlet_A to invoke Servlet_B. If they are both in the same directory, you could accomplish this by incorporating the following code fragment in either the service method or the doGet method of Servlet_A:

RequestDispatcher dispatcher = getRequestDispatcher("Servlet_B"); dispatcher.forward( request, response ); where request, of type HttpServletRequest, is the first parameter of the enclosing service method (or the doGet method) and response, of type HttpServletResponse, the second. You could accomplish the same by

RequestDispatcher dispatcher=getServletContext().getRequestDispatcher( "/servlet/Servlet_B" ); dispatcher.forward( request, response ); Comments and alternative answers

RequestDispatcher Author: jamal Ghaus (http://www.jguru.com/guru/viewbio.jsp?EID=499352), Sep 18, 2001 Your answer is very good, however, does the forwarded request go to the Service() method of the second servlet? Can one specify which method to forward the request to. Re: RequestDispatcher Author: Eduardo Garcia (http://www.jguru.com/guru/viewbio.jsp?EID=1145466), Feb 11, 2004 Hello ,how you doing? After reading your question, i resolved it passing a GET parameter in the calling of the servlet, and then, in the doGet method compare this parameter and call the apropiate method inside the forwarded servlet, something like this: public class servlet_that_forward extends HttpServlet { public void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { RequestDispatcher RD = getServletContext).getRequestDispatcher("forwarded_servlet?param=method1"); RD.forward(); } } public class forwarded_servlet extends HttpServlet { public void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String param; param = request.getParameter("param"); if (param.compareTo("method1")==0) { method1(); } } public void method1() { //Do something } } Hope that can be helpful, :) Re[2]: RequestDispatcher

Author: Narciso Rodrigues (http://www.jguru.com/guru/viewbio.jsp?EID=1155821), Mar 19, 2004 I try your code ... and i get this error... HTTP Status 405 - HTTP method GET is not supported by this URL Any Idea ? My code is: import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class chamado extends HttpServlet { public void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException { String param; param = request.getParameter("param"); if (param.compareTo("method1")==0) { try { method1(); } catch (Exception ex) {} } } public void method1() { //Do something } } import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class chamador extends HttpServlet { public void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { RequestDispatcher RD = getServletContext().getRequestDispatcher("/chamado?param=method1"); RD.forward(request, response); } }

Where is the log file (written by ServletContext.log()) for JavaWebServer2.0? Location: http://www.jguru.com/faq/view.jsp?EID=206818

Created: Sep 15, 2000 Modified: 2001-07-19 15:42:11.116 Author: Shirish Bathe (http://www.jguru.com/guru/viewbio.jsp?EID=206816) Question originally posed by Hong Shi (http://www.jguru.com/guru/viewbio.jsp?EID=9628 [Running on a WinNT4.0. Looked into the event_log but it's not there.] Hi, Logs generated by ServletContext.log() or GenericServlet.log() are stored as event either in a file or displayed. You have four choices to select from: [Where do you set this option? -Alex] 1. Rolling File - Rolling files enable you to remove the old logs without affecting the running service. A rolling file collects log data until it reaches the size set in the Rollover File Size setting. 2. Single File - A file that collects log data until it reaches the maximum size allowed. 3. Standard Output - In most cases, the terminal screen of the machine running Java Web Server. 4. Standard Error - The default error log for the system running Java Web Server. By default (for JavaWebServer2.0 running on a WinNT4.0) logs are stored in Rolling file "event_log" with buffer of 8KB. As this option uses the file cache you can not find your log entries in the file unless the cache is written to disk. You can reduce cache size to 0KB (i.e. No Cache Option) and see your messages are written to disk. Option 2 i.e. Single File does not uses any cache. So you can see your message Immediately Option 2 and 3 dumps messages on standard output/error device. for this you have to start (Under Winnt 4.0) Start your Web server from DOS Window (not as service). Hope this will solve your query.. Shirish How to allocate a certain amount of memory to JVM when starting Sun Java Web Server? Location: http://www.jguru.com/faq/view.jsp?EID=206856 Created: Sep 15, 2000 Modified: 2000-09-17 14:06:58.087 Author: Davanum Srinivas (http://www.jguru.com/guru/viewbio.jsp?EID=2011) Question originally posed by Michael Mitiaguin (http://www.jguru.com/guru/viewbio.jsp?EID=4719

With the latest JWS 2.0, There are two options. The first one is to specify a command line argument -vmargs. The second one is to specify the arguments in vmargs.txt. Check the release notes for more information. http://www.sun.com/software/jwebserver/techinfo/jws20/release_notes.html How to write a servlet which can transfer data written in ISO8859-1 into GB2312 or another kind of character encoding? Location: http://www.jguru.com/faq/view.jsp?EID=207294 Created: Sep 15, 2000 Modified: 2000-10-08 13:23:39.851 Author: Jonhi Ma (http://www.jguru.com/guru/viewbio.jsp?EID=131047) Question originally posed by Jonhi Ma (http://www.jguru.com/guru/viewbio.jsp?EID=131047 You can use this method to transfer your data from one standard encoding to another one. I have written it out and tested it under JSDK 2.0, and it runs well. The following is the java code I have written. import java.io.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; public class commonServlet extends HttpServlet { /*the method of Convert transfer data in typeof String (String Input) from one format(StandardFrom) to another format(StandardTo)*/ public static String convert (String Input, String StandardFrom, String StandardTo) { byte[] bytes; String conResult = new String(); try { bytes = Input.getBytes(StandardFrom); conResult = new String (bytes, StandardTo); } catch(Exception e) { //debugging begins here System.out.println(e); //debugging ends here return("null"); } return conResult; }//method convert ends here //Do nothing within methods doGet & doPost public void doGet(HttpServletRequest req, HttpServletResponse res) res) }

{ } public void doPost(HttpServletRequest req, HttpServletResponse {

}

swarraj kulkarni also contributed to this answer and adds: You should always check and verify character encoding and Supported Encodings. In addition, the international version of the JDK/JRE is required to have all the encodings available. Comments and alternative answers

I have tried the above code. But the from standard... Author: Dalia Reji (http://www.jguru.com/guru/viewbio.jsp?EID=62488), Oct 18, 2000 I have tried the above code. But the from standard (StandardFrom) always need to be Cp1252 or 8859_1. The following is the scenario what I have tried, I have an entry.jsp whose character encoding is set to Cp1256. In this jsp I am entering an arabic character and submitting to another jsp display.jsp. Display.jsp also uses the Cp1256 encoding. Since the JSP cannot understand the encoding of the request, to get the actual string submitted, I have to do the following conversion. String sName = request.getParameter("name"); bytes[] b = sName.getBytes("Cp1252"); String sActual = new String(b, "Cp1256");

I changed my system property file.encoding to CP1256, thinking that I don't need the above conversion. But still, to get the correct string back I have to specify the source encoding as Cp1252. (My default system file.encoding is Cp1252). I am using weblogic 5.1 with SP4. Can you explain why the JVM always require Cp1252 as the source encoding? Lia Re: I have tried the above code. But the from standard... Author: Ivan Lee (http://www.jguru.com/guru/viewbio.jsp?EID=787737), Mar 8, 2002 It depends on your regional settings. If you were using Chinese(Traditional) within the regional settings in Start-> Settings-> Control Panel-> Regional Settings, then your default encoding would be GB2312. The JVM, when started always looks at the regional settings of the PC. How to encoding string from iso-8859-1 to GB2312 charset : data = new String( data.getBytes("iso-8859-1"), "GB2312") Author: seokjin seo (http://www.jguru.com/guru/viewbio.jsp?EID=817440), Feb 23, 2004 try { String data = request.getParameter("data"); if(data != null) { data = new String( data.getBytes("iso-8859-1"), "GB2312"); } catch(Exception e) {

}

How to throw a dynamic xml page from a Servlet to Cocoon ? Location: http://www.jguru.com/faq/view.jsp?EID=208318 Created: Sep 17, 2000 Modified: 2000-09-17 15:45:10.007 Author: Davanum Srinivas (http://www.jguru.com/guru/viewbio.jsp?EID=2011) Question originally posed by John P James (http://www.jguru.com/guru/viewbio.jsp?EID=125241 In Cocoon's parlance, you need to write a "Producer" servlet which can generate a valid XML file from the HttpServletRequest parameters. An example FileProducer bundled into Cocoon can load a requested file from disk. Another sample DummyProducer is at: http://xml.apache.org/cocoon/dynamic.html Does context.RequestDispatcher expect an absolute path to be relative to the webapp root or the server root? What about response.sendRedirect()? Location: http://www.jguru.com/faq/view.jsp?EID=208370 Created: Sep 17, 2000 Modified: 2000-09-21 11:01:33.779 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) According to the Servlet 2.2 spec, "The getRequestDispatcher method takes a String argument describing a path within the scope of the ServletContext. This path must be relative to the root of the ServletContext." Thus, for a webapp (context) called "shopping", the URL http://www.foo.com/shopping/service/support.html is accessed with the call context.getRequestDispatcher("/service/support.html") However, the response.sendRedirect() method expects its path parameter to be relative to the server root, not the webapp root. Thus, to send a redirect to the above URL from a servlet running on www.foo.com, you must say response.sendRedirect("/shopping/service/support.html"); or, more generally, response.sendRedirect(request.getContextPath() + "/service/support.html"); Note that a path beginning with "/" is often called an "absolute URL," but this is misleading, since • •

A URL must begin with a protocol and hostname ("http://www.foo.com"), so it's actually a path, not a URL. The path is not technically absolute, since it's sometimes relative to the server root, as described above.

Comments and alternative answers

Perhaps the Servlet Specs should be more specific about...

Author: lee yeow leong (http://www.jguru.com/guru/viewbio.jsp?EID=3804), Dec 26, 2000 Perhaps the Servlet Specs should be more specific about relative URL. For Websphere 3.5, sendRedirect("/a.jsp")

would mean

http:///<servlet context>/a.jsp

while in IAS6.0, it resolves to http:///a.jsp

How do I discover the size of an image file (GIF or JPEG) on disk? Location: http://www.jguru.com/faq/view.jsp?EID=208401 Created: Sep 17, 2000 Modified: 2000-09-18 18:00:36.238 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Mohamed Abu Zur (http://www.jguru.com/guru/viewbio.jsp?EID=103782 First, load the image. If you have Swing, you can use

ImageIcon icon = new ImageIcon(args[0]); Image image = icon.getImage(); If you do not have Swing, you will need access to a toolkit, a component, and a media tracker. See "How do I make sure an Image is loaded before I try to display it?"http://www.jguru.com/jguru/faq/view.jsp?EID=20617 Once you have loaded the image, you can use its getHeight() and getWidth() methods, which work as expected. Comments and alternative answers

You can also do it by looking at the JPEG header. It... Author: James Thrasher (http://www.jguru.com/guru/viewbio.jsp?EID=301019), Jan 12, 2001 You can also do it by looking at the JPEG header. It saves lots of time loading the image. Here's source to a class that does that: http://www.gjt.org/servlets/JCVSlet/list/gjt/org/gjt/jjt/jpeginfo No getWidth() Author: Csongor Fagyal (http://www.jguru.com/guru/viewbio.jsp?EID=538458), Nov 4, 2001 Actually no getWidth() or getHeight() methods are available (at least in 1.3.1), you can only use getHeight(ImageObserver) and getWidth(ImageObserver, or a BufferedImage, which does have getHeight() and getWidth(). What is a Servlet Context? Location: http://www.jguru.com/faq/view.jsp?EID=208612

Created: Sep 17, 2000 Modified: 2000-09-18 08:57:21.158 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by navin kumar (http://www.jguru.com/guru/viewbio.jsp?EID=202883 A Servlet Context is a grouping under which related servlets (and JSPs and other web resources) run. They can share data, URL namespace, and other resources. There can be multiple contexts in a single servlet container. The ServletContext object is used by an individual servlet to "call back" and obtain services from the container (such as a request dispatcher). Read the JavaDoc for javax.servlet.ServletContext for more information. You can maintain "application global" variables by using Servlet Context Attributes. Since Servlet spec 2.1, a servlet context is more-or-less equivalent to a web application ("webapp"). Comments and alternative answers

Servlet Context Author: Srini Pillai (http://www.jguru.com/guru/viewbio.jsp?EID=485621), Aug 28, 2001 I am not able to digest the fact that a servlet container can have multiple Servlet Context. If it has multiple Contexts, then how can you maintain an "application scope" variables using the Servlet Context's setAttribute method. Re: a servlet container can have multiple Servlet Contexts Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Sep 7, 2001 Each context represents a separate application. So "application scope" variables are stored as Servlet Context Attributes. That means that separate contexts/applications do not share variables (unless you use an external method like the database or file system). Comparend to a sigleton? Author: Fredric Palmgren (http://www.jguru.com/guru/viewbio.jsp?EID=1092794), Mar 31, 2004 Today I am using a singleton to supply application wide parameters like different caches. Would server context be a better alternative then the singleton? Does the RequestDispatcher expect a relative URL to be relative to the originally-called servlet or to the current servlet (if different)? Location: http://www.jguru.com/faq/view.jsp?EID=210214 Created: Sep 19, 2000 Modified: 2000-09-20 11:18:59.269 Author: swarraj kulkarni (http://www.jguru.com/guru/viewbio.jsp?EID=121306) Question originally posed by Alex Chaffee PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=3

Since the RequestDispatcher will be passing the control (request object and response object) from the current Servlet, the relative URL must be relative to the current servlet. The originally called servlet has passed the control to the current servlet, and now current servlet is acting as controller to other resourses. Comments and alternative answers

That's not clear enough Author: Amos Shapira (http://www.jguru.com/guru/viewbio.jsp?EID=4346), Jun 6, 2001 I've read the same text in the Servlet 2.2 spec and arrived here after that because it confuses me. It seems that Tomcat 3.2 and ServletExec 3.0 treat relative paths in RequestDispatcher.forward() differently. Tomcat, as far as I've analysed it, treats the relative path to be relative to the web application's "base", as I would expect, but ServletExec seems to require an absolute path (not absolute URL, just path, with a "/" in front of it) in order to reach the same relative resource. I'm talking about a RequestDispatcher obtained via the Request, not the ServletContext. Can someone clarify what is the defined behaviour to be expected? Thanks. What is the difference between in-process and out-of-process servlet containers? Location: http://www.jguru.com/faq/view.jsp?EID=211289 Created: Sep 20, 2000 Modified: 2000-09-21 10:13:32.784 Author: swarraj kulkarni (http://www.jguru.com/guru/viewbio.jsp?EID=121306) Question originally posed by Mahesh Devendran (http://www.jguru.com/guru/viewbio.jsp?EID=204413 For the best explaination of this question pl. see the apache site: Information about servlet containers at Apache The in-process Servlet containers are the containers which work inside the JVM of Web server, these provides good performance but poor in scalibility. The out-of-process containers are the containers which work in the JVM outside the web server. poor in performance but better in scalibility In the case of out-of-process containers, web server and container talks with each

other by using the some standard mechanism like IPC. In addition to these types of containers, there is 3rd type which is stand-alone servlet containers. These are an integral part of the web server. Comments and alternative answers

Commerical examples of in & out process containers Author: neal ravindran (http://www.jguru.com/guru/viewbio.jsp?EID=17737), Mar 2, 2002 Could you provide the commericial names of a few famous in & out process containers? In BEA Weblogic - Is it possible to load a Servlet, without mentioning an alias name in the weblogic.properties file? Location: http://www.jguru.com/faq/view.jsp?EID=212120 Created: Sep 21, 2000 Modified: 2000-09-21 10:40:07.487 Author: Igor Royzis (http://www.jguru.com/guru/viewbio.jsp?EID=212112) Question originally posed by Nitin Baligar (http://www.jguru.com/guru/viewbio.jsp?EID=207743 Yes. This is how: http://www.weblogic.com/docs51/classdocs/API_servlet.html#134798 Comments and alternative answers

Answer Yes it is very much possible to do this. We... Author: shilpa Tiwari (http://www.jguru.com/guru/viewbio.jsp?EID=138841), Sep 21, 2000 Answer Yes it is very much possible to do this. Weblogic provides a ServletServlet which could be used to call other servlets. You need to register this servlet in the weblogic.properties file with an alias. e.g. weblogic.httpd.register.servlet=weblogic.servlet.ServletServlet You can now use ServletServlet to serve another servlet. e.g. http://localhost:7001/servlet/examples/servlets/HelloWorldServlet. Here "servlet" ( in the above url) is the alias name of the ServletServlet servlet in the properties file . The rest of the url which is examples/servlets/HelloWorldServlet is understood by ServletServlet as the PATH_INFO as examples.servlets. HelloWorldServlet ( a "/" in the PATH_INFO is understood as "." by the ServletServlet.) This class examples.servlets.HelloWorldServlet is searched in the system CLASSPATH of WebLogic or the servlet classpath. A servlet called using the ServletServlet will behave like any other servlet in that the init() method is executed the first time the servlet is called.

(Versions of WebLogic Server prior to version 5.1 re-initialized a servlet called from the ServletServlet each time the servlet was called. Also, once the servlet class is loaded, it is not loaded again when subsequent servlet objects are instantiated. ) NOTE : ServletServlet does not enforce any security access over the servlets in the weblogic server. Anyone having access to ServletServlet can invoke any other servlet running in the server. You might not want to use it in a production environment. You might want to refer to this link : http://www.weblogic.com/docs51/classdocs/API_servlet.html#134798 How is SingleThreadModel implemented in Tomcat? In other containers? [I would assume that Tomcat uses its connection thread pool, and creates a new instance of the servlet for each connection thread, instead of sharing one instance among all threads. Is that true?] Location: http://www.jguru.com/faq/view.jsp?EID=212826 Created: Sep 21, 2000 Modified: 2000-09-28 19:24:28.15 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) Question originally posed by Eric Armstrong (http://www.jguru.com/guru/viewbio.jsp?EID=201746 The question mixes together two rather independent aspects of a servlet container: "concurrency control" and "thread pooling". Concurrency control, such as achieved by having a servlet implement the SingleThreadModel interface, addresses the issue of thread safety. A servlet will be thread-safe or thread-unsafe regardless of whether the servlet container used a thread pool. Thread pooling merely eliminates the overhead associated with the creation and destruction of threads as a servlet container tries to respond to multiple requests received simultaneously. It is for this reason that the specification document for Servlet 2.2 API is silent on the subject of thread pooling -- as it is merely an implementation detail. However, the document does indeed address the issue of thread safety and how and when to use SingleThreadModel servlets. Section 3.3.3.1 of the Servlet 2.2 API Specification document says that if a servlet implements the SingleThreadModel it is guaranteed "that only one request thread at time will be allowed in the service method." It says further that "a servlet container may satisfy this guarantee by serializing requests on a servlet or by maintaining a pool of servlet instances." Obviously, for superior performance you'd want the servlet container to create multiple instances of a SingleThreadModel type servlet should there be many requests received in quick succession. Whether or not a servlet container does that depends completely on the implementation. My experiments show that Tomcat 3.1 does indeed create multiple instances of a SingleThreadModel servlet, but only for

the first batch of requests received concurrently. For subsequent batches of concurrent requests, it seems to use only one of those instances. Comments and alternative answers

"My experiments show that Tomcat 3.1 does indeed... Author: Eric Armstrong (http://www.jguru.com/guru/viewbio.jsp?EID=201746), Oct 2, 2000 "My experiments show that Tomcat 3.1 does indeed create multiple instances of a SingleThreadModel servlet, but only for the first batch of requests received concurrently. For subsequent batches of concurrent requests, it seems to use only one of those instances." --thank you. That is the information I needed. Apparently, then, it *tries* to do efficient processing, but only succeeds part of the time... Which servlet containers have persistent session support? Specifically, does Tomcat 3.1? Location: http://www.jguru.com/faq/view.jsp?EID=212858 Created: Sep 21, 2000 Modified: 2000-09-28 19:28:27.817 Author: Avi Kak (http://www.jguru.com/guru/viewbio.jsp?EID=26410) Question originally posed by Abhay Bhanushali (http://www.jguru.com/guru/viewbio.jsp?EID=202848 All servlet containers that implement the Servlet 2.2 API must provide for session tracking through either the use of cookies or through URL rewriting. All Tomcat servlet containers support session tracking. See also the jGuru Servlets FAQ entries by Alex Chaffee and Simon Wong. Comments and alternative answers

Thank you for a response I am more interested in ... Author: Abhay Bhanushali (http://www.jguru.com/guru/viewbio.jsp?EID=202848), Sep 28, 2000 Thank you for a response I am more interested in persistant implementation of session supported by the Application Server providers. WebSphere supports persistant session implementation. This is required for to add scalability to App Servers. My investigation shows Tomcat does not implement persistant session management. Are there any freeware App Servers that support this feature? Re: Thank you for a response I am more interested in ... Author: zalla rouge (http://www.jguru.com/guru/viewbio.jsp?EID=1167200), Apr 29, 2004

I have tried to code persistency of the tomcat 4 sessions (only for client data) and I made it work, but I have never tested it in a heavy load production envrironment.

Can I use JAAS as the authentication technology for servlets ? Location: http://www.jguru.com/faq/view.jsp?EID=213499 Created: Sep 22, 2000 Modified: 2000-10-05 19:14:36.497 Author: reshma deshmukh (http://www.jguru.com/guru/viewbio.jsp?EID=132478) Question originally posed by Lieven Trappeniers (http://www.jguru.com/guru/viewbio.jsp?EID=111554 Yes, JAAS can be used as authentication technology for servlets. One important feature of JAAS is pure Java implementation. The JAAS infrastructure is divided into two main components: an authentication component and an authorization component. The JAAS authentication component provides the ability to reliably and securely determine who is currently executing Java code, regardless of whether the code is running as an application, an applet, a bean, or a servlet. Comments and alternative answers

Can I use JAAS authorization part in a servlet without... Author: Eric Touchard (http://www.jguru.com/guru/viewbio.jsp?EID=208811), Oct 16, 2000 Can I use JAAS authorization part in a servlet without its authentication part? (The authentication is done via a web server or a servlet engine.) Re: Can I use JAAS authorization part in a servlet without... Author: tippu sultan (http://www.jguru.com/guru/viewbio.jsp?EID=417083), Jun 26, 2001 No , It is not at all possible to use JAAS with out authentication, With JAAS authentication only we can do authorisation other wise you will get exeception say trying to authorise unautenticated subject. JAAS not implemented in J2EE containers Author: martin smith (http://www.jguru.com/guru/viewbio.jsp?EID=260406), Mar 23, 2001 The best way to do security for most apps seems likely to be to rely on the security services provided by J2EE containers (app servers.) However, my research so far indicates that common J2EE containers have not implemented JAAS. E.g., Tomcat and Allaire's JRun. I assume this is because they were developed before JAAS was finalized, and I assume (hope) this will be corrected and standardized in future releases of these products (and perhaps made mandatory for J2EE certification.) Martin How can I see/access the response headers? Request headers can be accessed using request.getHeaderNames() but how to access the response

headers? Location: http://www.jguru.com/faq/view.jsp?EID=213901 Created: Sep 23, 2000 Modified: 2000-09-28 19:32:44.797 Author: gopala krishna kakani (http://www.jguru.com/guru/viewbio.jsp?EID=209882) Question originally posed by nitin k (http://www.jguru.com/guru/viewbio.jsp?EID=137461 It is not (yet) possible to see response header information. How can I set a servlet to load on startup of the container, rather than on the first request? Location: http://www.jguru.com/faq/view.jsp?EID=218109 Created: Sep 28, 2000 Modified: 2000-09-28 21:54:41.937 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Jeremy Butler (http://www.jguru.com/guru/viewbio.jsp?EID=141352 The Servlet 2.2 spec defines a load-on-startup element for just this purpose. Put it in the <servlet> section of your web.xml deployment descriptor. It is either empty () or contains "a positive integer indicating the order in which the servlet should be loaded. Lower integers are loaded before higher integers. If no value is specified, or if the value specified is not a positive integer, the container is free to load it at any time in the startup sequence." For example, <servlet> <servlet-name>foo <servlet-class>com.foo.servlets.Foo 5 Some servlet containers also have their own techniques for configuring this; please submit feedback with information on these. Comments and alternative answers

Alternate method Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 2, 2001 For an alternative, see Bozidar Dangubic's post at calling init() Servlet after the Tomcat webserver ... See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 2, 2001 I want the servlet container to load one or more s... How does one do it in weblogic 5.1 without a web.xml file Author: Shailesh Kumar (http://www.jguru.com/guru/viewbio.jsp?EID=874140), Sep 16, 2002 How does one do it when there is no web.xml file.There is only a servlet

registered in the weblogic.properties file Is it possible to write a servlet that acts as a FTP server? Location: http://www.jguru.com/faq/view.jsp?EID=218390 Created: Sep 28, 2000 Modified: 2000-09-28 20:23:55.887 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by sharma MR (http://www.jguru.com/guru/viewbio.jsp?EID=4939 Yes. It would spawn a thread that opens a ServerSocket, then listens for incoming connections and speaks the FTP protocol. Unfortunately I don't know of any source for FTP Server code. You may want to look at http://www.jguru.com/jguru/faq/view.jsp?EID=107270 for more information. Generally, extending servlets to protocols other than HTTP is a quixotic enterprise. Just install a standalone FTP server and you'll be much happier. How can my servlet determine the appropriate MIME type to set in the response, based on the file extension of the file being sent? Location: http://www.jguru.com/faq/view.jsp?EID=218913 Created: Sep 29, 2000 Modified: 2000-10-03 10:26:24.607 Author: swarraj kulkarni (http://www.jguru.com/guru/viewbio.jsp?EID=121306) Question originally posed by Carfield Yim (http://www.jguru.com/guru/viewbio.jsp?EID=4648 There is no automatic way for the servlet to determine the MIME type as per the extension of the file being served to client. In the servlet code you can have the swich kind of code where you can set the MIME type as per the file extension type. Here is the link which specifies all the extension types and required MIME types: File Extensions and MIME types [You could also try to parse your web.xml file... -Alex] Comments and alternative answers

You can use the following statement to set in your... Author: Balaji Thraksha (http://www.jguru.com/guru/viewbio.jsp?EID=222075), Oct 4, 2000 You can use the following statement to set in your response. getServletContext().getMimeType(File2View) where File2View is the name of the file. String Parameter.

Is there a way to disable a user's ability to double-click a submit image/button (and therefore submitting duplicate data -- multiple submits)? Is there a way to do this with Javascript? Location: http://www.jguru.com/faq/view.jsp?EID=219433 Created: Sep 30, 2000 Modified: 2001-09-26 12:31:55.779 Author: Ken Beard (http://www.jguru.com/guru/viewbio.jsp?EID=219432) Question originally posed by Gregory Grondin (http://www.jguru.com/guru/viewbio.jsp?EID=211118 [I'm currently using Java Servlets as part of an administration program. I'm having a problem in that the user can double click the save button (a submit image) and save a record twice by accident.] Give the submit image (or button) an onClick() handler. Have the handler check if a flag is set and if not set the flag and submit the form and then clear the form. [That's fine, but... Got source? -Alex] Comments and alternative answers

Disallowing Multiple Submits/Clicks. Author: Prashant Rais (http://www.jguru.com/guru/viewbio.jsp?EID=484518), Jan 11, 2002 Is there a way to do it on the server side if I have the constraint of not using javascript? Re: Disallowing Multiple Submits/Clicks. Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 30, 2002 Yes, see Disabling Multiple Clicks Where can I find information about the i18n capabilities of the major browsers? Location: http://www.jguru.com/faq/view.jsp?EID=219545 Created: Sep 30, 2000 Modified: 2000-09-30 10:10:59.636 Author: Joe Sam Shirah (http://www.jguru.com/guru/viewbio.jsp?EID=42100) For Netscape see Welcome to Netscape International!. For Microsoft see International Home Pages. What are the main differences between Servlets and ISAPI? Location: http://www.jguru.com/faq/view.jsp?EID=221843 Created: Oct 3, 2000 Modified: 2000-10-04 11:57:03.041 Author: swarraj kulkarni (http://www.jguru.com/guru/viewbio.jsp?EID=121306) Question originally posed by Bharadwaja Cheruvu (http://www.jguru.com/guru/viewbio.jsp?EID=216253 The first difference is obviously that Servlets is the technology from Sun Microsystems and ISAPI is from Microsoft.

Other Differences are: Servlet is a simple .class file and ISAPI is a DLL Servlets run in the Servlet containers and may be in-process or out of process. ISAs run in the same address space as the HTTP server Servlet container preprocesses and postprocesses the data communication between the client and server. ISAPI Filters provide the capability of pre-processing and post-processing of all data sent between the client and the server Java is the only choice for writing Servlets, VC++/MFC is used to write ISAPI code Servlets works on most of the Web servers plus third party containers can be integrated with other web servers to provide servlets on them. ISAPI works on only ISAPI-compliant Web server (for example, Microsoft Internet Information Server) Servlets can connect to the Databases through JDBC as well as jdbc-odbc bridges. ISAPI can connect to Databases through only ODBC Servlets have access to many server-side technologies like EJB and etc. ISAPI is limited in scope Multiple commands can be implemented in a servlet by using pathinfo. ISAPI allows multiple commands in one DLL, implemented as member functions of the CHttpServer object in the DLL. Content generation and content presentation can be done seperately in Servlets with the help of JSP. ISAPI code has to generate HTML code itself. You can find more info here: ISAPI Information Servlets information Is ASP's "response.redirect" equivalent to the Servlet API's "response.sendRedirect"? Location: http://www.jguru.com/faq/view.jsp?EID=222059 Created: Oct 4, 2000 Modified: 2000-10-04 11:59:57.426 Author: Rajakumar Makapur (http://www.jguru.com/guru/viewbio.jsp?EID=129728) Question originally posed by Vinaykumar Nagubandi (http://www.jguru.com/guru/viewbio.jsp?EID=116693 Yes it is. response.sendRedirect(String url) is equivalent of ASP's response.redirect method. Comments and alternative answers

it this true? Author: Korey Sed (http://www.jguru.com/guru/viewbio.jsp?EID=488552), Sep 1, 2001 From what I read in the documentation, it seems to be the same, but when I tried it, it only printed that the page that I was requesting is not in another location, where another location was the string URL I provided to sendRedirect. I'm a little puzzled!

Can a JavaBean access methods/implicit objects of the JSP page which created it? Location: http://www.jguru.com/faq/view.jsp?EID=222393 Created: Oct 4, 2000 Modified: 2000-10-05 21:51:18.598 Author: Ryan Breidenbach (http://www.jguru.com/guru/viewbio.jsp?EID=45212) Question originally posed by Bruno Randolf (http://www.jguru.com/guru/viewbio.jsp?EID=94633 Yes, they can, but not by virtue of the fact that they are being used in a JSP page. In order for a JavaBean to access the methods/implicit objects of a JSP page, it has to be initialized with a handle or reference to the page itself. For instance, your JavaBean could have the following code: private JspPage jspPage; public JspPage getJspPage() { return jspPage; } public void setJspPage(JspPage jspPage) { this.jspPage = jspPage; } Then, from within your JSP page, you could invoke: <jsp:useBean id="yourBean" class="your.package.YourBean" /> <% yourBean.setJspPage(this); %> Now, your bean can access the implicit objects and methods of the calling JSP page. How can I call C or C++ code from servlets? Location: http://www.jguru.com/faq/view.jsp?EID=222735 Created: Oct 4, 2000 Modified: 2000-12-01 09:05:18.686 Author: Alexander Krapf (http://www.jguru.com/guru/viewbio.jsp?EID=221775) You have two major options, JNI and CORBA. JNI is Java's gateway to languages that can link with C. CORBA is OMG's Common Object Request Broker Architecture. Both are pretty hard to use. [See the jGuru JNI FAQ and CORBA FAQ for more information on using these technologies. -Alex Chaffee] JunC++ion is a product that is built on top of JNI and makes the Java/C++ interoperability problem basically a non-issue. JunC++ion generates proxy classes for compiled Java classes, for example for a Servlet class. It also performs the task of the javah compiler but goes one step further: it generates an implementation of the native method that delegates to a C++ method. This allows you for example to implement a native servlet method in C++ like this:

void _cmj_Java_MyServlet_doHandleGet( jcpp_localenv * _env, MyServlet & _this, HttpServletRequest & _req, HttpServletResponse & _resp ) { ServletOutputStream os = _resp.getOutputStream(); char buffer[ 512 ]; os.println( "" ); try { sprintf( buffer, "This is a message from %s\n", call_cpp_api() ); os.println( buffer ); } catch(...) { throw MyException( "something bad happened" ); } os.println( "" ); } JunC++ion is currently available on Wintel but is actively being ported to Solaris, AIX, Linux and HP-UX. More information is available at http://www.codemesh.com [Note that Alexander Krapf, the author of this answer, is the president of CodeMesh. -Alex Chaffee] How do I invoke CORBA from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=223605 Created: Oct 6, 2000 Modified: 2000-10-06 13:03:48.628 Author: zhu jiang (http://www.jguru.com/guru/viewbio.jsp?EID=14031) Question originally posed by Jiyong Jon (http://www.jguru.com/guru/viewbio.jsp?EID=88580 Just treat the servlet as normal CORBA client. First , put the code which you used to invoke CORBA object in client application's main() method to the doGet() method of your servlet. Second, register servlet to web server. And at last you can send request for that servlet from your browser. In this way, you have invoked CORBA from the servlet. If you are not familiar with how to invoke CORBA from a normal CORBA client application, you can find the code somewhere in the FAQs of CORBA. Can I associate a servlet with a particular mime-type, so if the client requests a file of that type, my servlet will be executed? Location: http://www.jguru.com/faq/view.jsp?EID=223689 Created: Oct 6, 2000 Modified: 2000-10-06 13:02:44.867 Author: Wellington Silva (http://www.jguru.com/guru/viewbio.jsp?EID=223085) Question originally posed by Dmitry Ryzhevich (http://www.jguru.com/guru/viewbio.jsp?EID=208194 In web.xml you can use a mime-mapping to map the type with a certain extension and then map the servlet to that extension. e.g. <mime-mapping> <extension> zzz

<mime-type> text/plain <servlet-mapping> *.zzz <servlet-name> MyServlet So, when a file for type zzz is requested, the servlet gets called. How can I use Apache's http://xml.apache.org/fop software embedded into a servlet to generate a PDF output file? Location: http://www.jguru.com/faq/view.jsp?EID=223692 Created: Oct 6, 2000 Modified: 2000-10-06 14:01:17.777 Author: Wellington Silva (http://www.jguru.com/guru/viewbio.jsp?EID=223085) Question originally posed by Shannon Wenzel (http://www.jguru.com/guru/viewbio.jsp?EID=116219 Take a look on Cocoon demo apps. There's a demo for this in there. [Does anyone have a URL for this demo? -Alex] Comments and alternative answers

The Cocoon FAQ provides an answer at http://xml.ap... Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7), Oct 7, 2000 The Cocoon FAQ provides an answer at http://xml.apache.org/cocoon/faqs.html#faqfopimages. What are the different cases for using sendRedirect() vs. getRequestDispatcher()? Location: http://www.jguru.com/faq/view.jsp?EID=223732 Created: Oct 6, 2000 Modified: 2000-10-06 12:59:31.857 Author: Wellington Silva (http://www.jguru.com/guru/viewbio.jsp?EID=223085) Question originally posed by Vinaykumar Nagubandi (http://www.jguru.com/guru/viewbio.jsp?EID=116693 When you want to preserve the current request/response objects and transfer them to another resource WITHIN the context, you must use getRequestDispatcher or getNamedDispatcher. If you want to dispatch to resources OUTSIDE the context, then you must use sendRedirect. In this case you won't be sending the original request/response

objects, but you will be sending a header asking to the browser to issue a request to the new URL. If you don't need to preserve the request/response objects, you can use either. If my servlet or JSP contains international characters (like "Ýðüö"), how do I ensure they are displayed correctly? Location: http://www.jguru.com/faq/view.jsp?EID=224631 Created: Oct 8, 2000 Modified: 2000-10-08 18:15:10.571 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Berrin Altuntas (http://www.jguru.com/guru/viewbio.jsp?EID=216891 The simplest way is to write your JSP (or strings in your servlet) to use the HTML entity escape characters for Unicode. For instance, the string "Ýðüö" would be represented as Ýðüö or Ýðüö I have written a method, htmlescape(), that converts a Unicode string (one containing two-byte Unicode characters) into the HTML-escaped equivalent. It is available at http://www.purpletech.com/code/src/com/purpletech/util/Utils.java. (If the site is currently unavailable, please send me email.) Another option is to set the character encoding for the response and output binary (Unicode) data directly. From the Javadoc for ServletResponse: The charset for the MIME body response can be specified with setContentType(java.lang.String. For example, "text/html; charset=Shift_JIS". The charset can alternately be set using setLocale(java.util.Locale). If no charset is specified, ISO-8859-1 will be used. The setContentType or setLocale method must be called before getWriter for the charset to affect the construction of the writer. See the Internet RFCs such as RFC 2045 for more information on MIME. Protocols such as SMTP and HTTP define profiles of MIME, and those standards are still evolving. In addition, the international version of the JDK/JRE is required to have all the encodings available. See also • • • • •

http://hotwired.lycos.com/webmonkey/reference/special_characters/ What is the difference between URL encoding, URL rewriting, and HTML escaping? character encoding Supported Encodings How to write a servlet which can transfer data written in ISO8859-1 into GB2312 or another kind of character encoding?

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Oops Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Sep 25, 2001 Note that I just fixed a serious bug in my htmlunescape method... Sorry about that... Download at http://www.purpletech.com/code/src/com/purpletech/util/Utils.java Where should I place a properties file in the java web server 2.0? How will you access the properties file using Resource Bundle? Location: http://www.jguru.com/faq/view.jsp?EID=225511 Created: Oct 9, 2000 Modified: 2000-10-24 10:18:11.38 Author: Shirish Bathe (http://www.jguru.com/guru/viewbio.jsp?EID=88588) Question originally posed by ganesan ganesan (http://www.jguru.com/guru/viewbio.jsp?EID=211734 [Short answer: put it in your CLASSPATH. -Alex] All Resources are located and loaded as normal class. The task is performed by the ClassLoader class. The ClassLoader class uses a delegation model to search for classes and resources. Normally, the Java virtual machine loads classes from the local file system in a platform-dependent manner. For example, on UNIX systems, the virtual machine loads classes from the directory defined by the CLASSPATH environment variable. To access properties file using Resource Bundle. Please refer to NotePad Application Demo. It is avaliable with JSDK 2.0. Thanks Shirish ([email protected]) Comments and alternative answers

Resource Bundle on Web Server Author: Fintan Conway (http://www.jguru.com/guru/viewbio.jsp?EID=452521), Aug 20, 2001 The pertinent thing here is to add the directory where your Resource Bundle properties file is located, to the CLASSPATH on your Web Server PC. HTH, Fintan How do I access the value of a cookie using JavaScript? Location: http://www.jguru.com/faq/view.jsp?EID=225605

Created: Oct 10, 2000 Modified: 2000-10-15 12:58:18.458 Author: Shirish Bathe (http://www.jguru.com/guru/viewbio.jsp?EID=88588) Question originally posed by Seshadri Venkatesh (http://www.jguru.com/guru/viewbio.jsp?EID=121699 You can manipulate cookies in JavaScript with the document.cookie property. You can set a cookie by assigning this property, and retrieve one by reading its current value. The following statement, for example, sets a new cookie with a minimum number of attributes: document.cookie = "cookieName=cookieValue"; And the following statement displays the property's value: alert(document.cookie); The value of document.cookie is a string containing a list of all cookies that are associated with a web page. It consists, that is, of name=value pairs for each cookie that matches the current domain, path, and date. The value of the document.cookie property, for instance, might be the following string: cookieName1=cookieValue1; cookieName2=cookieValue2; Shirish ([email protected]) Comments and alternative answers

You should go to the cookies page at javascript.in... Author: Melanie Munden (http://www.jguru.com/guru/viewbio.jsp?EID=138305), Oct 16, 2000 You should go to the cookies page at javascript.internet.com. It has lots of free examples: http://javascript.internet.com/cookies/ How do I convert my existing applets and/or CGI programs to servlets? Location: http://www.jguru.com/faq/view.jsp?EID=227520 Created: Oct 12, 2000 Modified: 2000-10-15 12:55:10.277 Author: Ryan Breidenbach (http://www.jguru.com/guru/viewbio.jsp?EID=45212) Question originally posed by Philip Ly (http://www.jguru.com/guru/viewbio.jsp?EID=111844 This is really two different questions. I'm not really sure how/why you would convert an applet to a servlet. Applets are small applications that run on a client computer, typically with a GUI interface. Servlets process request to a server. So there doesn't seem to be a clear way/reason to convert an applet to a servlet.

CGI scripts and servlets do basically the same job - back end processing on a server. Basically, all you have to do is alter any web pages that post to a CGI script to now post to a corresponding servlet. Then you would simply have the servlet perform the same processing that the CGI script did. And, as I am sure you are aware, converting from CGI scripts to servlets is a good idea. This should not only increase the performance of your web application, but give all the benedits of programming in Java. Comments and alternative answers

See also What are the Servlet equivalents to all the... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Oct 15, 2000 See also What are the Servlet equivalents to all the CGI environment variables? You cannot replace applets with servlets, however if... Author: Andrew Howard (http://www.jguru.com/guru/viewbio.jsp?EID=225016), Oct 16, 2000 You cannot replace applets with servlets, however if your applet happens to connect to a server using a specific port other than 80 you will realise that you can have security issues with client's firewalls. This is where servlets come in. With servlets you can create your own protocol within HTTP which is called HTTP Tunnelling this allows the servlet to use the Serializable interface of ojects to copy the object through the HTTP protocol and then the applet can use this object as it pleases. How do I write to a log file using JSP under Tomcat? Can I make use of the log() method for this? Location: http://www.jguru.com/faq/view.jsp?EID=228620 Created: Oct 14, 2000 Modified: 2001-07-19 15:42:34.817 Author: Serge Knystautas (http://www.jguru.com/guru/viewbio.jsp?EID=100012) Question originally posed by Peter Gelderbloem (http://www.jguru.com/guru/viewbio.jsp?EID=91670 Yes, you can use the Servlet API's log method in Tomcat from within JSPs or servlets. These messages are stored in the server's log directory in a file called servlet.log. Is there a clean way to interface with CyberCash CashRegister service from a java servlet or EJB? Location: http://www.jguru.com/faq/view.jsp?EID=228899 Created: Oct 15, 2000 Modified: 2000-10-24 08:36:27.44 Author: Alexandros Kotsiras (http://www.jguru.com/guru/viewbio.jsp?EID=64209) Question originally posed by Celia Jia (http://www.jguru.com/guru/viewbio.jsp?EID=142900 I haven't been able to find a "clean" way to do this. The way cybercach MCK works is the following :

You submit the order to directpaycredit.cgi which connects to the Cybercash Server and from there to the Financial institution. The directpaycredit.cgi depending on the success or failure of the transaction sends it's response to a success.tem file or a failure.tem file. MCK provides a way to retrieve in those files inside hidden fields all the values of the input fields (CC_Number, Customer_Name etc.) that the user entered when he submitted the final form. The problem is that you need to dump all the order details that you now have in the hidden fields into a database and MCK doesn't do this for you. So what i did was use some javascript in the success.tem file that does the following : So the user receives the success response from Cybercash into a success.tem page which doesn't stay for long because it autosubmitts to a success.jsp page which can retrieve all the order/customer data from the hidden fields of success.tem and dump them into a database, send confirmation email , etc. It works but the main problem is that if the user presses the browser's "Back" button from the success.jsp he will go to the success.tem which will autosubmit again and try to redump all the same order data to the database. Unfortunately you cannot tell MCK to send the order response directly to a .jsp page and do it the right way. You are supposed to know CGI programming and customize directly the directpaycradit.cgi script and dump all the transaction details from within that script before it forwards to the success.tem file. I haven't been able to find a better way... Thanks, Alex. How can we send a POST request when we call getRequestDispatcher() functions ? It is easy to make a GET request but I don't know how for POST one. Location: http://www.jguru.com/faq/view.jsp?EID=231318 Created: Oct 18, 2000 Modified: 2000-10-24 10:33:52.192 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by APAN Cyril (http://www.jguru.com/guru/viewbio.jsp?EID=211969 Unfortunately, the servlet spec does not allow you to change the HTTP method of a dispatched request (from GET to POST or vice versa). This is a problem if you want to call a servlet that only responds to a POST request, or that has different implementations for doGet and doPost. (This is poor servlet design, but using someone else's servlet, you may not have a choice.)

You can work around this by using a URLConnection as in http://www.jguru.com/jguru/faq/view.jsp?EID=62798 See also http://www.jguru.com/jguru/faq/view.jsp?EID=740 How can I use a servlet to print a file on a printer attached to the client? Location: http://www.jguru.com/faq/view.jsp?EID=232366 Created: Oct 19, 2000 Modified: 2001-06-24 11:04:49.495 Author: Serge Knystautas (http://www.jguru.com/guru/viewbio.jsp?EID=100012) Question originally posed by sonali khanolkar (http://www.jguru.com/guru/viewbio.jsp?EID=213541 The security in a browser is designed to restrict you from automating things like this. However, you can use JavaScript in the HTML your servlet returns to print a frame. The browser will still confirm the print job with the user, so you can't completely automate this. Also, you'll be printing whatever the browser is displaying (it will not reliably print plug-ins or applets), so normally you are restricted to HTML and images. [The JavaScript source code for doing this is: -Alex] How do I invoke the command-line Java interpreter from a web server or servlet (assuming there is a java application on the machine where the webserver is located)? Or, can I invoke Java with CGI? Location: http://www.jguru.com/faq/view.jsp?EID=232370 Created: Oct 19, 2000 Modified: 2000-10-24 10:30:51.799 Author: Serge Knystautas (http://www.jguru.com/guru/viewbio.jsp?EID=100012) Question originally posed by syahriar rizza (http://www.jguru.com/guru/viewbio.jsp?EID=223435 First you should consider how you want to run your command-line Java interpreter. Do you want this to happen within the same Java Virtual Machine (JVM), i.e., the same memory space, that the servlet is running or do you want it to be a separate process? If you want to run it within the JVM, you can call the static main() method on the class you were going to run on the command-line. You would create a String array with whatever command-line arguments you were going to pass, and pass this to the main() method. If you want to run this in a separate JVM, you would use the java.lang.Runtime.exec() method. You would use the exec() method to run the new command-line and more than likely, wait for the command-line program to finish executing. Here is some sample code: Runtime rt = Runtime.getRuntime(); Process process = rt.exec("java MyClass arg1 arg2"); try { process.waitFor(); } catch (InterruptedException ie) {

ie.printStackTrace(); } [ See also http://www.jguru.com/jguru/faq/view.jsp?EID=209356 ] [ You can also bypass servlets altogether using the JavaCGI package. -Alex] Comments and alternative answers

I run the java program in a separate JVM on WIN NT.... Author: Michael Wu (http://www.jguru.com/guru/viewbio.jsp?EID=141930), Jan 14, 2001 I run the java program in a separate JVM on WIN NT. A separate console window always opens and then closes. How can I run the java program in the background or at least hide the console window? Michael Wu How can I use a servlet to print a file on a printer attached to the server? Location: http://www.jguru.com/faq/view.jsp?EID=232378 Created: Oct 19, 2000 Modified: 2000-10-24 10:19:16.647 Author: Serge Knystautas (http://www.jguru.com/guru/viewbio.jsp?EID=100012) Question originally posed by sonali khanolkar (http://www.jguru.com/guru/viewbio.jsp?EID=213541 This depends on how your printers are attached to your computer. I can think of two basic ways you can print to a printer attached to the server. One approach is to create a java.awt.Frame, and then use java.awt.Toolkit's getPrintJob method to print that Frame to the printer. This will return a java.awt.PrintJob object if it works. The second approach is more OS specific. You could create a temporary file and copy that file to the printer device. This would allow you more flexibility and ease in terms of what you could print, but would tie you into how your OS provided printer devices. [See also http://www.jguru.com/jguru/faq/view.jsp?EID=98857] How do I set up a virtual host? That is, I want http://www.foo.com/ to be served off my own machine. Location: http://www.jguru.com/faq/view.jsp?EID=234896 Created: Oct 24, 2000 Modified: 2000-10-24 11:03:35.284 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by venkata prasad earanti (http://www.jguru.com/guru/viewbio.jsp?EID=210033 First off, if www.foo.com is going to be the only hostname served off your machine, then it's not technically a virtual host. Virtual hosting is when you want multiple hostnames to be served off the same machine. If there's only one hostname, then it's an "actual" host :-)

In any case, you need to contact your ISP and ask them to set up a DNS mapping from www.foo.com to your machine's static IP address, and configure your machine and/or web server so it thinks "www.foo.com" is its own name. Technical details of this process are outside the scope of this FAQ (though if someone wants to submit a feedback with a pointer to instructions, please do). There are two techniques for true virtual hosting. (Both require the involvement of your DNS ISP, as above.) 1. Name-based virtual host: Multiple hostnames mapped to the same static IP address. 2. IP-based virtual host: Multple hostnames, each mapped to a different static IP address, but one machine responding to all of those multiple IP addresses. These are often called "IP aliases" or "multiple interfaces" (here "interface" refers to the TCP/IP interface, not any of the other infinite definitions of "interface"). See the references below for more information on enabling IP aliasing for your OS. From this point, configuration details vary widely based on your operating system, your web server, and your servlet engine. We will defer answering them here; instead, we request specific FAQ questions on each combination of web server and servlet engine. If your servlet engine supports the Servlet spec 2.2 or greater, you will probably need to re-map the "default context", so "/" maps to "/mywebapp/". See this FAQ for doing this on Tomcat. See also: • • • • • • • • • •

Unix Split Personality: How to Virtual Host Linux IP-Alias mini-HOWTO Apache Virtual Host documentation Does anyone know how to do IP aliasing on Windows? How do I use servlet aliasing, so the URL "http://foo.com/mywebapp/servlet/a.b.c.MyServlet" can become "http://foo.com/mywebapp/Thingy"? Can I configure Tomcat so that the name of the webapp is not used in the URL? E.g. http://localhost/servlet/HelloWorld, instead of http://localhost/examples/servlet/HelloWorld How do I set up virtual hosting on Tomcat in standalone mode? How do I set up virtual hosting on Tomcat with Apache? How do I set up virtual hosting on Java Web Server? How do I set up virtual hosting on Allaire JRun?

How can I serve a "Linearized" PDF file from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=236545 Created: Oct 25, 2000 Modified: 2001-07-23 09:59:30.715 Author: Garth Somerville (http://www.jguru.com/guru/viewbio.jsp?EID=225821) Question originally posed by Richard Williams (http://www.jguru.com/guru/viewbio.jsp?EID=2390

[More question: I am using a servlet to stream out the bytes of a PDF file to a user's browser. No problem there, it's just streaming out a file. The problem is in dealing with what Acrobat refers to as "Linearized" files. When served by a Netscape Enterprise server, these "linearized" files display the first page of the PDF file in the Acrobat Reader while subsequent pages are still being loaded. When displayed using my servlet as the file source, the entire document must download before I can see the first page.] In order to make the document appear to load more quickly, the Acrobat Reader relies on two features. First, you must of course make sure the PDF file is in the linearized format which the author of the PDF should be able to do. Second, since you are serving the file from a servlet, you must support the HTTP protocol features that Acrobat is depending on. In short summary, when Acrobat receives the first part of file it can determine that it is in linearized form. This enables it to cache the tables that are present at the beginning of the file and then close the connection, preventing the entire document from downloading all at once. From then on Acrobat fetches each page or object as it is needed from the web server. It does this by using the HTTP byte range headers in requests, and your servlet needs to support these for it to work properly. The byte range headers are described in the HTTP/1.1 RFC #2616 section 14.35, but a brief description is that in any HTTP request there may be extra headers that indicate the client is requesting only part of the entity, rather than the full entity. These headers indicate a byte range, or offest and length, that the client is asking for. An example is:

GET /example.pdf HTTP/1.1 Range: bytes=0-1023

Here, the client is asking for only the first 1K of the file. The key to making this work in HTTP 1.1 is in the way the server responds to such requests. If the server does not understand the byte range headers, it will reply in ignorance with the usual "200 OK" and send the entire file. But if it does understand the byte range headers, it replies with a "206 Partial Content" and sends only the requested portion of the file. Looking at the response code is how different client programs are able to display whether a server supports "resumable downloads." If you can program your servlet to support these requests for partial content, I think you'll get the result you want. [Hmm, sounds a little dubious... Has anyone tried this? -Alex] Comments and alternative answers

I tried to do this with IE5.0 Author: Colin Yates (http://www.jguru.com/guru/viewbio.jsp?EID=772727), Feb 26, 2002 Hi, I have tried to do this but I cannot get IE to request the byte ranges? It is using http1.1 but I have checked all the headers, all the parameters etc. and it never asks for the bytes. I have tried simply setting the status to 206, but it doesn't do anything. If

someone could figure out how to extract the byte range I will carry on. Cheers Colin Yates Re: I tried to do this with IE5.0 Author: Sylvainn Lesagee (http://www.jguru.com/guru/viewbio.jsp?EID=1222412), Jan 20, 2005 Hi please forward the code, i am doing something similar work. Thanx Re: I tried to do this with IE5.0 Author: Sylvainn Lesagee (http://www.jguru.com/guru/viewbio.jsp?EID=1222412), Jan 20, 2005 Hi, please forward the code at: slesage "at" neuf.fr i am doing something similar work. Thanx I have done this Author: Robert Wind (http://www.jguru.com/guru/viewbio.jsp?EID=418623), Mar 22, 2002 I've written a servlet that responds appropriatly to byte-range requests. If anyone's interested, I'll post the code. Re: I have done this Author: Colin Yates (http://www.jguru.com/guru/viewbio.jsp?EID=772727), Mar 23, 2002 Please post, I am *very* interested! Could you please also email to [email protected] Cheers Re[2]: I have done this Author: Robert Wind (http://www.jguru.com/guru/viewbio.jsp?EID=418623), Mar 25, 2002 The code appears to be too large to post here, so I'll email it to you. If anyone else is interested, email me at [email protected]. Re[3]: I have done this Author: Sudheendra Galgali (http://www.jguru.com/guru/viewbio.jsp?EID=868107), Jul 21, 2004 Hi, I am interested in this code too. Can you send it to me? Thanks, -SG Re[2]: I have done this Author: John Hayward (http://www.jguru.com/guru/viewbio.jsp?EID=1195083), Aug 24, 2004 Did you get the source code for serving bytes from a servlet? I'm interested in doing this myself. Could you email that source code to me also? I'm at [email protected] thank you. Re[3]: I have done this Author: Jan Pelegrin (http://www.jguru.com/guru/viewbio.jsp?EID=1243379), May 10, 2005

Is it possible to have the source code also. Mailto jan.pelegrin#4st.be Thanks Re[2]: I have done this Author: Rajesh Boopalan (http://www.jguru.com/guru/viewbio.jsp?EID=1206250), Oct 19, 2004 We also handling the similer one,could you please send the code to mail id. [email protected] Thanks in Advance, B.Rajesh. Re: I have done this Author: chatla prathap (http://www.jguru.com/guru/viewbio.jsp?EID=28780), Apr 7, 2004 please send me the code as iam interested in it. thanks in advance. Re[2]: I have done this Author: m k (http://www.jguru.com/guru/viewbio.jsp?EID=1174232), May 27, 2004 I'm looking to do the same thing with a servlet, is the code still available? Thank you please forward the code Author: aarthi vad (http://www.jguru.com/guru/viewbio.jsp?EID=1195392), Aug 25, 2004 please forward the code, i am doing something similar work. Re: please forward the code Author: Antony Lawrence (http://www.jguru.com/guru/viewbio.jsp?EID=1199791), Sep 17, 2004 Can I have it too ([email protected]).... Thanx Re[2]: please forward the code Author: Nitin Goyal (http://www.jguru.com/guru/viewbio.jsp?EID=1204913), Oct 13, 2004 Can I have the code too? ([email protected]) Thanks. Re[3]: please forward the code Author: Nav Gupta (http://www.jguru.com/guru/viewbio.jsp?EID=1208992), Nov 3, 2004 Could someone please send me ([email protected]) the code as well? Re: I have done this Author: Nitin Goyal (http://www.jguru.com/guru/viewbio.jsp?EID=1204913), Oct 13, 2004 I have implemented it successfully for single byte-range requests but the browser does nothing when it requests for multipart/byteranges. I have followed RFC2616

conventions to send the multipart/byteranges but browser does not seem to respond to it. Do I have anything other than specified in RFC2626 for multipart? Re: I have done this Author: Cathy Hui (http://www.jguru.com/guru/viewbio.jsp?EID=1207626), Oct 27, 2004 Hi Robert, Could u pleaset post the code online for us to share please? Thanks! Cathy How can I serve a "Linearized" PDF file from a servlet? Author: Murray Bob (http://www.jguru.com/guru/viewbio.jsp?EID=1209589), Nov 6, 2004 Can I get the code as well Re: I have done this Author: lana shapiro (http://www.jguru.com/guru/viewbio.jsp?EID=1213053), Nov 25, 2004 Hi Robert. Could you please e-mail me this code? My e-mail address is [email protected] . Thank you very much. « previous

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Could you show me an example of using doPut() method? Location: http://www.jguru.com/faq/view.jsp?EID=236578 Created: Oct 25, 2000 Modified: 2001-07-15 22:49:41.473 Author: Garth Somerville (http://www.jguru.com/guru/viewbio.jsp?EID=225821) Question originally posed by Daniel Mayor (http://www.jguru.com/guru/viewbio.jsp?EID=66226 [Short answer: no modern browser uses HTTP PUT for anything meaningful, so doPut() is never used, except for a custom protocol. If you want to upload a file, see How do I upload a file to my servlet? -Alex] A simple example would be a source code repository application consisting of a Java Applet on the client and a Servlet on the server -- it would be entirely appropriate to upload new files into the system by having the applet send an HTTP PUT request, which would be processed by the servlet's doPut() method. I am guessing there is more to this question. It is important to understand that in the HTTP 1.1 protocol, each request indicates a resource (the request path) and an action (the method) to be taken. In HTTP/1.1 the methods supported are OPTIONS, GET, POST, HEAD, PUT, DELETE, and TRACE. Each of these is clearly defined and differentiated in the HTTP/1.1 RFC. In particular, POST and PUT do not mean the same thing. POST means to apply the content accompanying the request to the entity in the request URI, usually in the sense that the entity processes the content and returns some data as the result. Servlets and CGI scripts fit this description.

PUT means very simply that the accompanying content *is* the entity described by the request URI, and the server is being asked to store it as such. So the following conversation makes sense when PUT is used: ->GET /file.dat HTTP/1.1 <-HTTP/1.1 404 Not Found ->PUT /file.dat HTTP/1.1 Content-Length: 6 Content-Type: text/plain Hello! <-HTTP/1.1 200 OK ->GET /file.dat HTTP/1.1 <-HTTP/1.1 200 OK Content-Length: 6 Content-Type: text/plain Hello! The above exchange makes no sense if POST is used instead of PUT. However, when it comes to servlet programming, the distinctions among HTTP methods have been largely lost, in particular the difference between GET and POST. When it comes to servlets, it is essentially up to the author to define what his doPost() or doPut() means but it probably makes sense to keep in mind what these mean in HTTP and try to use them accordingly. Is there only one ServletContext instance associated with all the servlets running in a 2.1 (or prior) compliant servlet engine? Location: http://www.jguru.com/faq/view.jsp?EID=236603 Created: Oct 25, 2000 Modified: 2000-10-26 09:44:27.876 Author: Garth Somerville (http://www.jguru.com/guru/viewbio.jsp?EID=225821) Question originally posed by sharad gupta (http://www.jguru.com/guru/viewbio.jsp?EID=100198 Essentially the answer is yes, although even in the 2.1 specification it would have been permissible for a container to define multiple contexts either based on virtual hosts or based on part of the request URL, the same way it is done in 2.2. But I think the practical answer is yes, there is one context. What does the exception "java.net.SocketException: Connection reset by peer" mean? How can this be avoided? Location: http://www.jguru.com/faq/view.jsp?EID=237557 Created: Oct 26, 2000 Modified: 2000-10-26 09:45:16.207 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Nivedita Dixit (http://www.jguru.com/guru/viewbio.jsp?EID=224747

It usually happens when the connection was reset by the peer -- that is, when the client unexpectedly closed the socket. This happens when the user clicks "stop", or "reload", or "back", or enters a new URL, or closes his Internet connection, while a resource is still being downloaded (before your server gets to close its socket). This is normal behavior and you shouldn't worry about it. Comments and alternative answers

But why does it happen only when I use Netscape as... Author: Manish Bhatnagar (http://www.jguru.com/guru/viewbio.jsp?EID=12550), Mar 1, 2001 But why does it happen only when I use Netscape as my browser ? My servlets work very fine with Internet Explorer. They cry with this error only when I use Netscape as my browser. Re: But why does it happen only when I use Netscape as... Author: John Scudder (http://www.jguru.com/guru/viewbio.jsp?EID=252439), Apr 26, 2001 open up /conf/server.xml change your Logger "tc_log" tag's verbosityLevel to "WARNING" rather than "INFORMATION". There are five different options, and "WARNING" won't place any garbage on our standard output. See the comments in server.xml for more details. Re: Re: But why does it happen only when I use Netscape as... Author: Dinu Jose Varghese (http://www.jguru.com/guru/viewbio.jsp?EID=440122), Jun 16, 2001 Thank u very much. i was very much worried about this socket error coming on the console. When the verbosity level is set to warning in the server.xml ,these error messages are gone from the console. Craig says Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 19, 2001 Craig McClanahan says, on the tomcat-dev mailing list: The server is reporting "connection reset by peer" in the middle of a request. That means one of the following things: • •

•

• •

The browser started a request and the user pressed STOP. The browser started an request in one frame and JavaScript on another frame told it to go somewhere else (which has the same effect as a user pressing STOP). You have a meta refresh reload someplace that is firing so fast that the previous request hasn't had a chance to complete yet. The five second periodicity makes me pretty suspicious of this. You have some network component in between (a router or proxy) that is misbehaving. You have some completely separate connection attempts going on that are disobeying the HTTP protocol (such as doing a telnet connection to port 8080

and then disconnecting).

Re: Craig says Author: Xavier Haurie (http://www.jguru.com/guru/viewbio.jsp?EID=471764), Aug 8, 2001 I had an interesting instance of Craig's second point: "The browser started an request in one frame and JavaScript on another frame told it to go somewhere else (which has the same effect as a user pressing STOP)." The problem was a submit button in a form which had its onClick attribute set to "location=URL". Upon clicking the button, javascript wants to go to URL while the form wants to go to its own url as specified by its action attribute The problem is solved by adding "return false" to the onClick attribute to prevent the onClick event from being passed on to the form:

Re: Craig says Author: sathish r (http://www.jguru.com/guru/viewbio.jsp?EID=1180043), Jun 19, 2004 I get this error when i do multi threading from client side. Client is a java app which talks to a Directory server. I made the code to execute parallely, this is causing this exception in tomcat servlet which is the client. I do not understand how multithreading affects networking behaviour? Another question on this.... Author: Michael Shelnutt (http://www.jguru.com/guru/viewbio.jsp?EID=483318), Aug 24, 2001 Actually, does anyone know how I can catch this behavior in my servlet? If the user submits a form which in turn starts a long query on my db, if the user clicks STOP or BACK, I want to stop the query from processing. Any thoughts? Re: Another question on this.... Author: Adam Flint (http://www.jguru.com/guru/viewbio.jsp?EID=477446), Aug 28, 2001 The approach I took was to get the servlet to set the response in the doPost method and then go off and do its processing. This only worked for me because I did not need to know the response of the servlet, I just needed it to go and do something. But this stops the connection reset by peer problem because the servlet responds straight away.

Re[2]: Another question on this.... Author: Suresh Addagalla (http://www.jguru.com/guru/viewbio.jsp?EID=449405), Feb 7, 2002 Hi, I can understand if 'Connection reset by peer' is reported by web server when the user presses stop or reload. I am facing a problem where JRun is reading a request from iPlanet, and JRun thows this exception. Any ideas as to what could be wrong? Thanks in Advance, Suresh Re: Another question on this.... Author: Lee Johnson (http://www.jguru.com/guru/viewbio.jsp?EID=999672), Sep 16, 2002 Michael, Did you ever find a solution to this? We also need to catch this exception. However, this exception does not appear to be catchable since jrun handler already catches it ? java.net.SocketException:Connection reset by peer Author: pradnya korde (http://www.jguru.com/guru/viewbio.jsp?EID=1011016), Oct 11, 2002 hello, i am getting the same problem to be more elaborate i am trying to use the concept of applet - servlet communitcation. an applet is connecting to a servlet using URLConnection.. the applet is wrinting an object of type vector to the ouputstream using hte writeObejct function of the Objectouptutstream class however the servlet is not able to read it from the inputstream... at this time it throws the excption java.net.SocketException:Connection reset by peer what can be the problem any idea..? thank you so much in advance Pradnya Re: java.net.SocketException:Connection reset by peer Author: Jon Dean (http://www.jguru.com/guru/viewbio.jsp?EID=1161759), Apr 9, 2004 has anyone given an answer for this? i am communicating with a servlet using a regualar java application. the app and servlet are communicating back and forth just fine. the servlet in the end should send out an email but instead returns the connection reset exception to the app. i'm running tomcat which seems to work great for my other servlets. i'm kind of stumped as to what this means and therefore can't really pinpoint the errors in my code and the component i'm writing with this is due in a few days! thanks:) Re[2]: java.net.SocketException:Connection reset by peer Author: Jon Dean (http://www.jguru.com/guru/viewbio.jsp?EID=1161759), Apr 9, 2004 well nevermind i found the answer to my own question, although i didn't

realize this forum has been dead for well over a year anyway. in case anyone happens to come across this the problem was that i was using a mal-formed smtp server address (a stupid problem i had in searching an array list and pulling out the wrong string). it seems that this exception will be thrown just about any time an error causes the connection to be aborted (at least that's what i gather from the problem i had). I use a servlet to export WML on the Nokia Toolkit. Why can't I output a Chinese String (GB2313 or UNICODE)? Location: http://www.jguru.com/faq/view.jsp?EID=238455 Created: Oct 27, 2000 Modified: 2000-11-02 15:32:26.224 Author: Brian O'Byrne (http://www.jguru.com/guru/viewbio.jsp?EID=38567) Question originally posed by chile wang (http://www.jguru.com/guru/viewbio.jsp?EID=138876 The WAP protocol gaurantees only 7-bit ASCII, which limits you to the most basic character sets. Most 'phones will support 8-bit ASCII. AFAIK none support Unicode. Is there a way to determine what cookies or headers are being sent in a response? [I'm assuming the response was passed in from a request dispatcher or something... -Alex] Location: http://www.jguru.com/faq/view.jsp?EID=243705 Created: Nov 2, 2000 Modified: 2000-11-02 15:43:34.369 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Martin Hinds (http://www.jguru.com/guru/viewbio.jsp?EID=137914 Not with Servlet spec 2.2. The next version of the spec will allow you to pass in your own response object to the request dispatcher, which can intercept header and cookie setting calls, and record them for your later inspection. See also http://www.jguru.com/jguru/faq/view.jsp?EID=213901 Comments and alternative answers

You can use the containsHeader() method of HttpSer... Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7), Nov 3, 2000 You can use the containsHeader() method of HttpServletResponse to see if a response is there, just not get its value. When I'm using the getCookies() method (of HttpServletRequest) I get only the cookie(s) I set. How can I get all the cookies on my HD? Location: http://www.jguru.com/faq/view.jsp?EID=245303 Created: Nov 4, 2000 Modified: 2000-11-04 19:07:10.516 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question

originally posed by Zvi Septon (http://www.jguru.com/guru/viewbio.jsp?EID=226023 You can't. That's a security feature. See What is a cookie?. How do I share sessions between two server instances, one secure (HTTPS) and one normal (HTTP)? Location: http://www.jguru.com/faq/view.jsp?EID=245672 Created: Nov 5, 2000 Modified: 2000-11-30 08:57:13.73 Author: Ryan Breidenbach (http://www.jguru.com/guru/viewbio.jsp?EID=45212) Question originally posed by ewhale ewhale (http://www.jguru.com/guru/viewbio.jsp?EID=133291 The management of sessions is handled by your servlet container. That is, you will never have to write any custom code so you can share sessions between servlets - it is already handled for you. The entry point from the servlet container to your servlet will always be the service(HttpServletRequest req, HttpServletResponse res) method. Since this method takes an HttpServletRequest object as a parameter, you can always call getSession() to access the HttpSession. As far as having two servlets - one for HTTP and one for HTTPS - these should behave basically the same. All of the HTTPS encryption/decryption is hidden from the servlet. Unless your HTTPS servlet needs to have some code to ensure it is processing a request whose protocol is HTTPS, these two servlets should be pretty much the same. See also Can I move between http and https-based resources while sharing the same session? in the JSP FAQ. [If the two servers are actually distinct, then you'd have to find some way of tunneling the data across. Hidden fields are probably your best bet, although that may not suit your security policy. -Alex] Comments and alternative answers

Session cookies and the cookie domain... Author: Daniel Leong (http://www.jguru.com/guru/viewbio.jsp?EID=796580), Mar 14, 2002 I'm not sure your answer is 100% true. As I understand it, the JSP session is usually maintained in a cookie (expcet for URL rewriting). Cookies that are expected to work for SSL sites too probably need to specify a cookie domain. This gets mentioned briefly in this article here, in context of Weblogic. I know Websphere can do the same, but I'm not sure about Tomcat. Re: how do I share sessions between two server instances... Author: alberto rosa (http://www.jguru.com/guru/viewbio.jsp?EID=351649), May 8, 2002 I think the point is sharing session data between 2 instances. As the servlet spec says, session scope is web application (=servlet context) domain. So, there is no garanty to

share session data between 2 web applications, neither so between 2 instances. But, this depends on the vendor's implementation (see vendor's session manager details for more information). For example, Websphere 3.5 is not compliant with servlet spec, so you can share session data between 2 web applications in the same instance. Hope this makes sense for you... Regards, Alberto. Re[2]: how do I share sessions between two server instances... Author: m lar (http://www.jguru.com/guru/viewbio.jsp?EID=918866), Jun 19, 2002 Could you give me a more deeper explanation about sharing session between 2 web applications? I work with Websphere 4.0.3 Thanks in advance, Marta Re[3]: how do I share sessions between two server instances... Author: alberto rosa (http://www.jguru.com/guru/viewbio.jsp?EID=351649), Jun 19, 2002 Marta: Websphere 4 is already servlet 2.2 compliant, so the concept of web application is added in that version. In previous versions, web applications session domain was not isolated from others, but this is no longer running on WAS 4.x. Hope this is clearer for you. Where and how can I define an application level variable that gets initialized at container startup? Something like the Application_OnStart Sub in the global.asa file of MicroSoft ASP. Location: http://www.jguru.com/faq/view.jsp?EID=245909 Created: Nov 5, 2000 Modified: 2000-12-07 21:15:56.603 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Mattias Deny (http://www.jguru.com/guru/viewbio.jsp?EID=227945 Make an InitServlet and initialize it in there. See I want the servlet container to load one or more servlets when the container is first fired up, as opposed to when a client issues a request for the servlets. How do I do that under Servlet 2.2 API?. Create it, then put in as a ServletContext Attribute. MyData mydata = new MyData(); getServletContext().setAttribute("some.attribute.name", mydata); Comments and alternative answers

If you want to share the information in non servlet... Author: Niclas Meier (http://www.jguru.com/guru/viewbio.jsp?EID=245132), Nov 7, 2000 If you want to share the information in non servlet classes (connection pools, etc) you can create a "Singleton" object (kind of) that holds all the data you want to share. For

flexible data sharing a map would be a good idea. Create the instance of the Object in the described startup servlet and access it in the hole application with a static getInstance()-method. [statics are almost always a bad idea. Use an application (context) variable instead. Then you won't get burned by, e.g., multiple applications using the same code. -Alex] How can I output audio or video from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=245939 Created: Nov 5, 2000 Modified: 2001-07-23 09:18:07.365 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by sathish baboo (http://www.jguru.com/guru/viewbio.jsp?EID=203430 For downloading an image, sound, or video file (GIF, JPEG, MP3, WAV, AVI, et al.), see How do I download a (binary, text, executable) file from a servlet or JSP? and How do I create an image (GIF, JPEG, etc.) on the fly from a servlet? . There is no explicit support for streaming media protocols in the Servlet API. You would have to write, or locate, your own RealAudio or ShoutCast server (for example). Comments and alternative answers

Actually, it is possible (and not that hard) to send... Author: Ivar Vasara (http://www.jguru.com/guru/viewbio.jsp?EID=262588), Nov 25, 2000 Actually, it is possible (and not that hard) to send binary info from a servlet. You have to call getOutputStream() on your response object, and feed it your data. Included is a snippet from the output portion of a servlet I wrote that dynamically generates JPEGS. Note: don't forget to set the correct MIME type. res.setContentType("image/jpeg"); ServletOutputStream sout = res.getOutputStream(); JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(sout); encoder.encode(workingImage,JPEGparams);

[Thanks! I don't think that deserves an "Actually" though -- that technique is documented in the above referenced FAQs. - Alex] Still unclear to me how to play output video from a servlet to a browser Author: Amit Rosner (http://www.jguru.com/guru/viewbio.jsp?EID=433821), Jun 5, 2001

I would like to send video to a servlet to the browser (ie5) , so that the video will play within the browser itself. Currently, following the suggestions here, I used the "sendRedirect" to send the MPG to the browser but it opened it with "Windows Media Player". How can I play in within the browswer itself? Can anyone send me a sample code that does that? Amit. HTML suggestion Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 15, 2001 ramanujam ragavan suggests: Hi, You can always embed vedios using the <Embed src="filename.mpg"> as part of the HTML output specified by the PrintWriter.println() statement. ex: PrintWriter display=response.getWriter(); response.setContentType("text/html"); display.println("...."); display.println("<embed src="success.mpeg">"); display.println("Any output Text");

Re: HTML suggestion Author: Marta Santana (http://www.jguru.com/guru/viewbio.jsp?EID=873616), May 10, 2002 Hi evreybody, I have another question related to this, How can I embed video when that video is a query result. I make it on the fly!! Can anyone help me!! Thanks a lot marta I want to use hidden variables for session tracking. How can I get the session object? Since the Servlet API 2.1 there is no method request.getSession ( String sessionId ) Location: http://www.jguru.com/faq/view.jsp?EID=246613 Created: Nov 6, 2000 Modified: 2000-12-07 19:18:18.944 Author: reshma deshmukh (http://www.jguru.com/guru/viewbio.jsp?EID=132478) Question originally posed by Thomas Hirschböck (http://www.jguru.com/guru/viewbio.jsp?EID=225611 In ServletAPI 2.1 a new method is added which is: HttpSession HttpServletRequest.getSession() With which you can get Session object. See http://java.sun.com/products/servlet/2.1/changes.html . In jsdk 2.1 there are two methods for getting session 1) HttpSession getSession(boolean create) Gets the current valid session associated with this request, if create is false or, if necessary, creates a new session for the request, if create is true. 2)HttpSession getSession() Gets the current valid session associated with this request, if create is false or, if necessary, creates a new session for the request.

[Yes, but that doesn't answer the question -- is there a way to get the session a priori without the server doing it automagically for you? -Alex] Comments and alternative answers

Home-rolled session IDs and using the HttpSession object. Author: Richard Robinson (http://www.jguru.com/guru/viewbio.jsp?EID=395750), Apr 7, 2001 I have a similar question. I have a servlet application that has been in existence for 2 years now. I rolled it using my own session IDs, which I pass in the URL or hidden fields on POSTs. There are quite a few methods that depend on the format of the Session ID as it is. And I will lose all that if I go to the Java HTTPSession object's creation of sessions. Is there no way I can enjoy all the benefits of HttpSession object -- WHILE using my same session IDs (and their baggage logic/format)? Re: Home-rolled session IDs and using the HttpSession object. Author: M. washu (http://www.jguru.com/guru/viewbio.jsp?EID=1217388), Dec 21, 2004 I'm interested to know if there is an alternative to this question ? I want to hide the "jesessionid" in a hidden form field but don't know how to recover the session from the servlet without using the deprecated class HttpSessionContext ? Thanks in advance. How do I set up virtual hosting on Allaire JRun? Location: http://www.jguru.com/faq/view.jsp?EID=246903 Created: Nov 6, 2000 Modified: 2000-12-07 20:23:40.845 Author: reshma deshmukh (http://www.jguru.com/guru/viewbio.jsp?EID=132478) Question originally posed by Alex Chaffee PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=3 Refer Alliare knowledgebase: http://www.allaire.com/support/KnowledgeBase/search.cfm My applet is sending a request to a servlet (using tomcat 3.1 + Apache). I cannot know upfront how long the processing will take (from 10 seconds to 10 hours). Should the applet send a request from time to time to check if the response has arrived? I can't wait for the response in the servlet because I will run into the HTTP timeout. I tried to use the Keep-alive connection and from the servlet send a "ping" message (an object) to the applet but the content is not flushed until the response is completed even though I call flush(), because of the HTTP mechanism.

Any idea to avoid pinging the server uselessly? Location: http://www.jguru.com/faq/view.jsp?EID=248491 Created: Nov 8, 2000 Modified: 2000-12-07 20:43:37.099 Author: Jens Dibbern (http://www.jguru.com/guru/viewbio.jsp?EID=9896) Question originally posed by Nicolas Cohen (http://www.jguru.com/guru/viewbio.jsp?EID=235112 [There's no real problem with "pinging" from the applet to the servlet every 30 seconds. The load per request is still pretty low. Keep-alive / server-push is an OK solution, but it sounds like it's more trouble than it's worth. But flush() should still work -- maybe there's a bug in your servlet engine? -Alex] A good solution for long running transactions in servlets is to use a Thread for it and store the thread in the Session. After starting the Thread you can response a "wait" message and send following requests from the applet asking for the result every 30 seconds (or whatever interval you like). The servlet should respond with wait messages as long as the Thread is alive and after that respond with your results. Comments and alternative answers

Thanks all for your answers. Here is what I had im... Author: Nicolas Cohen (http://www.jguru.com/guru/viewbio.jsp?EID=235112), Dec 8, 2000 Thanks all for your answers. Here is what I had implemented right after asking the question: the applet sends the initial request. Then it just sends a ping message from time to time. The backend server processes the request and the servlet stores the answer in the session. On the next ping from the applet, the answer is then transferred to the applet. It works quite well, the GET call is only 59 bytes. This is the same idea as Jens' solution except I don't store any thread, but Jens couldn't know I had sockets between middleware and backend too ;) facing the same problem !!! Author: hacene khellaf (http://www.jguru.com/guru/viewbio.jsp?EID=454113), Sep 14, 2001 i'm facing the same problem, i created a thread to keep the servlet alive and i send to the applet a wait message the problem is that the stream is closed as soon as i start the thread, is there any special meaning of " store the thread in the session" ? thanks for any help How do you do servlet aliasing with Apache and Tomcat? Location: http://www.jguru.com/faq/view.jsp?EID=250363 Created: Nov 9, 2000 Modified: 2000-11-21 03:04:34.094 Author: Serge Knystautas (http://www.jguru.com/guru/viewbio.jsp?EID=100012) Question originally posed by Felix Wong (http://www.jguru.com/guru/viewbio.jsp?EID=102927

Servlet aliasing is a two part process with Apache and Tomcat. First, you must map the request in Apache to Tomcat with the ApJServMount directive, e.g., ApJServMount /myservlet /ROOT Second, you must map that url pattern to a servlet name and then to a servlet class in your web.xml configuration file. Here is a sample exerpt: <servlet> <servlet-name>myservlet <servlet-class>com.mypackage.MyServlet <servlet-mapping> <servlet-name>myservlet /myservlet Comments and alternative answers

Hi, I have tried doing what you have suggested, but... Author: Alex Korneyev (http://www.jguru.com/guru/viewbio.jsp?EID=326128), Feb 11, 2001 Hi, I have tried doing what you have suggested, but it is not working. this is what i have in web.xml <servlet> <servlet-name> FitnessApplicationServlet <servlet-class> com.fitness.web.FitnessApplicationServlet <servlet-mapping> <servlet-name> FitnessApplicationServlet /fitness and this in my_tomcat_httpd.conf ApJservMount /fitness /ROOT

but if i try going to http://server_name/fitness/login i get this error:

2001-02-11 04:37:14 - Ctx( /fitness ): 404 R( /fitness + /login + null) null

there is nothing in the error logs. thanks for your help Servlet Aliasing Author: Robert Hector (http://www.jguru.com/guru/viewbio.jsp?EID=412771), Apr

30, 2001 It seems the suggested approach does NOT work under Tomcat v 3.2.1. It does work, however, under v 3.1.1. Is there a bug in 3.2.1 or does it have to be done differently in 3.2.1? Thanks, Bob Hector What about with mod_jk? Author: javier Beringola (http://www.jguru.com/guru/viewbio.jsp?EID=345612), Jun 14, 2001 This works perfect with jserv but do you know how to do it with mod_jk? Servlet Aliasing Author: Premjith SunTec (http://www.jguru.com/guru/viewbio.jsp?EID=739544), Jan 30, 2002 Hi, I am Premjith working at Suntec trivandrum ,india.I have done the servlet aliasing and is working fine. My requirement was to change the context root name "Servlet" to OSI i.e http://localhost/online/servlet/Login to http://localhost/online/OSI/Login when i changed the content of Web.xml,Server.xml,and all CONF files of tomcat to incorporate it it was working till i restart Apache server.Later i tried by copying the configured files to a temporory directory and overwriting the conf files with these files .I included this copy command in "startup" file of tomcat.i expectsome comments on this reply Re: Servlet Aliasing Author: Nancy Roberts (http://www.jguru.com/guru/viewbio.jsp?EID=739557), Jan 30, 2002 Hi, Thanks man,that was a very tricky and cool way of solving it.i tried it and working fine.we were badly looking for a solution .this works well with Jserv also. Nancy Re: Servlet Aliasing Author: Dave Peter (http://www.jguru.com/guru/viewbio.jsp?EID=739566), Jan 30, 2002 Hi Premjith, Superb way of changing the context root of tomcat,working fine .Thanks and can u try this with Jserv. Dave I want my servlet page to redirect to a login page if the session has timed out. How can I know if my session has timed out? Location: http://www.jguru.com/faq/view.jsp?EID=251532 Created: Nov 11, 2000 Modified: 2000-12-07 20:00:51.64 Author: Dieter Wimberger (http://www.jguru.com/guru/viewbio.jsp?EID=25708) Question originally posed by Amit Jain (http://www.jguru.com/guru/viewbio.jsp?EID=111841 If the servlet engine does the time-out, following code should help you: //assume you have a HttpServletRequest request if(request.getSession(false)==null) { //no valid session (timeouted=invalid)

//code to redirect to login page } [See also Servlets API Specification 2.2] Note that the code should work under 2.0 and 2.1 as well. Comments and alternative answers

I think this code will help U Author: srinivas kandagatla (http://www.jguru.com/guru/viewbio.jsp?EID=1150943), Mar 2, 2004 HttpSession session = request.getSession(false); boolean takeToLogin = false; if(session == null) takeToLogin = true; if(takeToLogin) { forward(request, response, "Login.jsp"); return; } Can I force the browser to save a downloaded file with a name I specify, rather than the name of the URL? Location: http://www.jguru.com/faq/view.jsp?EID=252010 Created: Nov 12, 2000 Modified: 2001-07-23 09:18:44.093 Author: Alexandros Kotsiras (http://www.jguru.com/guru/viewbio.jsp?EID=64209) Question originally posed by sameet Joshi (http://www.jguru.com/guru/viewbio.jsp?EID=234380 Assuming that you want to save the file as "myFile.txt" you have to set the ContentDisposition response Header as follows : response.setHeader("Content-Disposition", "attachment;filename=myFile.txt"); Note that even if the file is of a type that the browser can display ( .html .txt etc.) because you set the disposition type as "attachment", the browser will not open it but it will instead pop up a "save as" box. See HTTP/1.1 specs at: ftp://ftp.isi.edu/in-notes/rfc2616.txt See also How do I download a (binary, text, executable) file from a servlet or JSP? (especially the feedback) Comments and alternative answers

I want to download XML File with IE5.5SP1. But IE don't... Author: Tiara Milk (http://www.jguru.com/guru/viewbio.jsp?EID=304749), Jan 17, 2001 I want to download XML File with IE5.5SP1. But IE don't open save as dialog. IE open XML File,alose DTD File. Please let me know to download XML file with save as dialog. My code as follows: -res.setContentType("application/download"); res.setHeader("Content-Disposition", "inline;filename=myFile.txt"); res.setContentLength((int)file.length()); ---

I tried to write [attachment] word. But I got a download.htm. Why? Try use [extension-token] (see rfc2183) Author: Evgeny Dementiev (http://www.jguru.com/guru/viewbio.jsp?EID=312081), Jan 25, 2001 Try use [extension-token] (see rfc2183) In my servlet I am trying to let the user download... Author: Mike Jewson (http://www.jguru.com/guru/viewbio.jsp?EID=313341), Jan 26, 2001 In my servlet I am trying to let the user download a file using the following code: response.setHeader("Content-Disposition","attachment;filename=myFile.txt"); Works fine in Netscape, but when trying to do this in IE the filename is the name of the servlet. Is there anyway to fix this? Re: In my servlet I am trying to let the user download... Author: seema bhatnagar (http://www.jguru.com/guru/viewbio.jsp?EID=429391), May 28, 2001 Have u found the solution for this problem.I too am facing the same problem.In the save as dialog box it displays servlet name.Another starnge problem is that if i don't provide space in the word "content- disposition" the hour glass waits forever but gives the correct file name in IE.But in NS it works fine in all the conditions. Please suggest something. Re: Re: In my servlet I am trying to let the user download... Author: david peter (http://www.jguru.com/guru/viewbio.jsp?EID=471669), Aug 21, 2001 Remove the attachment keyword from the response.setHeader statement. It then downloads which ever file name you give Thanks Re: In my servlet I am trying to let the user download... Author: Surya Rani (http://www.jguru.com/guru/viewbio.jsp?EID=212310), Aug 30, 2001 Hey I used the same code But, it works fine with IE4.7,5.0,5.5SP2 It is not working in NS. In NS the file name is servlet name. Can you help me in this. In response to what I had just previously wrote. I... Author: Mike Jewson (http://www.jguru.com/guru/viewbio.jsp?EID=313341), Jan 26, 2001 In response to what I had just previously wrote. I found that IE does not like a fully qualified path for the filename like : filePath = "c:\temp\file.txt";

Make sure that it is just the filename and no directory information. Then it will work in both Netscape and IE. Thanks. Re: In response to what I had just previously wrote. I... Author: Markus Jon Nagel

(http://www.jguru.com/guru/viewbio.jsp?EID=429404), May 28, 2001 According to the RFC mentioned above, absolute filenames such as "C:\foodir\foofile.txt" are not allowed, supported, you got to hell for it, etc... ;-) You MUST specify a filename WITHOUT any reference to a directory. So it seems IE is more standard - compliant that NS is (funny enough). What happened in NS anyway (just curious)? Best regards, Markus J. Nagel it could not be done Author: durgesh patel (http://www.jguru.com/guru/viewbio.jsp?EID=1218492), Dec 28, 2004 hi. it could not be done I have too this problem. Even if a put file path =... Author: Alexander Mazurok (http://www.jguru.com/guru/viewbio.jsp?EID=313062), Jan 30, 2001 I have too this problem. Even if a put file path = only file. Can anybody help me? please, send comments to [email protected] Thanks. I' sorry. I mistake a file name in this source.... Author: Tiara Milk (http://www.jguru.com/guru/viewbio.jsp?EID=304749), Feb 3, 2001 Thanks. I' sorry. I mistake a file name in this source. I want to download a XML file with XML extension at the save-dialog. -res.setContentType("application/download"); res.setHeader("Content-Disposition", "inline;filename=myFile.xml"); res.setContentLength((int)file.length()); ---

I tried to use the extension-token, for example, x-force-download ,and so on. But IE5.5SP1 think maybe only the file extension. I tried to use the no full Path. But it worked same thing. My research result is following: IE5.01 is OK.( can open savedialog ) IE5.5SP1 is NG.( open the file at the Browser). Is it IE5.5Sp1 BUG? Thaks. Second posting - I didn't see the first so I am re... Author: Scott Rolfson (http://www.jguru.com/guru/viewbio.jsp?EID=341761), Mar 1, 2001 Second posting - I didn't see the first so I am resending. I apologize if this is a duplicate. There is a bug in IE 5.5 SP1. If the content-disposition is "attachment", then IE 5.5 SP1 will open the referrer document (i.e. download.htm) rather than the intended document in the URL. See Microsoft support article Q281119 (http://support.microsoft.com/support/kb/articles/Q281/1/19.ASP?LN=ENUS&SD=gn&FR=0&qry=q281119&rnk=1&src=DHCS_MSPSS_gn_SRCH&SPR=MSALL)

Prior to IE 5.0 Microsoft didn't honor the content-disposition field, so it was never an issue. A fix to mshtml.dll is available on request from Microsoft. The fix works, I tested it. Re: Second posting - I didn't see the first so I am re... Author: Brian Kreulen (http://www.jguru.com/guru/viewbio.jsp?EID=428360), May 25, 2001 I must just be blind or something, but I couldn't find ANYTHING on MS support about obtaining this file. I followed the link from the MS Bug Page that you provided and tried to get some "web based support" from them, but I had to sign up for a Passport account. I tried that, it said my email was already in use. When I tried to log in using my email, it said that account didn't exist. Arghh!! I searched everywhere else on that site, to no avail. Can you point me in the right direction to find this simple little thing?? Thanks! Re: Re: Second posting - I didn't see the first so I am re... Author: Scott Rolfson (http://www.jguru.com/guru/viewbio.jsp?EID=341761), May 25, 2001 Update your BIO with an email address or post it here and I will send you the files. Re: Re: Re: Second posting - I didn't see the first so I am re... Author: Brian Kreulen (http://www.jguru.com/guru/viewbio.jsp?EID=428360), May 28, 2001 I do have an email listed in my bio... did you mean that you wanted a nonyahoo or non-hotmail email? Re: Re: Re: Re: Second posting - I didn't see the first so I am re... Author: Scott Rolfson (http://www.jguru.com/guru/viewbio.jsp?EID=341761), May 28, 2001 I can't see your email addy. You can make it visible to all users if you go to the member page button on the top right of the page and add your email (any address is OK) in the BIO textbox below the quotation textbox. If you don't want to do that, then send me your email address to [email protected] so I can reply with the files. Re: Re: Re: Re: Re: Second posting - I didn't see the first so I am re... Author: Brian Kreulen (http://www.jguru.com/guru/viewbio.jsp?EID=428360), May 29, 2001 Got it... it should be up there now...

Just in case it didn't...... [email protected] I want give an option to download several files.. Author: Ramesh Juluru (http://www.jguru.com/guru/viewbio.jsp?EID=434906), Jul 4, 2001 How can i give an option to download several files as alex told for one file. Awaited reply. regards, ramesh

saving text file... Author: Chris Chan (http://www.jguru.com/guru/viewbio.jsp?EID=1150403), Mar 1, 2004 I'm trying to write the text file based on the result set form the command. The thing is, I don't want the file saved on the server, rather have the file saved on the client machine. Is there a way to attach this text file when it technically hasn't been created? I tried the execCommand to use the saveAs dialog, but it defaults everything to unicode, even though I clearly state it is "text/plain". thanks in advance. file download dialog on IE browser Author: ramaa Davanagere (http://www.jguru.com/guru/viewbio.jsp?EID=1184629), Jul 8, 2004 This article is very useful for me but I want to find out if we can take this a step further. What I mean by this is, can we find out if the user clicked "Open" or "Save" or "Cancel" buttons on the file download dialog? Is there a handle that I returned with the what the user clicked. I'm more inter ested to know if the user clicked cancel button. I need to take specific actions when the user clicks cancel button or the save button. Please help me. Thanks a ton. If you know the answer (or any ideas) Thanks. Ramaa « previous

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Can Tomcat be configured to interpret all, or selected, .html files within a given context as JSP? Or, do JSP files have to end with a .jsp extension? Location: http://www.jguru.com/faq/view.jsp?EID=254460 Created: Nov 15, 2000 Modified: 2000-12-07 19:59:03.193 Author: swarraj kulkarni (http://www.jguru.com/guru/viewbio.jsp?EID=121306) Question originally posed by Tom Boyd (http://www.jguru.com/guru/viewbio.jsp?EID=230240 yes you can do that by modifying the web.xml file. You will have to invoke the org.apache.jasper.runtime.JspServlet for all the requests having extension .html. You can do that by changing the Servlet mapping code: <servlet-mapping>

<servlet-name> jsp *.html And comment out the following block <mime-mapping> <extension> html <mime-type> text/html What is the difference between request attributes, session attributes, and ServletContext attributes? Location: http://www.jguru.com/faq/view.jsp?EID=255157 Created: Nov 16, 2000 Modified: 2000-12-01 13:12:10.11 Author: Wellington Silva (http://www.jguru.com/guru/viewbio.jsp?EID=223085) Question originally posed by Bhalinder Singh (http://www.jguru.com/guru/viewbio.jsp?EID=205994 A ServletContext attribute is an object bound into a context through ServletContext.setAttribute() method and which is available to ALL servlets (thus JSP) in that context, or to other contexts via the getContext() method. By definition a context attribute exists locally in the VM where they were defined. So, they're unavailable on distributed applications. Session attributes are bound to a session, as a mean to provide state to a set of related HTTP requests. Session attributes are available ONLY to those servlets which join the session. They're also unavailable to different JVMs in distributed scenarios. Objects can be notified when they're bound/unbound to the session implementing the HttpSessionBindingListener interface. Request attributes are bound to a specific request object, and they last as far as the request is resolved or while it keep dispatched from servlet to servlet. They're used more as comunication channel between Servlets via the RequestDispatcher Interface (since you can't add Parameters...) and by the container. Request attributes are very useful in web apps when you must provide setup information between information providers and the information presentation layer (a JSP) that is bound to a specific request and need not be available any longer, which usually happens with sessions without a rigorous control strategy. Thus we can say that context attributes are meant for infra-structure such as shared connection pools, session attributes to contextual information such as user identification, and request attributes are meant to specific request info such as query results.

Is there any way I can assign different values of CLASSPATH to different contexts? Location: http://www.jguru.com/faq/view.jsp?EID=255582 Created: Nov 16, 2000 Modified: 2000-12-07 21:18:37.38 Author: Tim McNerney (http://www.jguru.com/guru/viewbio.jsp?EID=210140) Question originally posed by Dennis Cook (http://www.jguru.com/guru/viewbio.jsp?EID=232644 One way to get the functional equivalent is to put the files in question in either "/WEB-INF/classes" or "/WEB-INF/lib", depending on whether you are talking about a .class or .jar. The CLASSPATH for a given webapp will include WEB-INF/classes and all the .jar files found in WEB-INF/lib. Say you had utils.jar and form-taglib.jar in WEB-INF/lib, the resulting classpath would look like: $CLASSPATH:/WEB-INF/classes:/WEBINF/lib/utils.jar:/WEB-INF/lib/form-taglib.jar [...but remember, it's built automatically by the servlet container. -Alex] Are singleton/static objects shared between servlet contexts? Location: http://www.jguru.com/faq/view.jsp?EID=256911 Created: Nov 17, 2000 Modified: 2000-12-07 21:20:21.071 Author: kedar choudhary (http://www.jguru.com/guru/viewbio.jsp?EID=99914) Question originally posed by kurt kessel (http://www.jguru.com/guru/viewbio.jsp?EID=237344 [Question continues: For example if I have two contexts on a single web server, and each context uses a login servlet and the login servlet connects to a DB. The DB connection is managed by a singleton object. Do both contexts have their own instance of the DB singleton or does one instance get shared between the two?] It depends on from where the class is loaded. The classes loaded from context's WEB-INF directory are not shared by other contexts, whereas classes loaded from CLASSPATH are shared. So if you have exactly the same DBConnection class in WEB-INF/classes directory of two different contexts, each context gets its own copy of the singleton (static) object. When building web applications, what are some areas where synchronization problems arrise? Location: http://www.jguru.com/faq/view.jsp?EID=259083 Created: Nov 21, 2000 Modified: 2000-12-07 21:24:13.745 Author: Brian O'Byrne (http://www.jguru.com/guru/viewbio.jsp?EID=38567) Question originally posed by rob g (http://www.jguru.com/guru/viewbio.jsp?EID=47931 In general, you will run into synchronization issues when you try to access any shared resource. By shared resource, I mean anything which might be used by more than one request. Typical examples include: •

Connections to external servers, especially if you have any sort of pooling.

• •

Anything which you include in a HttpSession. (Your user could open many browser windows and make many simultaneous requests within the one session.) Log destinations, if you do your own logging from your servlets.

How do I identify the device (browser) the request is coming from? Location: http://www.jguru.com/faq/view.jsp?EID=259332 Created: Nov 21, 2000 Modified: 2000-12-07 23:56:27.149 Author: Michael Szlapa (http://www.jguru.com/guru/viewbio.jsp?EID=241392) Question originally posed by Pankaj Mishra (http://www.jguru.com/guru/viewbio.jsp?EID=238618 To some degree you can find the information about the browser from HTTP request header "User-Agent". For example if the page was called by IE5.5 the header value would be: Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 4.0) To read it you can do something like this: request.getHeader("User-Agent"); See also servlet examples coming with the Jakarta-Tomcat. The bad news is that event if you know the type of the browser you still do not know about some features that user may have had customized: e.g Java may be off, or JavaScript may be off, etc. Good luck, Michael My HTML pages take too long to load. Where can I find advice on how to optimize the rendering time? Location: http://www.jguru.com/faq/view.jsp?EID=259570 Created: Nov 21, 2000 Modified: 2000-12-07 23:55:34.537 Author: Troy Niven (http://www.jguru.com/guru/viewbio.jsp?EID=219893) Question originally posed by Ely Yang (http://www.jguru.com/guru/viewbio.jsp?EID=238563 There are several tools available on the internet for this. The most effective one that I've found is Net Mechanic http://www.netmechanic.com They have an image optimizing utility, as well as utilities to tell you about anything else that may be wrong with your HTML code. TROY ASP provides an Ad Rotator component for using banners on a web site. Is there an equivalent way to rotate ad banners in Servlets? Location: http://www.jguru.com/faq/view.jsp?EID=259608

Created: Nov 21, 2000 Modified: 2000-12-13 10:03:05.992 Author: Troy Niven (http://www.jguru.com/guru/viewbio.jsp?EID=219893) Question originally posed by Avinash Kapoor (http://www.jguru.com/guru/viewbio.jsp?EID=239024 None that I know of. There is such thing as a Javascript that will do it though. Here's an example. The script is free to use, and easily customized. TROY How can I explicitly load a servlet ? Location: http://www.jguru.com/faq/view.jsp?EID=260178 Created: Nov 22, 2000 Modified: 2000-12-07 20:02:47.939 Author: Omar Khan (http://www.jguru.com/guru/viewbio.jsp?EID=232689) Question originally posed by Rajesh Ajmera (http://www.jguru.com/guru/viewbio.jsp?EID=47656 Servlets can be loaded automatically when a servlet engine starts, using configuration parameters. They depend on which servlet engine you are using. For instance, JRun 2.2 has a configuration parameter that is called Pre-Load. See also http://www.jguru.com/jguru/faq/view.jsp?EID=218109 Comments and alternative answers

Java Web Server does not automatically load the se... Author: prajakt samant (http://www.jguru.com/guru/viewbio.jsp?EID=272793), Dec 11, 2000 Java Web Server does not automatically load the servlet. You need to do : Class.forname("servletclass");

to load the Servlet How do I identify the device (browser) the request is coming from? Location: http://www.jguru.com/faq/view.jsp?EID=262330 Created: Nov 25, 2000 Modified: 2000-11-29 11:18:23.363 Author: Russell Quong (http://www.jguru.com/guru/viewbio.jsp?EID=262328) Question originally posed by Pankaj Mishra (http://www.jguru.com/guru/viewbio.jsp?EID=238618 public void doGet (HttpServletRequest req, HttpServletResponse resp) .... { String browser = req.getHeader("User-Agent"); ... } On Linux I get something like: Mozilla/4.73 [en] (X11; U; Linux 2.2.17 i686) You'll see "MSIE" somewhere for internet explorer. Surprisingly, on both IE (on NT) and Netscape return "Mozilla" as part of the response.

[It's not surprising, it's just stupid. :-) The reason IE pretends to be Mozilla goes back to the days when Netscape (aka Mozilla) was the only browser that supported certain features, e.g. Tables. Certain CGI scripts would check the user-agent header, and only output tables if the UA contained the string "Mozilla." Otherwise, they would output a lame < PRE > version, or nothing at all. Naturally, the authors of IE wanted their browser to show these tables, so they *had* to lie. The solution would have been if the Netscape browser sent a different, capabilitiesoriented header (e.g. "Accepts: Tables") but Netscape was a hastily written, poorlythough-out piece of junk. IMHO. :-) Initiatives like CC/PP and UAProf are attempting to fix the problem for both Web and WAP browsers but their acceptance remains to be seen. -Alex] I have a Servlet that does an extensive search which may take up to 1-2 minutes to finish. I would like to display a "Please wait ...." page while the search is being performed and before the search results are displayed. How can I do this? Location: http://www.jguru.com/faq/view.jsp?EID=263573 Created: Nov 27, 2000 Modified: 2001-07-23 10:20:21.168 Author: Perry Tew (http://www.jguru.com/guru/viewbio.jsp?EID=60814) Question originally posed by ethan c (http://www.jguru.com/guru/viewbio.jsp?EID=240218 Ethan, I've written a servlet that does this same thing (well, it executes a long query). What I did was to create a class that spawned a thread to do the query. I then set flags to indicate the query was underway. Whenever a request came in, I checked the flags and output html based on whether the query was done or not. I added some extra bells and whistles, such as how many records had been retrieved so far. I put it together pretty quickly, so it may not be the most professional solution, but you're welcome to look at the code to gain an idea of how I did it. (You may have to scrape out some query code, but it's not much.) You may view the code at my home page (http://www.geocities.com/perry_tew/jsp_code/refreshservlet/). There are three source files: a bean, a servlet, and a web.xml file. If you have any questions, let me know. Comments and alternative answers

Here's a stripped down version of the code. It uses... Author: Perry Tew (http://www.jguru.com/guru/viewbio.jsp?EID=60814), Dec 1, 2000 Here's a stripped down version of the code. It uses two classes: LongTaskBean and LongTaskServlet. Note: I'm not threading expert, so if someone sees room for improvement, please post about it. Thanks!

=============================================

//LongTaskServlet.java import java.io.*; import javax.servlet.*; import javax.servlet.http.*;

public class LongTaskServlet extends HttpServlet{ LongTaskBean longTask = null;

public void init() throws ServletException { longTask = new LongTaskBean();

}

public void doPost( HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{ doGet( request, response ); }

/** * Handle the HTTP GET method by building a simple web page. */

public void doGet (

HttpServletRequest request,

HttpServletResponse response) throws ServletException, IOException{

PrintWriter out;

// set content type and other response header fields first response.setContentType("text/html");

// then write the data of the response out = response.getWriter();

if ( request.getParameter("doTask") != null) { longTask.doLongTask(); }

out.println( "");

if ( longTask.isDoingTask() ) { out.println(

"<meta http-equiv=refresh content=10>" + "\n" ); }

out.println( "" + "\n" + "

Long Task

Page

" + "\n" + "

Current

Status

" + "\n" + "" + "\n" );

out.println( "" + "\n");

out.println( "" + "\n");

out.println("

Last Error:	"); out.println( longTask.getLastError() ); out.println( "
Current Status:	"); out.println( longTask.getStatus() ); out.println( "
" + "\n"); if ( longTask.isDoingTask() ) { out.println( "This page will automatically refresh every 10 seconds."); } else { out.println( "No refresh is taking place. Click the button to begin."); } out.println( "

" + "\n");

if ( !longTask.isDoingTask() ) { out.println( " " + "\n" + " " + "\n"

+ " " + "\n" + " " + "\n" + " " + "\n" + " " + "\n" ); }

out.println( ""); out.close(); } }

//===========================================

//LongTaskBean.java public class LongTaskBean{ private boolean inLongTask = false; private String status = "No Status Available"; private String lastErrorMsg = "NONE";

public LongTaskBean(){}

public boolean isDoingTask(){ return inLongTask; }

private void setTaskFlag( boolean flag ){ inLongTask = flag; }

public String getLastError(){ return lastErrorMsg; }

private void setLastError(String msg){ lastErrorMsg = msg; }

public String getStatus(){ return status; }

private void setStatus( String s ){ status = s; }

public void doLongTask(){ if( !isDoingTask() ){ setTaskFlag(true); new LongTaskThread( "Refresh Part Master" ).start(); } return; }

private class LongTaskThread extends Thread{ public LongTaskThread( String str ){ super( str ); }

private void exitWithError( String error ){ // not using sync

method to prevent possible lock lastErrorMsg = error; inLongTask = false; }

public void run(){ /* reset the lastErrorMsg */ setLastError("NONE (Beginning Long Task)");

//======= DO TASK HERE ================// for ( int i = 0; i < 10; i++ ){ setStatus("I'm sleeping #" + i + ". Check back later"); try { sleep( 5000 ); } catch (InterruptedException e){} }

setLastError("NONE: Completed Successfully"); setTaskFlag(false);

} }

}

Re: Here's a stripped down version of the code. It uses... Author: Seema K (http://www.jguru.com/guru/viewbio.jsp?EID=380850), Mar 29, 2001 Hi Perry, The code has has been put in very well but I faced a small problem while running the servlet. Internet Explorer gives me the following error "This page cannot be refreshed without resending the information" Click on Retry or Cancel. We need to keep clicking on Retry if the servlet has to proceed. Can you suggest a way out for this ? As far as I am concerned, this arises a new question:... Author: Thanos Varias (http://www.jguru.com/guru/viewbio.jsp?EID=44391), Dec 3, 2000 As far as I am concerned, this arises a new question: Many web appservers I have used get really angry when you start opening and closing threads in their execute threads context. Can anybody think of a way to deliver the same result avoiding threads? Thanks, Thanos Varias Another solution is to display the text "Loading,... Author: shahbaz chaudhary (http://www.jguru.com/guru/viewbio.jsp?EID=268763), Dec 7, 2000 Another solution is to display the text "Loading, please wait..." using java script at the top of the page (before executing the query) and hide the text after the query is done. Re: Another solution is to display the text "Loading,... Author: Padma Killi (http://www.jguru.com/guru/viewbio.jsp?EID=479480), Aug 19, 2001 Can I have the Javascript code for displaying an intermediate html page like "Wait Please"..while a jsp page executing the java bean. Your quick assistance would be appreciated. Thanos - EJB Servers forbid threads; however, servlet... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Dec 8, 2000 Thanos - EJB Servers forbid threads; however, servlet engines allow them. You just have to be careful using "distributed" servlets (running on more than one load-

balanced server) that you know what you're doing. IMHO, all previous answers in this page are wrong ... Author: Stephane Boisson (http://www.jguru.com/guru/viewbio.jsp?EID=1512), Dec 14, 2000 IMHO, all previous answers in this page are wrong solutions. You should return a multipart response thanks to the "multipart/x-mixed-replace" content type. This kind of response also permits push media, webcam feed, chat, etc... Here is a short example: public void service(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { res.setContentType("multipart/x-mixedreplace;boundary=\"boundary\""); ServletOutputStream out = res.getOutputStream(); // Here is the first part out.print("\n\r--boundary\n\r"); out.print("Content-Type: text/html\n\r\n\r"); out.println("

Waiting...

"); out.flush(); // Here is the long work (here, a sleep) try { Thread.sleep(3000); } catch (Exception e) { // ignore } // Here is the second part out.print("\n\r--boundary\n\r"); out.print("Content-Type: text/html\n\r\n\r"); out.println("

Done

"); out.print("\n\r--boundary--\n\r"); out.flush(); }

Re: IMHO, all previous answers in this page are wrong ... Author: veljo otsason (http://www.jguru.com/guru/viewbio.jsp?EID=384089), Mar 21, 2001 hmm.. this is really something i didn't know before. but if i called that example with IE, i got the page like this: --boundary

Content-Type: text/html

Waiting...

--boundary Content-Type: text/html

Done

--boundary--

with NS i got no answer at all:( what'd be the problem? Re: Re: IMHO, all previous answers in this page are wrong ... Author: Roland Röder (http://www.jguru.com/guru/viewbio.jsp?EID=389526), Apr 4, 2001 i tried your code and the page was shown in the same way as above (without recognizing the boundary; but this seems to be a little bit browser dependant). But i got another problem: the page was displayed after leaving the method and not after the out.flush() call. Any suggestions what to do? Re: Re: IMHO, all previous answers in this page are wrong ... Author: Bjoern Schmidt (http://www.jguru.com/guru/viewbio.jsp?EID=431451), May 31, 2001 Hi! If you just copy and paste the posted examplen, it really looks like this. You have to tell your Browser that you're sebding HTML. Just insert something like this: out.println("<TITLE>this is a test\n");

Don't forget to close the tags at the end of the document. Now this should work! Regards Bjorn Re: IMHO, all previous answers in this page are wrong ... Author: Raja kannan (http://www.jguru.com/guru/viewbio.jsp?EID=433245), Jun 3, 2001 Hi i have just executed ur program but the first "waiting" message does not hide when the "done" message is displayed Here is the code i have written: (which does not work right) import javax.servlet.*; import javax.servlet.http.*; import java.io.*;

public class wait extends HttpServlet { public void init() throws ServletException { } public void service(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { res.setContentType("multipart/x-mixedreplace;boundary=\"boundary\""); ServletOutputStream out = res.getOutputStream(); // Here is the first part out.print("\n\r--boundary\n\r"); //out.print("Content-Type: text/html\n\r\n\r"); res.setContentType("text/html"); out.println("Wait page"); out.println(""); out.println("

Waiting...

"); out.println(""); out.println(""); out.flush(); // Here is the long work (here, a sleep) try { Thread.sleep(3000); } catch (Exception e) { // ignore } // Here is the second part out.print("\n\r--boundary\n\r"); //out.print("Content-Type: text/html\n\r\n\r"); res.setContentType("text/html"); out.println("Done page"); out.println(""); out.println("

Done

"); out.print("\n\r--boundary--\n\r"); out.println(""); out.println(""); out.flush();

}

public void destroy(){ } }

If u have any new ideas pls share with me Re: Re: IMHO, all previous answers in this page are wrong ... Author: Pramod Vuppalapanchu (http://www.jguru.com/guru/viewbio.jsp?EID=453652), Jul 11, 2001 Iam facing the same problem. I tried the sample code here , and the initial "wait" message does not go after the "done" message. This is a problem. Does anyone have an idea how to handle this ? I cannot use http-refresh technique from the "wait" page, because my servlet gets many parameters from the requests object and if I refresh from the wait page these parameters are null. Any help would be greatly appreciated. Thanks. Re: IMHO, all previous answers in this page are wrong ... Author: Stephane Boisson (http://www.jguru.com/guru/viewbio.jsp?EID=1512), Jun 11, 2001 Well, it appears that Microsoft Internet Explorer don't support multipart MIME responses.. so multipart/mixed response won't work either.. ( MS Support KB article) An alternative is to test the UserAgent and use a different strategy with IE (for example Refresh directive in HTTP header)

Stephane, Thanks for the post! I'm still learning... Author: Perry Tew (http://www.jguru.com/guru/viewbio.jsp?EID=60814), Feb 2, 2001 Stephane, Thanks for the post! I'm still learning html, so I really enjoyed your comments. I did some research on what you were talking about, and I thought I would post some articles and notes I found on multipart/x-mixed-replace. Netscape has a nice introduction to using your technique here. There's also an interesting mailing list message talking about different ways to perform client pulls and server pushes. Anyways, thought I'd pass on what I've learned to those after me. Perry Tew Re: Stephane, Thanks for the post! I'm still learning... Author: Vanathi Manivannan (http://www.jguru.com/guru/viewbio.jsp?EID=460199), Jul 23, 2001 Any update on this? I'm now facing the similar issue. Did you get any solution for this The simplest solution for displaying "Please Wait" Page.(if you don't want to monitor the percentage of download occured)

Author: Sanjay Panchal (http://www.jguru.com/guru/viewbio.jsp?EID=464765), Jul 31, 2001 when a particular page is requested, show the please wait page which contains html meta tag "<META HTTP-EQUIV=\"REFRESH\" CONTENT=\"0\">" and set the session variable. Due to refresh tag the page is recalled now remove the session variable and do the computation. Untill the browser gets the actual computed page, it will wait and will not refresh the Please wait page. Meanwhile, Please wait page will be displayed. public void doGet ( HttpServletRequest req, HttpServletResponse res ) {

throws ServletException, IOException res.setContentType( "text/html" ); HttpSession session = req.getSession( true ); PrintWriter out = res.getWriter(); if ( session.getValue( "WAIT" ) == null ) { session.putValue( "WAIT", "" );

out.println( "" ); out.println( "" ); out.println( "<TITLE>Please Wait..." ); out.println( "<META HTTP-EQUIV=\"REFRESH\" CONTENT=\"0\">" ); out.println( "" ); out.println( "" ); out.println( "" ); out.println( "

Download in Progress

" ); out.println( "

Please wait.

" ); out.println( "" ); out.println( "" ); out.println( "" ); out.close(); } else { session.removeValue( "WAIT" ); out.println( "" ); out.println( "<TITLE>Actual Page" ); out.println( "" ); out.println( "

Actual Page is being displayed

" ); out.println("Started computation
"); for ( int i = 1; i < 6; i++ ) //do your time consuming Process {

out.println("Inside computation"+i+"
"); try { Thread.sleep( 2000 ); } catch ( InterruptedException e ) { } } out.println("Finished computation"); out.println( "" ); out.println( "" ); out.println( "" ); out.close(); } }

Re: The simplest solution for displaying "Please Wait" Page.(if you don't want to monitor the percentage of download occured) Author: Maurizio Turatti (http://www.jguru.com/guru/viewbio.jsp?EID=734356), Jan 25, 2002 It works! It's really a good solution, thank you. I'm using it in a jsp page, like this: <% if (session.getAttribute("WAIT") != null && request.getParameter("event").equals("COUNT_USERS")) { session.removeAttribute("WAIT"); Communithink Administration Tool: waiting.... <meta http-equiv='Refresh' content='1'>

Waiting...

<% } else { session.setAttribute("WAIT", new String()); %> ... ... <% } %>

How to implement Waiting message.....in <iframe> Author: Java Boy (http://www.jguru.com/guru/viewbio.jsp?EID=282622), Feb 12, 2002 This solution is very good but in my JSP page i have differnt iframe which contains differnt jsps and that take time to load . The main jsp

contains 4 iframes even if i write the above code in each jsp user can't see it because jsps are down in the page and user has to scroll down the page. So pl. help me How to display waiting message in this case. Thanks in adv. Re: How to implement Waiting message.....in <iframe> Author: Bill Allen (http://www.jguru.com/guru/viewbio.jsp?EID=764191), Feb 19, 2002 use a little ballen script! Re[2]: How to implement Waiting message.....in <iframe> Author: Java Boy (http://www.jguru.com/guru/viewbio.jsp?EID=282622), Feb 20, 2002 What do u mean by that? I don't understand. « previous

beginning

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How do I use the security manager to grant persissions for the servlet to call the java.lang.Runtime.exec() method to run a native application on the server? Location: http://www.jguru.com/faq/view.jsp?EID=264256 Created: Nov 28, 2000 Modified: 2000-11-30 19:42:23.753 Author: Jeff Williams (http://www.jguru.com/guru/viewbio.jsp?EID=231946) Question originally posed by Donghua Liu (http://www.jguru.com/guru/viewbio.jsp?EID=13364 On most app servers, the sandbox is not enabled, so all you have to do is call Runtime.exec(). You must be VERY careful about checking the parameters -- especially if they were derived from the HTTP request. Remember RULE #1 for web app programming is "NEVER trust the HTTP request." A hacker can manipulate all the headers, parameters, form data, hidden fields, etc... Client side checking (JavaScript) is meaningless to security. IF you have enabled the sandbox on your server, then you simply have to have a Policy file that grants exec permission on that file. See Security Permissions for a great description of the permissions and their risks. // Grant to code in foobar directory grant codeBase "file:/foobar/-" { permission java.io.FilePermission "${/}bin${/}myapplication", "read,exec"; } You also want to be very sure about the native app you are calling with exec. If it hangs and you are blocked reading from the child, you're toast. I wrote a framework

that starts a separate monitoring thread and calls child.destroy() if the timeout is reached. Good luck! What is the difference between apache webserver, java webserver and tomcat server? Location: http://www.jguru.com/faq/view.jsp?EID=265204 Created: Nov 29, 2000 Modified: 2000-11-29 11:05:01.175 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by SREEDHAR REDDY (http://www.jguru.com/guru/viewbio.jsp?EID=111571 Apache is an HTTP server written in C that can be compiled and run on many platforms. See http://www.apache.org Java WebServer is an HTTP server from Sun written in Java that also supports Servlets and JSP. Tomcat is an open-source HTTP server from the Apache Foundation, written in Java, that supports Servlets and JSP. It can also be used as a "plug-in" to native-code HTTP servers, such as Apache Web Server and IIS, to provide support for Servlets (while still serving normal HTTP requests from the primary, native-code web server). See http://jakarta.apache.org/tomcat Comments and alternative answers

I thought Tomcat could be used as a http server for non-production purposes? Author: Emm R (http://www.jguru.com/guru/viewbio.jsp?EID=1154361), Mar 15, 2004 I thought Tomcat could be used as a http server for non-production purposes? .. therfore there is no difference in their over all purpose except the languages used to write them. ( ? ) Author: Gene G (http://www.jguru.com/guru/viewbio.jsp?EID=1172699), May 21, 2004 ... if tomcat is both an http server and a servelet container, why is apache necessary in projects where tomcat is used ? Thx, Re: .. therfore there is no difference in their over all purpose except the languages used to write them. ( ? ) Author: Vijay Dogra (http://www.jguru.com/guru/viewbio.jsp?EID=1175631), Jun 2, 2004 Apache is a web server (mainly support static html). Tomcat is a servlet container (mainly support servlets) Re[2]: .. therfore there is no difference in their over all purpose except the languages used to write them. ( ? ) Author: ramu vempati (http://www.jguru.com/guru/viewbio.jsp?EID=1183164), Jul 1, 2004

Can we maintain every thing (static html , JSP and servlets) with tomcat itself?. When do we need both Apache and Tomcat running on the server. Thank You Re[3]: .. therfore there is no difference in their over all purpose except the languages used to write them. ( ? ) Author: Richa Ai (http://www.jguru.com/guru/viewbio.jsp?EID=1255954), Aug 1, 2005 Yes Tomcat alone is good enuf Why Author: Moe Binkerman (http://www.jguru.com/guru/viewbio.jsp?EID=1216498), Dec 15, 2004 Why does the server need to understand servlets? Does apache "understand" html? does apache "understand" cgi programs? How are servelets different that a cgi program? Web Servers Author: Yashavantha Nagaraju (http://www.jguru.com/guru/viewbio.jsp?EID=1242357), May 4, 2005 I think most of uses Tomcat web server. Even i need know what is the reason for that... How can I call a servlet from a CGI script (written in Perl)? Location: http://www.jguru.com/faq/view.jsp?EID=266269 Created: Nov 30, 2000 Modified: 2000-12-13 10:14:08.683 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) Question originally posed by devabhaktuni mahendra (http://www.jguru.com/guru/viewbio.jsp?EID=243752 Calling a servlet from a perl script is no different than getting information from any other URL. The perl script has no clue its a servlet and doesn't need to know this. [In other words: use HTTP, and the standard Perl HTTP libraries, but open the connection to localhost if it's on the same box. -A] Does Tomcat 3.1 support Java Servlet API 2.0 specifications? The documentations refers to API 2.2, but is it downward compatible? Location: http://www.jguru.com/faq/view.jsp?EID=266873 Created: Nov 30, 2000 Modified: 2000-12-08 00:04:07.932 Author: Stefan Tryggvason (http://www.jguru.com/guru/viewbio.jsp?EID=266869) Question originally posed by Maureen Boyce (http://www.jguru.com/guru/viewbio.jsp?EID=243448 Tomcat 3.1 supports the servlet API 2.2. Certain methods including the getServlet, getServlets and getServletNames methods of ServletContext have been deprecated since 2.0. The ServletContext methods above, while still available, no longer return anything useful. There are a few other differences too.

Where do I install the JDBC driver ZIP files, JAR files & DLLs? How do I ensure they're in Tomcat's CLASSPATH? Location: http://www.jguru.com/faq/view.jsp?EID=268823 Created: Dec 4, 2000 Modified: 2000-12-20 10:15:28.017 Author: Ignacio J. Ortega (http://www.jguru.com/guru/viewbio.jsp?EID=98626) Question originally posed by Allwyn Pinto (http://www.jguru.com/guru/viewbio.jsp?EID=245385 Since version 3.2, all the JARS present in the %TOMCAT_HOME%/lib directory are automatically appended to Tomcat's classpath, but only the jars are appended. To have a ZIP automatically appended rename it to *.jar ( as a jar is only a renamed zip ) and voila.... [There are two other options: 1. Put the jar file in your webapp's WEB-INF/lib/ directory. This set of JARs is added to the classpath for your webapp only. Be careful, however: if a different driver for the same JDBC URL is already on the system classpath, then it may (may!) be loaded instead of yours. (Whether it is or not depends on whether that driver has already been loaded yet.) 2. Change the Tomcat CLASSPATH environment variable, or "-classpath" command-line option, to contain your JAR or ZIP. This is set in the Tomcat startup script, tomcat.bat/tomcat.sh. Read that file for details on how to edit it. - Alex ] Comments and alternative answers

I try to install and not working Author: Frans Thamura (http://www.jguru.com/guru/viewbio.jsp?EID=384571), Mar 21, 2001 I install mysql in my PC, install tomcat 3.2.1, and copy the mysql_comp.jar to c:\tomcat\lib, but still have an error cannot attempt to access. error: at Class.forName("org.gjt.mm.mysql.Driver"); Regards, Frams Re: I try to install and not working Author: Vasant Kumar (http://www.jguru.com/guru/viewbio.jsp?EID=53644), May 16, 2001 Hi unzip the jar file and copy the 'org...' dircetory structure to 'web-inf\classes' directory. I had the same problem... I put it in classpath...and everywhere. I m using Win 2K Adv server. Thanks Vasant Re[2]: I try to install and not working Author: Eric Deandrea (http://www.jguru.com/guru/viewbio.jsp?EID=899305), May 31, 2002 I am having the exact same problem under tomcat 3.3. Has anyone got this working? Tomcat 3.3 use of JDBC mm.mysql-2.0.6 driver

Author: Paul Shields (http://www.jguru.com/guru/viewbio.jsp?EID=464686), Jul 30, 2001 I am using Tomcat 3.3 on Solaris 2.6 and had to place the mm.mysql-2.0.6.jar file in the $TOMCAT_HOME/lib/common directory and restart the Tomcat server to get the jsp engine to find the driver. I had originally placed the jar file in $TOMCAT_HOME/lib directory as directed by the Tomcat installation instructions, but this resulted in a class not found exception on org.gjt.mm.mysql.Driver Re: Tomcat 3.3 use of JDBC mm.mysql-2.0.6 driver Author: grant8411 grant8411 (http://www.jguru.com/guru/viewbio.jsp?EID=1038095), Dec 15, 2002 put the jar file inside c:\jdkXXXX\jre\lib\ext folder I want to insert a blob retrieved from a form field (with type='file') into a database. How can I convert the data returned by request.getParameter() to a BLOB type? Location: http://www.jguru.com/faq/view.jsp?EID=275076 Created: Dec 11, 2000 Modified: 2000-12-24 21:47:29.092 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) Question originally posed by Jewel Chen (http://www.jguru.com/guru/viewbio.jsp?EID=265610 Given a set of bytes, see How do I upload SQL3 BLOB & CLOB data to a database? for how to insert it into a database that supports BLOBs. Joe Sam Shirah adds: To upload file data from a browser to a servlet, see: How do I upload a file to my servlet?. Jorge Jordão, Eduardo Estefano, and Trapix Smith also contributed to this answer. Comments and alternative answers

Some code that may help you. Author: Paul Hunnisett (http://www.jguru.com/guru/viewbio.jsp?EID=504117), Sep 27, 2001 The following code will do what you want once you have got hold of your file as a file. conn.setAutoCommit(false); String prepare = "insert into news_xml values(" + id + ", empty_blob())"; String cmd = "SELECT * FROM news_xml where id=" + id + " for update"; Statement stmt = conn.createStatement( ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE); stmt.executeUpdate(prepare); ResultSet rset = stmt.executeQuery(cmd);

rset.next(); BLOB blob = (BLOB)((OracleResultSet)rset).getBlob(2); FileInputStream instream = new FileInputStream(f); OutputStream outstream = blob.getBinaryOutputStream(); int size = blob.getBufferSize(); byte[] buffer = new byte[size]; int length = -1; while ((length = instream.read(buffer)) != -1) outstream.write(buffer, 0, length); instream.close(); outstream.close(); conn.commit();

Should I use HTML Java libraries (eg. BEA's konaHTML) or raw HTML to generate my pages? What are the pros and cons? Location: http://www.jguru.com/faq/view.jsp?EID=277048 Created: Dec 13, 2000 Modified: 2000-12-13 10:50:41.948 Author: Jeff Williams (http://www.jguru.com/guru/viewbio.jsp?EID=231946) Question originally posed by andrew boddy (http://www.jguru.com/guru/viewbio.jsp?EID=242163 I don't see many 'pros' to using print statements with raw HTML. I've used kona and the Java apache project's ECS with great results. The major pro is that you can build reusable components so that you don't have to repeat stuff. That said, I can definitely understand those folks who like the MVC pattern and want to separate the GUI (view) from the logic. I think the best approach for this is to use a master servlet that handles security and parameters, then loads and sends the appropriate JSP (the view). --Jeff What is the difference between an Application Server and a Web Server? Location: http://www.jguru.com/faq/view.jsp?EID=282323 Created: Dec 19, 2000 Modified: 2000-12-20 10:05:22.308 Author: sharad chaudhary (http://www.jguru.com/guru/viewbio.jsp?EID=62937) A Web Server understands and supports only HTTP protocol whereas an Application Server supports HTTP,TCP/IP and many more protocols. Also many more features such as Caches,Clusters,Load Balancing are there in Application Servers which are not available in Web Servers. We can also Configure Application Servers to work as Web Server. In short, Applicaion Server is a super set of which Web Server is a sub set. [See also What are all the different kinds of servers? (Such as Web Servers, Application Servers, etc) ] Comments and alternative answers

Web servers do offer caches, clustering and load b...

Author: Dan Christopherson (http://www.jguru.com/guru/viewbio.jsp?EID=39644), Dec 21, 2000 Web servers do offer caches, clustering and load balancing - in fact, these are far easier to implement for web servers than application servers, because web servers are far simpler. Also, HTTP is an application layer protocol that runs over TCP/IP. Your final summary is fairly good, but I think the best description is that Web servers are HTTP servers, whereas an application server runs application code in the context of some higher level API (servlets, EJB, ASP, Enhydra's compiled HTML thingy) Now, given Apache's module APIs, is it a web server or an application server? Re: Web servers do offer caches, clustering and load b... Author: Balaji Sundararajan (http://www.jguru.com/guru/viewbio.jsp?EID=439659), Jun 15, 2001 Even if we take it literally, a web server serves web pages so an application server should serve with application (logic). The application logic (here, the business logic) is embedded in some form, let that be an EJB or CORBA component, and the application server allows us to get the services provided by those components. IMHO, the qualities such as load balancing, fail-over support, caching are all nonfuntional requirements that are applicabale to any distributed application (web server, db server, app server etc.)

Re[2]: Web servers do offer caches, clustering and load b... Author: Barath Ganesan (http://www.jguru.com/guru/viewbio.jsp?EID=1212633), Nov 23, 2004 In my context,a web server is just a publishing server.whereas an application server provides some services like security, and as said before clustering and caches on its own.we jus have to configure in order to use these services.in case of a web server it is the burdon of the programmer to do all these. A web server provides services only to web clients whereas an application server provides services to any application which is running in a distributed environment. Re: Web servers do offer caches, clustering and load b... Author: Matt Rokenbrod (http://www.jguru.com/guru/viewbio.jsp?EID=955561), Jul 18, 2002 Can multiple Application Servers Run on the same webserver on the same

computer? Re: Web servers do offer caches, clustering and load b... Author: Krupakar Jonnalagadda (http://www.jguru.com/guru/viewbio.jsp?EID=1204169), Oct 8, 2004 Apache's module apis is an application server. WebServer just serves HTTP Request, while Application... Author: Anurag Goel (http://www.jguru.com/guru/viewbio.jsp?EID=285633), Dec 25, 2000 WebServer just serves HTTP Request, while Application Server consist of Servlet Engine, and serve WebServer. WebServer contains only HTML files and send only HTML file any other file requested which has to be compiled dynamically based on the request, Webserver will get it from Application Server. Application Server consist of Servlet Engine,JVM and other parsers which interpret the required class files and send it to Webserver. It should also be noted that while many AppServers... Author: Alex Varanese (http://www.jguru.com/guru/viewbio.jsp?EID=334606), Feb 20, 2001 It should also be noted that while many AppServers (such as BEA's WebLogic) are indeed a superset of web server functionality, they aren't generally used that way. WebLogic is often used for it's enterprise capabilities and then augmneted by allowing Apache to handle the strictly HTTP-related side of things. Re: It should also be noted that while many AppServers... Author: Sanjay Kumar Gupta (http://www.jguru.com/guru/viewbio.jsp?EID=1083738), May 12, 2003 Summary: A normal web server can handle Http request means it can provide static web pages, images, css etc. For generating dynamic web contents it requires support for JSP, Servlets etc in Java & ASp in Microsoft respectively. So A javaenabled webserver means it has JVM & servlet engine which can run java servlets or JSp if it has JSP container. In such a case, the web server on receiving http request which can be handled by a servlet, passes it on to servlet which will handle it & may generate an HTML page which web server delivers to webbrowser. An application server can provide services based on various protocols including HTTP, meaning web service can be inbuilt or can be configured with it. Application servers serve application code to application clients. It provides several services like transaction processing, resource pooling i.e. database connection pooling, Security features, clustering etc. Re[2]: It should also be noted that while many AppServers... Author: prasenjit biswas (http://www.jguru.com/guru/viewbio.jsp?EID=1228123), Apr 8, 2005 You can't run EJB or any business logic in Javawebserver.An application server should have the capability to run business logic in it.That's why we can't

say that JWserver a application server. Application vs Webserver Author: siraj ahmed (http://www.jguru.com/guru/viewbio.jsp?EID=405469), Apr 18, 2001 If application server has inbuilt jvm and servlet engine then why we call javawebserver2.0 as "webserver" it can handle the servlet request then its also an application server. Please comment.... Re: Application vs Webserver Author: rahul bose (http://www.jguru.com/guru/viewbio.jsp?EID=219615), Sep 4, 2001 can a web server exists by itself without any appserver Thanks, rahul Re: Re: Application vs Webserver Author: praveen Kumar Nagunoori (http://www.jguru.com/guru/viewbio.jsp?EID=542975), Nov 13, 2001 Yes Webserver can exists by itself as it supports all the basic facilties to serve the purpose of a simple webhosting How can you embed a JavaScript within servlets / JSP pages? Location: http://www.jguru.com/faq/view.jsp?EID=284607 Created: Dec 22, 2000 Modified: 2000-12-22 12:27:24.197 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) Question originally posed by ashok GS (http://www.jguru.com/guru/viewbio.jsp?EID=284597 You don't have to do anything special to include JavaScript in servlets or JSP pages. Just have the servlet/JSP page generate the necessary JavaScript code, just like you would include it in a raw HTML page. The key thing to remember is it won't run in the server. It will run back on the client when the browser loads the generate HTML, with the included JavaScript. Comments and alternative answers

You can include JavaScript inside JSP code in two ... Author: vijay kumar (http://www.jguru.com/guru/viewbio.jsp?EID=286766), Dec 27, 2000 You can include JavaScript inside JSP code in two manner: <script language="javascript" src = "pagename.js">

or At any point of time in between JSP code, <script language ="javascript"> --jsp code--

Re: You can include JavaScript inside JSP code in two ... Author: erni meded (http://www.jguru.com/guru/viewbio.jsp?EID=1232501), Mar 14, 2005 How did you include JavaScript in the servlet?? I am having problem with that for couple days. I can include everything,but the line <SCRIPT LANGUAGE="JavaScript"> is giving me so many problems. Whatever I try it does not work. How can I make a POST request through response.sendRedirect() or response.setStatus() and response.setHeader() methods? Location: http://www.jguru.com/faq/view.jsp?EID=285822 Created: Dec 26, 2000 Modified: 2000-12-26 06:02:05.853 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Hemant Desai (http://www.jguru.com/guru/viewbio.jsp?EID=250843 You can't. It's a fundamental limitation of the HTTP protocol. You'll have to figure out some other way to pass the data, such as • • •

Use GET instead Make the POST from your servlet, not from the client Store data in cookies instead of passing it via GET/POST

Search the FAQ for questions relating to the above. I have synchronized doGet() and doPost() methods in my servlets. Will this create any problem? Should i use the single thread model instead? Location: http://www.jguru.com/faq/view.jsp?EID=285904 Created: Dec 26, 2000 Modified: 2000-12-28 09:46:07.137 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Parvez Kapadia (http://www.jguru.com/guru/viewbio.jsp?EID=263972 This question is answered in the main Servlets/Threading question, http://www.jguru.com/jguru/faq/view.jsp?EID=150, especially point 4. Don't use SingleThreadModel either, since there are many pitfalls. Unfortunately, there's no shortcut to thread safety. Just learn the techniques, synchronize access to shared data only, and you'll be OK. My servlet's destroy() method is never called. Is this a bug in WebSphere, or am I doing something wrong? Location: http://www.jguru.com/faq/view.jsp?EID=286603 Created: Dec 26, 2000 Modified: 2000-12-27 08:16:42.353 Author: Kris Srikanth (http://www.jguru.com/guru/viewbio.jsp?EID=283258)

Question originally posed by Ken Xu (http://www.jguru.com/guru/viewbio.jsp?EID=285652 No it is not at all a bug. but it is a good practice if you write the destroy() method and destroy your servlet because if many servlets running on the same webserver are not destroyed explicitly, then the performance of the web server falls down. [In other words, destroy() is not guaranteed to be called... but if it is, you should make sure it works right. -Alex] Comments and alternative answers

I have this problem while using Websphere 3.0.2 for... Author: Ken Xu (http://www.jguru.com/guru/viewbio.jsp?EID=285652), Dec 27, 2000 I have this problem while using Websphere 3.0.2 for NT. After I install the patch for Websphere, the problem is solved. Now my servlet's destroy() method is called when the servlet is unloaded. [Yay! So it *was* a bug in WebSphere! -Alex] What is a better way of writing servlets 1. A Single servlet which uses something like command pattern. i.e same servlet based on incomming paramter does different things. Or 2. Different servlet for different operations. Like Login Servlet, Logout Servlet, Preferences Servlet etc. Any thoughts on how either of them will effect performance in case of heavy loads? Location: http://www.jguru.com/faq/view.jsp?EID=286913 Created: Dec 27, 2000 Modified: 2001-01-04 05:38:13.174 Author: Badri Kuppa (http://www.jguru.com/guru/viewbio.jsp?EID=98194) Question originally posed by Modha Kumar (http://www.jguru.com/guru/viewbio.jsp?EID=253506 I think the 2nd option is best, becauase 1. By using the first one, you will have lots of if..else..conditions and even the code won't be easily readable! 2. Performance increases by 2nd option as the load on one single servlet is less. [This is not necessarily so, since any servlet is just code being executed in a JVM thread; unless it's synchronized, then you can have as many requests as you want inside a single servlet. -Alex] 3. IBM states "Do one thing at a time, Do it well" which suggests the 2nd option. 4. Easy to mentain the code if it is broken by functionality. I hope this helps you. --Badri Comments and alternative answers

I prefer the 1-servlet solution. Especially when... Author: Alexander Jesse (http://www.jguru.com/guru/viewbio.jsp?EID=293364), Jan 4, 2001 I prefer the 1-servlet solution. Especially when coupled with a file/jdbc based state-machine and external processor classes, it makes a neat system. The processor classes might even be servletindependent, giving them a chance to be reused. If you can use JSDK 2.2 and JSP 1.1 in your project, you should check out jakarta's Struts-project (which also uses the 1-servlet approach). Their concept rocks (and knowing the people behind their software will do the same). At the end it will depend on personal likings. -- Alexander first one Author: anish malanthara (http://www.jguru.com/guru/viewbio.jsp?EID=1105417), Jul 31, 2003 IBM's recommendation is not meant to be taken literally. The spirit of it is that 'one thing' means one functionality/area etc. In this case, login/logout is one functionality, and one servlet can handle that. And as any experienced developer can tell you, if/else is not a bad thing. It can be the elegant solution when used properly. just imagine if every possible action had a servlet to handle that in a Web-UI environment. The same solution can be applied to data access/editing etc. However, these exist much better ways of handlign those scenarios than just servlets. I open my servlet database (JDBC-ODBC) connection in the init() method. I close it in the destroy() method. My database is configured to close the connection automatically after 10 minutes of idle time. This creates problems since the servlet does not call the destroy() method and the init() method remains in the memory. within that time and after 10 minutes if a user requests that servlet it throws an exception saying : not logged on. why is this happening and if you can provide a solution to this problem by giving a sample code? Location: http://www.jguru.com/faq/view.jsp?EID=287341 Created: Dec 27, 2000 Modified: 2001-01-04 05:48:02.297 Author: Jorge Jordão (http://www.jguru.com/guru/viewbio.jsp?EID=275762) Question originally posed by Parvez Kapadia (http://www.jguru.com/guru/viewbio.jsp?EID=263972 The problem seems to be the server takes longer than 10 minutes to release a servlet instance. This can probably be configured, but what you should do instead is open the connection, execute the statements and close the connection all in the service (doGet or doPost) method, instead of keeping it opened. You can still load the driver class in init, since that needs to be done only once.

Example: (notice I'm using String constants for DB access for simplicity, I should be reading that information from an outside source): import import import import

javax.servlet.*; javax.servlet.http.*; java.io.*; java.sql.*;

public class DBServlet extends HttpServlet { private static final String "sun.jdbc.odbc.JdbcOdbcDriver"; private static final String private static final String private static final String

DB_DRIVER = DB_URL = "jdbc:odbc:Northwind"; DB_USER = ""; DB_PASSWORD = "";

public void init(ServletConfig config) throws ServletException { try { Class.forName(DB_DRIVER); } catch (ClassNotFoundException ex) { throw new UnavailableException("JDBC Driver " + DB_DRIVER + " not found."); } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { try { Connection conn = DriverManager.getConnection(DB_URL,DB_USER,DB_PASSWORD); // execute statements (and process results) conn.close(); } catch (SQLException ex) { // handle exception } } } If you find this approach too slow, consider using a connection pool. Comments and alternative answers

Can't you reconfigure your database so it doesn't time... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 4, 2001 Can't you reconfigure your database so it doesn't time out connections? Or, you could implement a timer task that releases and reestablishes the connection every 9 minutes. See java.util.Timer. This would have to be carefully synchronized, in case a servlet asks for the connection while it is in the process of being reupped.

Can I generate Microsoft Excel documents using JSP or servlets? Location: http://www.jguru.com/faq/view.jsp?EID=288029 Created: Dec 28, 2000 Modified: 2002-03-01 14:15:23.141 Author: Jorge Jordão (http://www.jguru.com/guru/viewbio.jsp?EID=275762) Question originally posed by Saravanan Shankaran (http://www.jguru.com/guru/viewbio.jsp?EID=232649 Apart from using C++ and JNI directly, there are (at least) two ways to read/write an MS Excel file in Java.

1. Using a Java-COM bridge (Please view my previous answer to How can I get email addresses out of an MS Outlook database, and add new ones?).

2. Using Formula One, which is a Reporting Engine API for Java that allows you to manipulate MS Excel 95/97/2000 files (including charts, formulas and functions).

Comments and alternative answers

You can also generate reports using Excel,by setting... Author: Priya Venkatesan (http://www.jguru.com/guru/viewbio.jsp?EID=129496), Jan 2, 2001 You can also generate reports using Excel,by setting the response.setContentType("application/vnd.ms-excel") in a JSP page. Doing so,you will be able to view the report(lets say you created one using

in html.)If you set this contentType, you will be able to see the generated report in Excel. Re: You can also generate reports using Excel,by setting... Author: Nandakumar Adikesavan (http://www.jguru.com/guru/viewbio.jsp?EID=585789), Jan 10, 2002 Hai, i am using Apache tomcat 4.0. I tried 2 ways: (1) <%@ page contentType="application/vnd.ms-excel" %> (2) response.setContentType("application/vnd.ms-excel"); i didn't get any proper o/p. If u have to know, pls reply me. Re[2]: You can also generate reports using Excel,by setting... Author: Javier Ramos Saralegui (http://www.jguru.com/guru/viewbio.jsp?EID=782130), Mar 5, 2002 You should atke a look a the POI project at apache.org there is a full API to manage Excel files. Can I rename the name of the output file? Author: Raul Cosio (http://www.jguru.com/guru/viewbio.jsp?EID=531530), Jan 18, 2002 I have created an example using response.setContentType(...) and ...

It works fine but before displaying the result a dialog box appears asking if I want to view the result in the page or save to disk. Is it possible to avoid this dialog?. If not, is it possible to make the dialog have another file

name like report.xls instead of report.jsp ? Thanks Re: Can I rename the name of the output file? Author: Suren Raj (http://www.jguru.com/guru/viewbio.jsp?EID=814033), Mar 27, 2002 Hi Raul, iam using weblogic server 6.1. Iam trying to open/save an excel file on the click of hyper link. But it opens in a normal text instead opening an excel window. Whats the problem in the following code. Or if u have some sample pl. email to [email protected] Thanx in advance Test.jsp: <TITLE> <% response.setContentType("application/vnd.ms-excel"); %> Regards Suren Re: Can I rename the name of the output file? Author: Raul Cosio (http://www.jguru.com/guru/viewbio.jsp?EID=531530), Mar 31, 2002 Maybe the problem is you are calling response.setContentType() after ... and content type is already written to the client. In my code I'm using a table because each cell will be displayed in your Excel spreadsheet. The table doesn't include any header tags... <START OF FILE> <%@page contentType="text/html"%> <%response.setContentType("application/vnd.ms-excel");%>

cell1

cell2

<END OF FILE>

Hope this helps Re[2]: Can I rename the name of the output file? Author: Mark Mac (http://www.jguru.com/guru/viewbio.jsp?EID=1157650), Mar 25, 2004 Raul, I tried to implement your scripts above, but it won't display in Excel, it would appear as a normal page in my browser. Can you please give me some light on this? Are there any configuration/setting needed to be check? Re: You can also generate reports using Excel,by setting... Author: anu doddapuneni (http://www.jguru.com/guru/viewbio.jsp?EID=1159013), Apr 2, 2004 Can some one tell me how to generate and save excel by clicking on a link.. I am using hssf framework to create a excel file. By default it saves on server side, but i want a dialogbox to open to give an option to user to save or open.. I appriciate ur help.. This is what i am doing.. HSSFWorkbook wb = new HSSFWorkbook();

HSSFSheet sheet = wb.createSheet <-- code to create rows and cells and cell data here--> String fileName = "test.xls"; FileOutputStream fileOut = new FileOutputStream(fileName); response.setContentType("application/vnd.msexcel"); response.setHeader("Content-Disposition", "inline; filename="+fileName); wb.write(fileOut); fileOut.close(); What if the conditions are as follows: 1. the webserver... Author: Joanna Chua (http://www.jguru.com/guru/viewbio.jsp?EID=349162), Mar 11, 2001 What if the conditions are as follows: 1. the webserver should be platform-independent. 2. it doesn't require IIS or for the web client to be using windows platform. (that means linux-based platform user/web clients should be to access this also, as to how please tell me so.) So based on the above conditions, the use of COM Excel object or any of the Windows stuff are out of the question. JSP Excel, easy... Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7), May 21, 2001 Just set the appropriate content type and provide a tab delimited file for the output and you've generated yourself an Excel spreadsheet. <%@ page contentType="application/vnd.ms-excel" %> This is a test 1 2 3 4 5 6 7 8

Re: JSP Excel, easy... Author: Jennifer Hunt (http://www.jguru.com/guru/viewbio.jsp?EID=434241), Jun 5, 2001 I'm quite new to JSP. I have created a .jsp file based on the example provided. The output to the browser is: This is a test 12345678 - not in excel. Please tell me what I'm doing wrong.... Re: JSP Excel, easy... Author: Anand Sundarraman (http://www.jguru.com/guru/viewbio.jsp?EID=477083), Aug 14, 2001 I am using this for technique for creating excel files from Java servlets. Now what I want to do is create multiple sheets with specific names. Is this possible? If so pls let me know. Re: Re: JSP Excel, easy... Author: Anil Passi (http://www.jguru.com/guru/viewbio.jsp?EID=494831), Sep 12, 2001

Anand can u send me the code u r having. I too need it and will it run on sun solaris machine with iplanet webserver installed ........ My requirement is to create an Excel sheet without using odbc ... any windows tool ... I have to do it on sun solaris iplanet machine ..... Any advice on this will be of big help to me... mail me at [email protected] regards anil Re[2]: JSP Excel, easy... Author: ambudu ambudu (http://www.jguru.com/guru/viewbio.jsp?EID=851513), Apr 23, 2002 Hi Anand could you pls send me the code u use to create excel file from a servlet Thanks Siva Re: JSP Excel, easy... Author: Nandakumar Adikesavan (http://www.jguru.com/guru/viewbio.jsp?EID=585789), Jan 10, 2002 hai, John I would like to know, where i want to specify my ".xls" files ???? how to open Excel ???? Pls, reply me..!!! Thanks.. Re: JSP Excel, easy... Author: Mark Mac (http://www.jguru.com/guru/viewbio.jsp?EID=1157650), Mar 25, 2004 John, I tried to implement your script but I wasn't successful in running it on my PC. What are the possible reasons why it will open as a normal JSP Page instead of Excel. Im running at Windows 2000, Service Pack 4, Internet Explorer 6.0. Thanks ahead. See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jun 27, 2001 Check out Access Microsoft Excel data through serv... and Generation of excel file. see also Author: Laurent Mihalkovic (http://www.jguru.com/guru/viewbio.jsp?EID=407112), Apr 10, 2002 You can also have a look at the HSSF project from the apache group. It is a pure Java implementation of the Excel '97(-2002) file format. cheers Re: see also Author: avish Khode (http://www.jguru.com/guru/viewbio.jsp?EID=1262142), Sep 13, 2005 Hi , I have a from with some Text Boxes in which user fills the data (Date range etc) Once user Press a Submit button i am Calling javaScript which will submit the Data to the another Url whih will generate the .xls file as Response . But My problem i that My file opens in same Browser window for which i have sumbmited the from , I want .xls file to be opened in some other Window . Plz tell

me How can i o this. Plz mail me if anyBody Knows Solution My email id [email protected] How can I automatically invoke a servlet periodically at specified time intervals, like cron? Location: http://www.jguru.com/faq/view.jsp?EID=293013 Created: Jan 4, 2001 Modified: 2001-09-07 09:35:17.145 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Ram Prasad.K (http://www.jguru.com/guru/viewbio.jsp?EID=108201 You can do this using Java Threads. 1. Schedule a servlet to load on server startup. See How can I set a servlet to load on startup of the container, rather than on the first request? 2. In this servlet's init() method, spawn a thread. 3. In this thread's run() method, calculate the number of milliseconds to wait until the task should be performed. Then call Thread.sleep(msec). Then do the task, and loop (infinitely). The java.util.Timer class can help a lot. See • •

How do I schedule a task to run at a certain time? How do I schedule a task to run repeatedly?

See also How can I automatically invoke a servlet at regular time intervals using Resin? Comments and alternative answers

See "run-at" parameter in servlet config... Author: Pavel Bernshtam (http://www.jguru.com/guru/viewbio.jsp?EID=274236), Jan 4, 2001 See "run-at" parameter in servlet configuration for Resin (www.caucho.com) Servlet Engine spawned thread does not always get destroyed Author: Doug Straka (http://www.jguru.com/guru/viewbio.jsp?EID=499147), Sep 18, 2001 This works great, although I have noticed that the spawned thread (infinite loop) does not always get destroyed when I bring down the application server. Any ideas on how to prevent this from happening? Re: spawned thread does not always get destroyed Author: John Mark Mark (http://www.jguru.com/guru/viewbio.jsp?EID=579145), Dec 10, 2001

Try setting setting the damon to true then if the thread that opened it is killed .. the spawned thread should die as well. How do I pass a request object of one servlet as a request object to another servlet? Location: http://www.jguru.com/faq/view.jsp?EID=293386 Created: Jan 4, 2001 Modified: 2001-01-05 06:12:50.287 Author: chris lambrou (http://www.jguru.com/guru/viewbio.jsp?EID=293366) Question originally posed by Lalit Choudhary (http://www.jguru.com/guru/viewbio.jsp?EID=257176 Use a Request Dispatcher. Please look at http://java.sun.com/docs/books/tutorial/servlets/communication/requestdispatcher.html. [Also the other FAQs in the topic Servlets:Message Passing -Alex] Is there anything available in the HttpServletRequest which would tell me whether the request came through HTTP or WAP originally, letting me set my content type on the response accordingly? I want something a bit more reliable than the user-agent in the header. Location: http://www.jguru.com/faq/view.jsp?EID=293952 Created: Jan 5, 2001 Modified: 2001-01-05 05:40:21.901 Author: Edward Williams (http://www.jguru.com/guru/viewbio.jsp?EID=241100) Question originally posed by Edward Williams (http://www.jguru.com/guru/viewbio.jsp?EID=241100 Since submitting this I have found out the solution myself - or at least one solution, there are probably others. The answer lies in "accept" part of the header. Basically, if it contains the directive for WAP and WML then the content type of the response can be set for WML. i.e. /** Content type string for HTML */ public static final String CONTENT_TYPE_HTML = "text/html"; /** Content type string for WML */ public static final String CONTENT_TYPE_WML = "text/vnd.wap.wml"; /** The header which contains the available content types. */ public static final String HEADER_ACCEPT = "accept"; /** Returns a content type based on the requesting content type * @param request Servlet request object * @return The content type */ public static String getContentType( HttpServletRequest request ) { String retval = CONTENT_TYPE_HTML; // Default return. if (null != request) { String mimeTypes = request.getHeader( HEADER_ACCEPT ); if ( null != mimeTypes ) {

if ( 0 != mimeTypes.trim().length() ) { if ( -1 != mimeTypes.toLowerCase().indexOf(CONTENT_TYPE_WML) ) { retval = CONTENT_TYPE_WML; } // Put any other content type conversions in here. } } } return retval; } This will set the content type to HTML by default, unless the user agent accepts WML. Comments and alternative answers

The problem with relying on the User-Agent header is... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 5, 2001 The problem with relying on the User-Agent header is that new user agents (browsers) are released all the time, and you don't have any way of knowing what they can or can't do. However, current browsers are actually pretty good at sending *unique* User-Agent headers. What's needed is an up-to-date database describing the capabilites of each User-Agent. You can then find out, not only whether it supports WML, but also other markup languages (e.g. CHTML or HDML), what image types (JPG, BMP, etc.), screen size, color, etc. Such a database exists in several places; one is in the Morphis open-source project, in a file called device.xml. I expect that as new browsers are released, they will update this list on an ongoing basis. [As of this writing, this site is still in beta, so be gentle :-) ] How can I set a System property in a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=294938 Created: Jan 6, 2001 Modified: 2001-01-07 16:57:23.424 Author: Chandra Patni (http://www.jguru.com/guru/viewbio.jsp?EID=33585) Question originally posed by Ankit Doshi (http://www.jguru.com/guru/viewbio.jsp?EID=255153 You can simply use System.setProperty("propertyKey", "PropertyValue") method in a servlet. What is the basic need to use servlets? Location: http://www.jguru.com/faq/view.jsp?EID=295100 Created: Jan 6, 2001 Modified: 2001-01-15 08:43:05.66 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Anupama Mohan (http://www.jguru.com/guru/viewbio.jsp?EID=207040 Everyone needs a servlet!

That's right, it filets, it chops, it dices, slices, Never stops, lasts a lifetime! It mows your lawn It picks up the kids from school It gets rid of unwanted facial hair, it gets rid of embarrassing age spots, It delivers a pizza, It lengthens, it strengthens It entertains visiting relatives, It turns a sandwich into a banquet It gets rid of your gambling debts, it quits smoking It's a friend, it's a companion. It's the only product you will ever need It gives you dandruff, and it finds you a job, It is a job (Apologies to Tom Waits) See also What is a servlet? Comments and alternative answers

good question! Author: Ali Khurram Abbas (http://www.jguru.com/guru/viewbio.jsp?EID=295141), Jan 6, 2001 good question! I call a servlet as the action in a form, from a jsp. How can I redirect the response from the servlet, back to the JSP? (RequestDispatcher.forward will not help in this case, as I do not know which resource has made the request. request.getRequestURI will return the uri as contained in the action tag of the form, which is not what is needed.) Location: http://www.jguru.com/faq/view.jsp?EID=295190 Created: Jan 6, 2001 Modified: 2001-01-08 17:12:23.721 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Vinod Amladi (http://www.jguru.com/guru/viewbio.jsp?EID=280439 You'll have to pass the JSP's URI in to the servlet, and have the servlet call sendRedirect to go back to the JSP. For example:

Then in the servlet...

response.sendRedirect(request.getParameter("redirect")); Comments and alternative answers

Another thing you can do is just redirect to the r... Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7), Jan 7, 2001 Another thing you can do is just redirect to the referer of the referer of the page, if you don't want to hardcode the page. [Can you give a code example? -A] String callingPage = request.getHeader("Refe... Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7), Jan 8, 2001 String callingPage = request.getHeader("Referer"); response.sendRedirect(callingPage); should do the trick I suppose you can also use request.getRequestURI()... Author: Harikrishna Neerkaje (http://www.jguru.com/guru/viewbio.jsp?EID=69829), Jan 13, 2001 I suppose you can also use request.getRequestURI() to get the address of the jsp page. request.getRequestURI() gives this request's URI, not... Author: Rajah Kalipatnapu (http://www.jguru.com/guru/viewbio.jsp?EID=116593), Mar 7, 2001 request.getRequestURI() gives this request's URI, not the Referer's URI. Re: request.getRequestURI() gives this request's URI, not... Author: Clarence Tan (http://www.jguru.com/guru/viewbio.jsp?EID=815644), Mar 31, 2002 how come when compiled, the reponse object is not found? this is the eRRoR regis.java:138: cannot resolve symbol symbol : variable response location: class regis response.sendRedirect(path); ^ 1 error Re[2]: request.getRequestURI() gives this request's URI, not... Author: Garrett Smith (http://www.jguru.com/guru/viewbio.jsp?EID=733867), Aug 16, 2002 In the jsp:

In the action servlet: String location = request.getParameter("location");

; What is the ServletConfig object, and why is it useful? Location: http://www.jguru.com/faq/view.jsp?EID=295514 Created: Jan 7, 2001 Modified: 2001-01-08 08:01:45.047 Author: Troy Niven (http://www.jguru.com/guru/viewbio.jsp?EID=219893) Question

originally posed by Dhiraj Asrani (http://www.jguru.com/guru/viewbio.jsp?EID=276883 The ServletConfig object is an interface. It contains the methods getInitParameter getInitParameterNames getServletContext getServletName You can use the methods to determine the Servlet's initialization parameters, the name of the servlets instance, and a reference to the Servlet Context the servlet is running in. getServletContext is the most valuable method, as it allows you to share information accross an application (context). There is more information in the Javadoc documentation that is provided. See also http://www.jguru.com/jguru/faq/view.jsp?EID=35085 and http://www.jguru.com/jguru/faq/view.jsp?EID=208612 Would response.sendRedirect work for an https: URL on a secured server (SSL)? For example, would response.sendRedirect("https://www.host.com/page.html") work? Location: http://www.jguru.com/faq/view.jsp?EID=295807 Created: Jan 7, 2001 Modified: 2001-01-08 07:53:04.272 Author: wee yap ng (http://www.jguru.com/guru/viewbio.jsp?EID=35233) Question originally posed by wee yap ng (http://www.jguru.com/guru/viewbio.jsp?EID=35233 Sorry to ask this trivial question here, I am answering my own query here. I had recently tried in a few servlet engines and sendRedirect works for HTTPS. I had initially got this problem with a certain brand of servlet engine that seems to be incomplete. [That's OK! It's a valid question (though easy to check for yourself). What servlet engine was broken? -Alex] Comments and alternative answers

I had previously work with a early release of JRUN... Author: wee yap ng (http://www.jguru.com/guru/viewbio.jsp?EID=35233), Jan 8, 2001 I had previously work with a early release of JRUN with Netscape Enterprise Server. Yes it does. Author: Shailesh Dangi (http://www.jguru.com/guru/viewbio.jsp?EID=97397), Jan 12, 2001 Yes it does.

How can I get system environment variables from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=296467 Created: Jan 8, 2001 Modified: 2001-01-08 08:13:41.598 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Marek Koniew (http://www.jguru.com/guru/viewbio.jsp?EID=280673 Short answer: you can't :-( See http://www.jguru.com/jguru/faq/view.jsp?EID=11422 However, you can read the equivalent of most of the CGI environment variables from the ServletRequest object. See http://www.jguru.com/jguru/faq/view.jsp?EID=11699 Comments and alternative answers

Slightly longer answer... Author: Jim Chrystal (http://www.jguru.com/guru/viewbio.jsp?EID=382923), Mar 20, 2001 One way of doing it would be through JNI, I believe. You could write your own native application to perform this function. Performance would take a hit, however. Your best bet would probably be to store your environment information in properties file. Happy computing, Jim Where can I learn techniques for building Internet applications using servlet and JSP technology? Location: http://www.jguru.com/faq/view.jsp?EID=296763 Created: Jan 8, 2001 Modified: 2001-01-15 08:03:46.903 Author: Frank Carlos (http://www.jguru.com/guru/viewbio.jsp?EID=296761) There's a user session handling tutorial on the developerWorks Java Zone that teaches techniques using servlet and JSP technology. A key point is to enable session handling, so the servlet knows which user is doing what. The tutorial shows a URL bookmarking system in which multiple users access a system to add, remove, and update an HTML listing of bookmarks. The servlet uses JSP technology to handle the user interaction. Does RequestDispatcher.forward() return to the caller ? Location: http://www.jguru.com/faq/view.jsp?EID=297164 Created: Jan 8, 2001 Modified: 2001-01-15 08:07:51.31 Author: sampreet kaur chawla (http://www.jguru.com/guru/viewbio.jsp?EID=296185) Question originally posed by phil brackel (http://www.jguru.com/guru/viewbio.jsp?EID=260432 Yes, like any Java method call, RequestDispatcher.forward() returns to the caller. Hence we should ensure that, the caller should not be using PrintWriter() or getOutputStream() object, as it results in IllegalStateException. Neither should the call be followed by another call of RequestDispatcher.forward() or RequestDispather.include().

[The idea of RequestDispatcher.forward is that the first servlet sets things up, and the second one prints. Unfortunately, that architecture is somewhat limited. If you want both to print, you must use RequestDispatcher.include instead. -Alex] How do I create a formatted Microsoft Word document from Java? Location: http://www.jguru.com/faq/view.jsp?EID=299081 Created: Jan 10, 2001 Modified: 2001-03-02 07:28:41.274 Author: Stephen Silber (http://www.jguru.com/guru/viewbio.jsp?EID=10161) Question originally posed by Vijay kumar (http://www.jguru.com/guru/viewbio.jsp?EID=294344 [More Q: (I know how to set the content-type from a servlet, but I require formatted bordered table oriented output in the word doc.) ] The simplest way, since the Word format is messily binary, is to write out an RTF file, which is mostly ASCII-oriented. This technique works just well--check out the RTF output from an SEC filing at www.FreeEDGAR.com to see some nice examples of programmatically-generated RTF. The RTF spec is at http://msdn.microsoft.com/library/default.asp?PP=/library/toc/specs/specs10.xml&t ocPath=specs10&URL=/library/specs/rtfspec.htm [See also http://www.jguru.com/jguru/faq/view.jsp?EID=3696] Comments and alternative answers

Also, you could just write an HTML file, and set its... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 15, 2001 Also, you could just write an HTML file, and set its Content-Type header to "application/ms-word". This will cause Windows to open it using Word. (Not sure what will happen on other platforms, but you sound fairly Windows-centric.) See also http://www.jguru.com/jguru/faq/view.jsp?EID=3696 Re: Also, you could just write an HTML file, and set its... Author: Christophe MOUSTIER (http://www.jguru.com/guru/viewbio.jsp?EID=1074991), Apr 9, 2003 Hmmm...HTML loses many information that WORD & RTF format have. I've tried to handle the RTF file which is a somehow good idea, but I have a file which weights 8MB in WORD and 120MB in RTF !!! So far, I cannot afford handling so huge data (not the computer, but rather the time of load/save action spent for the user) Any other Idea ? Can i generate the Word document using java class.There... Author: Sumit Gangrade (http://www.jguru.com/guru/viewbio.jsp?EID=36802), Feb 27, 2001 Can i generate the Word document using java class.There is an API for PDF

generation com.lowagie which generates PDF file using java class. Is there any API for MS Word document generation? Is it possible to do load balancing from one web server to multiple Tomcat servers? Location: http://www.jguru.com/faq/view.jsp?EID=299385 Created: Jan 10, 2001 Modified: 2001-01-15 08:04:26.868 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) Question originally posed by John Smith (http://www.jguru.com/guru/viewbio.jsp?EID=110025 Tomcat 3.x supports load balancing through Apache (mod_jserv). Tomcat 4.x supports it natively. Comments and alternative answers

load balancing thru' mod_jserv Author: randall phillips (http://www.jguru.com/guru/viewbio.jsp?EID=410389), Apr 26, 2001 how about thru' mod_jk? Re: load balancing thru' mod_jserv Author: Michael Erdely (http://www.jguru.com/guru/viewbio.jsp?EID=726279), Jan 18, 2002 I know tomcat 3.x can load balance with mod_jk. Catalina and Load Balancing Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727), Jan 30, 2002 John, Actually, I think that Tomcat 4.0.1 does not support Load Balancing natively, but version 4.0.2 (at this time still in beta) it will. Re: Catalina and Load Balancing Author: Venkatesh Sangam (http://www.jguru.com/guru/viewbio.jsp?EID=424561), Mar 12, 2002 I dint actually understand what do you mean by Load balaning. If there is only one webserver, then it alone will handle all the requests. what does load balancing mean in this case. ?? Re[2]: Catalina and Load Balancing Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Mar 13, 2002 Load balancing is for when there's more than one server. It balances the load, so one (Tomcat) server gets half the requests, and the other server gets the other half. Re[3]: Catalina and Load Balancing

Author: hee lee (http://www.jguru.com/guru/viewbio.jsp?EID=1035338), Dec 7, 2002 hello, Can anybody tell me how to achieve Load balancing in Tomcat..??? According to my view, A load balancing is useful when one server(say Tomcat1) which is serving all jsp/servlets is shutdown then the serving automatically taken care of by another server(say tomcat2) in the cluster WITHOUT LOOSING THE "SESSION" between the pages that we are navigating. I hope i may be wrong, if so, please suggest me what is Load balancing and how could we acheive it.

What does "request-timeout" parameter in Resin configuration mean? Location: http://www.jguru.com/faq/view.jsp?EID=299567 Created: Jan 11, 2001 Modified: 2001-01-15 08:52:05.695 Author: Praveen Singh (http://www.jguru.com/guru/viewbio.jsp?EID=299541) Question originally posed by Pavel Bernshtam (http://www.jguru.com/guru/viewbio.jsp?EID=274236 Hi Pavel, I'm Praveen. I'm not sure about this thing in Resin server but in other servers it's a setting for the servlet request, means whatever value you set to this property, your client will wait for a response for that period of time from a servlet after that time expires it breaks the connection to your servlet. my mail address is:[email protected] Comments and alternative answers

Unfortunatly it is not work in this way :( I make... Author: Pavel Bernshtam (http://www.jguru.com/guru/viewbio.jsp?EID=274236), Jan 15, 2001 Unfortunatly it is not work in this way :( I make simple servlet which do Thread.sleep(), but client does not breaks connection ... Thanx anyway

How can we make tree widgets, like in Swing, in an HTML page? Location: http://www.jguru.com/faq/view.jsp?EID=299847 Created: Jan 11, 2001 Modified: 2001-01-15 08:12:07.349 Author: Michael Szlapa (http://www.jguru.com/guru/viewbio.jsp?EID=241392) Question originally posed by hatinder vohra (http://www.jguru.com/guru/viewbio.jsp?EID=216890 I can think of three options: 1. Use the JavaScript to built the tree in the browser. Various JavaScript trees are available on the internet, including free implementations. JavaScript will usually offer the highest performance. Unfortunatelly due to the differences in JavaScript support in various browsers I would only recommend it for intranet solution where you can standarize browser settings and version. [Does anyone have links to these JavaScript trees? -A] 2. Build an applet and place it on the JSP page. Applets tend to be less browser dependent. Large applets may be slow to load over low-bandwidth connections and they are also slow to start on older computers. Also applets may be disabled in the browser or not be available inside the firewall. [Does anyone have links to these Applet trees? -A] 3. Build your tree logic on the server side using JSP or servlet technology. Avery node is the hyperlink, when clicked the server side generates new page where given node is expanded/colapsed. This is potentially the slowest but the most robust solution - works always. This solution will not allow you to use drag and drop functionality. Regards, Michael Comments and alternative answers

There's a nice JavaScript tree component at http:/... Author: Jorge Jordão (http://www.jguru.com/guru/viewbio.jsp?EID=275762), Jan 15, 2001 There's a nice JavaScript tree component at http://www.treemenu.com. Hello. CoolServlets.com also has a tree bean for free... Author: Perry Tew (http://www.jguru.com/guru/viewbio.jsp?EID=60814), Jan 17, 2001 Hello. CoolServlets.com also has a tree bean for free use. See http://coolservlets.com/CSTreeBean/.

Best of luck, Perry Tew In option 3, is there a way to remember the states.... Author: Vaidhy Kumar (http://www.jguru.com/guru/viewbio.jsp?EID=26604), Feb 5, 2001 In option 3, is there a way to remember the states. For examples let's say I show a list of items a,b,c,d in a browser and I first expand b and later d. Is it possible to show b and d in the expanded state? I've heard concerns that applets using Swing trees... Author: Pratap Das (http://www.jguru.com/guru/viewbio.jsp?EID=129542), Mar 5, 2001 I've heard concerns that applets using Swing trees (which must use plug-ins on the browser side) have some portability issues - i.e works on some browsers & not on others. Could someone comment on how this would affect a design choice between Javascript trees & Applet trees? Would an AWT implementation of a tree remove the need for plug-ins? Is such an implementation available somewhere? See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Oct 30, 2001 How can I display content in the form of a Tree using JSP? I have a global variable in a servlet class. What will happen to this global variable if two requests hit on the same time? Location: http://www.jguru.com/faq/view.jsp?EID=300129 Created: Jan 11, 2001 Modified: 2001-01-15 08:10:23.982 Author: Renato Michielin (http://www.jguru.com/guru/viewbio.jsp?EID=255654) Question originally posed by guan ho (http://www.jguru.com/guru/viewbio.jsp?EID=126860 What will happen is an unforeseeable event. The best way to establish a default occurrence (the servlet handles a request at a time) is to synchronize the access to the global variable or alternatively to create a servlet that implements the SingleThreadModel interface. [See How do I ensure that my servlet is thread-safe? for more information. Note also that using SingleThreadModel may not work, if other servlets/classes access the global (static) variable as well. -Alex] Comments and alternative answers

Unforseen Events Author: David Tomlinson (http://www.jguru.com/guru/viewbio.jsp?EID=423613), May 17, 2001

In the old days, they would say that "results are undefined"! David Another good one Author: Sean Foley (http://www.jguru.com/guru/viewbio.jsp?EID=499258), Sep 18, 2001 In most of the API javadocs they like to call it "non-deterministic" behavior. How can you select multiple files for upload to a servlet? The browse button on my form only allows me to choose one file at a time. Location: http://www.jguru.com/faq/view.jsp?EID=303625 Created: Jan 16, 2001 Modified: 2001-07-23 10:18:08.076 Author: Jorge Jordão (http://www.jguru.com/guru/viewbio.jsp?EID=275762) Question originally posed by Vai Patel (http://www.jguru.com/guru/viewbio.jsp?EID=270553 Just as an component only allows you to specify a single (text) value, an component only specifies one file. You'll have to put as many file components in your page as the number of files you want to upload. Remember to assign a different NAME attribute value to each. [See also How do I upload a file to my servlet? ] [Does anyone have a more elegant solution? -Alex] Comments and alternative answers

I've found only one other (non-applet) solution: upload... Author: Joe Humphreys (http://www.jguru.com/guru/viewbio.jsp?EID=40248), Jan 17, 2001 I've found only one other (non-applet) solution: upload the files one at a time. You generally want to reload the page after each upload and display a list of files that have already been uploaded. The advantage to this method is that it allows an arbitrary number of files and doesn't clutter up your interface with lots of unwieldy file input controls. The down side is that you have to store the files as they're uploaded. If you're writing a Web mail application, for instance, you might prefer to get all the attachments at once and send them straight through to the mailer. Also, storing the files means you need to clean them up if the user aborts halfway through.

how to upload a file (HTML,BMP,Gif,..) using servlets? Author: Arunachalam P (http://www.jguru.com/guru/viewbio.jsp?EID=90631),

May 1, 2001 hi friends, well. sorry for the question posted here. I have to get the answer, I hope u people know the answer for" uploading the file". Pls suggest me to upload a file using servlets. I have finished the client-side using Pls show me the way to proceed.. Thanx a lot to the accessors Re: how to upload a file (HTML,BMP,Gif,..) using servlets? Author: durgababu koka (http://www.jguru.com/guru/viewbio.jsp?EID=434371), Aug 22, 2001 the best and easy way to upload the file(in my view) using MultipartRequest class provided by orielly. just go to the orielly.com then download the MultipartRequest class and import into ur servlet. in ur form(in which ur "file" type is mentioned) just include this line like

then in ur servlet method. just include this code.. MultipartRequest multi = new MultipartRequest(req,directory,filesize) so it will upload ur file what ever u choosen. i hope u stand. thanks.. Re: I've found only one other (non-applet) solution: upload... Author: Jasmin Mehta (http://www.jguru.com/guru/viewbio.jsp?EID=726950), Jan 21, 2002 Hi Joe, Can you please send me the code of this technique for multiple file upload. I'm looking for exactly same thing in my website. Pls send me code on [email protected] Thx Jasmin Try Zip files Author: Carl Jabido (http://www.jguru.com/guru/viewbio.jsp?EID=416360), May 6, 2001 One method I'm playing around with right now is using Zip files to receive a single archive of multiple files. Look through java.util.zip for info. Basically you can read the Zip file, and get multiple ZipEntry objects which represent the individual files, which you can manipulate with at will. I'm doing the exact opposite right now. We've got PDFs stored in an Oracle database, I pull out multiple PDFs, create a new ZipOutputStream around the ServletOutputStream, and then put each PDF as a new ZipEntry. You can specify the filename as you create the new ZipEntry. It works great, and the user can choose which PDFs he wants and then receives an archive of all of them. Another brick in the wall :p Author: Asim Ali (http://www.jguru.com/guru/viewbio.jsp?EID=474093), Aug 11, 2001 You can also try using the file list . You can browse several times and keep on adding the fiiles to a list and then upload the list of files one by one .

Can you recommend some good books on servlets? Location: http://www.jguru.com/faq/view.jsp?EID=303632 Created: Jan 16, 2001 Modified: 2001-01-19 14:18:19.009 Author: Jorge Jordão (http://www.jguru.com/guru/viewbio.jsp?EID=275762) Question originally posed by preeti loomba (http://www.jguru.com/guru/viewbio.jsp?EID=266963 If you like the (very nice) tutorial at http://www.apl.jhu.edu/~hall/java/ServletTutorial you should like the Sun Press book it inspired. The Java Servlets O'Reilly book is very good, but it is a bit outdated (it covers API 2.0). An update will be coming though, check it out at the author's web site. Comments and alternative answers

good starting book Author: Bert Guzenski (http://www.jguru.com/guru/viewbio.jsp?EID=415329), May 4, 2001 I'd recommend "Java - Servlet Programming" from O'Reilly Press. See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Dec 28, 2002 Can you recommend some good books on servlets? Can you recommend some good books on servlets? Location: http://www.jguru.com/faq/view.jsp?EID=303778 Created: Jan 16, 2001 Modified: 2001-01-16 15:15:45.281 Author: Dominik Hasek (http://www.jguru.com/guru/viewbio.jsp?EID=297336) Question originally posed by preeti loomba (http://www.jguru.com/guru/viewbio.jsp?EID=266963 Instead of a good book, i have a cheaper solution. After reading this, even a newbie can code servlets. An excellent web tutorial : http://www.apl.jhu.edu/~hall/java/Servlet-Tutorial/ Comments and alternative answers

There is a comparative review of Servlet books at ... Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7), Jan 16, 2001 There is a comparative review of Servlet books at JavaWorld that I wrote: Java servlet books: A comparative review. Since that came out in March 2000, one decent book should be added. It is reviewed at Which JSP book serves up the best lesson?. THe new one is Core Servlets from Marty Hall. One other thing worth mentioning is the Wrox book liked in the first review is out in a second edition: Professional Java Server Programming, J2EE Edition Does the session mechanism use cookies by default? Location: http://www.jguru.com/faq/view.jsp?EID=304626

Created: Jan 17, 2001 Modified: 2001-01-19 14:04:59.079 Author: Jorge Jordão (http://www.jguru.com/guru/viewbio.jsp?EID=275762) Question originally posed by mohan kumar (http://www.jguru.com/guru/viewbio.jsp?EID=31319 According to the Servlet 2.2 Specification, "Session tracking through HTTP cookies is the most used session tracking mechanism and is required to be supported by all servlet containers", so it should be the default on all servers. Comments and alternative answers

Cookies in Session Mechanism Author: Vikram Sharma (http://www.jguru.com/guru/viewbio.jsp?EID=846457), Apr 19, 2002 HTTP by inception is stateless, hence any session tracking mechanism makes it imperative to have an identifier for each session created. Cookies happnes to be the most effective way of mainatining sessions, as they supply this uniques Id for each request to the server. Web server on its end compares the session id with its stored session ids. Per session cookies (not downloaded or set on client browser) communicates with the web server. This cookies is set by default. Please correct me if i'm off target. hope this info helps Suppose I have 2 servers, server1 and server2. How can I take data in a cookie from server1, and send it to server2? Location: http://www.jguru.com/faq/view.jsp?EID=304637 Created: Jan 17, 2001 Modified: 2001-01-19 14:17:51.598 Author: Jorge Jordão (http://www.jguru.com/guru/viewbio.jsp?EID=275762) Question originally posed by Soumendu Das (http://www.jguru.com/guru/viewbio.jsp?EID=264142 You'll have to create a (new) similar cookie on server 2. Have a ReadCookieServlet running on server1 that • •

Reads the cookie, using request.getCookies() Redirects to WriteCookieServlet running on server2, passing the cookie name, value and expiration date as request parameters, using response.sendRedirect().

Have a WriteCookieServlet running on server2 that • •

Reads the cookie name, value and expiration date request parameters, using request.getParameter(). Creates a similar cookie, using response.addCookie().

Comments and alternative answers

If the two servers are in the same domain you can set...

Author: Fabio Moratti (http://www.jguru.com/guru/viewbio.jsp?EID=63024), Jan 23, 2001 If the two servers are in the same domain you can set the "domain" attribute for the cookie, in this way it is sent to both servers. When will WebSphere support WAR files? Location: http://www.jguru.com/faq/view.jsp?EID=308027 Created: Jan 20, 2001 Modified: 2001-01-27 04:26:32.246 Author: Robert Castaneda (http://www.jguru.com/guru/viewbio.jsp?EID=4362) Question originally posed by Sven Resch (http://www.jguru.com/guru/viewbio.jsp?EID=251030 Version 3.5.2 of WebSphere supports WAR files and the Servlet 2.2 specification see section 8.7 of this Red Book for details. My servlet application has been uploaded on a website with JRun support. We access our servlets from behind a proxy. When two or more persons from behind the proxy try and access the same sevlets netscape gives an error to one saying "No Data found" and the other gets the data which the first one had requested. What should I do to prevent this? Location: http://www.jguru.com/faq/view.jsp?EID=310114 Created: Jan 23, 2001 Modified: 2001-01-27 04:36:34.974 Author: Joe Morse (http://www.jguru.com/guru/viewbio.jsp?EID=310104) Question originally posed by Parvez Kapadia (http://www.jguru.com/guru/viewbio.jsp?EID=263972 This sounds like the servlet you have may be implementing the SingelThreaded interface. Is this true? Also, you really need to watch your use of class-level variables. Any variables you display to your user should probably be declared and assigned from within the scope of the doPost, doGet, or service methods. Are you able to post your servlet code here? That might be instructive. How can I pass data from a servlet running in one context (webapp) to a servlet running in another context? Location: http://www.jguru.com/faq/view.jsp?EID=311485 Created: Jan 24, 2001 Modified: 2001-01-27 04:31:51.328 Author: Ryan Breidenbach (http://www.jguru.com/guru/viewbio.jsp?EID=45212) Question originally posed by nagaraj thota (http://www.jguru.com/guru/viewbio.jsp?EID=34847 There are three ways I can think of off the top of my head: 1. Store the information you want to share in a persistant format, such as in a file system or database. That way, any servlet that is running in a JVM that can "see" these resources can get to this information. 2. If persisting this information is not an option, you can bind this information to a context that is accessible to all servlet contexts, such as the application server's context. This way, you can keep the data you want to share in memory.

3. Use the old fashion way of passing information to a servlet - HTTP. One servlet could foward a request to another servlet and include the data that needs to be shared as parameters in the request. Hope this helps! [See also http://www.jguru.com/jguru/faq/view.jsp?EID=50791] Comments and alternative answers

Pleeeeeeeease exapnd on 2. How do you use and access... Author: john grimes (http://www.jguru.com/guru/viewbio.jsp?EID=323228), Feb 7, 2001 Pleeeeeeeease exapnd on 2. How do you use and access the servers application context? [Answer: Read the docs on Servlet.getServletContext() and ServletContext.setAttribute() and ServletContext.getAttribute(). -Alex] Also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Oct 25, 2001 This question is also answered at: • • • •

Is there a simple way to share a single Session object across multiple ServletContexts? How can I share data between two different web applications? How can I pass data from a servlet running in one context (webapp) to a servlet running in another context? Can two web applications (servlet contexts) share the same session object?

How can I join a session with a given sessionId without using cookies? Assume I get the session from the HttpSessionContext passing the session Id. Location: http://www.jguru.com/faq/view.jsp?EID=314666 Created: Jan 28, 2001 Modified: 2001-01-29 07:39:30.678 Author: Ravindra Babu katiki (http://www.jguru.com/guru/viewbio.jsp?EID=313843) Question originally posed by Jayaprakash A (http://www.jguru.com/guru/viewbio.jsp?EID=284375 It is better to use URL Rewriting. Generate a session id by your self and append that session id to the URL at the end. For more details, see this site's FAQs for URL Rewriting in Servlet OR JSP section. URL rewritng is better option for your case because Session uses cookies and without cookies you can not use sessionid.

[Still doesn't quite answer the question: is there a way to get the session a priori (if you know the session ID)? -Alex] How can I write an "error page" -- that is, a servlet or JSP to report errors of other servlets? Location: http://www.jguru.com/faq/view.jsp?EID=318806 Created: Feb 1, 2001 Modified: 2001-07-16 15:14:03.037 Author: Subrahmanyam Allamaraju (http://www.jguru.com/guru/viewbio.jsp?EID=265492) Question originally posed by Junming Zhu (http://www.jguru.com/guru/viewbio.jsp?EID=280800 The Servlet 2.2 specification allows you to specify an error page (a servlet or a JSP) for different kinds of HTTP errors or ServletExceptions. You can specify this in deployment descriptor of the web application as:

<error-page> <exception-type>FooException /error.jsp where FooException is a subclass of ServletException. The web container invokes this servlet in case of errors, and you can access the following information from the request object of error servlet/JSP: error code, exception type, and a message. Refer to section 9.8 of Servlet 2.2 spec. [See also How can I debug my servlet?] Comments and alternative answers

error-page element documentation Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 16, 2001 Alessandro A. Garbagnati adds: You should check the dtd of the Web Application Descriptor (web.xml). There is an element that it's just for that: The error-page element contains a mapping between an error code or exception type to the path of a resource in the web application The error-code contains an HTTP error code, ex: 404 The exception type contains a fully qualified class name of a Java exception type.

The location element contains the location of the resource in the web application

Re: error-page element documentation Author: Tommy Chan (http://www.jguru.com/guru/viewbio.jsp?EID=493508), Sep 10, 2001 Would someone teach me how to customize the Error Message of Error500 in TOMCAT? I've tried to add the <error-page> tag in the web.xml file, but it doesn't work. I've uploaded a copy of my web.xml file in http://www.geocities.com/hkust2000/web.xml for reference. Can anyone tell me what's wrong with my settings (I haven't changed anything, all are by default)? Will there be other places apart from web.xml file which can affect the setting of customizing the Error500 page? Re[2]: error-page element documentation Author: Garrett Smith (http://www.jguru.com/guru/viewbio.jsp?EID=745187), Mar 23, 2002 Has anyone (besides Alex) gotten this to work? Re[3]: error-page element documentation Author: Ron R (http://www.jguru.com/guru/viewbio.jsp?EID=907416), Jun 7, 2002 Yes. I used the following syntax: <error-page> <error-code>404 /test.html Note: it wouldn't work without the '/' preceding test.html and the parser is real picky about where in the file you place the definitions. This is after the <servlet-mapping> element. Re[4]: error-page element documentation Author: Garrett Smith (http://www.jguru.com/guru/viewbio.jsp?EID=733867), Jun 8, 2002 Yeah, it definitely works. I forgot to include the DTD. This obviously caused a problem. Re[5]: error-page element documentation Author: jim michael (http://www.jguru.com/guru/viewbio.jsp?EID=930383), Jun 27, 2002 I'm still lost on this... I looked at every message in this thread, and still can't figure out how to get it working. Obviously, the <errorpage> tag needs to go in web.xml, but whats this about the DTD?

I tried to analyze what the above message with all the stuff is doing, but I just don't get it. What *exactly* do I need to put in web.xml to trap a 404? Re[6]: error-page element documentation Author: Garrett Smith (http://www.jguru.com/guru/viewbio.jsp?EID=745187), Jun 27, 2002 You don't need to understand the DTD semantics completely to write the document, but it would definitely help! Here is the document I am using. It works for me:

<web-app>

<error-page> <error-code>404 /error404.jsp

Make changes one at a time, so you can tell where you went wrong and what works and what doesn't. It's not like HTML. If you have a mistake, it will cause problems with tomcat and you won't even be able to start it! Re[7]: error-page element documentation Author: jim michael (http://www.jguru.com/guru/viewbio.jsp?EID=930383), Jun 27, 2002 Ok, thanks! Got that working now. Now I have an even harder question: What about trapping 500 errors, such as:

"HTTP Status 500: No context configured to process this request." Since there *is* not context configured in this case, <errorpage> can't go in a deployment descriptor of a web app. So, I thought perhaps I could put <error-page> in the server's main web.xml. The server doesn't complain about it being there, but it doesn't work, either. This does not seem to work: <error-page> <error-code>500 /error500.html Is it impossible to trap such an error? My ultimate goal is to have a web site that doesn't throw *any* "ugly" errors no matter how bad a user might mess with the URL, etc. Am I dreaming? Re[8]: error-page element documentation Author: Garrett Smith (http://www.jguru.com/guru/viewbio.jsp?EID=745187), Jun 27, 2002 To answer your question, Error handlers are for runtime errors, not configuration errors. A context error... I have never had that problem, so I don't know how much I can help out here. Usually you don't have to add a context. You can just go to http://hostname.com/webappname/ and Tomcat finds it. Look in $CATALINA_HOME/conf/server.xml. You can add a context by copying another context and changing it. the examples context looks like this:

You can add a new context by copying and changing the

examples context. If this is hosted, it should be done by the host. Users should probably not have access to this unless tomcat is shared among users (via tomcat manager). A good (yet somewhat advanced) example is on IBM Devworks. You can download and run the filter example: http://www-106.ibm.com/developerworks/java/library/jtomcat/?open&l=101,t=grj,p=TomcatTricks It explains how to add a context for the filter example. If you are too impatient for all of that, copy and change the examples context. Here is an example of a webapp context that I made:

Note that these changes will not take be applied until you restart Tomcat. The same is true with web.xml. [ I am using this for the examples in David Geary's 'Advanced JavaServer Pages.' ] Re[9]: error-page element documentation Author: jim michael (http://www.jguru.com/guru/viewbio.jsp?EID=930383), Jul 1, 2002 Thanks. I understand contexts, etc. Here's the scenario I was trying to avoid. Say I have an app on my web page that you get to via http://myserver.com/mywebapp. Now imagine that someone bookmarks the app and they get to it via that bookmark for years. Now imagine someday during a site redesign I move the app to http://myserver.com/mynewwebapp If the person tries their bookmark, it will throw the "500 No context configured" because "mywebapp" no longer exists. I was hoping for a way to trap these sorts of errors so that if such a thing happened the user would see a nice error message instead of the scary Tomcat one . Re[10]: error-page element documentation

Author: Peter O'Brien (http://www.jguru.com/guru/viewbio.jsp?EID=1045105), Jul 28, 2003 One solution would be to have a single page in a web app that redirects to mynewwebapp and register the former web app at mywebapp. So when the browser bookmark is used, the browser gets redirected to the new URL. Or the page could display an appropriate message to ask the user to update their bookmarks. Re[7]: error-page element documentation Author: Fabio Moratti (http://www.jguru.com/guru/viewbio.jsp?EID=63024), Sep 11, 2003 Hi, I used the confiugration described for a 404 error and works just fine: the error page I specified (404.jsp) is indeed invoked. The problem I am experiencing is that Explorer refuses to show my error page and shows his. I thied with different browsers (Mozilla, Konqueror) and the output of the 404.jsp page is nicely shwn. The thing I do not understand is that the "Tomcat" error page is correctly shown: I used a sniffer to compare the HTTP sent by Tomcat with his error page and by the 404.jsp and the headers are identical. Any pointers? This problem is driving me mad... :( I am using Tomcat 4.1.24 and jdk 1.4.1. Thanks in advance, Fabio

Re[8]: error-page element documentation Author: Balázs Csepregi-Horváth (http://www.jguru.com/guru/viewbio.jsp?EID=1170494), May 13, 2004 Explorer catches the HTTP message code 404 and replaces all the content with its own error page. To switch this feature off go to: Tools -> Internet Options... -> Advanced. Then look for "Show friendly HTTP error messages" and uncheck it. Click OK. Re[9]: error-page element documentation Author: Fabio Moratti

(http://www.jguru.com/guru/viewbio.jsp?EID=63024), May 27, 2004 Hi, I further researched and experimented with the behaviour of Explorer and error pages. The custom error pages are catched and replaced if they are "too small". Looks like that Explorer thinks your "small" page is too ugly and so decides to show his. If the page weights a few Kb then it is shown: so you can either create a nice looking page or you can add some extra spaces to you page to meet the Explorer's expectations. Of course the advice of Balázs works ok, but sometimes it is not possible to customize the client's behaviour. Fabio Re[9]: error-page element documentation Author: Michael Witherspoon (http://www.jguru.com/guru/viewbio.jsp?EID=1236233), Apr 2, 2005 Wow. Those sneaky dogs! I've been working on this problem for more than 2 hours only to find out that I had been doing it correctly from the first try. But, since Microsoft thinks they own the whole world, they have their own default settings that defeat the J2EE standards! What a bunch of losers! Anyway, thank you so much for posting the secret hint about the browser settings. I can't see why they call their crappy replacement for my "very friendly error page" a "friendly error message". There was nothing friendly at all about the browser overriding my error page. At least I have it working now. Spoon Error page element Author: Jeni Richards (http://www.jguru.com/guru/viewbio.jsp?EID=1014062), Feb 20, 2003 I am sucessfully using error-code element and it works great for links within the web app. Is there any way of testing a link to ensure the page is there when the link is outside the web app?

Deployment Descriptor excerpts need context Author: Michael Witherspoon (http://www.jguru.com/guru/viewbio.jsp?EID=1236233), Apr 2, 2005 It is very, very important when providing answers that include excerpts from deployment descriptors to include enough skeleton descriptor so that the excerpt has enough context so that someone using the answer knows where it goes. For example, including <error-page> <error-code>404 /errorpages/html404.html is fine but nobody can tell where in the web.xml file it goes. Sure, we can then go look it up in the DTD and maybe figure out that cryptic syntax to determine where it goes, but since YOU know the answer, YOU already know where it goes, so tell us. Instead, an excerpt with context might look like this: <web-app> ... <servlet> ... ... <welcome-file-list> ... <error-page> <error-code>404 /errorpages/html404.html ... ... so that we know the error-page stuff goes between the welcome-file-list and the taglib stuff. While learning J2EE, I have found hundreds of partial answers like these which cause more confusion than help. In the future, I wish more people would take the time to provide a complete answer that simply removes doubt instead of creating more.

Please always include enough context in one's Deployment Descriptor answers so that people know where the excerpt goes. If the above answer had been done this way, the ensuing pile of questions others had about where it goes and why it wasn't working could have been avoided. It's not just you, almost everybody makes these types of mistakes when answering questions and it simply drives me insane. Spoon How can I maintain the session-specific Transport / Store objects across multiple HTTP requests, Sun's implementations aren't serializable? Location: http://www.jguru.com/faq/view.jsp?EID=319276 Created: Feb 2, 2001 Modified: 2001-02-02 10:21:42.184 Author: Dieter Wimberger (http://www.jguru.com/guru/viewbio.jsp?EID=25708) Question originally posed by Mark K (http://www.jguru.com/guru/viewbio.jsp?EID=302688 If you are using a Java server side solution, like the JSDK (which I suppose) then you can store/retrieve the references in/from the HTTPSession object which you can get from the incoming HttpRequest object. For an example implementation you might want to take a look at: http://www.sourceforge.net/projects/jwebmail and/or http://www.sourceforge.net/projects/jwma Both are open source webmail solutions written in Java. I've written a servlet that was using JServ and now I upgrade to use Tomcat. What would I need to change? Location: http://www.jguru.com/faq/view.jsp?EID=321264 Created: Feb 5, 2001 Modified: 2001-02-06 07:44:37.919 Author: Tim Pierce (http://www.jguru.com/guru/viewbio.jsp?EID=19457) Question originally posed by Bapu Patil (http://www.jguru.com/guru/viewbio.jsp?EID=49941 The only thing you should have to change code-wise is whatever has been changed in the Servlet API between the API used in JServ and the api used it Tomcat... just a couple that come to mind are encodeURL() is now encodeUrl() and encodeRedirectURL is now encodeRedirectUrl(). You can get the entire list by looking at the specs for the servlet APIs on the java site. There is usually a section in the specs that is "What's New in the API". I've written a servlet that was using JServ and now I upgrade to use Tomcat. What would I need to change? Location: http://www.jguru.com/faq/view.jsp?EID=322048 Created: Feb 6, 2001 Modified: 2001-02-11 11:10:11.75 Author: Ryan Breidenbach (http://www.jguru.com/guru/viewbio.jsp?EID=45212)

Question originally posed by Bapu Patil (http://www.jguru.com/guru/viewbio.jsp?EID=49941 Well, there isn't any reason that your servlet itself would have any specific code in it that would not allow it to be deployed on Tomcat. By this, I mean the code in the init, service, deGet, etc. methods should be servlet-container independent. That being said, all you should have to do it register the new servlet with Tomcat. This requires modifing two files, server.xml and web.xml. The server.xml file is where you will register your web application (the context in which your servlet will operate). This would look something like this: <Server> The web.xml file is where you will configure your web application. This includes configuring your servlet's alias and initial parameters. This would look something like: <servlet> <servlet-name>myServlet <servlet-class>com.mypackage.MyServlet <param-name>param1 <param-value>true <servlet-mapping> <servlet-name>myServler /useMyServlet See the Tomcat Users Guide for more details. How do I port from Cold Fusion (CFM) to servlets? Location: http://www.jguru.com/faq/view.jsp?EID=322789 Created: Feb 7, 2001 Modified: 2001-02-11 11:10:44.047 Author: philip chittoor (http://www.jguru.com/guru/viewbio.jsp?EID=313112) Question originally posed by Rajith Raghu (http://www.jguru.com/guru/viewbio.jsp?EID=246237 ColdFusion is a Proprietary system with its own markup tags for doing the server side processing. Servlets again have a completely different architecture and they have their own way of processing the server side logic. You may have to re-write the code entirely when you migrate to Servlets. I would suggest ColdFusion to JSP is more appropriate migration if your application has more presentation content rather than heavy application logic.

Regards, Radhakrishnan Comments and alternative answers

ColdFusion and Java Author: Mike Viens (http://www.jguru.com/guru/viewbio.jsp?EID=420102), May 11, 2001 Check out www.tagservlet.com. They have a servlet that will parse ColdFusion pages without the need for ColdFusion server. Re: ColdFusion and Java Author: adam butler (http://www.jguru.com/guru/viewbio.jsp?EID=885134), May 20, 2002 check out the new version of coldfusion from macromedia. Coldfusion has been rewritten as a set of j2ee custom tags, retaining all the functionality and ease use of cfml with the benefits of j2ee. The Coldfusion mx server comes in two versions, a stand alone version based on a cut down version of jrun or a full j2ee version which can be plugged into other j2ee application servers currently jrun4, sun one and ibm websphere for full details go here http://www.macromedia.com/software/coldfusion/ I have a Web Application, that works perfect on Netscape Navigator, but when I use the method "POST" in a JSP, and use Internet Explorer as Browser, then the application stops working, I already done an analysis of the problem, and I discover that IExplorer, just "cuts" part of the information that the servlet target needs to do its job, so. How can I solve this problem?? (I have to work with the "POST" method) Example: The Object Request have 2912 characters(using Netscape), but using IExplorer, it reduces to 2362!!, and then the servlets stops working because of the lost of information. Location: http://www.jguru.com/faq/view.jsp?EID=326002 Created: Feb 11, 2001 Modified: 2001-02-11 11:12:19.104 Author: Dieter Wimberger (http://www.jguru.com/guru/viewbio.jsp?EID=25708) Question originally posed by Andres Rojas (http://www.jguru.com/guru/viewbio.jsp?EID=130022 I have encountered the same problem when submitting multipart/formdata via POST to a secure webserver (i.e. https). I verified this on Server side, with different CGI's and a test servlet, and submitted a Bug report. However, the bad news is that nobody cared, and there is nothing that can be done about it, despite checking the Microsoft Knowledge Base and waiting for updates to MSIE. The only real way to react is not to buy or use any of such products, however, we all know that this is hardly possible. Comments and alternative answers

This problem with multipart/form-data with POST on IE still persists...Is there a workaround??? Author: Chidambaram Ganapathi (http://www.jguru.com/guru/viewbio.jsp?EID=138126), Sep 11, 2001 I'm encountering the same problem as you guys have mentioned even now. Have you guys figured out any work-arounds. Apparently this happens very sporadically...it doesn't happen all the time and after this happens if you click Refresh, sometimes the proper page comes up.!!!!! And mine is not even a secure web server(I mean I'm still trying it with http and not https.) on JRun. Re: This problem with multipart/form-data with POST on IE still persists...Is there a workaround??? Author: Joe Smith (http://www.jguru.com/guru/viewbio.jsp?EID=535122), Oct 31, 2001 The problem has to do with not having enough memory allocated on your app server. trying upping it substantially and it should work. Re[2]: This problem with multipart/form-data with POST on IE still persists...Is there a workaround??? Author: KARTHIK JAYABALAN (http://www.jguru.com/guru/viewbio.jsp?EID=1149210), Feb 26, 2004 Did this problem ever solved? I'm still having problems with this. If you have solution, please let me know. Thanks. Using JServ, even if a request is coming from the same browser, I am getting a new session each time. I am using request.getSession(true).getId() to find out session Id and it's different for every request. What's going wrong ? Location: http://www.jguru.com/faq/view.jsp?EID=330061 Created: Feb 15, 2001 Modified: 2001-02-15 13:40:50.354 Author: Vikram Lele (http://www.jguru.com/guru/viewbio.jsp?EID=251314) Question originally posed by satish A (http://www.jguru.com/guru/viewbio.jsp?EID=222556 request.getSession(true) will always return a new session. You need to use request.getSession(false). If there is no session, it will return a null, in which case you need to create a new session. Typically, assuming you have a login page, the session should be created in the login validation servlet, and all other servlets just need to do request.getSession(false), and if this returns a null, they should serve the login page. If you don't have a login, you can do this:

thisSession = request.getSession(false); if(thisSession == null) thisSession = request.getSession(true); To make sure the session is properly maintained, you must call this method at least once before you write any output to the response. regards, - Vikram Comments and alternative answers

as per JSDK API, getSession(true) returns a new session... Author: satish A (http://www.jguru.com/guru/viewbio.jsp?EID=222556), Feb 15, 2001 as per JSDK API, getSession(true) returns a new session only if its not created yet. I am referring JSDK 2.1 rgds, satish Even though you specify request.getSession(true), until... Author: vijay somagudam (http://www.jguru.com/guru/viewbio.jsp?EID=306348), Feb 15, 2001 Even though you specify request.getSession(true), until u disable the cookies and persession cookies option in the browsers internet options u can't get the same session id! these options are there in internet options security tab inside this click on custom level and disable the cookies and persession cookies!! now u can get the same session id!!! Re: Even though you specify request.getSession(true), until... Author: M Hunt (http://www.jguru.com/guru/viewbio.jsp?EID=1099025), Jul 3, 2003 I've been having a 'mare with new sessions being created for each request, but have fixed it now! For me, using IE6 as I am, it was to do with the Internet Options - Privacy Advanced tab having the 'Always allow session cookies' checkbox checked. I simply un-checked the box, saved it, and lo and behold the session now persists! Cheers, Marcus. request.getSession(true) will not always return a new... Author: Koodal Kumaran Sailappan (http://www.jguru.com/guru/viewbio.jsp?EID=300552), Feb 15, 2001 request.getSession(true) will not always return a new session. If a session is already present, it returns a reference to it otherwise a new session is created.

Hey guys check the API ... !! If you refer to the... Author: Niclas Meier (http://www.jguru.com/guru/viewbio.jsp?EID=245132), Feb 16, 2001 Hey guys check the API ... !! If you refer to the API documentation you will see that the getSession(boolean create) method will only create a new session if no session is available. When a session aready exists this session will be used. Check if your browser is using cookies or if the session is properly appended to the link URL. To make it possible for the container to identify the session you can use cookies or append the session-id via response.encodeURL(String url). If neither cookies nor URL rewriting is used the servlet container cannot determine the session and will a new one every time. regards Niclas

It might be that netscape has cookies disabled. It... Author: Hans Halim (http://www.jguru.com/guru/viewbio.jsp?EID=116548), Feb 19, 2001 It might be that netscape has cookies disabled. It seems that Tomcat remembers session by cookies. Try setting netscape to accept cookies in Edit->Preferences under Advanced category Yes.. getSession(true) returns a new session only when... Author: ashok chindam (http://www.jguru.com/guru/viewbio.jsp?EID=83479), Feb 22, 2001 Yes.. getSession(true) returns a new session only when it is not created yet. You might have turned off cookies on ur browser. If so u have to encode the url to get the old session. Ashok. Session Author: Navaljit Bhasin (http://www.jguru.com/guru/viewbio.jsp?EID=404310), Apr 17, 2001 The answer given by you is misleading and totally wrong As per your answer request.getSession(true) always return new session. Sorry sir, go back to school and clear the concepts.No wrong advices. As per j2ee docs this is answer Parameter: true to create a new session for this request if necessary; Parameter : false- to return null if there's no current session Please note the if necessary in case the parameter is true. Why the hell you give wrong suggestions. Naval

Re: Session Author: rahul gagrani (http://www.jguru.com/guru/viewbio.jsp?EID=1167271), Apr 29, 2004 Hello can u please tell me what is the difference between request.getSession(true) and request.getSession() . After referring to the api docs i just dont find any difference as they both returns the session (if available) and if it is not available yet, creates one. How can I set timeout for servlet response? Location: http://www.jguru.com/faq/view.jsp?EID=330644 Created: Feb 15, 2001 Modified: 2001-02-16 15:07:26.829 Author: reshma deshmukh (http://www.jguru.com/guru/viewbio.jsp?EID=132478) Question originally posed by Pavel Bernshtam (http://www.jguru.com/guru/viewbio.jsp?EID=274236 [More info: I.e. if servlet not gives answers for 1 min. (it freezes, it makes too long SQL query etc), browser will receive some error message. I work with resin servlet engine, but if it is impossible in resin, solutions for other engines also are welcome. Of course, I can do this manualy (Timer, or just Thread with sleep()) but solution at config level is preferable. Thanx] For HTTP1.1 you can set status codes for response. (some browsers support for 1.0 also) You can call response.setStatus before sending any content via the PrintWriter. For setting timeout , status code is "SC_GATEWAY_TIMEOUT" with value 504. You can call response.setStatus(504)for that. You call call response.sendError also. The advantage of sendError over setStatus is that, with sendError, the server automatically generates an error page showing the error message. In your case it will be :

response.sendError(response.SC_GATEWAY_TIMEOUT, "Timeout"); [That doesn't answer the question directly; you still need to implement your own timeout in your servlet code before sending the 504 response. Is there a standard way to configure this irrespective of servlet code? -Alex] How can I write/read files using servlets, without getting java.io.FileNotFoundException: file_name(Permission denied). Location: http://www.jguru.com/faq/view.jsp?EID=333861 Created: Feb 20, 2001 Modified: 2001-02-25 17:44:38.071 Author: Darren Hobbs (http://www.jguru.com/guru/viewbio.jsp?EID=15939) Question originally posed by Sanjiv Mani Tripathi (http://www.jguru.com/guru/viewbio.jsp?EID=252168

First, remember that servlets run on the server-side, and therefore only have access to the file-system of the server. They cannot directly interact with clients, except through HTTP request/response. It could be that the servlet does not have sufficient permissions to write to the filesystem (which itself depends on what permissions the servlet container process has). Try explicitly specifying the full path to a directory that you know has full 'global' read/write access permissions. Comments and alternative answers

FileNotFoundException Author: rajiv k (http://www.jguru.com/guru/viewbio.jsp?EID=386332), Mar 24, 2001 your class shuld impliment Serializable interface .So add-- implements Serializable-to your class .It will work All built in classes have no problem Isn't. Try that also... Where should configuration files be stored in a web application? Location: http://www.jguru.com/faq/view.jsp?EID=338339 Created: Feb 25, 2001 Modified: 2001-02-25 17:32:51.684 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Guillaume Bilodeau (http://www.jguru.com/guru/viewbio.jsp?EID=283171 The current servlet spec (2.2) doesn't mention specifically where to store configuration files. The new version (2.3) will have a more explicit way of accessing them. In the meantime, a good technique is to put them in the *root* level of your WEBINF/classes directory. (e.g. "mywebapp/WEB-INF/classes/config.txt".) Since this directory is automatically on your classpath, you can load the files using

InputStream in = this.getClass().getResourceAsStream("/" + filename); if (in == null) throw new IOException("Resource " + filename + " not found"); Comments and alternative answers

Updating Config files Author: Jason Rumney (http://www.jguru.com/guru/viewbio.jsp?EID=549612), Nov 16, 2001 Recommending the use of WEB-INF and getResourceAsStream() for storing config files is all very well, but increasingly servers are running web applications straight out of war files, so if you need to update the configuration dynamically, the code to do so becomes messy and unportable. So is there a portable way to update config files in

2.3, or do I have to invent my own? How can I develop a servlet or JSP which can comunicate with an applet showing the list of all the other users? This applet should also allow the user to send messages to specific users in the list (More or less like the applet in myYahoo when a Yahoo messenger is not installed) Location: http://www.jguru.com/faq/view.jsp?EID=338370 Created: Feb 25, 2001 Modified: 2001-02-25 17:30:54.792 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Abey Mullassery (http://www.jguru.com/guru/viewbio.jsp?EID=268841 Oddly enough, I've developed such an applet/servlet combo :-) I'm calling it "Combadge." It's still not ready for release, but I'll be releasing it soon. Please bug me via email. See also Jabber and the Jabber Applet for inspiration and source code. Comments and alternative answers

To communicate with your servlet/jsp, your applet ... Author: Sylvain Colomer (http://www.jguru.com/guru/viewbio.jsp?EID=320970), Feb 26, 2001 To communicate with your servlet/jsp, your applet simply has to establish a HTTP connection to the servlet which answers with the list of users (in plain text or XML for example). What is the difference between ServletContext and ServletConfig? Location: http://www.jguru.com/faq/view.jsp?EID=339337 Created: Feb 26, 2001 Modified: 2001-03-02 07:17:03.47 Author: Ryan Breidenbach (http://www.jguru.com/guru/viewbio.jsp?EID=45212) Question originally posed by vishal gupta (http://www.jguru.com/guru/viewbio.jsp?EID=44954 A ServletContext represents the context in a servlet container of a servlet instance operates. A servlet container can have several contexts (or web applications) at one time. Each servlet instance is running in one of these contexts. All servlets instances running in the same context are part of the same web application and, therefore, share common resources. A servlet accesses these shared resource (such as a RequestDispatcher and application properties) through the ServletContext object. This notion of a web application became very significant upon the Servlet 2.1 API, where you could deploy an entire web application in a WAR file. For more specifics on web application, please see this FAQ. Notice that I always said "servlet instance", not servlet. That is because the same servlet can be used in several web applications at one time. In fact, this may be

common if there is a generic controller servlet that can be configured at run time for a specific application. Then, you would have several instances of the same servlet running, each possibly having different configurations. This is where the ServletConfig comes in. This object defines how a servlet is to be configured is passed to a servlet in its init method. Most servlet containers provide a way to configure a servlet at run-time (usually through flat file) and set up its initial parameters. The container, in turn, passes these parameters to the servlet via the ServetConfig. See also What is a Servlet Context?. Comments and alternative answers

Both are interfaces. The ServletConfig interface is... Author: P Manchanda (http://www.jguru.com/guru/viewbio.jsp?EID=344357), Mar 5, 2001 Both are interfaces. The ServletConfig interface is implemeneted by the servlet engine in order to pass configuration information to a servlet. The server passes an object that implements the ServletConfig interface to the servlet's init() method. The ServletContext interface provides informaion to servlets regarding the enviornment in which they are running. It also provides standard way for servlets to write events to a log file. Re: Both are interfaces. The ServletConfig interface is... Author: suresh durai (http://www.jguru.com/guru/viewbio.jsp?EID=1207057), Oct 25, 2004 As u mentioned that both are interfaces.if interface means how can we create the object for this interface. How can you use Servlet Session Tracking with WAP? Location: http://www.jguru.com/faq/view.jsp?EID=340156 Created: Feb 27, 2001 Modified: 2001-03-02 07:19:08.339 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Luke Studley (http://www.jguru.com/guru/viewbio.jsp?EID=10174 [More question: I am trying to implement a simple access - login - re-direct mechanism using WAP / WML, however the WAP browser does not seem to support normal session tracking. Do I have to explicitly (and dynamically) place the sessionid in the login form?] Many WAP browsers and/or proxies do not understand cookies and/or redirects. This means you will have to use URL rewriting for your session management. Feel free to

complain to the WAP product vendors -- these are basic HTTP features that really should be implemented. See also How do I send a redirect to a WAP device? How many cookies can one set in the response object of the servlet? Also, are there any restrictions on the size of cookies? Location: http://www.jguru.com/faq/view.jsp?EID=340982 Created: Feb 28, 2001 Modified: 2001-03-02 07:18:07.991 Author: Jorge Jordão (http://www.jguru.com/guru/viewbio.jsp?EID=275762) Question originally posed by mpavanu muni (http://www.jguru.com/guru/viewbio.jsp?EID=253970 If the client is using Netscape, according to the Client-Side JavaScript Reference, the browser can receive and store • • •

300 total cookies 4 kilobytes per cookie (including name) 20 cookies per server or domain

Which classes implement the interfaces from the standard servlet API such as HttpSession, HttpServletRequest, etc.? Location: http://www.jguru.com/faq/view.jsp?EID=342634 Created: Mar 2, 2001 Modified: 2001-03-02 07:07:04.753 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Artyom Malyshkov (http://www.jguru.com/guru/viewbio.jsp?EID=284237 The server vendors must write those classes, and pass them in to your servlets. The beauty of interfaces is that each server vendor can implement their own version of the same interface, and your code need not change. Under what circumstances will a servlet be reloaded? Location: http://www.jguru.com/faq/view.jsp?EID=343098 Created: Mar 2, 2001 Modified: 2001-03-03 11:26:56.965 Author: swarraj kulkarni (http://www.jguru.com/guru/viewbio.jsp?EID=121306) Question originally posed by Narugopal Sahu (http://www.jguru.com/guru/viewbio.jsp?EID=303532 That depends on the Servlet container. Most of the Servlet containers reload the servlet only it detects the code change in the Servlet, not in the referenced classes. In Tomcat's server.xml deployment descriptor, if you have mentioned

debug="0" reloadable="true" trusted="false" > The reloadable = true makes the magic. Every time the Servlet container detects that the Servlet code is changed, it will call the destroy on the currently loaded Servlet and reload the new code. But if the class that is referenced by the Servlet changes, then the Servlet will not get loaded. You will have to change the timestamp of the servlet or stop-start the server to have the new class in the container memory. There are many good answers here at jGuru related to this question. You may find them useful: Servlet reload problem Comments and alternative answers

Servlets get reloaded in Ajache/Jserv whenever the... Author: Harpreet Singh (http://www.jguru.com/guru/viewbio.jsp?EID=106255), Mar 12, 2001 Servlets get reloaded in Ajache/Jserv whenever the timestamp on the servlet code changes. If any of the other objects that the servlet references change, the classes do not get reloaded because servlet run in a different container and knows nothing about the change in other classes. A quick fix for this is to just 'touch' the servlet whenever your supporting objects change. What is a Servlet Filter? (see Servlet Spec 2.3) Location: http://www.jguru.com/faq/view.jsp?EID=344253 Created: Mar 4, 2001 Modified: 2001-03-05 16:01:34.401 Author: Allen Fogleson (http://www.jguru.com/guru/viewbio.jsp?EID=344251) Question originally posed by Saravanan Jayachandran (http://www.jguru.com/guru/viewbio.jsp?EID=91462 A filter is basically a component that is invoked whenever a resource is invoked for which the filter is mapped. The resource can be something like a servlet, or a URL pattern. A filter normally works on the request, response, or header attributes, and does not itself send a response to the client. [That's great, but a little brief -- anyone want to elaborate with more details, code samples, etc.? -Alex] Comments and alternative answers

see Jason Hunter's excellent article on Servlet 2.3:... Author: Stefan Hoehn (http://www.jguru.com/guru/viewbio.jsp?EID=284266), Mar 15, 2001 see Jason Hunter's excellent article on Servlet 2.3: New Features exposed under

http://www.javaworld.com/jw-01-2001/jw-0126-servletapi.html I am using the RequestDispatcher's forward() method to redirect to a JSP. The problem is that the jsp's url is now relative to the servlet's url and all my url's in the jsp such as

will be corrupt. How do I solve this problem? Location: http://www.jguru.com/faq/view.jsp?EID=344412 Created: Mar 5, 2001 Modified: 2001-03-07 13:27:52.885 Author: Dmitry Ivlev (http://www.jguru.com/guru/viewbio.jsp?EID=341551) Question originally posed by Tobias Åkeblom (http://www.jguru.com/guru/viewbio.jsp?EID=76237 You can use absolute urls like: <% String base = request.getContextPath(); %>

or write out a BASE tag like: <% String base = request.getContextPath(); %>

That should take care of the problem. Comments and alternative answers

Another solution: Author: Juergen Staebler (http://www.jguru.com/guru/viewbio.jsp?EID=424068), May 23, 2001 Well, I tried it and got NO gif's at all. (Problem is the request.getContextPath, its null.) So I handle it on a similar way: Inside the servlet set-up a session attribute, e.g.: request.setAttribute("mySourceDir", "/src/package/"). In the JSP use the getAttribute: e.g: String stringSource = (String)request.getAttribute("mySourceDir"). So, now you have a variable to handle. But be sure, this variable MUST END with a '/', without you need to add it in your 'img src'-tag. With this, you also can now use a html-dev.tool (like dreamveawer ultradev) without having problems in showing and binding your gifs. The img src shows: e.g.:

src="/src/package/gfx/transp.gif" with JSP Tag: src="<%=stringSource%>gfx/transp.gif" regards J.Staebler Re: Another solution: Author: alejandro avila (http://www.jguru.com/guru/viewbio.jsp?EID=409805), May 31, 2001 if you follow the J2EE WAR specification format you don't have to worry about, absolute paths, becuase everything is going to be in the document root. How can I pass language specific characters through a query string to a servlet thats running on Tomcat 3.1 / Apache / mod_jserv? Location: http://www.jguru.com/faq/view.jsp?EID=347167 Created: Mar 8, 2001 Modified: 2001-03-12 11:36:32.476 Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985) Question originally posed by Mikael Lichtenstein (http://www.jguru.com/guru/viewbio.jsp?EID=222454 [It works fine when I use Tomcat as standalone. However, when passing the query string through Apache 1.3.12 and mod_jserv.so the query string gets cut where the language specific characters start. I can see that Apache writes the language specific characters in the access log. So I guess something is happening with the query string on the way from Apache to Tomcat. I'm using Red Hat Linux 6.2. Is there a way to put these language specific characters all the way through? The characters in question are swedish (åäöÅÄÖ). Or do I have to do some gismo with mod_rewrite?] Try using %nn (where nn is the hex ASCII key code) in the GET request. [Also, make sure you're using the latest version of mod_jk (not mod_jserv) -Alex] Comments and alternative answers

Use encoding Author: amit singi (http://www.jguru.com/guru/viewbio.jsp?EID=380857), Apr 27, 2001 When u r passing a query string don't pass it directly just convert it into following format. %xx (where xx is the hex ASCII key code) You can do this by using function encode of java class URLEncoder in net package. But for this you need to get the bytes in the specific encoding from the string and then construct string. If u want to pass s(String) in query then use this URLEncode.encode(new String(s.getBytes("Shift_JIS"))) where shift_jis is the encoding for that language and while retrieving the request parameter use shift_jis to get the string value.

Are there any editors for developing servlets? Location: http://www.jguru.com/faq/view.jsp?EID=348070 Created: Mar 9, 2001 Modified: 2001-03-12 11:41:39.731 Author: JP Moresmau (http://www.jguru.com/guru/viewbio.jsp?EID=127279) Question originally posed by Surendra Kumar (http://www.jguru.com/guru/viewbio.jsp?EID=300649 Most commercial Java IDEs now have servlet support and debugging build in (at least in their "enterprise" versions...). I know that Inprise JBuilder and Oracle JDevelopper do for example... Try Allaire JRun studio if you are using JRun. Comments and alternative answers

visual cafe and visual age for java also support s... Author: sree mam (http://www.jguru.com/guru/viewbio.jsp?EID=31208), Mar 14, 2001 visual cafe and visual age for java also support servlets. Free Forte Community Edition Author: Michael Murphy (http://www.jguru.com/guru/viewbio.jsp?EID=385872), Mar 23, 2001 I use Forte and I love it. It fairly scaled back from a 'not-free' IDE, but you can configure it pretty easily and 2.0 version has servlet support. I set mine up with Oracle jars, Mysql jars and my own customer jars and it manages my projects pretty well. However it is a serious hog so I suggest a fair amount of RAM >=128Mb. I use 256Mb, but I do so much other stuff (Oracle Apps) at the same time as well. the Community Edition is great as is free go to java.sun.com NetBeans IDE 3.1 Author: Jazci Nijjar (http://www.jguru.com/guru/viewbio.jsp?EID=408880), Apr 24, 2001 I currently use NetBeans IDE 3.1 which is very similar to Forte and its also free!!! Forte for Java, Internet Edition Author: Juergen Hoeller (http://www.jguru.com/guru/viewbio.jsp?EID=236151), Apr 30, 2001 My team uses Forte 2.0 Internet Edition for JSP and servlet development, and we really appreciate it. IMHO Forte IE is the best environment for developing Java web applications, especially if you want to write portable applications that do not rely on some proprietary server features. In this case, Forte is the far better choice than any IDE that is associated with some particular application server vendor. And if you do not use EJB, it easily beats JBuilder 4 in terms of web application support, JSP debugging facilities and - important too - price. BTW, NetBeans is the open source project behind Sun's branded Forte product line. And watch out for the upcoming Forte for Java 3.0, I expect some new useful features introduced there! Editor for Servlet

Author: ramanujam ragavan (http://www.jguru.com/guru/viewbio.jsp?EID=429317), Sep 10, 2001 There is a superb editor for creating srevlets . It gives you a million options to play with and there is no limit to customizing servlets. It is got the simplest interface you can ever imagine. With one menu bar , a tool bar and a popup menu to add to the editor panel, you can cut copy and paste and also select all and word wrap. You can also print from it. you can save and open files --- So many facilities you will adore for the rest of your life.... IT IS CALLED NOTEPAD ! ALL THE BEST Which servlet engines support HTTPS (SSL) connections? Location: http://www.jguru.com/faq/view.jsp?EID=352812 Created: Mar 16, 2001 Modified: 2001-03-16 09:55:38.966 Author: Richard Raszka (http://www.jguru.com/guru/viewbio.jsp?EID=7963) Question originally posed by Angel Sierra (http://www.jguru.com/guru/viewbio.jsp?EID=346227 Most Servlet Engines should support HTTPS (SSL) Connections if they are used as a plug-in to common HTTP servers such as Netscape, IIS and Apache. The reason for this is that the Web Server will provide the HTTPS connection between the client and the Web Server. However, one draw back of this mechanism is that the communication from the Web Server to the Servlet engine may not be HTTPS but either a proprietory protocol (such as OSE for WebSphere for remote installs) or a TCP/IP connection to the Servlet engine or via the plug-in protocol (if local). In most cases this may not be an issue but if data is still required to be encrypted between the Web Server and Servlet Engine an IPSec or SOCKS solution can be provided to handle comms to the Servlet Engine. Comments and alternative answers

SSL via built-in web server Author: Juergen Hoeller (http://www.jguru.com/guru/viewbio.jsp?EID=236151), Apr 30, 2001 The servlet engine "Resin" by Caucho (http://www.caucho.com/products/resin) supports SSL via its built-in web server, and it works perfectly. answer Author: John Smith (http://www.jguru.com/guru/viewbio.jsp?EID=431592), May 31, 2001 Think and read documentation What is the maximum length of a URL, including GET parameters? Location: http://www.jguru.com/faq/view.jsp?EID=384627 Created: Mar 21, 2001 Author: Manish Parmar (http://www.jguru.com/guru/viewbio.jsp?EID=288849)

Question originally posed by Adolfo Aladro (http://www.jguru.com/guru/viewbio.jsp?EID=288038 Re: What is the maximum length of a URL, including... It's very server-dependant. Check Server documentation. Please see 3.2.1 General Syntax section of ftp://ftp.isi.edu/in-notes/rfc2616.txt. The HTTP protocol does not place any a priori limit on the length of a URI. Servers MUST be able to handle the URI of any resource they serve, and SHOULD be able to handle URIs of unbounded length if they provide GET-based forms that could generate such URIs. A server SHOULD return 414 (Request-URI Too Long) status if a URI is longer than the server can handle (see section 10.4.15). Note: Servers ought to be cautious about depending on URI lengths above 255 bytes, because some older client or proxy implementations might not properly support these lengths. Manish Comments and alternative answers

Test Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Mar 22, 2001 Test Why do I get the compiler error "package javax.servlet does not exist" or "package javax.servlet not found in import"? Location: http://www.jguru.com/faq/view.jsp?EID=413601 Created: May 2, 2001 Modified: 2001-05-05 14:17:16.683 Author: Kursat Demirezen (http://www.jguru.com/guru/viewbio.jsp?EID=412558) Question originally posed by Kevin Fonner (http://www.jguru.com/guru/viewbio.jsp?EID=412162 Try this: Assume that you have tomcat location like: c:\tomcat at the command promt type: set classpath=c:\tomcat\lib\servlet.jar Comments and alternative answers

Why do I get the compiler error "Package javax.servlet not found in import"? Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), May 5, 2001 You need the servlet API libraries in your classpath. These are usually found in servlet.jar (although some servlet engines, IDEs, and earlier versions of the servlet package called them jsdk.jar or something else). Make sure servlet.jar is in your classpath and you should be all set. Here's one way to be sure your classpath is correct: run

javap -classpath my;class;path javax.servlet.Servlet If javap can't find it, then your classpath is wrong. If javap can find it, then your config file or script isn't setting the classpath correctly. Perhaps it's a syntax error or you're just confused about which script/config file/setting is really getting used. Or perhaps you're using a different install of Java -different JDKs can have different classpaths. See also How do I set my CLASSPATH for Servlets? Re: Why do I get the compiler error "Package javax.servlet not found in import"? Author: Monty Fury (http://www.jguru.com/guru/viewbio.jsp?EID=463799), Jul 27, 2001 I too have spent hours and hours trying to work out why, despite setting my CLASSPATH correctly to point to the servlet.jar archive in the Tomcat installation, the javac compiler refuses to find it and thus gives such messages as "package javax.servlet does not exist". By searching on Sun's java sites, the Tomcat site, and many mailing lists, I saw that tons of people were having the same problem, and the only replies offered were of the form "are you *sure* you've set the CLASSPATH properly?!" Naturally, I was sure I had, but as it turns out, I hadn't: There was a problem with case-sensitivity, at least on my system (Windows ME). The servlet.jar file was located as follows: C:\Program Files\Tomcat-3.2.3\lib\servlet.jar and I was setting CLASSPATH as follows: CLASSPATH=.;C:\PROGRA~1\TOMCAT~1.3\LIB\SERVLET.JAR (the ".;" bit placed at the start as recommended at http://www.apl.jhu.edu/~hall/java/Servlet-Tutorial/index.html) I was using DOS filenames because I *thought* that was the safest thing to do whenever programs like Tomcat that involve DOS are involved. But then I finally tried setting the path as: CLASSPATH=.;C:\PROGRA~1\TOMCAT~1.3\lib\servlet.jar and that solved the problem. My knowledge of computing has been entirely self-taught over the last year, and

there are some serious gaps - can anyone tell me why a DOS pathname should suddenly be case sensitive like that? Re: Re: Why do I get the compiler error "Package javax.servlet not found in import"? Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 27, 2001 Because DOS is stupid. Next question? :-) Re: Re: Why do I get the compiler error "Package javax.servlet not found in import"? Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 27, 2001 By the way, a good way to be sure you've set the class path is by using javap. In the above, typing "javap javax.servlet.Servlet" would have failed until you got the right class path. Re: Re: Why do I get the compiler error "Package javax.servlet not found in import"? Author: Amit Jain (http://www.jguru.com/guru/viewbio.jsp?EID=520788), Oct 15, 2001 Hi, I am facing same type of problem. Environment is : Windows ME, JRUN and Tomcat(tried on both), Apache web server. From last 2 days I have tried each possible combination for class path to servlet.jar but nothing is working. I am getting sick of restarting my computer each time I change my classpath ;(. Help will be really appriciated. Thanks, Amit Jain Re: Why do I get the compiler error Package javax.servlet not found in import? Author: devender bejju (http://www.jguru.com/guru/viewbio.jsp?EID=1204161), Oct 8, 2004 seems like the CLASSPATH itself is a biggest hurdle for newbies. anyways I too have the same problem, some where in the document ( http://www.coreservlets.com/Apache-Tomcat-Tutorial/#Set-CLASSPATH ) i found that we need to give the path in double quotes if tomcat is install dir has any spaces eg "C:\Program Files\Apache Software Foundation\Tomcat 5.0\common\lib\servlet-api.jar";"C:\Program Files\Apache Software Foundation\Tomcat 5.0\common\lib\jsp-api.jar" normally in dos envi, every thing after the first space is treated as parameters (importantly unlike the prior versions of tomcat (<5),for tomcat 5 its both the servlet-api.jar and jsp-api.jar) like in the above ex , without the double quotes dos treats c:\program as one and rest of the things as parameters in the same doc author said to put . and .. and ..\.. i understood it why its required but need to continue research , dont know how long it takes i will post when I solved

Re: Why do I get the compiler error Package javax.servlet not found in import? Author: Thanh Le Ngo (http://www.jguru.com/guru/viewbio.jsp?EID=1215714), Dec 10, 2004 you can set classpath .;C:\j2sdk1.4.2_04\lib;c:\j2ee\lib\j2ee.jar j2ee is j2ee home directory, in j2ee.jar has package javax.servlet (the default is c:\Sun\AppServer\lib\j2ee.jar) it's ok for me when i compile servlet Consistent errors using javap -classpath my;class;path javax.servlet.Servlet Author: David T (http://www.jguru.com/guru/viewbio.jsp?EID=1221377), Jan 15, 2005 This javap command consistly produced the following error in my windows 2000/tomcat 5.x configuration: "ERROR:Could not find javax.servlet.Servlet" Someone else posted the following command and I've had much better results using it: javap javax.servlet.Servlet I found the winning classpath command for my configuration...it looks like this: set classpath=.;C:\Java\Tomcat\common\lib\servletapi.jar;C:\Java\Tomcat\common\lib\jsp-api.jar;C:\Java\ Does TOMCAT provide JDBC Connection Pooling ? Location: http://www.jguru.com/faq/view.jsp?EID=415490 Created: May 4, 2001 Modified: 2001-07-16 15:05:15.13 Author: Nicola Ken Barozzi (http://www.jguru.com/guru/viewbio.jsp?EID=39153) Question originally posed by venu gopalan (http://www.jguru.com/guru/viewbio.jsp?EID=394235 No. Tomcat (talking about version 3.x.x) is the reference implementation of the webapp part of J2EE (ie, no EJB). In this spec connection pooling is not contemplated. You can however use pooling by using the JDBC 2.0 optional package instead of JDBC 2.0 directly. For additional info see the JGuru JDBC FAQ Forum and see How do I access a database from my servlet? in the Servlets FAQ. [Also, http://www.javaexchange.com hosts a fine implementation of a JDBC Connection Pool. -Alex] Comments and alternative answers

Another connection pool Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 16, 2001 Also, see http://www.codestudio.com/ for the poolman connection pool library. Re: Another connection pool Author: Sasha Maksimenko (http://www.jguru.com/guru/viewbio.jsp?EID=851934), Apr 24, 2002 From site codestudio.com: PoolMan is no longer available or supported through this site. It did exceedingly well during its lifetime, and I appreciate the important role it played in so many distributed applications over the past three years. If you are looking for connection and object pooling mechanisms, they can now be found in application servers such as JRun, Tomcat and the Jakarta Project, and other J2EE products and servers. Re[2]: Another connection pool Author: Shane Word (http://www.jguru.com/guru/viewbio.jsp?EID=68418), Jul 1, 2002 Or, if you don't want to use a J2EE or Servlet setup as part of your connection pooling, you could just use one of the many other freely available DB Connection pools, like the Open Source one at: http://sourceforge.net/projects/esw/ Tomcat 4.x and Tyrex Author: Mike Barlotta (http://www.jguru.com/guru/viewbio.jsp?EID=869607), May 23, 2002 Tomcat 4.x comes with Tyrex (another open source project from ExoLabs) which allows it to support JDBC connection pooling and JNDI naming contexts. Cool stuff -Mike Re: Tomcat 4.x and Tyrex Author: Denny Dedhiya (http://www.jguru.com/guru/viewbio.jsp?EID=1030707), Nov 28, 2002 Dear Mike After several attempts, I'm unable to setup and make distributed transactions to work in Tomcat. I am using Tomcat 4.0.4, Tyrex .97 and struts-1.1-b2. I have implemented the database connection pooling mechanism of struts using commons-dbcp package and I want to use transaction management using Tomcat. Can you please give me a running sample application which uses transcation mgmt?

Many many thanks in advance Denny Dedhiya

Re: Tomcat 4.x and Tyrex Author: prathap chandran (http://www.jguru.com/guru/viewbio.jsp?EID=1010464), Dec 10, 2002 does tomcat4.0.3 support dbcp connection pool? Thanks Prathap How can I return a readily available (static) HTML page to the user instead of generating it in the servlet? Location: http://www.jguru.com/faq/view.jsp?EID=415883 Created: May 5, 2001 Author: André Wolf (http://www.jguru.com/guru/viewbio.jsp?EID=310274) Question originally posed by Anthony Lew (http://www.jguru.com/guru/viewbio.jsp?EID=415782 To solve your problem, you can either send a "Redirect" back to the client or use a RequestDispatcher and forward your request to another page:

1. Redirect:

A redirection is made using the HttpServletResponse object: 2. if(condition) { 3. response.sendRedirect("page1.html"); 4. } else { 5. response.sendRedirect("page2.html"); 6. } 7. RequestDispatcher: A request dispatcher can be obtained through the ServletContext. It can be used to include another page or to forward to it. 8. if(condition) { 9. this.getServletContext() 10. .getRequestDispatcher("page1.html").forward(); 11.} else { 12. this.getServletContext() 13. .getRequestDispatcher("page2.html").forward(); 14.} Both solutions require, that the pages are available in you document root. If they are located somewhere else on your filesystem, you have to open the file manually and copy their content to the output writer. If your application server is set up in combination with a normal web server like Apache, you should use solution (1), because the the web server usually serves static files much faster than the application server. Comments and alternative answers

Further question... Author: Anthony Lew (http://www.jguru.com/guru/viewbio.jsp?EID=415782), May 5, 2001 Thanks, Andre. My page is working correctly now. But just one more query. Can I change something in the page that I sendRedirect to? Say, for example, I have a login page and I want to display the name of the user on the page that I redirect... I know that HTMLs are just static pages. So, just want to know whether there are any technologies that can handle this... Is there a way to detect when the session has expired, so that we can send a redirect to a login page? Location: http://www.jguru.com/faq/view.jsp?EID=415912 Created: May 5, 2001 Modified: 2003-01-08 14:08:04.407 Author: Michael Wax (http://www.jguru.com/guru/viewbio.jsp?EID=242559) Question originally posed by rbkadam raju (http://www.jguru.com/guru/viewbio.jsp?EID=405242 [In our Servlet framework, session timeout happens after 1hr. Currently if user tires to access the pages after 1hr, he gets null-pointer exception. Is there any way we can detect that session has been expired, so that we can show standard HTML Page to User, indicating that his session has expired, he has to LOGIN again.] ----------------After getting the session, check to see if it is new: HttpSession session = request.getSession(); if (!session.isNew()) { //do something which requires the session to exist } else { //new session was created - send new login page } [And see http://www.jguru.com/faq/view.jsp?EID=415883 for how to send a redirect to a static login page. -Alex] Comments and alternative answers

HttpSession class comes in handy for such requirements Author: Koodal Kumaran Sailappan (http://www.jguru.com/guru/viewbio.jsp?EID=300552), May 15, 2001 The idea is, Once the user has logged in, a new session is created. Typically, the Login page has the following code HttpSession session = request.getSession(true);

This does not gaurantee a new session always. If any Session is already active, then a reference to it, is returned. To inactivate any session that is already present and to have a new session,then the code is HttpSession session = request.getSession(false); if (session != null)

{

session.invalidate();

} session = request.getSession(true);

Then in other servlets where the session is used, the following code should be included. HttpSession session = request.getSession(false); if (session == null) { //redirect to login page } //other code

And when the user logs out, session can be invalidated. Re: HttpSession class comes in handy for such requirements Author: phillip gibb (http://www.jguru.com/guru/viewbio.jsp?EID=748715), Feb 28, 2002 Hi what I do now is have a bean in application scope that handles all the sessions. It stores logins in a hash table and has a thread to check for inactivity. The on the pages themselves I have a piece of javascript that starts up a method after a certain time - that method opens up a little window with a countdown and a "do you want to continue" question. Its works great. The only question is do I really have to store all users in an object(hashtable is what I use), or can I just use the HttpSession object and add an attribute to indicate whether a user has logged in or not. Phill Re[2]: HttpSession class comes in handy for such requirements Author: Koodal Kumaran Sailappan (http://www.jguru.com/guru/viewbio.jsp?EID=300552), Feb 28, 2002 The purpose is to alarm the user when his/her inactive time is nearing the session timeout, if I had understood it correctly. You could add an attribute in the HttpSession object storing the time, the user made last request. This value is updated as and when the user makes request. A thread would be monitoring the user inactivity time by comparing the "Last Request" time in session object with that of the "Current time". The thread's "sleep" time should be less than the "countdown" time. If the hashtable approach is follwed, then application has the burden of adding/removing the login into/from hashtable when user logs-in/logs-out.

Use a logon filter Author: Rick DeBay (http://www.jguru.com/guru/viewbio.jsp?EID=1182519), Jun 29, 2004 A simple logon filter will send the user to a logon page when their session is invalid, and forward them back to the page they were originally trying to access. This keeps you from putting any session management code in the JSP. If you require a warning that the session will expire soon, write a simple JSP tag which will write out an HTML meta refresh tag, which will forward to the warning page based on the session timeout. For browsers that don't support meta refresh or have it turned off, the tag should also generate a simple javascript timer to do the forward. How can I add or remove parameters from a request instance, before sending it to the RequestDispatcher? Location: http://www.jguru.com/faq/view.jsp?EID=415981 Created: May 5, 2001 Modified: 2001-09-26 12:39:50.595 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Antonio Hernandez (http://www.jguru.com/guru/viewbio.jsp?EID=2783 As of Servlet spec 2.2, it's impossible to add or remove parameters from a request object. Servlet spec 2.3 will have some mechanism to allow this functionality. (How difficult it will be in practice is not clear. It will definitely not be as easy as 'request.removeParameter("foo")', unfortunately.) In the meantime, using a wrapper class will work in some servlet engines but fail in others. The mechanism in 2.3 is to use the "HttpServletRequestWrapper" class. See the JavaDoc API. Comments and alternative answers

A tad misleading.... Author: Lukas Bradley (http://www.jguru.com/guru/viewbio.jsp?EID=35930), Dec 2, 2002 The 2.3 spec still does not allow access to the "innards" of the Servlet Container vendor specific implementation. Therefore, unless you are writing your own Servlet Engine, it still remains impossible to add or remove parameters from a request object. Workaround Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 9, 2003 http://www.jguru.com/forums/view.jsp?EID=1016603 Does anyone know of any detailed architectural design patterns for organizing a web application with multiple servlets (and optionally, JSPs)? Location: http://www.jguru.com/faq/view.jsp?EID=415984 Created: May 5, 2001

Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Barry Wythoff (http://www.jguru.com/guru/viewbio.jsp?EID=222348 [Textbook descriptions (many) that I have seen so far really don't go very far in this regard- they either are too vague (use servlets/JSP between the GUI and EJB) or too low level (connect two with getRequestDispatcher())... I am interested in "proper" organization and functional decompositon of a multiservlet application, and am sure that many people are dealing with this same issue- thanks for your kindness! Barry] Barry, You can consider the "MVC Design Pattern", a.k.a. "Model 2 Architecture". There is an interesting article on Javaworld: Understanding JavaServer Pages Model 2 architecture. In addition, you can take a look at Struts, one of the many projects of the Apache foundation regarding Java. [ Ross Keatinge adds: Also check out Webwork which is an MVC framework similar to Struts. For me as a Java newbie it was a lot easier to understand and get started with than Struts. ] What is the difference between static variables and instance variables in a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=416009 Created: May 5, 2001 Modified: 2001-07-02 20:13:53.756 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Krishna Reddy (http://www.jguru.com/guru/viewbio.jsp?EID=399043 According to the Java Language definition, a static variable is shared among all instances of a class, where a non-static variable -- also called an instance variable -is specific to a single instance of that class. According to the Servlet specification, a servlet that does not declare SingleThreadModel usually has one and only one instance, shared among all concurrent requests hitting that servlet. That means that, in servlets (and other multithreaded applications), an instance variable behaves very much like a static variable, since it is shared among all threads. You have to be very careful about synchronizing access to shared data. The big difference between instance variables and static variables comes when you have configured your servlet engine to instantiate two instances of the same servlet class, but with different init parameters. In this case, there will be two instances of the same servlet class, which means two sets of instance variables, but only one set of static variables. Remember that you can store data in lots of different places in a servlet. To wit: • • •

Local variables - for loop iterators, result sets, and so forth Request attributes - for data that must be passed to other servlets invoked with the RequestDispatcher Session attributes - persists for all future requests from the current user only

• • •

Instance variables - for data that persists for the life of the servlet, shared with all concurrent users Static variables - for data that persists for the life of the application, shared with all concurrent users -- including any other servlet instances that were instantiated with different init parameters Context attributes - for data that must persist for the life of the application, and be shared with all other servlets

(In the case of SingleThreadModel, there may be many instances of the same servlet class even with the same init parameters. SingleThreadModel is confusing and usually unnecessary.) See How do I ensure that my servlet is thread-safe? for more detail. Where can I find a description of the tags (elements and attributes) used in web.xml? Location: http://www.jguru.com/faq/view.jsp?EID=416037 Created: May 5, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Francois-Yanick Bourassa (http://www.jguru.com/guru/viewbio.jsp?EID=389655 Francois, The web.xml is the Servlet Web-Application descriptor. It's a standard XML file and the description and the full description (including the list of all the available tags) can be found in the Servlets 2.2 final specifications. You can get it from Sun's Java Servlet download page. Can multiple names be assigned to the domain of a cookie? Location: http://www.jguru.com/faq/view.jsp?EID=416038 Created: May 5, 2001 Modified: 2001-10-24 07:24:43.329 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Shilpa Kulkarni (http://www.jguru.com/guru/viewbio.jsp?EID=322579 [I am setting domain as '.abc.com' for a cookie. I want the same cookie to be accessible to '.abc.net'. How can this be achieved by using a single cookie?] I don't think you can do that. The cookie specification defines only one domain per cookie, so I don't think there is a way to read the same cookie from more than one domain. Comments and alternative answers

Use the URL Author: Jeff Williams (http://www.jguru.com/guru/viewbio.jsp?EID=231946), May 7, 2001 You can't do it with a cookie, but you might be able to accomplish what you want by using something else that the user sends in the HTTP request. Like the URL for

instance...try adding "?user=foobar" to the URLs for that user. Then you'll know who it came from when they come back -- even to your different domain. Caveat -- this is very insecure for a number of reasons. You might look at the 'one-time logon' products like Securant and Netegrity to see how they do this. How can I share data between two different web applications? Location: http://www.jguru.com/faq/view.jsp?EID=416043 Created: May 5, 2001 Author: Wayne Xin (http://www.jguru.com/guru/viewbio.jsp?EID=49940) Question originally posed by jean kunz (http://www.jguru.com/guru/viewbio.jsp?EID=384644 Different servlets may share data within one application via ServletContext. If you have a compelling to put the servlets in different applications, you may wanna consider using EJBs. [You can also use a database, or use the file system, but it's difficult to share the data inside the JVM. Even using statics may not work, since the two web applications may be using different classloaders. -Alex] Comments and alternative answers

Also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Oct 25, 2001 This question is also answered at: • • • •

Is there a simple way to share a single Session object across multiple ServletContexts? How can I share data between two different web applications? How can I pass data from a servlet running in one context (webapp) to a servlet running in another context? Can two web applications (servlet contexts) share the same session object?

How can I write to a log file from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=416048 Created: May 5, 2001 Modified: 2001-07-19 15:45:47.964 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by chenxiaoli chenxiaoli (http://www.jguru.com/guru/viewbio.jsp?EID=384584 Look for the method ServletContext.log(String) or GenericServlet.log(String). These will write to a servlet log file maintained by your servlet container. E.g.:

log("Servlet called with name " + request.getParameter("name")); If this is insufficient, you can use java.io classes to write your own files. See also: • •

Where does the output of System.out and System.err go in a servlet? Can I get at the OutputStream that is buried underneath ServletContext.log()?

If the cookies at client side are disabled then session don't work, in this case how can we proceed? Location: http://www.jguru.com/faq/view.jsp?EID=416057 Created: May 5, 2001 Author: Wayne Xin (http://www.jguru.com/guru/viewbio.jsp?EID=49940) Question originally posed by girish kumar (http://www.jguru.com/guru/viewbio.jsp?EID=322626 you may: 1. (from servlet) write the next page with a hidden field containing a unique ID that serves as "session ID". So next time when the user clicks submit, you can retrieve the hidden field. 2. If you use applet, you may avoid "view source" (so that people can't see the hidden field). Your applet reads back an ID from the servlet and use that from then on to make further requests. [Also, search the topic Servlets:Cookies, Sessions, and State Management for more information about sessions and cookies. -Alex] Comments and alternative answers

if is cookie is disabled on server Author: raj kapse (http://www.jguru.com/guru/viewbio.jsp?EID=714303), Jan 9, 2002 use encodeURL() method for all the URLs Re: if is cookie is disabled on browser Author: raj kapse (http://www.jguru.com/guru/viewbio.jsp?EID=714303), Jan 9, 2002 use encodeURL() for all the URLs I want to redirect to a particular page, but before that, I want to display a different HTML page containing a message. Location: http://www.jguru.com/faq/view.jsp?EID=416059 Created: May 5, 2001 Author: Troy Niven (http://www.jguru.com/guru/viewbio.jsp?EID=219893) Question originally posed by Avinash N (http://www.jguru.com/guru/viewbio.jsp?EID=346964

The User not validated and the Error Message doesn't get displayed at all . I first want it to be displayed , and then after 10 seconds , I want to redirect the servlet to my OpeningPage How is that possible ???] Try something like this instead then.

res.setHeader("refresh","10; URL=http://" +req.getServerName()+"/Openingpage.html"); out.println(" User not Validated"); out.println(e.getMessage()); out.close(); How to read a file from the WAR or webapp? If I have a configuration file, say an XML file, stored inside the WAR, how do I open it from a servlet? I.e.,

InputStream in = new FileInputStream(????); Location: http://www.jguru.com/faq/view.jsp?EID=416061 Created: May 5, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Alex Chaffee PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=3 The WAR file is automatically opened by the servlet container during the startup... at least this is what the servlet specs are saying (and it is happening with both Resin and Tomcat). Once you reach the servlet just use ServletContext.getRealPath() to get the file. For example if the file is in a 'template' dir under the root of the context, use

getRealPath("/template/file.xml"); Comments and alternative answers

Reading file from WEB-INF Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jun 17, 2001 Theoretically, this works for getting a file from the WEB-INF directory as well. getRealPathgetServletContext().getRealPath("/WEBINF/myconfig.xml") (may not work on some servlet containers, but it's supposed to). Re: Reading file from WEB-INF Author: drit . (http://www.jguru.com/guru/viewbio.jsp?EID=454295), Aug 5, 2001 Partly true. It depends on the container - BEA for example, requires that you have

to set the applicaton correctly in config.xml. I would probably use getResource() instead... Author: Chang Zhao (http://www.jguru.com/guru/viewbio.jsp?EID=466741), Aug 1, 2001 My specs might not be up to date, but it says <snip> ... This method returns null if the servlet container cannot translate the virtual path to a real path for any reason (such as when the content is being made available from a .war archive). so instead, maybe you can try getResource("/WEB-INF/whatever.xml"), get the url, and get it that way... just my $.02 What about writing a file within the context path? Author: nick orbit (http://www.jguru.com/guru/viewbio.jsp?EID=964690), Jul 25, 2002 So, now I know how to read a file from within my webapp root directory. What to I have to do in order to write a file. In my application is an XML file that is loaded on startup. It contains categories on three levels that could be edited. When edited the file including the modifications has to be stored on the servers hard disk in the same directory where it first has been read. If I use the same directory path my server/ application is not able to find the file. And I do not know what to do. Where and how should I tell my application to safe my edited file properly? Thank you, Nick

Re: I would probably use getResource() instead... Author: Travis Capener (http://www.jguru.com/guru/viewbio.jsp?EID=1099562), Jul 7, 2003 This worked for me. Here is a more complete code fragment from a JSP file. I put my test.properties file in the root of my context (i.e. where the JSP and HTML files are). URL myURL=application.getResource("/test.properties");

InputStream in = myURL.openStream(); Properties p = new Properties(); p.load( in ); out.println( p.getProperty("message") );

Thanks for the help.

using getResource() Author: Richa Sharma (http://www.jguru.com/guru/viewbio.jsp?EID=1223623), Jan 27, 2005 While using URL myURL=application.getResource("/test.properties"); Where should I place the test.properties file. I placed it, where I have my jsp files, but I am getting myURL=null. Also should I make any changes in web.xml How to read a file from war or webapp using servlet from weblogic Author: bodapati koteswararao (http://www.jguru.com/guru/viewbio.jsp?EID=1248895), Jun 16, 2005 Hi everybody, I know code of how to read the file from war or webapp using the servlet from weblogic. Thanks and regards, Kotewararao Re: How to read a file from war or webapp using servlet from weblogic Author: sun lee (http://www.jguru.com/guru/viewbio.jsp?EID=1253509), Jul 15, 2005 Hi Bodapati, I have this problem with WebLogic. Can you share your solution? By the way, I don't have the problem with Tomcat. Thankd, Sun How can I set the number of concurrent connections in Java Web Server 2.0? Location: http://www.jguru.com/faq/view.jsp?EID=416163 Created: May 6, 2001 Author: JIA Java Italian Association (http://www.jguru.com/guru/viewbio.jsp?EID=414973) Question originally posed by Chi Pong Lau (http://www.jguru.com/guru/viewbio.jsp?EID=415694 I don't have Java Web Server installed, but I've downloaded the manual and I've got the answer to all your question. Maybe you can do the same for future reference (aka: RTFM): Administration Tool: Service Tuning The Service Tuning page enables you to set or adjust properties that affect service performance [...] Handler Threads These settings affect the performance of threads within the service. Minimum: Sets the minimum number of threads the service maintains in its handler pool to service incoming requests. Because thread creation adds overhead to the service's response time, set this property to a non-zero value. The default is 10 threads.

Maximum: Sets the maximum number of threads the service maintains in its handler pool to service incoming requests. The default is 50 threads. Timeout: Sets the expiration timeout for an idle handler thread. The default is 300 seconds. On another page of the same manual, I've also found this note regarding Threads and explaining how they affect performance and concurrency connection: Tuning server performance Threads One thread is required per connection. Adding threads consumes more memory, but can yield better response time for your clients on a server that concurrently serves multiple connections that are either high latency or involve access to some highlatency resource (like a servlet accessing a database on the other side of the country). You see how useful a manual is? Regards. How do I pass a parameter from a servlet to a JSP? Location: http://www.jguru.com/faq/view.jsp?EID=416164 Created: May 6, 2001 Author: JIA Java Italian Association (http://www.jguru.com/guru/viewbio.jsp?EID=414973) Question originally posed by prashanth vaidyaraj (http://www.jguru.com/guru/viewbio.jsp?EID=415076 Check out this answer. The logic is the same, but it's reversed. You insert the object you need in the request scope with request.setAttribute() and then you use the RequestDispatcher to forward or include the jsp page. In the JSP page you use request.getAttribute() to get the object(s) back. If you need to read the form parameters, you just use the RequestDispatcher, because it passes the request object. See also: • •

How can I pass data retrieved from a database by a servlet to a JSP page? How can I call a servlet from a JSP page? .

Comments and alternative answers

Yes, but parameter != attribute Author: Roger Hand (http://www.jguru.com/guru/viewbio.jsp?EID=292314), May 7, 2001 The above answer is true enough, and frankly it's almost always the best method to use, but the original questioner asked about passing a parameter, not an attribute. For beginning jsp coders it is probably confusing that there is a specific mechanism for passing an http parameter from a jsp to a servlet, but not the other way around. Instead, rather than passing a parameter (limited to being a mere text string), you can

pass an attribute, which can be any object you'd like. Very handy! On the other hand, there are times when you do actually need to send an http parameter, as when you want to forward (to use the term loosely) a request to a legacy cgi script that's expecting POST style parameters to be passed. It can be done, but involves opening up streams, etc., and is rather messy . . . an ideal candidate for encapsulation in a utility class. (I'll upload mine if there's any interest.) Re: Yes, but parameter != attribute Author: Amos Shapira (http://www.jguru.com/guru/viewbio.jsp?EID=4346), May 12, 2001 We use such parameter passing (servlet forwarding the request to a JSP page) and it's very simple - use requestDispatcher and add "¶m=value" to the url passed from the servlet to the jsp. Re: Re: Yes, but parameter != attribute Author: susan borgrink (http://www.jguru.com/guru/viewbio.jsp?EID=441060), Jun 18, 2001 I am trying to do something simillar to what you have mentionned. But I am having problems getting it to work. Could you send me an example? Re: Re: Re: Yes, but parameter != attribute Author: Amos Shapira (http://www.jguru.com/guru/viewbio.jsp?EID=4346), Jun 18, 2001 It's really stright-forward, as the spec says: RequestDispatcher rd = request.getRequestDispatch("url?newparam=newvalue"); rd.forward(request, response);

As simple as that. Re: Yes, but parameter != attribute Author: Mayur Agrawal (http://www.jguru.com/guru/viewbio.jsp?EID=428828), May 25, 2001 Please send me the utility file , I wanna have a look at it! regards! Mayur [email protected] Re: Yes, but parameter != attribute Author: lakshmiramana bulusu (http://www.jguru.com/guru/viewbio.jsp?EID=461459), Jul 25, 2001 please upload your sample code, to pass a parameter from a servlet to a jsp page . same problem but with struts action classes Author: jn dl (http://www.jguru.com/guru/viewbio.jsp?EID=466056), Aug 1, 2001 I'm having the same problem, but using struts : how can I pass request parameters

from an ActionClass to a JSP ? the problem is, I can't use the requestDispatcher, I must return an ActionForward at the end of the perform method of the ActionClass. What is the meaning of foo? Location: http://www.jguru.com/faq/view.jsp?EID=416167 Created: May 6, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by BoonNam Goh (http://www.jguru.com/guru/viewbio.jsp?EID=409183 foo means... nothing. Literally. It's the name you give something to mean "this thing has no name." It means "fill in your own variable name here." As to the origin of the term... From The Jargon File: Used very generally as a sample name for absolutely anything, esp. programs and files (esp. scratch files). ... When `foo' is used in connection with `bar' it has generally traced to the WWII-era Army slang acronym FUBAR (`F**ked Up Beyond All Repair'), later modified to foobar. Early versions of the Jargon File interpreted this change as a post-war bowdlerization, but it it now seems more likely that FUBAR was itself a derivative of `foo' perhaps influenced by German `furchtbar' (terrible) - `foobar' may actually have been the original form. From Foo Fighters FAQ: Near the end of WWII, the U.S. Air Force patrolling German airspace encountered highly maneuverable balls of light in the area between Hagenau in Alsace-Lorraine and Neustadt an der Weinstrasse in the Rhine Valley. These unidentified flying objects came to be referred to as "Foo Fighters", or "Kraut Balls" by those who believed the objects were a secret German weapon. See also: • •

http://www.pla-net.net/~alucard/archives/humour/foo.html http://www.cs.oberlin.edu/students/jmankoff/FOO/FAQ

How can I reference an external CSS file from a Servlet? Location: http://www.jguru.com/faq/view.jsp?EID=416168 Created: May 6, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Ruhsar Soganci (http://www.jguru.com/guru/viewbio.jsp?EID=407801 [I have I servlet that generates a HTML page and I want to use a CSS file (named senior.css), so I wrote a statement like that:

out.print(" ") ] The statement is perfect, but remember that it is parsed by the browser so the file should reside in a directory that is accessible to the browser. I suggest you to put the CSS file in the rood of your context and have that statement point there. That's what I normally do. [That way, no matter where your page is located, it can find it at the root level if it's called "/senior.css" or "/foowebapp/senior.css". -Alex] Comments and alternative answers

Including Stylesheet on a JSP page Author: Girish Kshirsagar (http://www.jguru.com/guru/viewbio.jsp?EID=568296), Dec 6, 2001 Since browser must read the " Now, make sure that your css (Style.css) is in the root of the context (e.g. webapp\examples) in case of Tomcat. Re[2]: Including Stylesheet on a JSP page Author: Girish Kshirsagar (http://www.jguru.com/guru/viewbio.jsp?EID=568296), Dec 6, 2001 In case you want to have it relative to the context path you can also write LINK as Where, /util/CSS is a folder underneath your context path (e.g. /webapp/examples in case of a typical Tomcat set up). However, you must make sure that the entire path is accurately typed (i.e. is case sensitive). Hope this additional clarification helps.

What is an Application Event? (see Servlet Spec 2.3) Location: http://www.jguru.com/faq/view.jsp?EID=416170 Created: May 6, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Saravanan Jayachandran (http://www.jguru.com/guru/viewbio.jsp?EID=91462 If I've understood correctly, the Application Event of Servlet 2.3 is Sun's answer to one of the most request festures to servlets, which is an easy way to monitor, and reacts to, specific events that happen during the lifecycle of an application. The idea is very similar to a Swing event. A developer can set up listeners on the objects that needs to be monitored and receive an event object, so can react appropriately. For example a programmer can create a listener on a session object inplementing the HttpSessionListener interface, that has two methods: void sessionCreated(HttpSessionEvent evt) that is fired when a new session object is created; void sessionDestroyed(HttpSessionEvent evt) that is fired when a new session object is destroyed or invalidated; How do I change the default sessionID identifier name in Tomcat 3.2.1? The default identifier name is jsessionid. Location: http://www.jguru.com/faq/view.jsp?EID=416225 Created: May 6, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Henky Wibowo (http://www.jguru.com/guru/viewbio.jsp?EID=388711 Hi. I don't think you can change that identifier, because the name 'jsessionid' it's specified in Chapter 7 of the Servlet 2.2 specifications, that you can download here I don't really know what you would like to do, but I'm afraid that the only way to change it it's to manage your own session cookie with your own identifier and, eventually, using that cookie to map map your identifier with the jessionid. Comments and alternative answers

Java:API:Servlets:Cookies, Sessions, and State Management, Tools:AppServer:WebServer:Tomcat Author: joerg hartmann (http://www.jguru.com/guru/viewbio.jsp?EID=429981), May 29, 2001 Hi, you can't change this ID. The ID is hard-coded in the cource code org.apache.tomcat.request.package.SessionInterceptor.java and other classes. There are also constants defined in package org.apache.tomcat.core.Constants public static final String SESSION_COOKIE_NAME = "JSESSIONID"; public static final String SESSION_PARAMETER_NAME = "jsessionid"; but the constant is only used in the

Class SessionUtil... joerg How does Tomcat distribute servlet/JSP processing to the 20+ Java processes it creates? Location: http://www.jguru.com/faq/view.jsp?EID=416234 Created: May 6, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Daniel Yawitz (http://www.jguru.com/guru/viewbio.jsp?EID=241695 [How does Tomcat distribute servlet/JSP processing to the 20+ Java processes it creates? Is each client request serviced by a different Java process? If Tomcat received 100 simultaneous servlet requests, would it need to create 100 Java processes to handle them?] Theoretically yes, Tomcat will try to optimize the requests to handle as much simultaneous requests it can. [N.B.: Under Linux, each Java Thread appears in the process list (ps) as a separate process. This is because native Linux threads are implemented as lightweight processes. However, there is still only one Java process space -- the memory/CPU reported by each thread is actually shared among all threads. -A] Yes, the number of threads can be controlled for each connector in the server configuration file (normally server.xml). This is an extract from the Tomcat User Guide: [...] the (default) pool behaviour instructed by it is: Upper bound for concurrency of 50 threads. When the pool has more then 25 threads standing idle it will start to kill them. The pool will start 10 threads on creation, and it will try to keep 10 vacant threads (as long as the upper bound is kept). The default configuration is suitable for medium load sites with an average of 10-40 concurrent requests. If your site differs you should modify this configuration (for example reduce the upper limit). Configuring the pool can be done through the element in server.xml as demonstrated in the next fragment:

<Parameter name="handler" value="org.apache.tomcat.service.connector.Ajp12Connect ionHandler"/> <Parameter name="port" value="8007"/> <Parameter name="max_threads"

value="30"/> <Parameter name="max_spare_threads" value="20"/> <Parameter name="min_spare_threads" value="5" /> As can be seen the pool has 3 configuration parameters: max_threads - defines the upper bound to the for the concurrency, the pool will not create more then this number of threads. max_spare_threads - defines the maximum number of threads that the pool will keep idle. If the number of idle threads passes the value of max_spare_threads the pool will kill these threads. min_spare_threads - the pool will try to make sure that at any time there is at least this number of idle threads waiting for new requests to arrive. min_spare_threads must be bigger then 0. You should use the above parameters to adjust the pool behavior to your needs.[...] How do you pass parameters to servlets with web.xml? Location: http://www.jguru.com/faq/view.jsp?EID=416236 Created: May 6, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Craig Navin (http://www.jguru.com/guru/viewbio.jsp?EID=407103 If you want something general (for the entire context, you should use something like this: ... <param-name> NAME <param-value> VALUE ... [These are accessible from Java by calling ...? -A] If you need to set parameters for a single servlet, then use the tag inside the servlet tag: <servlet> <servlet-name>... <servlet-class>... <param-name> NAME <param-value> VALUE

[These are accessible from Java by calling getInitParameter("NAME") -A] See also How do I set init parameters in the servlet engine? Comments and alternative answers

Setting init params in web.xml Author: Kamran Dianat (http://www.jguru.com/guru/viewbio.jsp?EID=419421), May 10, 2001 My servlets do not "see" the web.xml file at all. Now I know it is being processed by Tomcat, since I get all these xml parse errors if the syntax is wrong. web.xml is under WEB-INF directory, and the syntax is correct. Any one can shed any light on this mystery. Thanks, Kamran. Still not work after changing web.xml Author: sa wa (http://www.jguru.com/guru/viewbio.jsp?EID=464624), Sep 27, 2001 Hi, I am really a beginner. Thanks for your answer there. At least I know where I should put my web.xml. I renamed original /conf/web.xml, then create my own web.xml in conf/, but once I started the Tomcat(4.0), it showed that : ----------------ERROR reading java.io.fileinputStream@39240e At Line 14 /web-app/servlet/ ERROR reading java.io.fileinputStream@246701 At Line 14 /web-app/servlet/ Starting service Tomcat-Apache Apatch Tomcat/4.0 -----------------Can you give me any hints? What is it? Here is my web.xml for a single TestServlet.java: ------------------ <web-app> <servlet> <servlet-name>test <servlet-class>com.stardeveloper.servlets.TestServlet <param-name>Name <param-value>sa wa ---------------Thanks in advance! sa wa

How can I distinguish between text file and binary file after I read a file onto my servlet? Location: http://www.jguru.com/faq/view.jsp?EID=416280 Created: May 6, 2001 Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985) Question originally posed by Shoukatali Sayyad (http://www.jguru.com/guru/viewbio.jsp?EID=412603 Reading it and checking the file's content: if it contains only chars in [a..z, A..Z, 0..9] and punctuation marks, it's a text file; viceversa, if it contains extended chars it isn't. Another good way, is to do it statistically: if it contains 85% (for example) of alphanumerical chars, probably it's a text file. You can take statistics on the first buffer read from the file to speed up checking. To recognize binary data format check also How do I know that a particular file is in binary or text format without relying on the extention of a file?. Comments and alternative answers

I think this is not i18n Author: Carfield Yim (http://www.jguru.com/guru/viewbio.jsp?EID=4648), May 6, 2001 If have to check for a i18n document, e.g.: Chinese, this method can't success. I think that we can use the method isDefine() in Character to see if the file contain defined character. http://www.javasoft.com/products/jdk/1.2/docs/api/java/lang/Character.html#isDefined(char) Actually I have never write some code for testing, may be isLetterOrDigit() is a better choice http://www.javasoft.com/products/jdk/1.2/docs/api/java/lang/Character.html#isLetterOrDigit(char) How can I get the path to the currently running servlet's .class file? For example, the function will return "C:\Test\Servlets\" when I locate the ABC.class in C:\Test\Servlets\ ? Location: http://www.jguru.com/faq/view.jsp?EID=416303 Created: May 6, 2001 Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985) Question originally posed by [missing] virtualsnack (http://www.jguru.com/guru/viewbio.jsp?EID=400551 Try this piece of code, it does work even for standard Java objects: String className = servlet.getClass().getName(); ClassLoader servletClassLoader = servlet.getClass().getClassLoader(); URL classFileURL = servletClassLoader.getResource(className + ".class"); System.out.println("classFileURL = " + classFileURL); Where servlet is an instance of your servlet. [Note: from inside a running servlet, use this.getClass() -Alex] If you don't have ready any instance of your servlet, you should replace Servlet.class where servlet.getClass() is used. [Note: this will return the path

to Servlet.class, not to MyServlet.class -- Servlet.class may be stored in a totally separate directory, based on the Servlet engine. -Alex] Comments and alternative answers

Nice tips Alex. Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985), May 6, 2001 Thanks for the notes Alex, I've learned a new thing. Still problems when the servlets are in jar files. Author: JIA Java Italian Association (http://www.jguru.com/guru/viewbio.jsp?EID=414973), May 6, 2001 I still getting a "null" result when the servlets are located in jar files. As I've mentioned, Some of my servlets are in a jar files in the common location /lib and some are in jar files under /WEB-INF/lib. Regards. Check this Author: Prathap Guptha (http://www.jguru.com/guru/viewbio.jsp?EID=344441), May 7, 2001 Have you tried with this , if not Can you please try with this it may be helpful for you. servletContext.getRealPath(request.getServletPath()); always get NULL Author: Börries Ludwig (http://www.jguru.com/guru/viewbio.jsp?EID=741941), Jun 12, 2002 Hi together, I still have a problem to get the location of a loaded class. I tried the three examples below and get always null ! What's wrong ??? I use Tomcat 4.0.1 and no Jar-files. My classes are in Tomcat\webapps\InfoNet\WEB-INF\classes, InfoNet is the name of the application. Help is very welcome. Boerries .............................. className = this.getClass().getName(); servletClassLoader = this.getClass().getClassLoader(); System.out.println("test 1: " + servletClassLoader.getResource(className + ".class")); servletClassLoader = Servlet.class.getClassLoader(); System.out.println("test 2: " + servletClassLoader.getResource(className + ".class"));

servletClassLoader = Thread.currentThread().getContextClassLoader(); System.out.println("test 3: " + servletClassLoader.getResource(className + ".class")); How to retrieve the IP address or the hostname of the client which is accessing a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=417475 Created: May 8, 2001 Author: JIA Java Italian Association (http://www.jguru.com/guru/viewbio.jsp?EID=414973) Question originally posed by Arunachalam P PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=90631 Wow, it's incredible, but I've just opened the javadoc of Servlet 2.2 and I've found these two incredible methods of the javax.servlet.ServletRequest: getRemoteAddr() Returns the Internet Protocol (IP) address of the client that sent the request. getRemoteHost() Returns the fully qualified name of the client that sent the request, or the IP address of the client if the name cannot be determinated. It's incredible how many strange things you can find when you decide to RTFM. Regards. [See also What are the Servlet equivalents to all the CGI environment variables? ] I converted an applet that displays a graphics to a servlet using the Acme Gif encoder. Why do the graphics look so poor now? Location: http://www.jguru.com/faq/view.jsp?EID=417520 Created: May 8, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Lukas Mueller (http://www.jguru.com/guru/viewbio.jsp?EID=407035 Hi, It is possible that the loss of quality it's done in the conversion to a GIF. Remember that that format only allows 256 colors and I don't know how the color reduction it's done. I've used that encoder few times for generating charts, where the number of color was limited. But I prefer to generate jpeg images using the jpeg encoder that it's now part of the Java 2 distribution, and it's way fater than the GIF Encder: import com.sun.image.codec.jpeg.*; ... ... BufferedImage image = ... your image ...; BufferedOutputStream bos = new BufferedOutputStream(response.getOutputStream()); JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(bos);

encoder.encode(image); ... You can even control the jpeg quality with the JPEGEncodeParam, just altering a little the above example: JPEGEncodeParam eP = JPEGCodec.getDefaultJPEGEncodeParam(image); eP.setQuality(1.0f, true); BufferedOutputStream bos = new BufferedOutputStream(response.getOutputStream()); JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(bos); encoder.encode(image, eP); If the result satisfy you, then probably the problem it's really in the reduction of the number of colors. [See also http://www.jguru.com/faq/view.jsp?EID=159 -Alex] What are all the enhancements/changes in the Servlet 2.3 spec (currently in Public Draft release)? Location: http://www.jguru.com/faq/view.jsp?EID=417543 Created: May 8, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Saravanan Jayachandran (http://www.jguru.com/guru/viewbio.jsp?EID=91462 JavaWorld has an interesting article Servlet 2.3: New features exposed that can give you a very good response to your question. Comments and alternative answers

Also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Mar 1, 2002 See also http://jcp.org/aboutJava/communityprocess/first/jsr053/index.html How do I create an alias in Java Web Server? Location: http://www.jguru.com/faq/view.jsp?EID=417546 Created: May 8, 2001 Author: sree mam (http://www.jguru.com/guru/viewbio.jsp?EID=31208) Question originally posed by Puneet Sachdeva (http://www.jguru.com/guru/viewbio.jsp?EID=28785 In javawebserver documentation you can find how to create alias.Here i am giving the same from Documentation. To Add a Servlet Alias: • •

1.In the Administration Tool, go to the Service->Manage->Setup->Servlet Aliases panel. 2.Click Add.

• •

3.In the Alias field, type the URL path name you want to use to invoke the servlet. 4.In the Serlvet Invoked field, type the name of the servlet that will be run in response to the alias. To specify arguments, type the name of the servlet followed by a ? then the arguments. Server redirects can be performed by providing arguments in this fashion to RedirectServlet. For example, you could alias /oldlocation to /RedirectServlet?http://www.newcompanyname.com/newinformation.) To specify a servlet chain, type the name of each servlet, separated by commas but no spaces (for example: finger,snoop,date). A servlet chain is two or more servlets linked together so that each servlet in the chain is called in succession by the previous servlet. All of the servlets in a servlet chain can be aliased to one alias name. When a request arrives for that alias, all the servlets in the chain will be invoked.

• •

5.Enter the name of the servlet. 6.Click Save.

To Delete a Servlet Alias: 1.In the Administration Tool, go to the Service->Manage->Setup->Servlet Aliases panel. 2.Select the alias from the list. 3.Click Remove. 4.Click Save. To Edit a Servlet Alias: 1.In the Administration Tool, go to the Service->Manage->Setup->Servlet Aliases panel. 2.Select an alias from the list. 3.Click Modify. 4.Remove the existing text and type new text, or append text to the existing information. 5.Press Return. 6.Click Save. Note: To move to a new field, click that field. Is there a common way (not servlet-container dependant) to precompile a jsp file without waiting for the first hit? Location: http://www.jguru.com/faq/view.jsp?EID=425278 Created: May 20, 2001 Modified: 2001-10-29 10:48:02.387 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Alessandro A. Garbagnati PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=32727

Yes, there is a common solution that it's defined in the JSP specification and it has to be implemented by any container that claim to be compliant. JSP 1.1 Specification paragraph 3.4.2 states: A request to a JSP page that has a request parameter with name "jsp_precompile" is a precompilation request. The "jsp_precompile" parameter may have no value, or may have values "true" or "false". In all cases, the request should not be delivered to the JSP page. The intention of the precompilation request is that of a hint to the JSP container to precompile the JSP page into its JSP page implementation class. The hint is conveyed by given the parameter the value "true" or no value, but note that the request can be just ignored in all cases. Moved to paragraph 8.4.2 in JSP 1.2 PDF 2 Specification So, to precompile 'myPage.jsp' it's enough to use 'myPage.jsp?jsp_precompile'. This feature is extremely interesting even for verifying the code inside a page that requires parameters, or that contains code like sql insert or delete queries, etc. In addition, many container have specific solution, some of them already covered by FAQs: Tomcat with a comment regarding Oracle or JRun. Comments and alternative answers

You can also use load-on-startup Author: Amos Shapira (http://www.jguru.com/guru/viewbio.jsp?EID=4346), May 27, 2001 You can also ask the page to be loaded when the server starts. This is done via the web.xml file, like this: <servlet> <servlet-name>login <jsp-file>/login.jsp 1

Re: You can also use load-on-startup Author: sari Pula (http://www.jguru.com/guru/viewbio.jsp?EID=435408), Jun 7, 2001 can u please specify steps to perform for precompiling JSP files,like which xml file has to be changed and where actually .class file generatedby jspc compiler has to be placed. Re[2]: You can also use load-on-startup Author: Kevin Weslowski (http://www.jguru.com/guru/viewbio.jsp?EID=921400), Jun 20, 2002 Hello, I'm also wondering about the steps to getting this working...I was wondering if you had any luck with this? Thanks, Kevin Common way to precompile jsp pages Author: jeff hancock (http://www.jguru.com/guru/viewbio.jsp?EID=1157795), Mar

26, 2004 Just an fyi... Using Tomcat 5 with Windows. Tomcat will NOT compile JSP pages on startup or with the ?Precompile commandline or using any other method. You can delete the class file and it still does not compile JSP pages. The only means is to use JSPC/JAVAC to compile JSP pages. How do I pass a variable into a thread that can be accessed from the run() method? Location: http://www.jguru.com/faq/view.jsp?EID=425562 Created: May 21, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Namrata Rai (http://www.jguru.com/guru/viewbio.jsp?EID=418726 Create a subclass of Thread with a custom instance variable and initialize it in the constructor. (This is basic object-oriented programming design, BTW.) For instance, to pass in a PrintWriter from the doGet method of a Servlet:

public MyThread extends Thread { private PrintWriter myWriter; public MyThread(PrintWriter writer) { myWriter = writer; } public void run() { ... myWriter.print(...); ... } } public void doGet(...) { ... MyThread mt = new MyThread(response.getWriter()); mt.start(); mt.join(); ... } This is a very dangerous technique, however, since the doGet() method may return before the thread finishes. So watch out. That's why you need the join() call -- it waits until the thread is finished. Comments and alternative answers

Re : How do I pass a variable into a thread that can be accessed from the run() method? Author: Venugopal V.V. (http://www.jguru.com/guru/viewbio.jsp?EID=467584), Aug 6, 2001 Hi Alex..I have a situation where i need to run the bean as a seperate thread. The bean method requires 6 parameters. And the above solution you gave can be applied there? I don't need any PrintWriter or i don't need to deal with any request or response objects. I have all the 6 parameters ready with me. I just need how to call the bean method using the above method you gave.. I have written in the following way. May be you can check on this and pour in your suggestions.. *** code public class MyThread extends Thread{ // the variables passed from the A.jsp private String stD; private String endD; private int uId; private int aId; private int orgId; private int empId; public MyThread(String s,String e,int u,int a,int o,int e){ Bean a = new Bean(); stD = s; endD = e; uId = u; aId = a; orgId = o; empId = e; } public void run(){ a.methodInBean (stD,endD,uId,aId,orgId,empId); } // end of run() } // end of MyThread() *** end of code

a.methodInBean takes all the 6 parameters and finish its task. This is what i want. Will the above code suffice what i wanted? Let me know if you have any comments.. - Venu Great Help Author: abhay sahai (http://www.jguru.com/guru/viewbio.jsp?EID=940140), Jul 18, 2002

Really I was looking to such help where I can start a new bean context with each thread and this gives me enough guidence. Thanks again How to make a cookie secure ? Are secure cookies encrypted ? Location: http://www.jguru.com/faq/view.jsp?EID=425611 Created: May 21, 2001 Modified: 2001-10-24 07:25:29.328 Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985) Question originally posed by vishal ganjoo (http://www.jguru.com/guru/viewbio.jsp?EID=382910 In a protected connection (SSL), everything is encrypted, cookies too. Yes you can implement an algorithm to encrypt cookies value, why not... but you have to encrypt/decrypt handly with your own code. Comments and alternative answers

How to make cookies secure... really... Author: Stansilav Illiogovich (http://www.jguru.com/guru/viewbio.jsp?EID=1188926), Jul 27, 2004 In addition to delivering the cookies over HTTPS (SSL), and encrypting the contents such that they cannot be manipulated via Man in the Middle attacks, there is an additional requirement. The cookie must also be marked as 'secure' per RFC2109 as in... //snip Set-Cookie:JSESSIONID:893ihewwydkq2764@&@09;Path=/;secure //snip Marking the cookies this way ensures they cannot be delivered over an unencrypted session such as http. Using these three methods together makes a cookie reasonably 'SECURE' In what order are objects unbound when a session expires? Location: http://www.jguru.com/faq/view.jsp?EID=425613 Created: May 21, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by joy stalnecker (http://www.jguru.com/guru/viewbio.jsp?EID=385118 Joy, The order of the objects that are unbound when the session exires is, theoretically, unknown. Mainly it depends how the servlet comntainer stores the attributes. Normally, the selection is a Hashtable or an unsorted collections, so the 'order' of the Enumeration that they use for removing them it's not guaranteed or defined.

I've checked Tomcat sources and they use an Hashtable, so when the expire() method is called, they get the Enumeration using getAttributeNames() and the remove the objects one by one. Comments and alternative answers

HttpSessionBindingEvent Author: Bill Fox (http://www.jguru.com/guru/viewbio.jsp?EID=501381), Nov 30, 2001 I have a similar need/question. But I am approaching the question from a diferent angle. When the Session sends signals to the Bound objects, does the session send signals to all objects before the first is unbound? Or Does the first object recieve the unbinding event message, get unbound, and then the next object recieves its message. In the first scenario we can be assured all objects are present. In this second scenario, we cannot be sure which object leaves the session first. (Elvis object has just left the session) I don't know the answer, but I'm looking.... Re: HttpSessionBindingEvent Author: Bill Fox (http://www.jguru.com/guru/viewbio.jsp?EID=501381), Dec 4, 2001 Answering my own question... After reviewing the Apache Tomcat implementation, the unbound object gets the HttpSessionBindingEvent message AFTER the object is removed from the HashMap in the session. Therefore, no guarantees about what order the objects are unbound, and no guarantee that one object will be in the session when another recieves the unbound event signal. When must I use clustering -- that is, a pool of web servers instead of a single web server? Location: http://www.jguru.com/faq/view.jsp?EID=425615 Created: May 21, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Federico Crivellaro (http://www.jguru.com/guru/viewbio.jsp?EID=418395 Federico,

It really depends on the load of your system, and the hardware that you are using (or plan to use). A pool of web servers will definitely serve a higher number of pages and it will be more safe in a case of a crash of a system but, obviously, it's more expensive. In addition you need to have a good solution for making sure that once a session on a system it's started, that user will be always redirected to the same system, otherwise you have to handle your own session with a database or (bad!) with a networked file system. A single web server is normally the "starting solution" and if the system it's good and powerful enough, it could handle a really good amount of traffic. [See What servlet engines support clustering -- that is, sharing of session data across multiple load-balanced web servers? for more information. -Alex] How can I enable SSI (server-side includes) under Tomcat/Apache? Location: http://www.jguru.com/faq/view.jsp?EID=425625 Created: May 21, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Maxim Senin (http://www.jguru.com/guru/viewbio.jsp?EID=21992 If the page that contains the server side includes is a servlet or a JSP page, the only reasonable way is to use a package like SSI for Java (http://www.areane.com/java/). Comments and alternative answers

Is that the output of a servlet to be included in the output of another one? Author: Koodal Kumaran Sailappan (http://www.jguru.com/guru/viewbio.jsp?EID=300552), Jun 21, 2001 Earlier, Servlet API has SERVLET tag that can be used in html files of extension .shtml.With Servlet API 2.2 and above RequestDispatcher's include method can be used. getServletContext().getRequestDispatcher().include("/servlet/...")

refer the book for method signature. SSI, Tomcat and Apache Author: Richard Robinson (http://www.jguru.com/guru/viewbio.jsp?EID=395750), Jul 29, 2001 I'm not sure if this is the intent of your question, but I had a conflict with SSIs and Apache/Tomcat. I already had a documentRoot that was serving *.shtml files. Then I installed Tomcat (3.2.1) (I have Apache 1.3.12). I mapped the webapp root onto my existing documentRoot. The *.shtml files suddenly weren't working any more. The reason is that the tomcat-

apache.conf file that Tomcat automatically generates was including an Apache Options directive that didn't include the "Includes" argument. Although my httpd.conf file (for Apache) DID have the Options Includes..., because httpd.conf was Including the tomcat-apache.conf file as the very last line in the httpd.conf file, tomcat-apache.conf's Options line was overwriting the httpd.conf's line. The workaround for me was to copy tomcat-apache.conf to tomcat.conf (or whatever name you choose), and then to modify httpd.conf to include IT. SSIs worked. But the disadvantage now is that I have to manually modify the tomcat.conf file now after any changes to Contexts in server.xml and after shutdown.sh/startup.sh sequence. Not only this, but also have to *remember* to do it. Both of which lead to errors. Not sure this answers *YOUR* question, but it may help someone else having similar problem with SSIs, Apache (1.3.12), and Tomcat (3.2.1)

How can I enable SSI (server-side includes) under Tomcat/Apache? Author: Börries Ludwig (http://www.jguru.com/guru/viewbio.jsp?EID=514317), Oct 26, 2001 Hi, I am using ordinary SSI like I created my own context in server.xml in web.xml I added: <servlet> <servlet-name>ssi <servlet-class>org.apache.catalina.servlets.SsiInvokerServlet <param-name>isVirtualWebappRelative <paramvalue>1 The isVirtualWebappRelative had problems until version 24102001 ... and it works. Hope that helps

Boeries Re: How can I enable SSI (server-side includes) under Tomcat/Apache? Author: Stephen Morad (http://www.jguru.com/guru/viewbio.jsp?EID=852710), May 31, 2002 I'm using Tomcat 4.0.3 In order to use org.apache.catalina.servlets.SsiInvokerServlet, I had to rename CATALINA_HOME/server/lib/servlets-ssi.renametojar to CATLINA_HOME/server/lib/servlets-ssi.jar and restart Tomcat. This allowed the above servlet code to not crash with a CLASS_NOT_FOUND error. But I still can't get SSI to work. Here's what I have done. Would someone please let me know what I'm doing wrong? Created the following files/directories: CATALINA_BASE/webapps/ssi CATALINA_BASE/webapps/ssi/WEB-INF/web.xml CATALINA_BASE/webapps/ssi/index.jsp CATALINA_BASE/webapps/ssi/index.html CATALINA_BASE/webapps/ssi/index.shtml CATALINA_BASE/webapps/ssi/header.html CATALINA_BASE/webapps/ssi/footer.html I added this line to web.xml: <servlet> <servlet-name>ssi <servlet-class>org.apache.catalina.servlets.SsiInvokerServlet <param-name>isVirtualWebappRelative <param-value>1 index.* are all identical and look like this: Include header: Include footer: When I connect to http://servername/ssi/index.*, the header.html and footer.html files are not included.

Thanks for your help! --Steve Morad Re[2]: How can I enable SSI (server-side includes) under Tomcat/Apache? Author: Holger Schulz (http://www.jguru.com/guru/viewbio.jsp?EID=426304), Jun 20, 2002 Hello Stephen! Maybe this is missing in your web.xml: <servlet-mapping> <servlet-name>ssi *.shtml

Greetings from Germany Holger Re[3]: How can I enable SSI (server-side includes) under Tomcat/Apache? Author: Stephen Morad (http://www.jguru.com/guru/viewbio.jsp?EID=852710), Jun 20, 2002 Yep, that was it. Thanks a lot! Does anyone know if Tomcat can parse both JSP and SSI within the same document? For example: test.jsp <%= "Hello World" %> I know that this is a terrible coding practice (since one should use JSP includes instead of SSI when coding a JSP file) but ServletExec with iPlanet allows this type of thing and we have legacy code with this requirement. Basically it looks like Tomcat would need to be told to parse every file of this type twice, once for JSP content, and once for SSI. Thoughts? Stephen

Re: How can I enable SSI (server-side includes) under Tomcat/Apache? Author: Sanket Taur (http://www.jguru.com/guru/viewbio.jsp?EID=1178189), Aug 26, 2004 Rename Apache Tomcat-installation-directory/server/lib/servlets-ssi.renametojar to Tomcat--installation-directory/server/lib/servlets-ssi.jar. Remove the XML comments from around the SSI servlet and servlet-mapping configuration in Apache Tomcat-installation-directory/conf/web.xml. Re[2]: How can I enable SSI (server-side includes) under Tomcat/Apache? Author: rambabu v (http://www.jguru.com/guru/viewbio.jsp?EID=1213098), Nov 25, 2004 I have faced the same problem. even after uncommenting the required things in web.xml and renaming the servlet-ssi.renametojar to servlet-ssi.jar and restarting the server also i am not able to run ssi in tomcat5. Pl. do the needful. Thks in Advance. Re[3]: How can I enable SSI (server-side includes) under Tomcat/Apache? Author: Ricardo Fernandes (http://www.jguru.com/guru/viewbio.jsp?EID=1232117), Mar 11, 2005 same problem here, after uncomment the lines in the web.xml and the renametojar my apache tomcat still ignores the includes How can I force the web browser to cache my images? Location: http://www.jguru.com/faq/view.jsp?EID=428820 Created: May 25, 2001 Author: Salman Khan (http://www.jguru.com/guru/viewbio.jsp?EID=303261) Question originally posed by Eike Hirsch (http://www.jguru.com/guru/viewbio.jsp?EID=44417 In JavaScript, do

var image1 = new Image(); image1.src = "xyz.gif";

And then use image1.src wherever you were using the xyz.gif This will cache the image. See also http://www.jguru.com/faq/view.jsp?EID=377 [Note: there seems to be a bug in IE 5.5 preventing this from working. See the forum thread for details. -A] Comments and alternative answers

RE: How can I force the web browser to cache my images? Author: Daniel Hooker (http://www.jguru.com/guru/viewbio.jsp?EID=1203506), Oct 5, 2004 Is there anyway of doing this server side only (e.g. no client script) Dan. Are there any good code examples demonstrating the use of Servlet 2.3 Filter API? Location: http://www.jguru.com/faq/view.jsp?EID=430553 Created: May 29, 2001 Author: surya mp (http://www.jguru.com/guru/viewbio.jsp?EID=425333) Question originally posed by Romin Irani (http://www.jguru.com/guru/viewbio.jsp?EID=73205 There is a good article at O'Reilly's OnJava.com portal demonstrating the use of Servlet Filters at http://www.onjava.com/pub/a/onjava/2001/05/10/servlet_filters.html Comments and alternative answers

Writing Servlet 2.3 Filters Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985), May 30, 2001 Also check Writing Servlet 2.3 Filters Re: Writing Servlet 2.3 Filters Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985), May 30, 2001 sorry it's the same. SiteMesh Author: Mathias Bogaert (http://www.jguru.com/guru/viewbio.jsp?EID=202039), May 30, 2001 SiteMesh uses Servlet 2.3 filters, and is open source. Check it out at http://www.opensymphony.com/sitemesh/. Where can I learn (more) about Java Applets? Location: http://www.jguru.com/faq/view.jsp?EID=431179 Created: May 30, 2001 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Check out the jGuru Applets FAQ. Where can I learn (more) about Application Servers? Location: http://www.jguru.com/faq/view.jsp?EID=431183 Created: May 30, 2001 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Check out the jGuru AppServer FAQ.

Where can I learn (more) about Java's suport for internationalization (I18N)? Location: http://www.jguru.com/faq/view.jsp?EID=431191 Created: May 30, 2001 Modified: 2001-08-18 19:04:05.76 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Check out the jGuru I18N FAQ. Where can I learn (more) about Java's I/O (input/output, IO) capabilities? Location: http://www.jguru.com/faq/view.jsp?EID=431192 Created: May 30, 2001 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Check out the jGuru IO FAQ. Where can I learn (more) about Java's reusable software components, JavaBeans? Location: http://www.jguru.com/faq/view.jsp?EID=431197 Created: May 30, 2001 Modified: 2001-06-16 16:04:06.477 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Check out the jGuru JavaBeans FAQ. Comments and alternative answers

Advanced Java Programming Author: Naveen Madenhalli (http://www.jguru.com/guru/viewbio.jsp?EID=1253053), Jul 13, 2005 If a applet client wants to send a request to a server, what are the various steps to be followed? Where can I learn (more) about the JavaScript scripting language? Location: http://www.jguru.com/faq/view.jsp?EID=431204 Created: May 30, 2001 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Check out the jGuru JavaScript FAQ. Where can I learn (more) about JDBC, Java's Database Connectivity solution? Location: http://www.jguru.com/faq/view.jsp?EID=431206 Created: May 30, 2001 Modified: 2001-07-24 09:55:24.202 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Check out the jGuru JDBC FAQ. Where can I learn (more) about Java JSP (JavaServer Pages)? Location: http://www.jguru.com/faq/view.jsp?EID=431214 Created: May 30, 2001 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4)

Check out the jGuru JSP FAQ. Comments and alternative answers

JSP Tutorial Author: Steve Erbert (http://www.jguru.com/guru/viewbio.jsp?EID=291279), Jun 26, 2001 www.jsptut.com has a very good beginners introduction to JSP. Re: JSP Tutorial Author: D.Narasimham Dhurjati (http://www.jguru.com/guru/viewbio.jsp?EID=460448), Jul 24, 2001 Yes. I need jsp tutorial Where can I learn (more) about Java's support for developing multithreaded programs? Location: http://www.jguru.com/faq/view.jsp?EID=431248 Created: May 30, 2001 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Check out the jGuru Threads FAQ. Where can I learn (more) about Apache's Java-based server, Tomcat? Location: http://www.jguru.com/faq/view.jsp?EID=431251 Created: May 30, 2001 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Check out the jGuru Tomcat FAQ. Comments and alternative answers

jakarta.apache.org Author: Norman Hanson (http://www.jguru.com/guru/viewbio.jsp?EID=462048), Dec 26, 2001 jakarta.apache.org is really the absolute source for info on tomcat. Re: jakarta.apache.org Author: Norman Hanson (http://www.jguru.com/guru/viewbio.jsp?EID=462048), Dec 26, 2001 bum link... jakarta.apache.org Where can I learn (more) about using various XML (eXtensible Markup Language) technologies (such as DTDs, Schemas, SOAP, DOMs, etc.) with Java? Location: http://www.jguru.com/faq/view.jsp?EID=431956 Created: May 31, 2001 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4)

Check out the jGuru XML FAQ. Where can I learn (more) about Sun's peer to peer, "Project JXTA"? Location: http://www.jguru.com/faq/view.jsp?EID=431963 Created: May 31, 2001 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Check out the Project JXTA site. How do I configure JAAS for use with servlets? Location: http://www.jguru.com/faq/view.jsp?EID=432434 Created: Jun 1, 2001 Author: tippu sultan (http://www.jguru.com/guru/viewbio.jsp?EID=417083) Question originally posed by manish sharan (http://www.jguru.com/guru/viewbio.jsp?EID=142288 There is no need for any special configuration for JAAS to be used with the Tomcat server. Make the settings as we do to execute an application program, i.e., changing the java.security,java.policy file in the jre/lib/security of the jdk1.3. Comments and alternative answers

Configurtion is needed Author: tippu sultan (http://www.jguru.com/guru/viewbio.jsp?EID=417083), Jun 2, 2001 The configuration will differ from server to server , and most of the server till today doesnot support jaas authorisation for ex., Websphere and weblogic . and the authentication is concerned weblogic supports jaas authentication . i don't have idea whether which other servers support jaas authentication ., Upto configure of jaas with servlets , configuration should be made with webserver not with servlets particularly for ex., for making jaas authentication in weblogic6.0 we should set the system property of weblogic.server.policy to the policy file (not a config file as we work in command prompt) to the policy file where we have mentioned about which login module it should use. finally, let me make it very clear configuration will differ from webserver to webserver till today JAAS Author: erdkal erdkal (http://www.jguru.com/guru/viewbio.jsp?EID=560642), Dec 4, 2001 Hi Sultan, you write, that is no need for any special configuration for JAAS to be used with the Tomcat server. That wondered me, because I don't found any example, tutorial, which describes the using of JAAS with Tomcat. So can you describe more details, what for example you make. Erdal Are there any monitoring tools in JRun? Location: http://www.jguru.com/faq/view.jsp?EID=433241 Created: Jun 3, 2001 Author: Alessandro A. Garbagnati

(http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by venu gopalan (http://www.jguru.com/guru/viewbio.jsp?EID=394235 I don't know anything about JRun, but I think that you can use any external profiler tools like the one mentioned in this answer: http://www.jguru.com/faq/viewquestion.jsp?EID=407939. I personally use OptimizeIt! (www.optimizeit.com) with Tomcat and Resin. The other one mentioned is JProbe (www.jprobe.com) How can I get a list of all the session objects in an application scope? Location: http://www.jguru.com/faq/view.jsp?EID=433242 Created: Jun 3, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Jose Compadre Junior (http://www.jguru.com/guru/viewbio.jsp?EID=260394 As many other guru have already told you, there is no way to do that with Servlets 2.2. Previously there were two methods, but they both have been deprecated and they return null. The new Servlets (2.3), even if they are not going to provide any direct method to do solve your problem, will provide additional tools for helping you building your own solution. I'm talking about the Application Events. You will be able to create a listener to a session object that will insert, the session id into, for example, an HashMap, and authomatically will remove it when the session is destroyed or invalidated. When using com.oreilly.servlet.MultipartRequest to upload files, I get a java.io.UnsupportedEncodingException: ISO-8859-1 -- What's up? Location: http://www.jguru.com/faq/view.jsp?EID=433243 Created: Jun 3, 2001 Modified: 2001-07-23 10:26:33.745 Author: tansel halic (http://www.jguru.com/guru/viewbio.jsp?EID=403072) Question originally posed by tansel halic (http://www.jguru.com/guru/viewbio.jsp?EID=403072 The problem is not come out as improper META tag of html. becasuse java is providing the ISO-8859-1 encoding standard. the problem source is com.oreilly package. i look inside the source and i realize that the econding type is written wrong. it is written as "ISO-8859-1". but it must be "ISO8859_1". i corrected it. i could do it because the source code is available. The same problem appears in Java Mail API. but i cant see the source and cant modify. Comments and alternative answers

JavaMail source Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7), Jun 3,

2001 You can always get the JavaMail source directly from Sun. It just doesn't come with the implementation. Oreilly Package Author: Rajanish Nagwekar (http://www.jguru.com/guru/viewbio.jsp?EID=285484), Jun 4, 2001 I am also using the code given in oreilly servlet book to upload files and it is working w/o any errors. And the encoding standard, which is hard coded, is ISO-8859-1. So I feel that the problem might not be with the encoding standard or at least not the one pointed out. Please correct me if I am wrong. Upload problem Author: Alex Skrypnik (http://www.jguru.com/guru/viewbio.jsp?EID=388047), Jul 31, 2001 When I put enctype="multipart/form-data" in the form description, after submit I got the following error:

The page cannot be displayed the same for jsp and servlets (in case of servlets using, I have doGet and doPost methods implemented). I use Tomcat 3.2.1, JBuilder5. html code (jsp handler) is the following:

Re: Upload problem Author: Alex Skrypnik (http://www.jguru.com/guru/viewbio.jsp?EID=388047), Jul 31, 2001 I checked Opera 512 browser - all is ok. I used MS IE 5.5 before. Re: Oreilly Package Author: Neil Hornbeck (http://www.jguru.com/guru/viewbio.jsp?EID=708152), Jan 7, 2002 We use the Oreilly package, and only experience this problem from certain machines using IE 5.5. I did a dump of the header, and found that certain values for headers were duplicated. (example: CONTENT_TYPE = multipart/form-data; boundary=---------------------------7d2dc1180a50, multipart/form-data; boundary=---------------------------7d2dc1180a50)

This confuses the Oreilly parser, which looks for the boundary to parse the data, and picks up the whole string after the first 'boundary='. How can I create a protected, "restricted" website? I.e., where someone can only access the site by e.g., entering a password. Location: http://www.jguru.com/faq/view.jsp?EID=439953 Created: Jun 15, 2001 Modified: 2001-06-17 14:04:04.509 Author: JIA Java Italian Association (http://www.jguru.com/guru/viewbio.jsp?EID=414973) Question originally posed by hendra winata (http://www.jguru.com/guru/viewbio.jsp?EID=425301 Normally web servers have their own protection system already in place. If you are running Apache, for example, or anothe NCSA compliant web server, you can rely on the standard basic authentication. You can take a look ath this interesting article for Apache, and eventually check the documentation of your web server to see if they have something similar. In addition, on the Servlet-Container side, I'll suggest you to take a look at the Servlet 2.2 Specification. Chapter 11 is entirely dedicated to the "Security" topic and can give you a clear understanding of what you can achieve with a Servlet Container. In addition, take a look at the DTD of web.xml, the Web Application Descriptor, Paragraph 3.12 and a security example at Paragraph 13.3.2. Comments and alternative answers

Look for FORM-BASED AUTHENTICATION Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jun 17, 2001 See What is FORM based login and how do I use it? Also, what servlet containers support it? Why does my Servlet request lose UTF-8 encoding in passed-in attributes? Location: http://www.jguru.com/faq/view.jsp?EID=440403 Created: Jun 17, 2001 Author: Rahul kumar Gupta (http://www.jguru.com/guru/viewbio.jsp?EID=4809) Question originally posed by Satish Murthy (http://www.jguru.com/guru/viewbio.jsp?EID=322353 [I use setAttributes() in the HttpServletRequest object to pass UTF-8 strings to a servlet. On the receiving servlet, I receive only '?' for each unicode character. What should I do?] There is no need to set the attribute ,you have to just the set the Content type in each and every page(JSP/ Servlets) and rest is atuomatically being taken care of. You can set the content type like this

String contentType= "text/html;charset=UTF-8";

response.setContentType(contentType); How do I display a page to the user when basic authorization fails or is cancelled? Location: http://www.jguru.com/faq/view.jsp?EID=440418 Created: Jun 17, 2001 Author: Nicolai Bartkowiak (http://www.jguru.com/guru/viewbio.jsp?EID=76332) Question originally posed by Nicolai Bartkowiak (http://www.jguru.com/guru/viewbio.jsp?EID=76332 As I wrote in my first message the apache web server does not perform the authentication in this case but the servlet does. So the web-server could not send his error- page because the browser does not send any information about pressing the cancel-button. The solution is, that you not only have to send an HttpServletResponse with res.setStatus(HttpServletResponse.SC_UNAUTHORIZED); but in addition you have to send content through the response's PrintWriter which is shown by the browser if the user cancels authentication. Can I use a java servlet to check if a browser is using 128 bit encryption? Location: http://www.jguru.com/faq/view.jsp?EID=444019 Created: Jun 23, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by james lee (http://www.jguru.com/guru/viewbio.jsp?EID=297098 [I know that for Netscape, the user agent in the request header has a "U;" that indicate that the browser is using 128 bit encryption. What about IE?] Unfortunately there is no standard way to get that piece of information. The one you've mentioned, as you probably know, it's not a standard solution and there is no way to guarantee that it will be maintained in the future. Comments and alternative answers

browser encryption Author: Orest Guran (http://www.jguru.com/guru/viewbio.jsp?EID=445770), Jun 26, 2001 I used the following bit of code to determine the browser encryption: String cipherSuite = (String)req.getAttribute("javax.net.ssl.cipher_suite"); This returns a string that looks something like: Netscape 4.73: RC4-Export_40 Netscape 6.0: RC4_128 IE5.01: RC4_128 From there you can see the Cyryptographic Suite and key length see: http://java.sun.com/products/servlet/2.1/api/javax.servlet.ServletRequest.html and http://java.sun.com/j2se/1.4/docs/guide/security/jsse/JSSERefGuide.html#CipherSuite and http://java.sun.com/security/ssl/API_users_guide.html for more details.

How can we hide the html source code when the user tries to view the source code from the browser's "view source" file menu option? Location: http://www.jguru.com/faq/view.jsp?EID=444156 Created: Jun 23, 2001 Modified: 2001-06-24 18:44:02.929 Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985) Question originally posed by ramesh babu (http://www.jguru.com/guru/viewbio.jsp?EID=411199 [Short answer: no, it's not possible, since the source code *is* the response. If the user wants to see your source, he can. However, here's a clever hack... -A] Yes it's possible, I've done it sometimes ago. You can make a JavaScript decoding algorithm executing it at runtime... But, it's very simple to reverse it for people knowing JavaScript... The following code will hide everything in most JavaScript enabled browsers: I've tried it with IE5 and Opera5 and it works perfectly, but Netscape decodes it when showing the source. Cut and paste this in an html file and open it... <SCRIPT LANGUAGE="JavaScript1.2">
+ + + + + + + + + + + + + + + + + + + +

"ifkefajbdbbbpahghchalbeacchalfjefeedbaaakbeaacleoekfmaiclbgalegf" + "ighbnbbbdbjh", "jGuru")); //--> Comments and alternative answers

Simple encoding routine of the previous example Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985), Jun 24, 2001 <SCRIPT LANGUAGE="JavaScript1.2"> > 4) + 97); } return encoded; } //-->

Re: Simple encoding routine of the previous example Author: Dan McTaggart (http://www.jguru.com/guru/viewbio.jsp?EID=1186345), Jul 15, 2004 How do you use the encoder? See also... Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jun 25, 2001 See also How can I disable the user viewing the source code... This is how you hide the code for your Internet explorer browser: Author: andreas strauman (http://www.jguru.com/guru/viewbio.jsp?EID=1255912), Jul 31, 2005 Maby this works on other explorers to, but iæve only tryed this in explorer.

if you write your code like this: <script> //
stuff>")); //-->

then the page will be blank.

you can of course write more code under the tag.

Why doesn't Tomcat find classes in jars in the WEB-INF/lib directory? Location: http://www.jguru.com/faq/view.jsp?EID=444337 Created: Jun 24, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Taruvai Subramaniam (http://www.jguru.com/guru/viewbio.jsp?EID=23676 According to the Servlet 2.2 specifications: 9.4: Directory Structure A web application exists as a structured hierarchy of directories. The root of this hierarchy serves as a document root for serving files that are part of this context. For example, for a web application located at /catalog in a web server, the index.html file located at the base of the web application hierarchy can be served to satisfy a request to /catalog/index.html. A special directory exists within the application hierarchy named “WEB-INF”. This directory contains all things related to the application that aren’t in the document root of the application. It is important to note that the WEB-INF node is not part of the public document tree of the application. No file contained in the WEB-INF directory may be served directly to a client. The contents of the WEB-INF directory are: • • •

/WEB-INF/web.xml deployment descriptor /WEB-INF/classes/* directory for servlet and utility classes. The classes in this directory are used by the application class loader to load classes from. - /WEB-INF/lib/*.jar area for Java ARchive files which contain servlets, beans, and other utility classes useful to the web application. All such archive files are used by the web application class loader to load classes from.

I've never had this problem with either Tomcat and Resin, unless the file was not a jar but a zip (It happened with Oracle's drivers that are packaged ina file called classes12.zip). Comments and alternative answers

Make sure the jar file has the correct path Author: Newman Shee (http://www.jguru.com/guru/viewbio.jsp?EID=445216), Jun 25, 2001 Hi, I ran into the exact same problem today with TomCat cannot find the classes in the jar file. After debugging through, it turns out that the problem is the jar file has the wrong path to the java class in it. After re-jar the java classes with the correct path, everything worked. Newman Shee Re: Make sure the jar file has the correct path Author: Aris Javier (http://www.jguru.com/guru/viewbio.jsp?EID=445452), Jun 26, 2001 There was a bug in tomcat 3.1 that did not permitted to perform this cool feature. Try to use tomcat 3.2.x or later and it will work, i'm using tomcat 3.2.2 and it is ok. Aris Re: Make sure the jar file has the correct path Author: Jan Viaccava (http://www.jguru.com/guru/viewbio.jsp?EID=505214), Oct 2, 2001 Hi, I have the same problem. What do you mean with wrong path??? And how can I fix the problem ??? Jan Re: Make sure the jar file has the correct path Author: Tim Cooke (http://www.jguru.com/guru/viewbio.jsp?EID=756423), Mar 14, 2002 Dear Newman I'm using Tomcat 4.0.1, and I have the same problem as logged by Taruvai, so I'm both interested and confused to hear that your JAR contained the "wrong" path for your classes. Please could you give an example of a wrong path and a right path? Kind regards Tim Cooke Re[2]: Make sure the jar file has the correct path Author: Newman Shee (http://www.jguru.com/guru/viewbio.jsp?EID=445216), Mar 14, 2002 The problem I ran into was an error on my part. The jar file that I used has the wrong path. By that I meant the class file should be under a directory called

com/avid/mmserver/util, but when I jar the class files, I put them under the wrong directory. I would suggest you do the following: 1. 1. do a jar tvf on the jar file and look at the directory where the class files live. 2. 2. take a look at the .class files in your build environment(when running outside of Tomcat0. 3. 3. make sure they are the same. Newman Re[3]: Make sure the jar file has the correct path Author: Tim Cooke (http://www.jguru.com/guru/viewbio.jsp?EID=756423), Mar 14, 2002 Newman Thanks for your very fast response and help. I've discovered something about the location of JAR files that makes it all work for me, and posted the information on another thread. Regards Tim Cooke Re[4]: Make sure the jar file has the correct path Author: Alan Lukens (http://www.jguru.com/guru/viewbio.jsp?EID=948053), Jul 12, 2002 I have had similar problems. The manifest.mf file in the META-INF folder stores the jar file information. See "java.sun.com/j2se/1.3/docs/guide/jar/jar.html" for details. Re[5]: Make sure the jar file has the correct path Author: Michael Civello (http://www.jguru.com/guru/viewbio.jsp?EID=935119), Jul 30, 2002 I'm seeing something even more odd... My app was running fine in tomcat 3.2.3 and as I developed I saved full copies of good working points. One day after a reboot, tomcat decided to stop seeing my jars in the webapp lib dir. I didn't change any of the tomcat libs or settings and I even restored to a previously working version of my app but it just doesn't find them anymore. If I dump the jar into the TOMCAT_HOME/lib, then it finds it. Anyone ever see such a change? I reinstalled tomcat and it continues... Solved!

Author: Michael Civello (http://www.jguru.com/guru/viewbio.jsp?EID=935119), Jul 31, 2002 My lib problem went away when I nuked the CLASSPATH that I had in my environment. It essentially was making TOMCAT have two classes111.zip files in the path once it included it's $TOMCAT_HOME/lib files. I don't know why that made a difference but it did. Thought you should know... MJC Re: Make sure the jar file has the correct path Author: Karl Stahmer (http://www.jguru.com/guru/viewbio.jsp?EID=1205657), Oct 15, 2004 Had the same problem with Tomcat 5.0.28. For me, this post was helpful. Say you're creating class files from a DOS (Windows) command window in the directory (folder) C:\Java and your class files are in the package: com.mycompany.mypackage

Assume your WEB-INF\web.xml deployment descriptor is correct. Then place your classes in the directory... C:\Java\com\mycompany\mypackage

Create your jar file, in the C:\Java directory, via jar cvf myclasses.jar com\mycompany\mypackage\*.class

Place myclasses.jar in WEB-INF\lib (you no longer need WEBINF\classes\*). Stop and restart Tomcat. Now Tomcat will find your com.mycompany.mypackage.*.class classes. How do I get the content (not the name) of an option in a choice box? Location: http://www.jguru.com/faq/view.jsp?EID=444351 Created: Jun 24, 2001 Modified: 2001-06-24 19:31:14.516 Author: thomas dietrich (http://www.jguru.com/guru/viewbio.jsp?EID=413665) Question originally posed by J Allen (http://www.jguru.com/guru/viewbio.jsp?EID=437322 [ The cleanest solution is to build the HTML yourself, and make the "value" attribute something you know, like the database id, or even the content itself. From getParameter() returns a value of a choice box, I ...:

Alessandro A. Garbagnati, Jun 19, 2001 Hi, If I've understood your problem, you have somthing like this: <select name=whatever> The request.getParameter("whatever") it's returning you the first value selected (or the only one in a case of a single selection), and there is no way, from the request object, to get the text. The reason it's simple. That information it's not part of the request when you submit the form. The only information passed it's the value. There are two solutions. One is to maintain the array (or map or whatever you use for generating the dropdown box) between responses so, when you get the request you read the value and you get back your text from the array (or map or etc.). The secon solution is to change the value of the option to include the text, maybe with some kind of separator (could use |), and when you get the value, you just split in the value and the text. Personally I consider cleaner the first solution. However, if you want to get clever, read on ... -Alex] Hello J Allen,

This is a working example of cheesiness at it's finest. :) the fields are fully qualified so that you can see what they look like before you start taking short cuts. Sincerely, Thomas Dietrich Is there a freeware or shareware Web forum application written in Servlet or JSP? Location: http://www.jguru.com/faq/view.jsp?EID=444360 Created: Jun 24, 2001 Author: Alessandro A. Garbagnati

(http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by James Chen (http://www.jguru.com/guru/viewbio.jsp?EID=441020 Check out Jive. From the site: Jive is forum software that allows threaded discussions on websites. It features excellent performance, user-defined "skins" to completely change the look, feel, and function of forums, and a plugin API that can provide advanced features such as onthe-fly translation, content filters, or almost anything else. Even better, Jive is Open Source. That means that it's completely free to use on your own site, and more importantly, has a dedicated community that continually improves the software. Comments and alternative answers

Need to know more about Jive Author: kvt kvt (http://www.jguru.com/guru/viewbio.jsp?EID=317336), Jun 25, 2001 What is the website of jive. Have you ever used the Jive Skin concept. I am really interested in the skin concept. Re: Need to know more about Jive Author: Jeff Judge (http://www.jguru.com/guru/viewbio.jsp?EID=447777), Jun 29, 2001 You can find jive at http://jivesoftware.com. I've set it up a few times, and I have to admit that it is very easy to setup and administer. Enjoy.. Re: Need to know more about Jive Author: Ritu kumar (http://www.jguru.com/guru/viewbio.jsp?EID=314981), Dec 11, 2001 I want to know more about applying skins to the jive forum. Do you know of any examples showing how to go about it ? Thanks, Ritu Another Alternative Author: Michael Rimov (http://www.jguru.com/guru/viewbio.jsp?EID=295251), Jul 17, 2001 JCorporporate's eForum provides another servlet-implemented online forum Re: Another Alternative Author: Michael Sun (http://www.jguru.com/guru/viewbio.jsp?EID=943802), Jul 10, 2002 Where can I find it ? Jive is nolonger an open project, is there any other alternative? Re[2]: Another Alternative Author: Sandy Canfield (http://www.jguru.com/guru/viewbio.jsp?EID=999432), Sep 15, 2002 Try: http://yazd.yasna.com/

Can somebody tell me the advantages/disadvantages of Allaire JRun versus Apache Tomcat? Location: http://www.jguru.com/faq/view.jsp?EID=444367 Created: Jun 24, 2001 Author: Nick Makris (http://www.jguru.com/guru/viewbio.jsp?EID=250647) Question originally posed by Anandanath Banerji (http://www.jguru.com/guru/viewbio.jsp?EID=440091 JRun is a J2EE compatible container. For this reason it supports (besides JSPs and Servlet) EJB as well. JRun is actually a plugin on a web server in order to redirect JSP and servlet calls from the web server (propably non java enable i.e IIS) into is's WEB container. Tomcat is a plugin itself but implements only the WEB container (i.e it can run only JSPs and Servlets -no EJB o JTS or other APIs of J2EE) Comments and alternative answers

Allaire JRun Author: Sergi Arrufat (http://www.jguru.com/guru/viewbio.jsp?EID=405615), Jun 25, 2001 Meanwhile Tomcat is open source, Jrun is proprietary software. If you are interested on a open source J2EE container, I recommend you Jboss. You can get it for free in http://www.jboss.org. Re: Allaire JRun Author: Ajay Prabhakaran (http://www.jguru.com/guru/viewbio.jsp?EID=481380), Oct 2, 2001 Do i have JDBC Connection Pooling support in Tomcat. This i beleive is available in JRun. Thanks in advance Re: Re: Allaire JRun Author: Ajay Prabhakaran (http://www.jguru.com/guru/viewbio.jsp?EID=481380), Oct 2, 2001 Does Tomcat support JDBC Connection Pooling.. This i beleive is available in JRun. Thanks in advance Re: Re: Re: Allaire JRun Author: Dev Ramachandren (http://www.jguru.com/guru/viewbio.jsp?EID=518866), Oct 12, 2001 No. Tomcat does not support JDBC Connection pooling. U will need a 3rd party 100% JDBC driver which implements all JDBC 2.0 and preferably 3.0 to do that for you. You could use other drivers but a 100% JDBC driver is better.

I have more questions/thoughts to pros/cons of Tomcat over JRun. Author: Ravi Mittal (http://www.jguru.com/guru/viewbio.jsp?EID=1134303), Jul 20, 2004 We have live JRun production server. Can I run JRun on port 80? I tried but it crashes very often. Is JRun 4 Updater 2 a stable patch to use? Can Tomcat work efficiently on dual/multi processor server than JRun? What is more advisable to use for production machine JRun/Tomcat? Can Tomcat produce extensive web logs like IIS (If I use the JRun connector to IIS) and in what format does the Tomcat logs are generated: W3C Log format? I need the logs because I need the webtrends log analyzer to parse to give me/everybody extensive web statistics reports. Where do I get source code for an Internet search engine? Location: http://www.jguru.com/faq/view.jsp?EID=445901 Created: Jun 26, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by dhrutiman mishra (http://www.jguru.com/guru/viewbio.jsp?EID=440184 See How do I add a search engine to my web site? (though this covers searching your site, not the whole Internet). Running a Web Crawler is a pretty big job. Do you have a couple of terabytes of free disk space? Inside a JSP, how to represent private methods and call them? Location: http://www.jguru.com/faq/view.jsp?EID=445904 Created: Jun 26, 2001 Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985) Question originally posed by Amit Rosner (http://www.jguru.com/guru/viewbio.jsp?EID=433821 [I wrote a servlet, and I want to convert it to a JSP file. Usually it is very simple - all of the code of the "doGet" method directly goes into the JSP. But now I have a private method in that servlet, that the “doGet” method calls with various arguments. How do I put that in a jsp? ] Use a declaration scriptlet:

<%!

private void foo() { System.out.println("foo"); }

%> <%

foo();

%> Comments and alternative answers

Two possible ways Author: Krishna Krishna (http://www.jguru.com/guru/viewbio.jsp?EID=440479), Jun 28, 2001 you can either place the methods enclosed within JSP tags <% ..... %> with in a JSP page directly OR you can convert the servlet into a Java Program with whatever methods and functionality u need and then use 'Bean' tag in the JSP page to invoke methods u need to access. This should help, Good Luck. The catch is that .... Author: drit . (http://www.jguru.com/guru/viewbio.jsp?EID=454295), Aug 1, 2001 The catch is that in private methods, you cannot split your htmls and java code! This is what I encountered with tomcat v3.2. I have worked around with <%@ include ... tag> but that is still ugly. I am interested to listen to any other workarounds. How can I submit an HTTP POST request when the user clicks a normal HREF link? Location: http://www.jguru.com/faq/view.jsp?EID=445910 Created: Jun 26, 2001 Author: Sonu TheKool (http://www.jguru.com/guru/viewbio.jsp?EID=3468) Question originally posed by puneet jain (http://www.jguru.com/guru/viewbio.jsp?EID=423518 You can post to a servlet using JavaScript through HREF in the following way. Any parameters you need to send can be sent using the "hidden" parameters. Comments and alternative answers

Another approach if separate form doesn't work... Author: Carol Lietz (http://www.jguru.com/guru/viewbio.jsp?EID=446419), Jun 27, 2001 If you can't wrap the href in it's own form, then you could call Javascript to do the submit. In this example, the action on the form (when user clicks the submit button) is to go to java.sun.com. But if the user follows the "go to www.ugs.com" link, then they would be directed there via post by the javascript. Servlet would output ...

JS: function submitMe() { document.MyForm.action="http://www.ugs.com/"; document.MyForm.target="targetName"; document.MyForm.submit(); return; } HTTP GET request Author: zong zhang (http://www.jguru.com/guru/viewbio.jsp?EID=491205), Sep 23, 2001 I am using the answer to GET html file from a servlet. I modified the code like this: But When I click the "Click Me", I got the message:"bad gateway, DNS error". Where am I wrong? Please Help. Thanks Zong Re: HTTP GET request Author: Sharat N (http://www.jguru.com/guru/viewbio.jsp?EID=502507), Sep 26, 2001 Check it doGet Method is defined in your servlet.. How do I assign the user's role without using a login form? Location: http://www.jguru.com/faq/view.jsp?EID=445915 Created: Jun 26, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Victor Serrato (http://www.jguru.com/guru/viewbio.jsp?EID=440450 Victor, Chapter 11 of the Servlet 2.2 specification is entirely related to Security. Basically the concept is that you can use the standard http authentication schemes (i.e.: basic, digest). This means that you can authenticate a user among a database (or, for example, another source) without developing html login forms. For Tomcat 3.2.x there is an interesting example of a JDBC Realm.

For additional info, I strongly suggest to read Chapter 11 (Security) and Chapter 13 (Deployment Descriptor) of the Servlet 2.2 specifications that you can download from Sun. [In Servlet 2.3 spec, the Security chapter is now 12. Also - There's no way to programmatically set the user (e.g. request.setRemoteUser), but if you need to, you can just use a session variable to let yourself know that this user is "ok." -Alex] Comments and alternative answers

But then ... Author: Christian Burger (http://www.jguru.com/guru/viewbio.jsp?EID=750308), Feb 7, 2002 ... I can not use the standard security features of the web container to protect some realms in accordance with the user group the user is belonging to ... Why doesn't Response.sendRedirect() work after the binding of Tomcat with Apache server? Location: http://www.jguru.com/faq/view.jsp?EID=445939 Created: Jun 26, 2001 Author: Oren Deri (http://www.jguru.com/guru/viewbio.jsp?EID=63019) Question originally posed by Tan HN (http://www.jguru.com/guru/viewbio.jsp?EID=40344 Tomcat communicates with the Apache server using localhost. When tomcat gets the request it's from the Apache on localhost, so it also redirects the response to localhost. Try the following:

response.sendRedirect( "http://" + request.getHeader("host") + "/" + yourFileName ); Comments and alternative answers

Redirect Author: Lee Evans (http://www.jguru.com/guru/viewbio.jsp?EID=454053), Jul 12, 2001 don't know if this applies to you but if authentication is required for a servlet before authentication for apache then the redirect does not work. if apache authentication has been gained first then the redirect works fine. the only way we have got it to work at the moment is using the HTML META tag with type refresh content 0 and the url of the redirection, this goes through apache again so works fine hope this helps you

Re: Redirect Author: Michael Smith (http://www.jguru.com/guru/viewbio.jsp?EID=970016), Jul 31, 2002 My test app will redirect but it takes at least minute to redirect..... I can open a new browser, paste in the URL and get to the page I want to go to before this command redirects me the page. Possible solution Author: Jermaine Stewart (http://www.jguru.com/guru/viewbio.jsp?EID=1176573), Jun 6, 2004 I too noticed this. However, I used javascript to over come this. Since my conditions to relocate were in an if statement, I changed... response.sendRedirect(url);

to %> <script type="text/javascript">location=url <%

Is there a way I can get the context name and the servlet path from the init method of a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=445946 Created: Jun 26, 2001 Author: Uwe Hanisch (http://www.jguru.com/guru/viewbio.jsp?EID=438858) Question originally posed by Jayaprakash A (http://www.jguru.com/guru/viewbio.jsp?EID=284375 Well, up to now the only way to get your context path is to call getContextPath() on a HttpServletRequest object. But this object you receive only with a HTTP request to your HttpServlet. E.g.: protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException,IOException { String ctxPath = req.getContextPath(); ... } I think it would be usefull, if you can obtain the context path also from the ServletContext. But at the moment I see no chance to get the context path in the HttpServlet init() method. Comments and alternative answers

Quite serious issue Author: David Tunkrans (http://www.jguru.com/guru/viewbio.jsp?EID=728671), Jan 21, 2002 There seems to be very few ways to query for deployment information from the runtime environment. eg

-> ask the servlet which application or context it belongs to. If anyone knows how to do this (or a "fix"), please let me know. ([email protected]) Re: Quite serious issue Author: Niko Schmuck (http://www.jguru.com/guru/viewbio.jsp?EID=408882), Mar 1, 2002 The only possibility i see at the moment is to use an ugly hack with the help of javax.servlet.ServletContext .getRealPath(java.lang.String path) (and use empty string for path). From the returned file path subtract the root path

(if you have one at hand) or just use the last fragment (directory) as the name of the web application context. I'm sorry, i know that this is far from optimal, but ... Niko Context path in init() Author: Mihai Iancu (http://www.jguru.com/guru/viewbio.jsp?EID=837190), Apr 13, 2002 The java servlet api does not have a method for getting the context path of an application other than for getContextPath() on a HttpServletRequest object. This can be too late for some applications. One can try to use the ServletConfig (actually the vendor specific implementation) to achieve this goal. But this means that the portability of your code is limited (but from my experience, developers will have a limited range of web/app server implementations anyways). The (ServletConfig) implementation for WebSphere 4.x is com.ibm.servlet.engine.webapp.WebApp and for WebLogic 6.x weblogic.servlet.internal.WebAppServletContext. Use for WebSphere 4.x: WebApp ibmWebApp = (WebApp)servletContext; String contextPath = ibmWebApp.getRootURI();

Use for WebLogic 6.x: WebAppServletContext beaWebApp = (WebAppServletContext)servletContext; String contextPath = beaWebApp.getContextPath();

For other implementations, one should consult the web/app server documentation. Re: Errata Context path in init()

Author: Mihai Iancu (http://www.jguru.com/guru/viewbio.jsp?EID=837190), Apr 13, 2002 I meant vendor specific ServletContext implementation... and not ServletConfig. How do i know from which page the request has come from? Location: http://www.jguru.com/faq/view.jsp?EID=446592 Created: Jun 27, 2001 Author: cedric chin (http://www.jguru.com/guru/viewbio.jsp?EID=383299) Question originally posed by Gopal Saha (http://www.jguru.com/guru/viewbio.jsp?EID=10163 [I have a JSP which can be called from multiple pages . On exiting from the page it must go back to the particular page from where it was requested.How do i know the URL of the calling page?] Try this:

String refererPage = request.getHeader("referer"); [Tim Delesio adds: You can also create a hidden field in the form and then use a if statement to check and route accordingly. Or, if the parameter you've added is called 'original',

response.sendRedirect( request.getParameter("original") ); -Alex] Comments and alternative answers

Referer isn't reliable Author: Frank Steidinger (http://www.jguru.com/guru/viewbio.jsp?EID=34216), Jun 28, 2001 I'd recommend you use the hidden field. While it is certainly more of a hassle it is also more reliable. The referer field can be stripped from the HTTP header by a proxy. In fact the browser isn't required to send the referer field in the header at all. Re: Referer isn't reliable Author: Thomas Andreas Schwob (http://www.jguru.com/guru/viewbio.jsp?EID=335784), Dec 3, 2001 Hidden field is very limiting, because it just can provide the name of the web page all the rest of the URL cannot be provided because its dynamic, therefore How do you want to store in a hidden field a URL context? This in certain cases must be provided because of cross-application links where the two applications reside in different URL contexts, or even worse on different machines (host). In such a case one absolutely needs a fully-qualified URL. Actually it is a lack in the specification of HTTP. 'referer' should not be a header

data but be sent mandatory in the request and therefore should be a HttpServletRequest API in the interface like 'getReferer' or 'getReferringURL'. This way a proxy has no chance to cut such data, which I think is not admissible anyway. Actually in regard to complex web applications implementing complex data workflow (let's assume a complex web-based production control system) it is every day more apparent to me that HTTP is not any more uptodate to the requirements of such applications and needs urgently a revision. I won't regard alternatives like integration to CORBA via IIOP, because this would lead too far here. Re[2]: Referer isn't reliable Author: Frank Steidinger (http://www.jguru.com/guru/viewbio.jsp?EID=34216), Dec 4, 2001 I'd fill the hidden field on the server using the request.getRequestURI() method if the path is sufficient or reconstruct the full URL with the HttpUtils.getRequestURL(request) if necessary. In my opinion that's still better than relying on data that may be missing. And it is not just a problem of proxies removing the referer field as there are other circumstances where the browser doesn't provide it. Some browsers even allow the user to disable referer logging (e.g. Opera). That HTTP isn't the best choice for complex application from a technical viewpoint goes without saying. Changing the HTTP specification wouldn't solve the problem for quite some time as you'd still have to support older browsers. How can I recognise which submit button (as images using the type="image" attribute) is pressed in a form containing multible (image) submit buttons? Location: http://www.jguru.com/faq/view.jsp?EID=446673 Created: Jun 27, 2001 Author: Nick Furiak (http://www.jguru.com/guru/viewbio.jsp?EID=431833) Question originally posed by Chris Woolmer (http://www.jguru.com/guru/viewbio.jsp?EID=418786 You should be able to include a name in the image tag <....NAME ="your name"...>. In your servlet you would put your code in conditional block headed by: if (request.getParameter("your name")!=null)

I have submit buttons on several different html pages that are responding nicely to this technique. Comments and alternative answers

multi submit html forms Author: Steve Ryan (http://www.jguru.com/guru/viewbio.jsp?EID=277716), Jun 29, 2001 This is OK until you want to replace the buttons by images. I've spent many painful hours trying to do this with javascript in both browsers. Dont bother. An easy example is ......

result <% if (request.getParameter("a1.x")!=null) out.println("b1 pressed"); if (request.getParameter("a2.x")!=null) out.println("b2 pressed"); %> Re: multi submit html forms Author: Charmaine Farrugia (http://www.jguru.com/guru/viewbio.jsp?EID=1072763), Apr 3, 2003 hi i am kind of new to this stuff and was wondering whether you could help me out with a few problems regarding an image button i am trying to use for a map. THE image buttin is on a JSP page and I want the image button to return the coordinates to a servlet however everytime i try reading the parameters from the servlet it keeps giving me null .. the code im using is as follows : in JSP :

and in servlet: if ((reqParam = request.getParameter("image.x"))!=null) { xStr = new Double(reqParam); System.out.print(xStr); } else System.out.print("empty x coordinate"); and it always returns empty x-co-ordiante Am i missing out on something?? I also want to set the tool i want to use once clicking on hte image button that is i either zoom in or zoom out but i cant figure out how to keep track of these .. so basically i have to first selcet zoom in and zoom out and then in some way pass them to the servlet Could i keep some session for these and then i could access the session directly from the servlet by any chance However if so how can this be

done cos im getting lost :( Another problem i have is that i have some links in the jsp that once i click them they cakll the same servlet i am using before yet this time the servlet redners an image and saves it to disk .. this image is in turn displayed on the JSP the links are on however, everytime i click on the link it redirects me to an empty page first and then if i go back and refresh , the image on the jsp chganges Any ideas pls"? Your help would be GREATLY appreciated Lost in java :( Charmaine Tried this - didn't work Author: Laurie Mecham (http://www.jguru.com/guru/viewbio.jsp?EID=1149931), Apr 30, 2004 I had already tried your solution prior to reading this. It isn't working for me and from reading other sites, I'd say I'm not the only one. I noticed in your reply you said you were using an html page (you didn't say you were going from a JSP to a servlet). Was that a slip? Do you have that code working for a JSP? Thanks, Hamilton Re: Tried this - didn't work Author: Laurie Mecham (http://www.jguru.com/guru/viewbio.jsp?EID=1149931), Apr 30, 2004 Oops, my message should have been to Nick How can I prevent Microsoft's so-called "SmartTags" from manipulating my web content? Location: http://www.jguru.com/faq/view.jsp?EID=446724 Created: Jun 27, 2001 Author: John Mitchell (http://www.jguru.com/guru/viewbio.jsp?EID=4) Well, supposedly, you can add the following meta tag to your pages and the XP versions of e.g., Microsoft Internet Explorer won't hack up your pages with their filth... <meta name="MSSmartTagsPreventParsing" content="TRUE"> I'm not holding my breath. :-( Comments and alternative answers

self.close()!! Author: Sriram Narasimhan (http://www.jguru.com/guru/viewbio.jsp?EID=105242), Jun 28, 2001 Hi, even if i use <meta name="MSSmartTagsPreventParsing" content="TRUE"> tag, the dialog box pops up(in IE5.0) asking me whether i need to close it !! This is a smart tag provided by IE and doesn' happen the same way with netscape !! here's the snippet i'm using !!

<meta name="MSSmartTagsPreventParsing" content="TRUE">

Re: self.close()!! Author: Charles Martin (http://www.jguru.com/guru/viewbio.jsp?EID=399771), Jun 28, 2001

Well, you may not have to worry now. According to the following article on Yahoo News, Microsoft h SmartTags from the upcoming release of Windows XP.

http://dailynews.yahoo.com/h/is/20010628/bs/microsoft_drops_controversial_tagging_feature_from_w Re: Re: self.close()!! Author: Sriram Narasimhan (http://www.jguru.com/guru/viewbio.jsp?EID=105242), Jun 28, 2001 Does that mean there are no solutions available at present to stop the dialog box when u close a window using self.close() ? Re: Re: Re: self.close()!! Author: Kevin Dorff (http://www.jguru.com/guru/viewbio.jsp?EID=445138), Jun 28, 2001 I don't see what this has to do with Start Tags, BUT, the answer is that self.close() has a warning (question) when you attempt to close a main browser window. If you pop-up a child window you can self.close() it without a problem or a question. This is a "security feature". Re: self.close()!! Author: philippe morel (http://www.jguru.com/guru/viewbio.jsp?EID=323839), Jul 2, 2001 I'm not completly sure of what I'm saying but as it is written on webdeveloper site : "Placement of META tags should always be placed in the head of the HTML document between the actual tags, before the BODY tag." Did you try ? Re: Re: self.close()!! Author: Sriram Narasimhan

(http://www.jguru.com/guru/viewbio.jsp?EID=105242), Jul 3, 2001 yeah ! But still the same problem. Re: Re: Re: self.close()!! Author: Stevens Gestin (http://www.jguru.com/guru/viewbio.jsp?EID=458859), Aug 24, 2001 This is a Javascript security problem ! Not Smart Tag. The only way our Self.close window won't show a warning dialog bax is if the current window was opened with a JavaScript function like window.open. Hope it could help This just in! Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jun 28, 2001 Microsoft has just announced it will drop Smart Tags from Windows XP. "At this time we just don't believe it's going to be ready when (Windows XP) ships in October," Microsoft spokesman Jim Cullinan said late Wednesday. "External feedback" was one of the factors that led the company to remove the feature, although he indicated it could be resurrected in later versions.

How can one Servlet Stop (and Re-Start) another Servlet? Location: http://www.jguru.com/faq/view.jsp?EID=448698 Created: Jul 2, 2001 Author: Ryan Breidenbach (http://www.jguru.com/guru/viewbio.jsp?EID=45212) Question originally posed by John Maring (http://www.jguru.com/guru/viewbio.jsp?EID=12155 [I am using JRun's JrunScheduler, but I need to re-start it whenever I modify it's Event.ini file. Any ideas?] A servlet's life-cycle is determined by the servlet container. Therefore, when the lifecycle methods(init, service and destroy) are called is determined by the container. So, unless your container - in this case JRun - provides specific hooks to do this, you can't. One question you may want to ask yourself is why you want to do this. Why do you want to restart a servlet? If you are restarting a servlet in order to refresh a cache or reload the state of something, you may want to move this functionality into another the class. That way, you can restart/refresh what ever class you need without depending upon a servlet's life-cycle. Hope this helps. Comments and alternative answers

Servlet accepts commands like "Refresh"

Author: Mahendra Goyal (http://www.jguru.com/guru/viewbio.jsp?EID=331192), Jul 7, 2001 I dont know if this is of help to you but i really do not like the idea of restarting the tomcat or servlet.What i have done is my servlet accepts commands like "Refresh" using getPathInfo().so the command would be like /servlet/MyServlet/Refresh.The sevlet then will ask for admin username and password and if authenticated and authorised it would refresh the content ,cache etc.Within init there wouldbe a call to an updating method and on receiving refresh command the servlet will again call the same method. How do I get the IP address of the real client, not the IP address of a proxy server? Location: http://www.jguru.com/faq/view.jsp?EID=448703 Created: Jul 2, 2001 Author: JIA Java Italian Association (http://www.jguru.com/guru/viewbio.jsp?EID=414973) Question originally posed by Andy Sun (http://www.jguru.com/guru/viewbio.jsp?EID=139266 If the client is using a proxy server, the real request to your servlets arrives fromt the proxy, and so you get the proxy's IP address. Some proxies will complete the request with an header like "X-Forwarded" or "XForward-IP", or something similar. That header will contain the 'real' IP address. Be aware that fortunately there are a lot of anonymous proxy servers and they do not pass any additional header (and sometimes they do not appear as proxy). ["Fortunately" for an anonymous user, but unfortunately for a server admin. Ah, the constant struggle between privacy and features... :-) -Alex] Comments and alternative answers

Is this a proxy setting or can I use a servlet? Author: neal ravindran (http://www.jguru.com/guru/viewbio.jsp?EID=17737), Nov 1, 2002 I have a webapp that needs to get the IP address of the client. I have not been successful so far. Is this a proxy setting you have here? Why do we somtimes encounter a "400 GET not supported" message? Location: http://www.jguru.com/faq/view.jsp?EID=448704 Created: Jul 2, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Danisment Gazi Unal (http://www.jguru.com/guru/viewbio.jsp?EID=404238 If you don't have a doGet method in your servlet, then that explains it. Someone's calling your servlet with a GET request, and your servlet (via the superclass implementation of doGet) is saying it can't do that.

Have your doGet call doPost and it should work fine. Aron Tunzi adds: Insert into you servlet the following code:

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request,response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //insert your code hier. } Comments and alternative answers

400 GET not supported Author: Danisment Gazi Unal (http://www.jguru.com/guru/viewbio.jsp?EID=404238), Jul 5, 2001 Hello, This my test application. I don't send GET to my servlet, I send POST. But, I saw a GET in web servlet log as below: 217.131.15.19 - - [30/Jun/2001:04:22:30 -0500] "GET /servlet/itrprof.itrprof HTTP/1.0" 400 163 "-" "Mozilla/4.77 [en] (Win98; U)" my question: how is this GET produced ? thanks...

Re: 400 GET not supported Author: Lalitha Sivaraman (http://www.jguru.com/guru/viewbio.jsp?EID=403897), Aug 17, 2001 Hi, We too have faced the same problem under Weblogic. The reason for our problem was - there is a file called web.xml which contains the list of all servlets, their class name etc. When we tried to call the servlet without including the details in web.xml we got the same error. Probably there will an equivalent file in ur server also - Checkout

Using VisualAge for Java, the servlet engine starts but while accessing it from the browser it is giving an error 503. Location: http://www.jguru.com/faq/view.jsp?EID=448722 Created: Jul 2, 2001 Author: Aron Tunzi (http://www.jguru.com/guru/viewbio.jsp?EID=446077) Question originally posed by Navnit Singh Mathur (http://www.jguru.com/guru/viewbio.jsp?EID=446821 [ Message:Application is currently unavailable for service Target Servlet: null ] The error message 503 means that the service is unavailable and the server can't respond. Did you test your servlet in the WebSphere Test Environment? Try to test the servlet and test it in a browser. What you need to do is: Click the "Edit Class Path..." button. Check all needed projects. Start the servlet engine In the brower edit: localhost:8080/servlet/xxx.yyy where xxx ist the package's name (eg my.java.test) and yyy the name of the class (eg TestServlet); now the full path is:http://localhost:8080/servlet/my.java.test.TestServlet Comments and alternative answers

WTE/Servlet Engine Author: Miriam Heffernan (http://www.jguru.com/guru/viewbio.jsp?EID=426294), Jul 3, 2001 I've got this error before too - it was resolved by adding/importing some features/projects to my workspace which were required in order for the code to compile properly Re: WTE/Servlet Engine Author: Diego Mansilla (http://www.jguru.com/guru/viewbio.jsp?EID=746347), Feb 4, 2002 It is also posible that you load some init Parameters in the servlet config, but you haven't called the super.init method in the servlet initilization. Check this if you use init parameters in your config.

What content type do I use when writing an object from an applet to a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=452687

Created: Jul 10, 2001 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) Question originally posed by Josep Grifell (http://www.jguru.com/guru/viewbio.jsp?EID=451431 On your URLConnection, add conn.setRequestProperty("Content-type", "java-internal/" + hash.getClass().getName()); The getClass().getName() is the general way to specify the class, you can hard code the value, like the following.... conn.setRequestProperty("Content-type", "javainternal/java.util.Hashtable"); Comments and alternative answers

What content type do I use when writing an object from an applet to a servlet? Author: nick varey (http://www.jguru.com/guru/viewbio.jsp?EID=454082), Jul 12, 2001 I believe you can also use a more general: conn.setRequestProperty("Content-type", "application/octet-stream"); This seems to work fine for me nick varey Re: What content type do I use when writing an object from an applet to a servlet? Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7), Jul 27, 2001 The receiving end needs to know the class type. At least one version of Tomcat requires the internal content type with class name. Re: Re: What content type do I use when writing an object from an applet to a servlet? Author: sam pitroda (http://www.jguru.com/guru/viewbio.jsp?EID=476938), Aug 14, 2001 setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); How are multiple servlet contexts defined or configured on Sun's Java Web Server? Location: http://www.jguru.com/faq/view.jsp?EID=454625 Created: Jul 13, 2001 Author: Sachin Patil (http://www.jguru.com/guru/viewbio.jsp?EID=280417) Question originally posed by Neal Criscuolo (http://www.jguru.com/guru/viewbio.jsp?EID=98107 In the Admin tool provided by Java Web Server-2 you have the option called manage/servlet, in which you can add (load), modify(Configure) servlets. while adding new or modifying existing servlet you have to give the path (java package)

and Aliases you set in servlet aliases. This automatically sets the context path for servlets. How do I process FDF files created by the Acrobat Forms plug-in? Location: http://www.jguru.com/faq/view.jsp?EID=455199 Created: Jul 15, 2001 Author: Arun Bharathan (http://www.jguru.com/guru/viewbio.jsp?EID=106958) Question originally posed by Christine Hutcheson (http://www.jguru.com/guru/viewbio.jsp?EID=452670 [ The files are uploaded with content type = application/vnd.fdf ] To update/complete or recover data from a FDF you need adobe java classes which are JNI for Adobe DLLs. I think it is available in Abobe's site There are some caveats at the site. Read it first before jumping in. And as for running it in VisualAge, you need FDFtk.jar file and the JfdfTk.DLL in the VAJ's classpath. Comments and alternative answers

Problems with current versions of FDF toolkit Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jul 15, 2001 FDF Toolkit Version 4.05 works with JDK 1.1 and below. There is no Java support in version 5 yet. :-( OS Binding Author: Don Kitchen (http://www.jguru.com/guru/viewbio.jsp?EID=585512), Dec 14, 2001 You are also tied into a Windows environment. This does limit you from being platform independent. Why do I sometimes get the error "ODBC Driver Manager ...function Sequence Error"? Location: http://www.jguru.com/faq/view.jsp?EID=455201 Created: Jul 15, 2001 Author: Pramod Vuppalapanchu (http://www.jguru.com/guru/viewbio.jsp?EID=453652) Question originally posed by Hema latha (http://www.jguru.com/guru/viewbio.jsp?EID=405076 We had the same problem and we found that 1)SUN has reported that this Function Sequence error is a bug in JDK 1.2 Check out Sun's BUG List for more info on this. 2) If you are using JDK 1.2 try switching to JDK 1.3. It helped us.

Cheers, Pramod. Comments and alternative answers

Sun JDBC-ODBC Bridge (JRE 1.2.2) Bug work-around Author: Darrell Teague (http://www.jguru.com/guru/viewbio.jsp?EID=517558), Oct 11, 2001 We ran into this same problem with the same symptoms (i.e. random Function Sequence Errors). As ugly as this is, it is possibly the only sure-fire work-around if you cannot change your JRE (such as when integrating with another company's product that ships with and will not change their JRE from 1.2.3. to 1.3.x): Close the statement and re-create it between each call: myStatement.close(); myStatement = myConnection.createStatement();

This is ugly and incurs a performance hit (though not as bad as recycling the connection object) but it does work (at least in our case). Hope this helps. Darrell Teague Architect Canopy International Re: Sun JDBC-ODBC Bridge (JRE 1.2.2) Bug work-around Author: Rahul Pawar (http://www.jguru.com/guru/viewbio.jsp?EID=520149), Oct 14, 2001 Hi Darrell, The work around you have suggested is not quite working for me. Instead of Statement object we are using the CallableStatement object in combi with stored procedures of MS SQL Server. I m doing exactly as suggested by you but then its not working. Pls try to delve into the problem. Thanks, Rahul Re: Re: Sun JDBC-ODBC Bridge (JRE 1.2.2) Bug work-around Author: Darrell Teague (http://www.jguru.com/guru/viewbio.jsp?EID=517558), Oct 15, 2001 Yours sounds like a slightly different situation (CallableStatement Interface and stored procedures on MS SQLServer). However, if you will post a code snippet with all of the relavent pieces (creation of the CallableStatement, stored procedure execution calls, creation of ResultSets, closing of ResultSets, closing of Statement, etc), I (and perhaps others) will be glad to take a look at it.

Re: Re: Re: Sun JDBC-ODBC Bridge (JRE 1.2.2) Bug work-around Author: Rahul Pawar (http://www.jguru.com/guru/viewbio.jsp?EID=520149), Oct 15, 2001 Hi, Thanks for the prompt reply. The code snippet follows: JavaBean code //get connection obj into mxConn var cs = mxConn.prepareCall("{call xt_someStoredProc(?)}"); cs.setInt(1,pk_activity); rs = cs.executeQuery(); while (rs.next()) { //do something; } rs.close(); cs.close(); //close connection in the finally block The error occurs even for a simple select query when the functionality is used simultaneously by many users. Declaring the cs & rs obj at class or function level made no difference My mail adddress is [email protected]. Pls mail if you require more info. Thanks How to allow the client to download and execute a .bat or .exe file? Location: http://www.jguru.com/faq/view.jsp?EID=455202 Created: Jul 15, 2001 Modified: 2001-07-23 09:57:16.236 Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985) Question originally posed by Vimaladhithan Palraj (http://www.jguru.com/guru/viewbio.jsp?EID=451132 You can just put a link like this execute runme When client clicks on it it will be asked to open the file (and execute it) or just to download it. This is general way to handle this (think about .exe installers... always you need to push on ok after choosing to execute the file instead of just download it) [But see How to copy the file from Server side into Client ... for words of warning about security... -A] What is a session and why is it required? Location: http://www.jguru.com/faq/view.jsp?EID=455205 Created: Jul 15, 2001 Author: Bozidar Dangubic (http://www.jguru.com/guru/viewbio.jsp?EID=433955)

Question originally posed by aruna rani (http://www.jguru.com/guru/viewbio.jsp?EID=405045 HTTP is a connectionless protocol -- meaning that after the request is served the connection between the client and the server is closed. A session allows you to overcome this limitation by storing client activities. It has many, many uses but one example could be shopping cart type application. You can use the session to track items clients have selected. See Topic Java:API:Servlets:Cookies, Sessions, and State Management How can I generate an output in CSV format from a database query? Location: http://www.jguru.com/faq/view.jsp?EID=455207 Created: Jul 15, 2001 Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985) Question originally posed by Ritu kumar (http://www.jguru.com/guru/viewbio.jsp?EID=314981 CSV stands for "Comma Separated Values", so just keep any record and separe each field with a comma and each record with a newline ('\n'). You'll have a perfect CSV file, easy readable by any program supporting this simple format. It's very common to put as first line the names of fields. Comments and alternative answers

There are libraries to help Author: Stephen Ostermiller (http://www.jguru.com/guru/viewbio.jsp?EID=576685), Jan 28, 2002 Comma Separated Values (CSV) in Java is an available library to help. It supports reading and writing the files. Re: There are libraries to help Author: Namita Prakash (http://www.jguru.com/guru/viewbio.jsp?EID=1024031), Nov 11, 2002 Hi, I need to convert MS Access files into CSV format.i cannot use the export function of MS Access coz it will require me to manually export a lot of files.how do i do it using JDBC-ODBC bridge. thaanks, namita Re[2]: There are libraries to help Author: Richard Rodger (http://www.jguru.com/guru/viewbio.jsp?EID=1220174), Jan 7, 2005 Use the ODBC Data Sources administration applet to define a DSN (data source name) for the CSV file. More details here: http://java.sun.com/j2se/1.3/docs/guide/jdbc/getstart/bridge.doc.html Can I spawn a background thread from my servlet? Location: http://www.jguru.com/faq/view.jsp?EID=455215 Created: Jul 15, 2001

Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Michael O Connor (http://www.jguru.com/guru/viewbio.jsp?EID=412596 You are allowed to spawn a thread from a Servlet. Sounds like you want to make a thread object and store it as an attribute in your application context. See the FAQ I want the servlet container to load one or more servlets when the container is first fired up, as opposed to when a client issues a request for the servlets for how to start it. Basically, you make a thread object, call mythread.start(), then call context.setAttribute("mythread", mythread). You can give your daemon object methods to activate and deactivate, but it will be accessible (almost a global) from any servlet at any time. This can be used to run, e.g., a chat server that accepts socket connections from an applet, independently of the Web server (and on a different port than 80 or 8080). Or a status-checker that performs some action periodically, like updating a cache or monitoring a database connection. Here's some simple (untested) code that spawns a daemon thread that keeps track of the number of seconds since it's been launched. public class DaemonStarter extends HttpServlet { public void init() { TimerDaemon d = new TimerDaemon(); d.start(); getServletContext().setAttribute("daemon", d); } } public class MyDaemon extends Thread { long secs = 0; public void run() { while (true) { Thread.sleep(1000); secs++; } } public long getSecs() { return secs; } } public class PrintSecs extends HttpServlet { public class doGet(...) { TimerDaemon d = (TimerDaemon)getServletContext().getAttribute("daemon"); response.getWriter().println( d.getSecs() ); } } Note that this can be dangerous in a load-balanced application, as when using the "distributed" flag in your web.xml. You must be aware if your background thread will be running in multiple VMs, and if that will cause any sychronization problems.

See Servlet Thread Topic for more information. Comments and alternative answers

Synchronization missing! Author: Boris Folgmann (http://www.jguru.com/guru/viewbio.jsp?EID=953582), May 12, 2005 As PrintSecs is running in parallel to MyDaemon, you have to synchronize the access on the variable secs. Note that getSecs() is called in the context of PrintSecs. public class MyDaemon extends Thread { long secs = 0; public void run() { while (true) { Thread.sleep(1000); synchronized (secs) { secs++; } } } public long getSecs() { synchronized (secs) { return secs; } } } public class PrintSecs extends HttpServlet { public class doGet(...) { TimerDaemon d = (TimerDaemon)getServletContext().getAttribute("daemon"); response.getWriter().println( d.getSecs() ); } }

While forwarding from one page to another by using RequestDispatcher, how do I avoid the error " OutputStream is already being used for this request" ? Location: http://www.jguru.com/faq/view.jsp?EID=455248 Created: Jul 15, 2001 Author: thomas dietrich (http://www.jguru.com/guru/viewbio.jsp?EID=413665) Question originally posed by kodandapani a (http://www.jguru.com/guru/viewbio.jsp?EID=415257 Just a few pointers: 1) First, when the servlet it called it should be the final action for that JSP. (I.E. the action of a form). 2) Second, redirection should be the final action of that servlet, like don't call the redirection, and then have the servlet try write to the response.

3) Third, and I'm not sure about this, I believe that you can't be already writing to the response page, before you call the redirection. Check these out, these were some of my probs trying to work with redirection in the past, and might be a little fuzzy too. Comments and alternative answers

Solution Author: Avi Sharma (http://www.jguru.com/guru/viewbio.jsp?EID=455502), Jul 16, 2001 This is additional point apart from the mentioned Dont use response object or out.println statement after RequestDispatcher statement. RequestDispatcher Forwarding.... Author: Srivathsan Santhanam (http://www.jguru.com/guru/viewbio.jsp?EID=480213), Aug 21, 2001 Hi Thomas Dietrich is correct.While forwarding a request to another page using RequestDisatcher te servlet expects that no ServletOutputStream is opened and no output stream is sent.Since a request is being forwarded to another page you cannot have an servlet output stream opened to write out another object.But this is not the case with ReuestDispatcher includes. Hope you got my point!!! Re: RequestDispatcher Forwarding.... Author: Mark Lesk (http://www.jguru.com/guru/viewbio.jsp?EID=440839), Aug 29, 2001 Actually, it is still an error to call response.getOuputStream() at anytime after a call to request.getWriter() is made. This is true whether it is before, after, or during a request.getRequestDispatcher().include() call. Currently, I have found in most servlet engines that the error is reported but an exception is not thrown so processing can continue normally. Typically this is not a problem because for a particular request usually html is being sent back via the use of getWriter() or a dataStream is being sent back via the use of getOutputStream(). Problems occur when code is sloppy and switches back and forth between these methods or in portal style applications where some of the portal has to be output to the stream before the portlet content is known. In these cases, you have to set your response buffer large enough so that the response is not committed before you have a chance to clear it out. In order to clear your response out you have to look at individual servers because it is implementation specific ... This is how I do it in WebLogic 6.0

ServletResponseImpl servletresponseimpl =

(ServletResponseImpl)response; if(response.isCommitted()) throw new IllegalStateException("Cannot process a data download on a response that is already committed"); ServletOutputStreamImpl servletoutputstreamimpl = (ServletOutputStreamImpl)servletresponseimpl.getOutputStreamNoCheck(); servletoutputstreamimpl.clearBuffer(); servletresponseimpl.reset();

How do I prevent users from viewing the contents of my WEB-INF directory? Location: http://www.jguru.com/faq/view.jsp?EID=455249 Created: Jul 15, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Danisment Gazi Unal (http://www.jguru.com/guru/viewbio.jsp?EID=404238 Servlet Engines (e.g. Resin or Tomcat) should not allow directory browsing of WEBINF. Tomcat 3.2, for example, had that same issue and they have fixed it in Tomcat 3.2.1. This was happening when Tomcat was used standalone (not just as a container, but even as a web server). If this problem happens with a specific version of a standalone Resin, you should consider to try the latest version (I'm running 1.2.5) and, eventually, send a bug to Caucho. Consider that this issue should happen when using the container in standalone mode. When the container (Resin, Tomcat or abother one) is used just for serving servlet & jsp behind a more reliable and complete web server, like Apache, the problem is on Apache, that is serving everything else. When you ask for WEB-INF, in fact, Apache doesn't even connect to Tomcat, there is no reason. So, if this is your scenario, you should add lines like these:

AllowOverride None Deny From All Inside the virtual host or whatever you think is appropriate and, obviously, changing "/WEB-INF" with the appropriate context. What is the difference between ServletContext.getInitParameter() and HttpServlet.getInitParameter() ? Location: http://www.jguru.com/faq/view.jsp?EID=455711 Created: Jul 16, 2001 Author: André Wolf (http://www.jguru.com/guru/viewbio.jsp?EID=310274) Question

originally posed by Rama krishna Maddipati (http://www.jguru.com/guru/viewbio.jsp?EID=433173 [Original Question: I am using Tomcat Web server.I am passing parameter in Web.xml using <param-name>server <param-value>xxxxxxx But when I am calling getInitParameter("server") in init method it is returning null value. How to resolve this? ] The tag is used to set an init parameter for the whole application context, it is accessible by all Servlets and JSPs. You have to use getInitParameter() of javax.servlet.ServletContext, not the similar method found in HttpServlet. Just try the following method call in your servlet, it should return the correct parameter: getServletContext().getInitParameter("server") Alternatively, you can set an init parameter for a specific Servlet, it will only be accessible by this Servlet: <web-app> <servlet> <servlet-name>myservlet <servlet-class>org.myorg.MyServlet <param-name>server <param-value>xxxxxxx ... To retrieve this parameter you just call getInitParameter() in your servlet. Comments and alternative answers

See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Sep 18, 2001 See also this forum thread: passing parameters through web.xml always returns ... Is there a way in Tomcat to set up zones for servlets like in jserv? Location: http://www.jguru.com/faq/view.jsp?EID=455766 Created: Jul 16, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by ryan wexler (http://www.jguru.com/guru/viewbio.jsp?EID=433624

Not really. Tomcat 4 has somewhat better management of classpaths and contexts and virtual hosts -- you might want to check it out. Why do I get "java.lang.NoClassDefFoundError: sun/tools/javac/Main" ? Location: http://www.jguru.com/faq/view.jsp?EID=455768 Created: Jul 16, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Sean K (http://www.jguru.com/guru/viewbio.jsp?EID=429709 java.lang.NoClassDefFoundError: sun/tools/javac/Main means that your classpath is not set correctly. Make sure your JAVA_HOME is set up right before you run the tomcat or startup scripts. If that doesn't do it, see these FAQs: • • •

How do I set my CLASSPATH for servlets? When starting Tomcat l get "java.lang.NoClass... java.lang.NoClassDefFoundError in unix

Comments and alternative answers

Search Comment On FAQ Entry Why do I get "java.lang.NoClassDefFoundError: sun/tools/javac/Main" ? Author: marion schwarz (http://www.jguru.com/guru/viewbio.jsp?EID=462656), Jul 26, 2001 Sometimes the installation of jdk does not include the tools.jar in the JAVA_HOME\lib directory. tools.jar contains the requested Main.class file. Copying the .jar into the \lib directory solves this problem. Re: Search Comment On FAQ Entry Why do I get "java.lang.NoClassDefFoundError: sun/tools/javac/Main" ? Author: Taswell Jeffries (http://www.jguru.com/guru/viewbio.jsp?EID=716794), Jan 11, 2002 Hi Marion, I am experiencing the same problem. I have a windows 2000 SP2 Server with IIS loaded. I have installed Tomcat 3.3. I have also installed j2re1_3_1_01-win. I cannot find any tools.jar on my filesystem. Should I juust get a copy of tools.jar and copy it into the library directory? Many thanx Taswell Jeffries Re[2]: Search Comment On FAQ Entry Why do I get "java.lang.NoClassDefFoundError: sun/tools/javac/Main" ? Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727), Jan 11, 2002 I think you have to install the full J2SE, not just the Runtime Edition (J2RE). Re[2]: Search Comment On FAQ Entry Why do I get "java.lang.NoClassDefFoundError: sun/tools/javac/Main" ? Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727), Jan 11, 2002

I think you have to install the full J2SE, not just the Runtime Edition (J2RE). Re: Search Comment On FAQ Entry Why do I get "java.lang.NoClassDefFoundError: sun/tools/javac/Main" ? Author: JOSE LUIS KUHLMANN (http://www.jguru.com/guru/viewbio.jsp?EID=1219050), Jan 2, 2005 I solve the problem of the following way: I have put initially(originally) of my program the name of the file .java of the following way, package Name of the file; NoClassDefFound Author: Emroz Habib (http://www.jguru.com/guru/viewbio.jsp?EID=467026), Aug 2, 2001 Make sure you have tools.jar in your runtime envoiurment.If you have j2ee.jar in your classpath, you should take it out cause tomcat will look into it to tools/javac/main Tomcat-NoClassDefFoundError:..... Author: Srivathsan Santhanam (http://www.jguru.com/guru/viewbio.jsp?EID=480213), Aug 21, 2001 Hello When installing Tomcat you should ensure the following things.. 1.your JAVA_HOME path oints to your jdk directory. i.e add the following line to your autoexec.bat file set JAVA_HOME=<jdk path> say for eg c:\jdk1.3 (as may be the case).This ensures that the tools.jar in the jdk1.3 folder is mapped to JAVA_HOME for running and also the claaspath should include the pointer to the bin directory where the java executable file is located. Re: Tomcat-NoClassDefFoundError:..... Author: Oleg Beregovich (http://www.jguru.com/guru/viewbio.jsp?EID=487671), Aug 30, 2001 Hello Srivathsan. I get this problem when I accessing jsp. I have tomcat 3.2.3 on win 2000 and jdk 1.3. I set JAVE_HOME and TOMCAT_HOME. When I run tomcat run or tomcat start it shows me CLASSPATH its setting and it has all the libraries including tools.jar in c:\jdk1.3\lib. I was trying reinstalling things and moving them around but I am getting this error for all examples and my jsps. My main surprise is that when I installed tomcat couple of weeks ago I didn't have any problems running jsp. Please advise what else can I try. Thank you Oleg Re: Re: Tomcat-NoClassDefFoundError:..... Author: suomi hasler (http://www.jguru.com/guru/viewbio.jsp?EID=517403), Oct 11, 2001 Hi every (body or not) I solved this problem this morning:

with the previous installation on tomcat-4.0, I had been able to run servlets but not JSP, where I always got the error msg you mention above. I then noticed that the JAVA_HOME env var was pointing to a directory (/usr/bin) which contained a link to both java as well as javac, nothing more. When I changed JAVA_HOME to point to the real thing (i.e. the java development kit) in /usr/java/jdk1.3.1/) and I restarte Tomcat, I could fiddle around with servlets as well as JSP. good luck. suomi Re[2]: Tomcat-NoClassDefFoundError:..... Author: Ale Kalyna (http://www.jguru.com/guru/viewbio.jsp?EID=1203697), Oct 6, 2004 I've got the same problem too! Well, now i'm updating Symantec Antivirus, couse it is the last hope. Even reinstalling JDE won't help (i tried this couple of times). I've even tried to reinstall Windows (just in case) and still it remains unsolved. I tried to ask more experienced people, and they said: 'Ëèáî õóåâà âèíäà, ëèáî áëÿäñêèå âèðóñû' which can be translated something like: 'I don't know either' :-) my solution Author: Yun Liu (http://www.jguru.com/guru/viewbio.jsp?EID=578122), Dec 9, 2001 Under Unix, includes the /usr/java/lib/tools.jar into your classpath. It should work... Re: my solution Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727), Jan 11, 2002 Hi, You should say: include /lib/tools.jar, because you cannot be sure that java resides under /usr on all system. Many system, and many administrator, in fact, can put java under /usr/local or even under /opt. java.lang.NoClassDefFoundError Author: Girish Kshirsagar (http://www.jguru.com/guru/viewbio.jsp?EID=704336), Dec 28, 2001 In general if classpath has been setup correctly the error should not occur. However, make sure that your classpath includes .; i.e. path to your current folder where the program is located. If not, the above error will show up and this may be all you need to fix your problem.

Re: java.lang.NoClassDefFoundError

Author: Indranil Poddar (http://www.jguru.com/guru/viewbio.jsp?EID=1242172), May 3, 2005 Thanks Girish..i tried a lot of other stuffs in vain before your advice solved my problem java.lang.NoClassDefFoundError Author: Gurvinder Singh Sethi (http://www.jguru.com/guru/viewbio.jsp?EID=1214917), Dec 7, 2004 Include the lib path of java directory which contains tools.jar in the classpath environment variable. This will solve the problem How do I implement a hit counter in Servlets or JSP? Location: http://www.jguru.com/faq/view.jsp?EID=456418 Created: Jul 17, 2001 Modified: 2002-12-04 21:51:15.09 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Hema latha (http://www.jguru.com/guru/viewbio.jsp?EID=405076 When implementing a hit counter, there are many decisions to make.

1. Are you sure you want to write it yourself? There are many free web-based hit counters out there that take care of a lot of the hassles for you. Most seem to serve up a GIF so you can embed it in your page as an IMG or JavaScript. See:

2.

o o o o What

How can I add a counter applet to my web page? http://www.theCounter.com http://www.jcount.com http://counter.bloke.com do you want to count?

The most common thing to count is individual hits to your site's home page, via an IMG reference (see below). You may instead want to count unique new user sessions (see the API for HttpSession for information on setting up a listener that listens for new sessions), or some other factor.

3. Where do you want to save the data? Servlets are transient. If you want your hit count to last past a server restart, you need to save it somewhere. This means using either a file system or a database. See o o o

How can I access or create a file or folder in the... Is there a standard place to write temporary files... How do I access a database from my servlet?

Aron Tunzi posted some great code for writing to a file in the forum thread for this question, at How do I implement a hit counter in Servlets or JSP

4. How do you want to display the results? You can either display the results as an image, or as embedded text or HTML. See below for information on image-based hit counters. To use embedded text, the easiest way is to write your hit counter as a JavaBean, with separate methods for incrementing the count and returning the current count. Then you can instantiate the bean, place it in the application context, and access it from any servlet using code like: HitCounter h = (HitCounter)getServletContext().getAttribute("hitcounter"); h.incrementCount(); out.print(h.getCount()); Returning an image simplifies some aspects of the system but means you have to deal with creating an offscreen image and rendering the text inside it. You may also want to make your hit counter be an applet. See How can I add a counter applet to my web page? and How can I pass an object from an applet to a servlet? for help there. How to build an image-based counter To build an image-based counter, write a servlet -- let's say /myapp/counter -- that works as follows: public void doGet(...) { incrementCount(); Image i = getImage(); writeImage(response); } Of course, you still have to write the incrementCount, getImage, and writeImage methods :-) See the AWT FAQ and the Servlets: Images topic for help on creating and sending images from a Servlet. In your client pages, output the following HTML:

and each client request will increment the count and display the image in a single shot. (This simple architecture would have been possible for text too, if only Marc Andreesen had simply implemented client-side include in Netscape, instead of wasting all his time on tables and frames, which totally suck. Oh well, maybe next life.) However, this technique is not always accurate, since it can count reloads, if the same user goes back to the home page. Also, you may end up counting hits to sub-

pages too. Adding a parameter, as in IMG SRC="/myapp/counter?page=home" may help distinguish these case. Comments and alternative answers

Bean Example Author: Tim Bardzil (http://www.jguru.com/guru/viewbio.jsp?EID=457044), Jul 18, 2001 Will a hit counter that is place in a bean with "application" scope be reset when the server is restarted? If so, is there any way to get around this? Re: Bean Example Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7), Jul 18, 2001 Read #3. How do I trap a 404 error inside my servlet if my servlet does a RequestDispatcher to a non-existent page ? Location: http://www.jguru.com/faq/view.jsp?EID=457102 Created: Jul 18, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Tim Owen (http://www.jguru.com/guru/viewbio.jsp?EID=455434 [See How can I write an "error page" -- that is, a serv... for the canonical FAQ on error pages. -A] In Tomcat, like in all the fully compliant servlet containers, you have the equivalent of the 'ErrorDocument' using the web application descriptor (web.xml). This is useful because you can handle either error codes (like the 404) or even exception. This is the extract of the web.xml DTD: Comments and alternative answers

What a moronic answer! Author: jack david (http://www.jguru.com/guru/viewbio.jsp?EID=462745), Jul 26, 2001 Everybody knows that. Copy and pasted the dtd. Atleast an example fragment of XML showing how to actualy use it would have been useful. Re: What a moronic answer! Author: Axel Stahlhut (http://www.jguru.com/guru/viewbio.jsp?EID=965487), Nov 18, 2004 What a moronic comment! Include the following in your deployment descriptor file (web.xml) Author: Ravindra Peddireddy (http://www.jguru.com/guru/viewbio.jsp?EID=510262), Oct 3, 2001 <error-page> <error-code>404 /ErrorPage.jsp When there is a 404 error it automatically redirects to "ErrorPage.jsp" in which you will typically display your custom error message. You may also trap exceptions by including the following :<error-page> <exception-type> java.lang.Exception /ErrorPage.jsp Note :- "ErrorPage.jsp" will not receive the actual exception occured unlike the error page that you specify using the JSP page directive with "errorPage" attribute which receives the actual exception through an implicit "exception" object. Re: Include the following in your deployment descriptor file (web.xml) Author: Mojmir Hanes (http://www.jguru.com/guru/viewbio.jsp?EID=730375), Jan 22, 2002 Hi, I have a problem redirecting error 500. Here is my web.xml <web-app> <error-page> <error-code>404 /errorPages/404.jsp <error-page> <error-code>500 /errorPages/500.jsp

<error-page> <exception-type>java.lang.Exception /errorPages/exception.jsp

I try to write page with syntax error <% str = Strin; %>

but without redirecting java.lang.exception in web.xml I see default Tomcat error page. I would like to see errorPages/500.jsp page. I use Apache 1.3.22 and Tomcat 4.01 Thank you very much :-) Miuek (sorry for my english :-) ) Re[2]: Include the following in your deployment descriptor file (web.xml) Author: Vijay Dogra (http://www.jguru.com/guru/viewbio.jsp?EID=1149724), Feb 27, 2004 I have same problem in customizing tomcat eror pages.I have added <errorpage> <error-code>500 /error.jsp in my web.xml file but still it doesnt work. I have tomcat 5.0.16 and jdk1.4.2 on XP machine. Kindly help me Re[3]: Include the following in your deployment descriptor file (web.xml) Author: Tim Hannaford (http://www.jguru.com/guru/viewbio.jsp?EID=1179663), Jun 17, 2004 Your problem could be as simple as not refreshing a cached paged when the error occurs. Or perhaps you have another runtime error in your error.jsp page. That was a problem I had, which made my exception handling appear not to work. I replaced the jsp with a static html as a test and it worked out for me. I hope that helps. Re[4]: Include the following in your deployment descriptor file (web.xml) Author: Vijay Dogra (http://www.jguru.com/guru/viewbio.jsp?EID=1149724), Jun 28, 2004 Yes thanks for the answer it was actually i was not flushing the buffer. Thanks!!!!! JSP:Include Author: vinay thakkar (http://www.jguru.com/guru/viewbio.jsp?EID=1193667), Aug 17, 2004 does this error handling holds true when the page mentioned in the jsp:include tag shows 404 error?

How can I automatically invoke a servlet at regular time intervals using Resin? Location: http://www.jguru.com/faq/view.jsp?EID=458416 Created: Jul 19, 2001 Author: Michael Strasser (http://www.jguru.com/guru/viewbio.jsp?EID=455820) Question originally posed by Harsh Sugandhi (http://www.jguru.com/guru/viewbio.jsp?EID=401509 You can configure Resin to run servlets at regular intervals. In /ref/servlet-config.xtp in the Resin docs, have a look at the run-at specification for resin.conf. I think that if you want every five minutes you need to use: :00 :05 :10 :15 :20 :25 :30 :35 :40 :45 :50 :55 Comments and alternative answers

Interested to know more about this.... Author: Karen Ng (http://www.jguru.com/guru/viewbio.jsp?EID=462255), Dec 19, 2001 Where can I get more info about the solution above? How do I download several files at the same time? Location: http://www.jguru.com/faq/view.jsp?EID=460087 Created: Jul 23, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Donatello Parigino (http://www.jguru.com/guru/viewbio.jsp?EID=451493 It's tough to get HTTP to return more than one file at a time. You could 1. just return a page listing all the files, and ask the user to click each link 2. package all the files into a Zip archive using the java.util.zip package classes, and download that file 3. write a JavaScript function that downloads each of the files in turn Not sure how well any of these will work. I'm pretty sure there's no easy way to just download several files in a row, waiting for one to finish before serving the next. [Keywords: file download multiple files several files many files at once] Comments and alternative answers

Multidownload by Javascript Author: Donatello Parigino (http://www.jguru.com/guru/viewbio.jsp?EID=451493), Aug 31, 2001

How I can perform point 3 of proposed solution ? Re: Multidownload by Javascript Author: Rick Tossavainen (http://www.jguru.com/guru/viewbio.jsp?EID=1153085), Mar 10, 2004 Was an answer to this ever determined as we have need to download multiple files via a browser with the click of one "download button"? When downloading a file to a client, how can I inform the client of the file size, so it can predict how long it will take? Location: http://www.jguru.com/faq/view.jsp?EID=460092 Created: Jul 23, 2001 Author: Donatello Parigino (http://www.jguru.com/guru/viewbio.jsp?EID=451493) Question originally posed by Jonas Lindgård (http://www.jguru.com/guru/viewbio.jsp?EID=447485 You must set the Content-length HTTP header. You can use the following code: response.setHeader("Content-disposition", "attachment;filename=name"); response.setIntHeader("Content-length", filelength); ServletOutputStream sos = response.getOutputStream(); ... Comments and alternative answers

Problem with JSP's Author: Rémi Vannier (http://www.jguru.com/guru/viewbio.jsp?EID=480640), Aug 30, 2001 I have a related problem... What if you forward a JSP page, and you don't know the content-length by advance ??? Re: Problem with JSP's Author: Jatinder Thind (http://www.jguru.com/guru/viewbio.jsp?EID=488511), Sep 8, 2001 When u forward a JSP page,the page is not actualy sent to the client.Its executed by the servlet container on the server side only.So the question of making the file length known to the client does not arise. Reaction to this answer Author: Rémi Vannier (http://www.jguru.com/guru/viewbio.jsp?EID=480640), Sep 8, 2001 I found the answer to my question myself. It is true that I don't have to set the contentlength of the request. In fact, I think it is not possible unless you can access the code of the JSP interpreter Since the JSP interpreter cannot know by advance the content

length, it uses a different transfer format : the Chunked transfer Encoding, used since HTTP 1.1. In the case of the chunked transfer encoding, the data is sent by chunks, whose length is specified in the first line of the chunk in hexadecimal format. U can deal with that by 2 ways : Either U use the w3c class 'ChunkedInputStream', which decodes the Chunked data... (package org.w3c.www.http) Either U code it yourself, since it is very simple... Here is the algorithm in pseudo language If transfer-encoding equals chunked { read Chunksize (use BufferedReader.readLine() in Java) while chunksize>0 { totalsize += chunksize read 'chunksize' bytes } } add the content length header with the value 'totalsize'. Bye all. Why do Frames suck? Location: http://www.jguru.com/faq/view.jsp?EID=460110 Created: Jul 23, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Alex Chaffee PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=3 Jakob Nielsen's article Why Frames Suck (Most of the Time) summarizes the issue pretty nicely. In general, if you are tempted to use frames, you should use tables instead. JSP's <jsp:include> tag allows you to share common code like nav bars. Comments and alternative answers

Arguments please Author: Patrick Willart (http://www.jguru.com/guru/viewbio.jsp?EID=460888), Jul 24, 2001 I think you are right. Most of the times frames suck. Using tables and <jsp:include> is a very good way to use common elements in you pages. Reasons not to use frames: • • • •

Not possible to bookmark Print problems Authoring problems (others steeling your content by displaying it in their own frameset) Search engine problems

Of course there are ways to work around most of these issues by using javaScript. My opinion is there are some cases where frames offer a nice solution under the condition that the designer knows what he is doing. Do they? Author: das Megabyte (http://www.jguru.com/guru/viewbio.jsp?EID=460934), Jul 24, 2001

I agree...frames cause havoc with bookmarking...but only for Netscape users. Netscape is a dead project comprising less than 14% of the browser market (less than 7% of traffic on OUR sites). Printing with frames has been a cinch since 1997, and since frames allow you to print just what you want (and not a lot of ugly header or navbar stuff that is useless on paper anyway) they are actually better for the user making a record of a sale or printing content to read later. If people are stealing your content, read the http referrer and if it's a common thief, stop display (you're in JSP...this is a CINCH). As for search engines...proper use of your robots.txt and a small snippet of JavaScript to check for your frameset fix those issues. While jsp:includes help make frames less necessary, they also create a lot of inefficiencies. If you're building a dynamic nav bar every time you load a page, you're beating on your servers needlessly, adding to your page download times what's usally a large amount of table code and generally increasing your bandwidth for code that isn't necesary to reload every time the page is. Frames are more efficient and allow you so many liberties -- one of my favorite tricks is to roll up a frame after a form submission that has a "Please Wait..." graphic, that the content page rolls back down when it's completed download. Re: Do they? Author: Anand Jayaraman (http://www.jguru.com/guru/viewbio.jsp?EID=449084), Jul 30, 2001 das Megabyte, Could you please show with the code how you show "Please Wait..." graphic, if it's okay with you ? Thanks. Anand. How can I display bar codes in my Java program? Location: http://www.jguru.com/faq/view.jsp?EID=462245 Created: Jul 25, 2001 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) IDAutomation has a set of commercial beans, applets, and servlets for dynamic bar code generation. Comments and alternative answers

Where can I find free barcode generator in java and javascript? Author: Philippe Corbes (http://www.jguru.com/guru/viewbio.jsp?EID=1238298), Apr 13, 2005 For a free java barcode generator visit: http://sourceforge.net/projects/barbecue for a free javascript barcode generator and free codes visite: http://philippe.corbes.free.fr/codebarre/jsbarcode/index.html (in french) or http://philippe.corbes.free.fr/codebarre/jsbarcode/index_en.html (in english)

How do I pass query parameters when I use Request Dispatcher? Location: http://www.jguru.com/faq/view.jsp?EID=472606 Created: Aug 9, 2001 Author: JIA Java Italian Association (http://www.jguru.com/guru/viewbio.jsp?EID=414973) Question originally posed by Preedesh Menon (http://www.jguru.com/guru/viewbio.jsp?EID=277934 [I am using: reqDisp = servletContext.getRequestDispatcher("/applicationsecurity/RedirectLogin .jsp") reqDisp.forward(req,res); ] Since you're working with a request, nstead of using the getRequestDispatcher() method of the ServletContext, you should use the getRequestDispatcher of the HttpServletRequest object. reqDisp =

request.getRequestDispatcher("/applicationsecurity/RedirectLogin.jsp" ); reqDisp.forward(req,res); Comments and alternative answers

Fails on WL6.1 Author: Michael Westbay (http://www.jguru.com/guru/viewbio.jsp?EID=572920), Dec 4, 2001 I'm using Struts for a web appliation, and it does just that: org/apache/struts/action/ActionServlet.java line 1751: RequestDispatcher rd = getServletContext().getRequestDispatcher(path); if (rd == null) { ... return; } rd.forward(request, response);

This works fine with Tomcat, JRun, WebLogic 6.0, and others. However, WebLogic 6.1 (on WinNT, Linux, Solaris, and FreeBSD) does not appear to forward the request parameters. Google searches have not shown up anything unusual, leaving me wondering if I'm the only one experiencing these problems. Well, Struts does this deep within its framework, so I guess the only way to find out is to write something a bit more contained to test it. If anyone else has experienced such strange behavior on WL61, though, I'd like to hear about it, and what you did as a work around.

What is the difference between a RequestDispatcher object obtained from the Request object and the RequestDispatcher object obtained from the ServletContext ? Location: http://www.jguru.com/faq/view.jsp?EID=473812 Created: Aug 10, 2001 Author: Raji Chawla (http://www.jguru.com/guru/viewbio.jsp?EID=467765) Question originally posed by Aejaz Sheriff (http://www.jguru.com/guru/viewbio.jsp?EID=18227

request.getRequestDispatcher("url").forward(request,response); and getServletConfig().getServletContext().getRequestDispatcher("url").forw ard(request,response); One : you can pass relative URL address when using request.getRequestdispather, and absolute URL address when using ServletConfig.getRequestDispatcher. Two: All request details are not passed when using ServletConfig.getRequestDispatcher. May be it is the query string parameters for the current page that does not reach the page where request is forwarded. (don't remember exactly..surf it out) Is there a recommended way to validate form data entered by the user? Should I do it on the client or the server? Location: http://www.jguru.com/faq/view.jsp?EID=473818 Created: Aug 10, 2001 Modified: 2001-09-26 12:17:44.267 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Ignacio Coloma (http://www.jguru.com/guru/viewbio.jsp?EID=466626 [When you show a form (POST or GET) to a user you can check for some required fields in javascript, but you should double check it again on the servlet. I mean, some fields are required, other need to be in a range (too many characters, too little number, NaN, and so on), and other simple checks. Is there a (more or less) standard way to achieve this? I'm using an XML config file where I say every argument that every servlet receives, if it's required or not, its type and limits, and so on. I was wondering if there was another way more appropiate to do this.] > Is there a (more or less) standard way to achieve this? No. You could create a monstrously complex method using reflection and a list of data types and expected values, but that gets unworkable really quickly. The problem is, you'll have your own types of valid data values, and any library that tries to solve the whole thing will become something like XSchema, which is really complicated and *still* doesn't handle certain common cases. I always find that when a "config" file format gets too complicated, you may as well throw it away and just use Java as your rules language.

My advice is to just make a method called "validate(HttpRequest)" for each servlet. It can return a null if they're OK and a String with an error message if they're not. The calling doGet() method can print the error message in whatever form is appropriate for your UI (divide and conquer). public void doGet(...) { String error = validate(req); if (error != null) { printError(resp, error); return; } // continue on with processing form ... } (Alternately, you could throw a ValidationException whose getMessage() field contains the error. My personal style is to avoid exceptions except in truly exceptional cases, and since you expect the user to enter bogus data at least some of the time, this doesn't qualify.) Then, once you've written a few of these, you will see repeated types of checks -like "make sure it's really a number" and "make sure it's between a given range." Factor these out into static utility methods, put them into a class (say, FormValidator). Then rewrite your old validate() methods to use these utility methods, and writing new validate() methods will become a little easier next time. Check Refactoring by Martin Fowler for inspiration on this sort of incremental programming. It's a lot more rewarding and efficient than trying to solve the whole problem all at once. Also, check Jakarta Regexp package if you're going to be validating string contents. Please see the forum threads: • •

Good idea - more simple than mine how to check whether the data entered is a number ...

for some more discussion of this problem. Comments and alternative answers

A comment from Leonard Grove Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Nov 11, 2001 use a pattern matching function in the ezVerify (http://www.ezverify.com) server-side validation tag library. Is there a simple example of how to use web application security in WebLogic? Location: http://www.jguru.com/faq/view.jsp?EID=479768 Created: Aug 20, 2001 Author: CustomWare Asia Pacific

(http://www.jguru.com/guru/viewbio.jsp?EID=139414) Question originally posed by CustomWare Asia Pacific PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=139414 Following is an example for WebLogic 6.x that protects all URLs that begin with /secure: WEB-INF/web.xml - Define a constraint and a role <web-app> <security-constraint> <web-resource-collection> <web-resource-name>SecurePages <description>Security constraint for resources in the secure directory /secure/*

POST

GET

<description>only let the admin role access the pages admin <user-data-constraint> <description>SSL not required NONE

BASIC <security-role> <description>A role to access the secured pages admin WEB-INF/weblogic.xml - Map the admin role to the system user in WebLogic. <weblogic-web-app>

<security-role-assignment> admin <principal-name>system Why do I get the error java.lang.IllegalStateException: Header already sent ? Location: http://www.jguru.com/faq/view.jsp?EID=480147 Created: Aug 20, 2001 Author: Nils Kulk (http://www.jguru.com/guru/viewbio.jsp?EID=337581) Question originally posed by Dave Brown (http://www.jguru.com/guru/viewbio.jsp?EID=459504 Hi, sounds like you're trying to set a header after you've written something to the response output stream. An HTTP repsonse message is composed as follows: an HTTP reponse code (something like "HTTP/1.1 200 OK") followed by zero or more headers (something like "ContentType: text/html") followed by the repsonse contents. This allows a server to send the headers to the client before sending the response contents. This way the client can determine some meta data about the repsonse (for example what the type of the content is). This means that as soon as the first byte of repsonse contents is written the reponse goes into a state where headers can't be set. Trying to do so, results in an IllegalStateException. So the wrong way is: OutputStream out = response.getOutputStream(); out.writeln("Hello..."); out.flush(); response.setContentType("text/html"); The right way is: response.setContentType("text/html"); OutputStream out = response.getOutputStream(); out.writeln("Hello..."); out.flush(); Comments and alternative answers

the same error in jsp Author: johnson johney (http://www.jguru.com/guru/viewbio.jsp?EID=527416), Oct 22, 2001

Hi, What does this mean if the same error happens in jsp, I am not using the forward tag or requestdispatcher anywhere in the jsp Are there any restrictions placed on applets loaded from HTML pages generated from servlets / JSP pages? Location: http://www.jguru.com/faq/view.jsp?EID=485955 Created: Aug 28, 2001 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) It is good practice to include the CODEBASE attribute in the APPLET tag and specify a directory other then the servlet directory for storing the applet-related classes. For example: out.println(<"APPLET CODE=Foo.class CODEBASE=/applets WIDTH=400 HEIGHT=400">); Some Web servers think that all classes loaded from the servlets directory are automatically servlets, thus causing the applet not to load. Is it possible to set the user name and password on an HTAccess certificate directly from my code rather than have the user do it from the HTAccess prompt? Location: http://www.jguru.com/faq/view.jsp?EID=492801 Created: Sep 7, 2001 Author: Bogdan Sheptunov (http://www.jguru.com/guru/viewbio.jsp?EID=310126) Question originally posed by Tim Smiser (http://www.jguru.com/guru/viewbio.jsp?EID=351009 Yes. This is the code for BASIC http authorization: // use this to encode the username/password private String encodeAuthorization String username, String password) { String authorization = username + ":" + password; sun.misc.BASE64Encoder enCoder = new sun.misc.BASE64Encoder(); return "Basic " + enCoder.encode(authorization.getBytes()); } // insert this piece into setting the connection properties, where encodedAuthorization is a result of the function given above: connection.setRequestProperty("Authorization", encodedAuthorization); Comments and alternative answers

Use Java.net.Authenticator Author: Bhiku Mhatre (http://www.jguru.com/guru/viewbio.jsp?EID=494523), Sep 10, 2001 I suggest you install a default Authenticator to achieve this. You could save your username/password in a file or read it in a Properties object (authProp). The code could look similar to this: import java.net.*; {.. ..

** add this before opening a URL connection> *** Authenticator.setDefault(new MyAuthenticator(authProp)); .. .. } // Add this class to your app class MyAuthenticator extends Authenticator{ MyAuthenticator(Properties myProp) { this.myProp = myProp; } protected PasswordAuthentication getPasswordAuthentication() { String username = myProp.getProperty("username"); String password = myProp.getProperty("password"); if (username==null || password==null) { System.err.println("MyAuthenticator: username or password is null.Returning null"); return null; } else return new PasswordAuthentication(username,password.toCharArray()); } }

How do I use a RequestDispatcher to call one servlet from another servlet? Location: http://www.jguru.com/faq/view.jsp?EID=492819 Created: Sep 7, 2001 Author: André Wolf (http://www.jguru.com/guru/viewbio.jsp?EID=310274) Question originally posed by Irene Espadas (http://www.jguru.com/guru/viewbio.jsp?EID=481137 To call another servlet you have to use a request dispatcher: RequestDispatcher rd = this.getServletConfig() .getServletContext() .getRequestDispatcher("/path-to-servlet"); rd.forward(); or rd.include(); See J2EE-API documentation for more information. Note that you cannot use a full qualified URL in getRequestDispatcher(). This must be the path of the servlet relative to the servlet context. For example: If your servlet context is called "/Select" and your servlet (which you want to dispatch to) is mapped to "/Select" within this context, you have to call getRequestDispatcher("/Select?TABLA="+param). You should also verify if the returned dispatcher object is not null before you call either include(request, response) or forward(request, response). As you can see in

the API documentation both methods require two parameters request and response, which are the same one you have defined in doGet(). I recommend you to read the API documentation, everything is very well explained in there. And I can recommend the Servlet Tutorial you can find at the SUN-Java webpage, especially the section "Invoking Other Web Resources". Comments and alternative answers

DoPost to DoGet??? Author: Irene Espadas (http://www.jguru.com/guru/viewbio.jsp?EID=481137), Dec 21, 2001 Thank for your answer. But...if I do this in a DoPost method it goes to the DoPost method of the other server. How can I do to go from DoPost to DoGet method????????? Thanks Re: DoPost to DoGet??? Author: Eduardo Garcia (http://www.jguru.com/guru/viewbio.jsp?EID=1145466), Feb 11, 2004 Hi Irene. Just make a call to doGet method inside the doPost method, like this: public void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response). } Hope that can be helpful :). how to forward from doPost Author: Satish Rapalli (http://www.jguru.com/guru/viewbio.jsp?EID=1233969), Mar 21, 2005 Hi, I'm unable to forward or include from doPost method,which i am successfull with doGet. Actually, i'm catching the information from a form whose method is post into a servlet class which has only doPost and then i'm trying to forward the request to another servlet class. The code inside the doPost method is: RequestDispatcher rd = request.getRequestDispatcher("/math"); rd.forward(request,response); The error when form is submitted : type Status report message HTTP method POST is not supported by this URL description The specified HTTP method is not allowed for the requested resource (HTTP method POST is not supported by this URL). Why do I get the error Http Method POST is not Supported by this URL? Location: http://www.jguru.com/faq/view.jsp?EID=492829 Created: Sep 7, 2001 Author: Jatinder Thind (http://www.jguru.com/guru/viewbio.jsp?EID=488511)

Question originally posed by Gopala Pulipaka (http://www.jguru.com/guru/viewbio.jsp?EID=487958 Most probably you have put only the doGet() method in your servlet. If the form you used to submit data has POST in its method tag, the above exception will be thrown. Change this tag to GET or add a doPost() method into your servlet. How do I parse hex integer Color codes passed as parameters to my servlet? Location: http://www.jguru.com/faq/view.jsp?EID=492831 Created: Sep 7, 2001 Author: Bogdan Sheptunov (http://www.jguru.com/guru/viewbio.jsp?EID=310126) Question originally posed by Allan Kamau (http://www.jguru.com/guru/viewbio.jsp?EID=484440 [ I am trying to pass Color values like 0xeeeeee or 0xEEEEEE as values to parameters from a get post (in the header). However I am unable to process the value into an integer value which is a requirement for the Color(int) constructor I will use to create the new color based on this passed value, I have tried int colorvalue=Integer.parseInt(req.getParameterValue("ColorParameter")); It is throwing an NumberFormatException which I am printing displaying the actual value of the parameter e.g NumberFormatException : 0xEEEEEE Could anyone kindly tell me how to process this value of the parameter into an integer value so I may pass it to the Color(int) constructor. Thanks. ] The keyword for you is Integer.decode(). Here is some sample code: String hexValue = "0x11"; Integer decodedInt = null; int result = 0; try { decodedInt = Integer.decode(hexValue); } catch (NumberFormatException e) { System.out.println("Cannot convert '" + hexValue + "': " + e.getMessage()); } if (decodedInt != null) { result = decodedInt.intValue(); } System.out.println(result); // prints out 17 Comments and alternative answers

Search Comment On FAQ Entry RE: How do I parse hex integer Color codes passed as parameters to my servlet? Author: Garrett Smith (http://www.jguru.com/guru/viewbio.jsp?EID=733867), May 20, 2002 Well, I don't think he wants the whole hex as a number, rather it would make sense to have a number each for red, green, and blue. String colorParameter; int r; colorParameter = reqest.getParameterValue("ColorParameter"); if(colorParameter != null && ! "".equals(colorParameter) && colorParameter.length == 8){ colorParameter = colorParameter.substring(2); r = Integer.parseInt(colorParameter.substring(0,2), 16);

You'd be much better off writing a class for handling this. It will be cleaner and more easily reusable. You can call a constructor, which can either throw an exception or have a private method for isValidHex. Also, you can call methods to set brightness, adjust the hue, find other related colors --basically apply all the color theory you know! So what are you going to do with this? How do I use Visual Cafe to debug my servlets running inside the WebLogic Web server? Location: http://www.jguru.com/faq/view.jsp?EID=492844 Created: Sep 7, 2001 Author: Irene Espadas (http://www.jguru.com/guru/viewbio.jsp?EID=481137) Question originally posed by srini k (http://www.jguru.com/guru/viewbio.jsp?EID=485364 You have to go to Project-Option-Server. In the button option "Manage Deployment Target" you have to configure the server, putting the password, server name and domain. You can do this in enviroment options for all the projects Run the servlet. It has to generate a web.xml and weblogic.xml file. I think you have to make a directory named classes in \config\mydomain\applications\DefaultWebApp_myserver\WEB-INF\classes. Make sure the xml files it generates have been put in \config\mydomain\applications\DefaultWebApp_myserver\WEB-INF\ Should I use one servlet supporting GET to show pages and POST to process forms, or two separate servlets? Location: http://www.jguru.com/faq/view.jsp?EID=497265 Created: Sep 14, 2001 Modified: 2001-09-15 12:33:34.676 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Raji Chawla (http://www.jguru.com/guru/viewbio.jsp?EID=467765

I prefer keeping my servlets as simple as possible. That means one servlet per page, and one per function. In this case, that would mean one servlet to show pages and another servlet to process forms. The trick is, all the servlets can communicate with the common data model, which is stored using session or application attributes. For example, I have one servlet (actually a JSP) that displays a form. The ACTION for that form is another servlet which processes the parameters. That servlet sends a redirect to the resulting page -- either the original form with an error message, or the "Thanks for filling out the form" page servlet (actually a JSP). This allows me to keep my UI design very flexible. For instance, I can have two different pages call the same "process form" logic servlet, allowing (e.g.) a "Search" box on every page and a separate Search page to use the same behind-the-scenes logic. (I prefer using browser redirects (sendRedirect()) over RequestDispatcher since it keeps bookmarks and Reload/Refresh logic clean.) It's definitely a style choice; I like my way because it's more flexible; lumping everything together can lead to brittle spaghetti code. And as for GET and POST in the same servlet, I think that's kind of messy. I actually like it when POST servlets can still respond to GET requests with the same semantics -- it makes it a lot easier to debug! (I can just type in my test case in the address bar.) Note that this requires that doGet() and doPost() have the same implementation, which is trivial in the Servlet API: public void doGet(HttpServletRequest req, HttpServletResponse res) { doPost(req.res); } You should also read the Forum Thread on this subject for many other good comments. Comments and alternative answers

One servlet or several servlets Author: Subrahmanyam Allamaraju (http://www.jguru.com/guru/viewbio.jsp?EID=265492), Sep 15, 2001 I've a few comments on Alex Chaffee's answer: •

Whether a servlet (typically a subclass javax.servlet.http.HttpServlet) chooses to support one or several HTTP methods, it inherits default behavior from the abstract super class. Given this, it is perfectly valid to support more than one method in a given servlet. For instance, a servlet may implement doGet, doPost and doHead. Having said this, for the sake of simplicity, I suggest that all such methods perform related functions.

•

The second point is about browser redirect vs. request dispatcher's forward mechanism. Browser redirects involve extra roundtrip between the server and the browser. One should be careful about this choice.

How do I load a file from inside a WAR file? Location: http://www.jguru.com/faq/view.jsp?EID=497268 Created: Sep 14, 2001 Author: Bozidar Dangubic (http://www.jguru.com/guru/viewbio.jsp?EID=433955) Question originally posed by Dean Sheppard (http://www.jguru.com/guru/viewbio.jsp?EID=14227 [getClass().getResource() is the wrong approach, since the WAR file is not in the current classloader's path. getServletContext().getResource() should work, but apparently fails under WebLogic. Fortunately... -A] I have done the same thing many times using ctx.getResourceAsStream("/relpath/filename") and it always works fine. I am not sure what is the problem in your case. try to access the file using getResourceAsStream() and see if that works. What is the best way to store a large object, such as a result set, across requests, but only for a short term, say for using the result set for printing for instance? Location: http://www.jguru.com/faq/view.jsp?EID=497495 Created: Sep 15, 2001 Modified: 2001-09-27 09:11:15.513 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Scott MacLellan (http://www.jguru.com/guru/viewbio.jsp?EID=51832 [ I am assuming to store it in the session object would not be the best option. Also I don't want to have to re-issue the query just to print it or do something else with it. ] First, as another poster pointed out, you should slurp the data from a ResultSet into an object (probably a JavaBean) immediately upon retrieval. That frees up database resources. Then, what do do with the bean? You could store it in the session. Despite your skepticism, that's probably the best plan. The session will be around the next time the user makes a request. If memory fills up, some servlet containers have the ability to swap the session data to disk; then, when the user needs it again, it will be automatically (and transparently to you) loaded back into memory. To assure this will work, make sure your bean implements the Serializable interface.

If the user gives up and goes away before using the data, then you needn't worry about memory leaks, since the session data will be released when the session expires. Once you're done with the data, however, you should remove it from the session immediately, allowing normal garbage collection to take effect. If the data set is too large to efficiently store into memory, then you can either serialize it to disk, or store it back into a database. However, those options require you to take responsibility for garbage collection -- you will need to have some algorithm for deleting old files or records -- and that can be a real pain in the neck. Comments and alternative answers

Check out Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Sep 27, 2001 Dmitry Namiot, Aug 20, 2001 writes: Check out cache taglib on http://www.servletsuite.com/jsp.htm for example. How can I implement returning part of a large (1000+ rows) result set to the client? Location: http://www.jguru.com/faq/view.jsp?EID=497499 Created: Sep 15, 2001 Author: Bozidar Dangubic (http://www.jguru.com/guru/viewbio.jsp?EID=433955) Question originally posed by Bryan James (http://www.jguru.com/guru/viewbio.jsp?EID=497040 Try RowSet. It is pretty fast and provides functionality you outlined above. However, you will never be able to return first n rows "while result set is being loaded." although that is a nice functionality, it would be tremendously hard to implement it in the JDBC driver. you have no control of how data is obtained from the database unless you wrote the JDBC driver yourself. therefore, no luck there. you can try to combine some logic to access first n number of rows from the database, but request for n+1, n+2... records would require additional queries to the database which can get overly complex. so try RowSets. I am sure that you will be satisfied with the performance and functionality. Comments and alternative answers

why cant you cache ResultSet and just use it as a cursor Author: sam pitroda (http://www.jguru.com/guru/viewbio.jsp?EID=476938), Nov 15, 2001 I am assuming that there is no problem in caching resultset in servlet which you can get back from session id.

Can anyone tell me the advantages and disadvantages between Tomcat, JRun, and JServ for Apache Web Server? Location: http://www.jguru.com/faq/view.jsp?EID=497500 Created: Sep 15, 2001 Author: Christopher Schultz (http://www.jguru.com/guru/viewbio.jsp?EID=138382) Question originally posed by Terry Kroukamp (http://www.jguru.com/guru/viewbio.jsp?EID=495999 Here's some quick-n-dirty facts:

Product Tomcat

• •

•

JRun

• • •

Apache JServ

Pros Free as in both beer and speech Active open-source development effort Very current in terms of servlet API compliance Free as in beer for developers Relatively speedy Supported by Allaire (Macromedia)

Free as in both beer and speech

•

Cons Not the fastest implementation on the planet

•

You're on your own for support

• •

Costs money for production use Versions that I've used (pre-3.0) had lots of configuration headaches

•

Slightly behind the times with updates (compared to open source projects) No longer in active development (Tomcat inherited this effort) Has some thread-leaking issues, in my experience Only supports servlet API 2.0 (not later)

• • •

•

You're on your own for support

Realistically, the support issues with Tomcat and JServ aren't really a problem. If you write good code, you'll never trip up these servers. Configuration management is fully documented, as is installation and troubleshooting for all of these products, online. My choice would be Tomcat, since it's an Open Source project (making it free and giving you access to the source code if necessary), stays on top of the servlet API developments, and works very well (I've never had any problems). I would personally stay away from JRun for the counterpoint reasons listed above, but have no technical reasons to poo-poo JRun. Allaire has good products, and I've heard that JRun 3.0 and above is a lot easier to work with in terms of configuration, etc.

Hope that helps, -chris Comments and alternative answers

What about Resin? Author: Kai Mysliwiec (http://www.jguru.com/guru/viewbio.jsp?EID=506836), Sep 29, 2001 Has anyone experince with Resin? Re: What about Resin? Author: Marc Schneider (http://www.jguru.com/guru/viewbio.jsp?EID=707299), Jan 2, 2002 Yes, Resin is similar to Tomcat, but: a) It's much much faster b) It's (slightly) easier to configure, and you have more options c) It's expensive in an Production environment ($500 per server, $4500 for a pack of 10) Hope that helps... JRun Author: K Makinen (http://www.jguru.com/guru/viewbio.jsp?EID=516487), Oct 10, 2001 In my understanding, JRun uses pretty weak session ID generation algorithms. So if security is an issue to be considered, JRun may not be the best choice. jrun == booty Author: Phillip Morelock (http://www.jguru.com/guru/viewbio.jsp?EID=523143), Oct 17, 2001 I must say, i used the developer version of JRun (the free-as-in-beer version) -- and it was the absolute biggest nightmare in terms of configuration and setup i have ever used in my entire life. Allaire products i've used: Homesite (excellent HTML and JSP dev tool), Cold Fusion (don't get me started -- nasty and slow), and JRun (configuration nightmare). Overall, i gotta say -- with Tomcat, I was up and running and focusing on my code in literally 10 minutes. Jrun -- i gave up after spending several hours over a couple of days. In fact, I tried JRun first, and it completely turned me off to servlet containers for a period of about three months. At that point, I tried Tomcat, and fell in love. The rest is history. Has Tomcat covered all functions of JServ? Author: amq zhang (http://www.jguru.com/guru/viewbio.jsp?EID=761045), Feb 16,

2002 I was trying to do some testing following doc http://java.apache.org/jserv/howto.loadbalancing.html I am not sure how different Tomcat is, will there still have got same functions? or I'd better just set up JServ, make life bit easier? Re: Has Tomcat covered all functions of JServ? Author: Kevin CHEUNG (http://www.jguru.com/guru/viewbio.jsp?EID=1061154), Feb 27, 2003 How about Orion AS? I've tested it and compared to Tomcat 4.x, Orion is even easier to configure but I guess the tradeoff is scalability as Tomcat is pretty scalable. I didn't have the Orion in production usage and the runtime performance against Tomcat 4.x is thus known. Is there experience sharing on the relative runtime performance? How do I load an applet from a servlet or JSP? Where do I place my applet class files? Location: http://www.jguru.com/faq/view.jsp?EID=499425 Created: Sep 18, 2001 Modified: 2003-01-05 05:53:08.134 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Chris Klumpp (http://www.jguru.com/guru/viewbio.jsp?EID=496701 An applet is executed on the client side (browser), not on the server side (servlet container). You need to place the applet class files in a location accessible from the browser, which means you have to treat them like normal files (like HTML or GIF files that you want the browser to load). Thus they need to go in the webapp directory tree, but not in the WEB-INF subdirectory. It is best to think of the set of applet class files as entirely different from the set of servlet class files. They will be loaded by different Virtual Machines, and may even have different versions of classes. It is a simple matter to configure your build environment (Ant or make) to create copies of common class files in the two different classpath directories. Since the concept of "current directory" is kind of fuzzy in the Servlet API, it is usually easiest to make a separate directory just for your applet class files, and use the optional CODEBASE parameter to the APPLET tag. Here is an architecture that works well: myapp/WEB-INF/classes/MyServlet.class myapp/WEB-INF/classes/Util.class myapp/index.html myapp/applets/MyApplet.class myapp/applets/Util.class Then if your servlet generates a line like: out.println("<APPLET CODE='MyApplet.class' WIDTH=50 HEIGHT=50 CODEBASE='/applets'>">;

The browser will be able to load MyApplet.class and Util.class from your /applets web directory. It will not be able to load anything from WEB-INF/classes, since those files are accessible only by the servlet engine. Note that loading an applet from a page generated by a servlet is much the same as loading an image. It is also easier to use a common "images" directory in that case, so that images can be loaded from any page regardless of "current" directory. See also: • • •

What is the Java Plug-In? (and the topics Applets:Plug-in and Browsers: Plugin) How do I set my CLASSPATH for servlets? Where do I store image files so my servlet's HTML pages can display them?

Comments and alternative answers

ok, so what if your applet class and your servlet class need to access common utility classes? Author: George Francis (http://www.jguru.com/guru/viewbio.jsp?EID=894160), Jun 27, 2002 If my web-app has utility classes that need to be accessed by both the applet and the servlets - where should they be deployed? Re: ok, so what if your applet class and your servlet class need to access common utility classes? Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 5, 2003 Unfortunately, you need to put common classes/jars in both places: both inside WEB-INF -- so the servlet can find them -- and inside the normal htdocs directories -- so the applet can find them. (As the original answer said, "It is a simple matter to configure your build environment (Ant or make) to create copies of common class files in the two different classpath directories.") Class Not Found Author: JASPER TAPIA (http://www.jguru.com/guru/viewbio.jsp?EID=1052495), Jan 31, 2003 I set up the directory structure like you said /usr/local/catalina/webapps/ESI/applets/HelloWorldApplet.class /usr/local/catalina/webapps/ESI/applet.html I just want to call a basic applet from a html page. [ESI]# less applet.html <TITLE>Hello World Applet

Hello World Applet

<APPLET code="HelloWorldApplet.class" width=350 height=120 codebase='/applets'> [applets]# less HelloWorldApplet.java

import java.applet.*; import java.awt.*; public class HelloWorldApplet extends Applet { static final String message = "Hello World"; private Font font; public void init() { setBackground(Color.white) ; font = new Font("SansSerif", Font.BOLD, 48); } public void paint(Graphics g) { g.setColor(Color.pink); g.fillOval(10, 10, 330, 100); g.setColor(Color.red); g.drawOval(10,10, 330, 100); g.drawOval(9, 9, 332, 102); g.drawOval(8, 8, 334, 104); g.drawOval(7, 7, 336, 106); g.setColor(Color.black); g.setFont(font); g.drawString(message, 40, 75); } } When I opened the html page I just got a grey box. When I scolled over it I saw load: class HelloWorldApplet not found in the bottom bar of my browser. Do I have to point to the class file in my web.xml file or set a CLASSPATH? Thanks in advance Re: Class Not Found Author: Ryan Swanson (http://www.jguru.com/guru/viewbio.jsp?EID=1246596), May 31, 2005 ok so i have a .jar file how would i load that? i have a specific class file inside the jar file i need to load. ne hlp plz. How do I pass params like -D to the JServ JVM? Location: http://www.jguru.com/faq/view.jsp?EID=500047 Created: Sep 19, 2001 Author: drit . (http://www.jguru.com/guru/viewbio.jsp?EID=454295) Question originally posed by sam pitroda (http://www.jguru.com/guru/viewbio.jsp?EID=476938 [I want to pass this parameters to JVM that runs my servlet. E.g. -Djava. naming.factory.initial = com.sun.jndi.cosnaming.CNCtxFactory] There is a file in apache/JServ known as "jserv.properties". Set your param in this wrapper.bin.parameters key. How do I use servlets to return dynamically generated PDF documents? Location: http://www.jguru.com/faq/view.jsp?EID=500656 Created: Sep 20, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Alex Chaffee PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=3 [Thanks to Greg Perkins, Aug 27, 2001:] You should take a look at iText. It's an open source PDF library for java, hosted over at sourceforge. They have an example of using servlets to return dynamic PDF documents. http://www.lowagie.com/iText/ [See also the forum thread for this topic: How do I use servlets to return dynamically genera... ]

Comments and alternative answers

Try XSL-FO Author: Shai Almog (http://www.jguru.com/guru/viewbio.jsp?EID=501707), Sep 22, 2001 We have a similar situation where we wanted a generic approach and decent separation of view/logic. XSL allows you to transform any XML document to many types of visual documents such as PDF and HTML. Thus your servlet can generate the data as XML and simply pass it through the processor. xml.apache.org has most of the things you need (an XSLT processor and an early yet functional XSL-FO implementation). One warning though, XSLT is a REALLY ugly language, but it is rappidly gaining popularity and it does have some nice features.

Re: Try XSL-FO Author: Dev eloper (http://www.jguru.com/guru/viewbio.jsp?EID=1183562), Jul 3, 2004 If you do not want to have to program your application to handle conversion from html to pdf, then you can look at a web service offered by Gilgamesh Solutions at http://gilgamesh-solutions.com/webservices.cfm. Using this service you will be able to send a URL to an html page you build on the fly on your server, and the service will actually crawl over your URL and convert your page to pdf! You can control many options including footers, headers, page breaks, page orientation (landscape vs. portrait), include high quality images (png, jpg, gif). The beauty about this service is that you are able to control the format of your generated pdf using html tags! If you have a coldfusion server, then you can actually buy the product for around $60 I believe. But you might want to go with the service option if you do not want to deal with installation, setting up your application, worrying about changing your application when you upgrade, if you use different languages and you want an application that is platform and web server independent. Give it a try, I believe that they have test environments on their web site where you can try their products live for free. Try xml.apache.org/fop Author: hotjaffa jaycee (http://www.jguru.com/guru/viewbio.jsp?EID=390693), Sep 22, 2001 Hi, We've had a simialr requirement recently and used fop from the apache project. Wihin 2 days we had solved our problem and had a serv;et + jsp dynamically generating XML/XSL -> FO file -> PDF. Nice 'n' easy and robust and open source Re: Try xml.apache.org/fop Author: Santanu Sen (http://www.jguru.com/guru/viewbio.jsp?EID=524215), Oct 18, 2001

I am a real beginner on Java. I am trying to compile a Servlet that we got from Software AG- an xml to pdf Servlet that will convert xml document to pdf on the fly. It is not compiling. Do you think you can share your Servlet source code with me ? Looks like yours one is doing the same job. Thanks Try XMLPDF also Author: James Childers (http://www.jguru.com/guru/viewbio.jsp?EID=761785), Feb 17, 2002 I have had some success with XMLPDF, as well. You can use it to generate a PDF from and XML template and data that has been stored in an XML file (or an in memory representation of an XML file.) Has worked great for me. How do I get a session object to perform a task before it is invalidated? Location: http://www.jguru.com/faq/view.jsp?EID=500657 Created: Sep 20, 2001 Author: Denis Navarre (http://www.jguru.com/guru/viewbio.jsp?EID=495283) Question originally posed by Tony Fagan (http://www.jguru.com/guru/viewbio.jsp?EID=226421 Hi Tony, You must implement the javax.servlet.http.HttpSessionBindingListener interface in your object stored in session. Two methods must be added to your object when you implement this interface: public void valueBound(HttpSessionBindingEvent arg1) and public void valueUnbound(HttpSessionBindingEvent arg1) These methods are called when the object is put in session (valueBound) and when the object is removed from the session (valueUnbound). To answer to your question: you have to put your code in the valueUnbound method to do some actions just before the object is removed (or replaced!) from the session. If the session expired or is invalidated, all objects are unbound from the session, and the method valueUnbound is called. I use this interface to delete temporary files and it works fine. Regards, Denis Navarre Comments and alternative answers

Re Author: Massimiliano Ragazzi (http://www.jguru.com/guru/viewbio.jsp?EID=945577), Jul 25, 2002

The valueUnbound doesn't function because when it's called the object is jaust removed See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Dec 9, 2002 Session Management - Clean up after session time out. Why do I get the error "IllegalStateException" when using the RequestDispatcher? Location: http://www.jguru.com/faq/view.jsp?EID=501393 Created: Sep 21, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Mark Gorenstein (http://www.jguru.com/guru/viewbio.jsp?EID=492823 When you use RequestDispatcher.forward or RequestDispatcher.include to call another servlet, you must pay very close attention to a fairly tricky detail of the servlet "chain of command." When a servlet is first called, the response object is fresh and new: its headers have not been set, its buffers are empty, and no data has been written to the client. However, as soon as either the status code or any of the headers have been written -- or potentially written -- to the client, or when data has been -- or may have been -- written to the body stream, then you may be susceptible to the IllegalStateException error. The problem that this exception is signalling is the new data that you are (or may be) writing is inconsistent with the data that's already been set and then irretrivably sent ("committed") to the client. Two common variants of this exception are "java.lang.IllegalStateException: Header already sent" and "java.lang.IllegalStateException: Cannot forward as Output Stream or Writer has already been obtained". "Header already sent" means that one or more headers have been committed to the client, so you can't set that header again. "Output Stream or Writer has already been obtained" means that since the calling servlet has already called response.getWriter() or response.getOutputStream(), that contaminates the data stream, since the response has been (or may have been) written to already, making it unsuitable for forwarding. (Some would argue that the exception is overkill; that the Servlet API should just silently log the problem, then continue as best it can, e.g. by simply not writing the new headers or status code or body text. However, the API as it stands is less forgiving, and it throws a hard exception.) A further complication is "side effects", where methods set the "committed" flag unnecessarily, or at least unexpectedly. For instance, calling response.flushBuffer() sets the "committed" flag (even if the buffer is empty). Furthermore, calling

RequestDispatcher.include() calls response.flushBuffer() (even if the "included" servlet doesn't actually write any data to the response). That means that you shouldn't ever call include() before calling forward(). This is due to the semantics of RequestDispatcher.forward() -- it's intended to be called only by servlets that do literally nothing to the response before forwarding (since the "forwardee" is supposed to be the master servlet). Unfortunately, this means that you can't do things that you might naturally expect, like forwarding from one servlet or JSP to another, where each one adds a little bit of data to the response. Also unfortunately, there are some scenarios where you *can* do exactly that, so when you encounter a scenario where the exception is thrown, it seems to come from out of the blue. What this all means is that the Servlet API is inadequate as a general framework for sending messages among active objects to form a data pipeline. Fortunately, you have an API that is perfectly adequate for that task: Java itself. Structure your application to use JavaBeans and Java method calls. Restrict your Servlets to two types: one type is all data-processing, and the other type is all response-writing. If you want your response-writers to be modular (one object to build the nav bar, one object to build the banner ad, one object to build the body, one object to build the page footer, etc.), you have two choices: 1. use JavaBeans or Java method calls to build up the HTML in the response, or 2. use RequestDispatcher.include() to bring in content from many little servlets from inside a master response-builder servlet. RequestDispatcher.include() is probably a safer method than RequestDispatcher.forward() for other reasons, since it leaves the request parameters alone (forward() changes the path etc. to be relative to the target servlet, not the original servlet). You may also look into Servlet 2.3 Filters as an alternative way to string page content together from multiple resources (though it too is quite complicated and ambiguous at times). See also: • • • • • •

Why do I get the error java.lang.IllegalStateExcep... While forwarding from one page to another by using... RequestDispatcher class: IllegalStateException ra... RequestDispatcher FAQ Topic If the output stream was not buffered at the time ... Using Tomcat and Xalan, why do I get the exception...

Comments and alternative answers

You should also explore Author: Phillip Morelock (http://www.jguru.com/guru/viewbio.jsp?EID=523143), Oct 17, 2001

at least on the output end, i use JavaBeans and custom Tags to do most of this work (like when the author of this answer described making the navbar with one component, the content with another, etc....). I find Tags to be the easiest way to modularize a response. But of course i defer to the author of this answer as someone with obviously more experience. It's just -- well, check out custom tagging and jsp's for your responses. They're pretty neat. Can I print the dynamic content output to my browser from a JSP page without showing the address URL? Location: http://www.jguru.com/faq/view.jsp?EID=502936 Created: Sep 24, 2001 Modified: 2001-09-26 08:39:43.115 Author: Matt Goodall (http://www.jguru.com/guru/viewbio.jsp?EID=450000) Question originally posed by king hw (http://www.jguru.com/guru/viewbio.jsp?EID=132496 You have no control how the browser decides to print a page. If layout matters that much then I would recommend writing a servlet to populate a PDF file with the data you have on your JSP. The servlet sends the PDF to the browser and the browser loads Adobe Acrobat to view the page. If you choose to do that take a look at FDF - PDF's form API. It's pretty easy to use, there are Java packages to help with the task and I'm sure FDF will have been mentioned on jguru before. Note that using PDF does mean that the client needs to have an Acrobat viewer installed. Comments and alternative answers

FDF Merge Author: Ranjan Banerjee (http://www.jguru.com/guru/viewbio.jsp?EID=505211), Sep 27, 2001 I have seen the results of FDF Merge and have been quite impressed by it. Re: FDF Merge Author: Archana Goud (http://www.jguru.com/guru/viewbio.jsp?EID=544525), Nov 30, 2001 How To Go About it can u be more detail. i generated a report in jsp. i need to take printout of it and the adress is been printed on top i want to eliminate it by using pdf how can i ? can u please help me out thank u Virtual directories Author: Nitin Baligar (http://www.jguru.com/guru/viewbio.jsp?EID=207743), Oct 17, 2001 To the best of my knowledge, you can show the output without showing the URL in

the browser. In the web server admin, you can create the virtual directories which will point to particular JSP page and if u just load like www.yourdomain.com/virtualDir it will load the particular JSp page which is linked in the web server admin. What is the difference between using getSession(true) and getSession(false) methods? Location: http://www.jguru.com/faq/view.jsp?EID=502938 Created: Sep 24, 2001 Modified: 2001-09-26 08:27:49.151 Author: sanjay pai (http://www.jguru.com/guru/viewbio.jsp?EID=385708) Question originally posed by arun vis (http://www.jguru.com/guru/viewbio.jsp?EID=474858 The difference is as follows: When you say getSession(true), this method will check whether already a session is existing for the user. If a session is existing, it will return that session object, OTHERWISE WILL CREATE A SESSION OBJECT EXPLICITLY AND RETURN TO THE CLIENT. When you say getSession(false), this method will check whether a session is existing. If yes, then it returns the reference of that session object, OTHERWISE IT WILL RETURN 'null'. Do objects stored in a HTTP Session need to be serializable? Or can it store any object? Location: http://www.jguru.com/faq/view.jsp?EID=504834 Created: Sep 26, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Dean Sheppard (http://www.jguru.com/guru/viewbio.jsp?EID=14227 Yes, the objects need to be serializable, but only if your servlet container supports persistent sessions. Most lightweight servlet engines (like Tomcat) do not support this. However, many EJB-enabled servlet engines do. Even if your engine does support persistent sessions, it is usually possible to disable this feature. Read the documentation for your servlet engine. Note that this means that a JDBC Connection should not be stored in a session, however convenient that would be. You can put it in an application scope variable, or in a "transient" field of a private class. Read the docs for the Serializable interface to learn more. How can I send a POST request from a Servlet or JSP? Location: http://www.jguru.com/faq/view.jsp?EID=504839 Created: Sep 26, 2001 Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985) Question originally posed by Juergen Havermann (http://www.jguru.com/guru/viewbio.jsp?EID=482830

There's nothing in the servlet API that let you to use the POST method for submitting data to any URL; but your servlet can enstablish a URL connection to the php page, send the parameters you need as HTTP body and print out the response in its body. See also the following FAQs: • • • • • • • • •

How can I make a POST request through response.sen... How can we send a POST request when we call getReq... How do I upload a file using a Java client (not a ... How do I call one servlet from another servlet? When you communicate with a servlet from an Applet... How do I capture a request and dispatch the exact... Can I call a CGI script from a servlet? How can an applet or application pass data to and ... How can my applet communicate with my servlet?

I've written some code (two servlets: a Source and a Target) to test this scenario:

import import import import import

javax.servlet.*; javax.servlet.http.*; java.io.*; java.net.*; java.util.*;

public class Source extends HttpServlet { private static final String CONTENT_TYPE = "text/html"; public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType(CONTENT_TYPE); URL url; URLConnection urlConn; DataOutputStream cgiInput; // URL of target page script. url = new URL("http://localhost:8086/servlet/Target"); urlConn = url.openConnection(); urlConn.setDoInput(true); urlConn.setDoOutput(true); urlConn.setUseCaches(false); urlConn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); // Send POST output. cgiInput = new DataOutputStream(urlConn.getOutputStream()); String content = "param1=" + URLEncoder.encode("first parameter") + "¶m2="

+ URLEncoder.encode("the second one..."); cgiInput.writeBytes(content); cgiInput.flush(); cgiInput.close(); // reads the CGI response and print it inside the servlet

content

BufferedReader cgiOutput = new BufferedReader(new InputStreamReader(urlConn.getInputStream())); PrintWriter servletOutput = response.getWriter(); servletOutput.print("

This is the Source Servlet

"); String line = null; while (null != (line = cgiOutput.readLine())){ servletOutput.println(line); } cgiOutput.close(); servletOutput.print(""); servletOutput.close(); } }

import import import import

javax.servlet.*; javax.servlet.http.*; java.io.*; java.util.*;

public class Target extends HttpServlet { private static final String CONTENT_TYPE = "text/html"; public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType(CONTENT_TYPE); PrintWriter out = response.getWriter(); out.print("

Target's output

<pre>"); } } Enumeration enum = request.getParameterNames(); while (enum.hasMoreElements()){ String param = (String) enum.nextElement(); String value = request.getParameter(param); out.println("param=" + param + " value=" + value); } out.print("");

If the user uploads a file with the same name as a previously uploaded one, how to overcome the overwriting of the first file? Location: http://www.jguru.com/faq/view.jsp?EID=504842 Created: Sep 26, 2001 Author: George Koras (http://www.jguru.com/guru/viewbio.jsp?EID=77493) Question originally posed by krishna kumar (http://www.jguru.com/guru/viewbio.jsp?EID=473175 [Hi! I am using com.oreilly.servlet.MultipartRequest up = new com.oreilly.servlet.MultipartRequest(request,"c:/test",10*1024) to upload a file into server.Can anyone help me in solving the prevention of overwriting of existing uploaded file? For example if i upload "paint.bmp",then this will be stored as "paint.bmp" in the server. Again if i upload a different picture under the same file name "paint.bmp" , the previous one is overwritten by the new one.This shouldnt happen.If the file "paint.bmp" already exists, some new filename should be generated for the new uploaded file and saved.can any one pass me source code for this problem.Thank you in advance... ] Did you try using the exists() method of the File object? e.g.: String pathname = "c:/test"; // I guess you meant "c:\\test"! File f = new File(pathname); if (f.exists()) { out.write("File already exists!\n"); } else { MultipartRequest up = new MultipartRequest (request, pathname,10*1024); } Comments and alternative answers

Download manually Author: Zeljko Trogrlic (http://www.jguru.com/guru/viewbio.jsp?EID=4607), Sep 28, 2001 There was a way to manually download a file. You can give any name to the file, so you should probably use automatically generated temp name. Procedure is described in documentation. This doesn't exist in old versions of the COS. Re: Download manually:Runs successfully on windows Author: nidhi tewari (http://www.jguru.com/guru/viewbio.jsp?EID=581714), Dec 13, 2001 import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import java.io.*; import java.io.IOException; import java.io.PrintStream; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.util.Hashtable; public class Download extends HttpServlet { public void doGet(HttpServletRequest req,HttpServletResponse res) throws ServletException,IOException { String strFileName = ""; ServletContext serContext = this.getServletContext(); ServletOutputStream sos = res.getOutputStream(); //UNC Path String dirName = "\\\\Gladiator\\eFM_API_CommonTestArea\\temp.txt"; String strContentType = getServletContext().getMimeType(dirName); res.setContentType(strContentType); File sFile = new File(dirName); String fileName=sFile.getName(); long lFileLength=sFile.length(); /* Read the file into a byte array */ byte[] FileinBytes = new byte[(int)lFileLength]; FileInputStream fis = new FileInputStream(dirName); /* Read the bytesarray into file input stream */ long lByteRead = fis.read(FileinBytes,0,(int)lFileLength); //ServletOutputStream sos = null; PrintStream ps = null; String header_info = req.getHeader("USER-AGENT"); if (header_info.indexOf("MSIE") != -1) { res.setHeader("Content-Disposition","attachment;fileName = " + fileName); } else { res.setHeader("Content-Disposition","attachment;fileName=\"" + fileName + "\";"); } sos = res.getOutputStream(); ps = new PrintStream(sos); ps.write(FileinBytes, 0, (int)lFileLength); ps.flush(); } } Re[2]: Download manually:Runs successfully on windows Author: Juan Carlos Erazo Montoya

(http://www.jguru.com/guru/viewbio.jsp?EID=897670), Jul 30, 2002 Yo can use defaultrenamepolicy(). Something like: mpreq = new MultipartRequest(request, tempFileDir, 20*1024, new defaultFileRenamePolicy()); How do I load a properties file from WEB-INF/classes? Location: http://www.jguru.com/faq/view.jsp?EID=506416 Created: Sep 28, 2001 Author: George McKinney (http://www.jguru.com/guru/viewbio.jsp?EID=21278) Question originally posed by Craig McDaniel (http://www.jguru.com/guru/viewbio.jsp?EID=443037 We use a number of properties files, both from the classes directory and from sub directories without any problem. For files directly in the classes directory, our code is like: Properties dbProps = new Properties(); //The forward slash "/" in front of in_filename will ensure that //no package names are prepended to the filename when the Classloader //search for the file in the classpath InputStream is = getClass().getResourceAsStream("/"+in_filename); if(null == is) { throw new ConfigException("Can't locate file:" +in_filename); } try { dbProps.load(is);//this may throw IOException return dbProps; } catch (IOException ioe) { System.err.println("Properties loading failed in AppConfig"); throw new ConfigException(ioe,"Can't locate file:" +in_filename); } Comments and alternative answers

Can I load a property file even if don't have WEB-INF dir? Author: Saurabh Bhargava (http://www.jguru.com/guru/viewbio.jsp?EID=526712), Oct 23, 2001 I am working with JServ which does not provides a WEB-INF directory. But still i

want to load a properties file. Is It possible? If Yes then How?

Regards

Saurabh

Re: Can I load a property file even if don't have WEB-INF dir? Author: brian ally (http://www.jguru.com/guru/viewbio.jsp?EID=530592), Oct 25, 2001 saurabh, with jserv, i use pretty much the same code - getResourceAsStream() just leave the properties file at the top of your classes directory. you'll want to be sure it's readable by jserv, which should be the same user apache is running as. regards, Re: Re: Can I load a property file even if don't have WEB-INF dir? Author: brian ally (http://www.jguru.com/guru/viewbio.jsp?EID=530592), Oct 25, 2001 don't forget the "/" before the props filename

not working Author: ram k (http://www.jguru.com/guru/viewbio.jsp?EID=865733), May 3, 2002 I tried to do classloader stuff in my java class which is not a servlet and it did not work. How do I write a tunneling HTTP proxy in Java? Location: http://www.jguru.com/faq/view.jsp?EID=506464 Created: Sep 28, 2001 Author: Martin Erren (http://www.jguru.com/guru/viewbio.jsp?EID=446238) Question originally posed by Alexandre Torres (http://www.jguru.com/guru/viewbio.jsp?EID=480684 [Note: the following is not a full-featured HTTP proxy. Other true HTTP proxies, like Squid, accept the CONNECT request, and can interpret the HTTP headers intelligently. This is a simple tunneling proxy, so it may not work correctly if you set it as your browser's proxy setting. Also, a more full-featured proxy has other features, like caching media. -Alex]

Recently I wrote a little Proxy in java and it works fine tunneling the requests with any ports to tomcat, but I didn't use apache (That's not the reason anyway) and NT instead of WIN98. I think it's either the configuration of the Proxy or the network configuration in your System try this: import java.net.*; import java.io.*; import java.util.*; class ProxyConnection extends Thread { Socket fromClient; String host; int port; long timeout; ProxyConnection(Socket s, String host, int port, long timeout) { fromClient=s; this.host = host; this.port = port; this.timeout=timeout; } public void run() { InputStream clientIn = null; OutputStream clientOut = null; InputStream serverIn = null; OutputStream serverOut = null; Socket toServer = null; int r0=-1,r1=-1,ch=-1,i=-1; long time0 = new Date().getTime(); long time1 = new Date().getTime(); try { toServer = new Socket(host,port); Proxy.display("open connection to:"+toServer+"(timeout="+timeout+" ms)"); clientIn = fromClient.getInputStream(); clientOut = new BufferedOutputStream(fromClient.getOutputStream()); serverIn = toServer.getInputStream(); serverOut = new BufferedOutputStream(toServer.getOutputStream()); while(r0!=0 || r1!=0 || (time1-time0)<=timeout) { while((r0=clientIn.available())>0) { Proxy.println(""); Proxy.println("<<<"+r0+" bytes from client"); Proxy.display(""); Proxy.display("<<<"+r0+" bytes from client"); for(i=0; i0) { Proxy.println(""); Proxy.println(">>>"+r1+" bytes from server"); Proxy.display(""); Proxy.display(">>>"+r1+" bytes from server"); for(i=0; i
clientOut.flush(); } if(r0==0 && r1==0) { time1 = new Date().getTime(); Thread.sleep(100); //Proxy.display("waiting:"+(time1-time0)+" ms"); } } } catch(Throwable t) { Proxy.display("i="+i+" ch="+ch); t.printStackTrace(System.err); } finally { try { clientIn.close(); clientOut.close(); serverIn.close(); serverOut.close(); fromClient.close(); toServer.close(); Proxy.quit(time1-time0); } catch(Exception e) { e.printStackTrace(System.err); } } } } public class Proxy { public static final String usageArgs =" <port> "; static int clientCount; public static synchronized void print(int i) { System.out.print((char) i); } public static synchronized void println(String s) { System.out.println(s); } public static synchronized void display(String s) { System.err.println(s); } public static synchronized void quit(long t) { display("...quit after waiting "+t+" ms"); clientCount--; } public void run(int localport, String host, int port,long timeout) { try { ServerSocket sSocket = new ServerSocket(localport); while(true) { Socket cSocket=null; try { display("listening..."); cSocket = sSocket.accept(); if(cSocket!=null) { clientCount++; display("accepted as #"+clientCount+":"+cSocket); ProxyConnection c = new ProxyConnection(cSocket,host,port,timeout); c.run(); } } catch(Exception e) { e.printStackTrace(System.err); } try { cSocket.close(); } catch(Exception e) { //fall thru } } } catch(Throwable t) { t.printStackTrace(System.err);

} } public static void main(String[] argv) { Proxy self = new Proxy(); if(argv.length>=3) { int localport = Integer.parseInt(argv[0]); String url = argv[1]; int port = Integer.parseInt(argv[2]); int timeout = 30000; try { timeout=Integer.parseInt(argv[3]); } catch(Exception e) {} self.run(localport,url,port,timeout); } else { System.err.println("usage: java " + self.getClass().getName() + usageArgs); } } }//class

Comments and alternative answers

correction Author: Martin Erren (http://www.jguru.com/guru/viewbio.jsp?EID=446238), Sep 29, 2001 This Proxy won't accept more than one client. To start the ProxyConnection as a real Thread (Line 127): ProxyConnection c = new ProxyConnection(cSocket,host,port,timeout); c.start(); ///!!!

instead of ProxyConnection c = new ProxyConnection(cSocket,host,port,timeout); c.run();

Note that java.net.Socket and java.net.ServerSocket allows setting a timeout by: void setSoTimeout(int timeout);

directly.

Re: correction Author: Hartmut Trüe (http://www.jguru.com/guru/viewbio.jsp?EID=547171), Nov 14, 2001 Hmm, r.start()

works fine, but r.run() throws an IOException with JDK 1.3.1_1. Maybe, it's a security exception for AccessController.doPrivileged()? Re[2]: correction Author: Troy Kinsella (http://www.jguru.com/guru/viewbio.jsp?EID=779766), Mar 3, 2002 Aren't you not supposted to call run() directly anyways? Multiple Clients Author: Rishath Rias (http://www.jguru.com/guru/viewbio.jsp?EID=1164187), Apr 19, 2004 I tried changing c.run() at line 127 to c.start() as mentioned in the comment section. But, I'm getting java.net.SocketException and java.lang.NullPointerException. How can I make this proxy to accept multiple clients? Plz Help! Re: Multiple Clients Author: Ole Sandum (http://www.jguru.com/guru/viewbio.jsp?EID=1184326), Jul 7, 2004 I believe the client socket is getting close()'d in two different places: 1) as fromClient.close() near the bottom of ProxyConnection and also 2) as cSocket.close() in Proxy. The last one, I believe, is a mistake. Once you start spawning threads, the client sockets will be closed (by the parent thread) before the worker thread gets any work done. Hope this helps. How can I get quotes in my servlet output so the string will be quoted for JavaScript? Location: http://www.jguru.com/faq/view.jsp?EID=507420 Created: Sep 30, 2001 Author: Marin Velikov (http://www.jguru.com/guru/viewbio.jsp?EID=36886) Question originally posed by Paul Reh (http://www.jguru.com/guru/viewbio.jsp?EID=483132 You need to escape the character with a \, like the following: out.println("var themessage = \"message: \";"); Comments and alternative answers

Client side JS includes and JSP Author: Alan Johnson (http://www.jguru.com/guru/viewbio.jsp?EID=241283), Oct 8, 2001 If you have much JS code that you can't include client side with the script tag (<script scr="filename.js" />) then you should consider JSP as an alternative to using the escape charater.

How do I retrieve parameters in the exact order in which they appeared on the HTML form? The method getParameterNames() does not preserve the order. Location: http://www.jguru.com/faq/view.jsp?EID=508859 Created: Oct 2, 2001 Modified: 2001-10-02 10:35:07.229 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Roger Hom (http://www.jguru.com/guru/viewbio.jsp?EID=486599 Use request.getQueryString() and parse the list in order yourself. You can use a StringTokenizer, something like this (untested code): StringTokenizer st = new StringTokenizer( request.getQueryString(), "&" ); while (st.hasMoreElements()) { String token = st.nextToken(); String name = token.substring(0, token.indexOf("=")); } See also • •

How do I get the name of the currently executing servlet? What is the difference between URL encoding, URL r...

By the way, the parameters are not guaranteed to be sent over in the order they were on the page, but I think most browsers do that anyway. Comments and alternative answers

getting parameter names from query string Author: Roger Hom (http://www.jguru.com/guru/viewbio.jsp?EID=486599), Oct 2, 2001 Am I still able to use the request.getQueryString() if the form is being sent using the post method? Re: getting parameter names from query string Author: Subrahmanyam Allamaraju (http://www.jguru.com/guru/viewbio.jsp?EID=265492), Oct 2, 2001 No. You can't do it for extracting parameters from the post request. Why is it required to depend on the order of parameters?. To make the application fail-safe, it is better to reconsider the approach and change it to not depend on the order of parameters.

Re: Re: getting parameter names from query string Author: Roger Hom (http://www.jguru.com/guru/viewbio.jsp?EID=486599), Oct 4, 2001

I am writing a generic form handler that needs to process any type of html form and output the results to an email message or written to a file on a server. The users would like the data to be in the same order as it was defined in their form. That is why I need the correct order of the parameters from the form. Re: Re: Re: getting parameter names from query string Author: Amos Shapira (http://www.jguru.com/guru/viewbio.jsp?EID=4346), Oct 6, 2001 Then consider ways like attaching an index to the parameter names, or some other way to associate order with them (e.g. extra index parameter which holds the index of each "form" parameter). Re: Re: Re: Re: getting parameter names from query string Author: Alan Johnson (http://www.jguru.com/guru/viewbio.jsp?EID=241283), Oct 7, 2001 Here is an example of a formmailer I wrote some time ago that implements Amos Shapira's suggestion. http://alan.datdec.com/formmailer.zip Feel free to use it but don't think there is any warrentee, expressed or implied, etc. Notice the FMCFormat Parameter. Here is another example of html calling to the mailer: http://www.finowen.com/contact.jsp

Re: Re: Re: Re: Re: getting parameter names from query string Author: Roger Hom (http://www.jguru.com/guru/viewbio.jsp?EID=486599), Oct 15, 2001 Thanks for the suggestions and code Amos and Alan, ... pretty cool How to get parameters in order using servlets, for a SendMail program using post, the working answer. Author: Renato Moscoso (http://www.jguru.com/guru/viewbio.jsp?EID=548467), Nov 15, 2001 Well all information about this, is wrong (for POST), and no code works, plz don't write scratch without warning about it because it really makes waste time by the way I needed a whole day to figure out how to do it, there no way using standar methods, because : - The applet server always get the data before one can get it, so its almost impossible o use HttpUtils libs, this lib sucks, I think is deprecated. - The main problem is about HashTables, they are always in disorder, why I don't know, some people said to Override the Hash table with a kind of OrderedHashTable, but I've tried

3 classes 2 downloaded and one modified and it doesn't work. The answer is really easy, and is in apache jserv page, we need to change the encoding type for the form, so the web server will not parse it, here the html :

Ok now we have enctype=text/plain, so what next, so we simply use a Reader and do parsing by hand here is the code : String mailData = ""; BufferedReader r=req.getReader(); String ssx; int t = 0; while ((ssx=r.readLine()) != null) { int i = ssx.indexOf("=")+1; if (ssx.startsWith("mailFrom=")) mailFrom = ssx.substring(i); else if (ssx.startsWith("mailTo=")) mailTo = ssx.substring(i); else if (ssx.startsWith("returnPage=")) returnPage = ssx.substring(i); else if (ssx.startsWith("subject=")) subject = ssx.substring(i); else if (ssx.startsWith("mailText=")) mailText = ssx.substring(i); else if ((!ssx.startsWith("Submit=")) && (!ssx.startsWith("Reset="))) { mailData += ssx+"\n"; } t ++; if (t > 1000) break; } // Validate Data // if (mailFrom == null) throw new ServletException("Se requiere el campo mailFrom."); if (mailTo == null) throw new ServletException("Se requiere el campo mailTo."); if (returnPage == null) throw new ServletException("Se requiere el campo returnPage."); if (subject == null) throw new ServletException("Se requiere el campo subject."); if (mailText == null) mailText = ""; mailText = mailText.replace('~','\n'); mailData = mailText + mailData; sendMail(mailFrom, mailTo, subject, mailData);

Simple and so easy, I don't know why we have to lead with this things having a programming languaje so powerfull like Java, writing this servlet is very even using a bach script. This is an awfull message, but I haved a really bad day, may english is really bad I speak spanish. Enjoy Coding :) Re: How to get parameters in order using servlets, for a SendMail program using post, the working answer. Author: John Westbury (http://www.jguru.com/guru/viewbio.jsp?EID=757563),

Feb 13, 2002 look like cobol Can two web applications (servlet contexts) share the same session object? Location: http://www.jguru.com/faq/view.jsp?EID=511752 Created: Oct 4, 2001 Modified: 2003-01-12 07:42:10.003 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Phuong Nguyen (http://www.jguru.com/guru/viewbio.jsp?EID=489857 By default, the session object is context-specific. Although a few servlet containers (Tomcat, Resin) may allow web applications to share session contexts by means of the "crosscontext" setting within the deployment descriptor, by default, that should not be allowed for security purposes and must be used cautiously only for admintype applications. [For example: -Alex] Comments and alternative answers

Also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Oct 25, 2001 This question is also answered at: • • • •

Is there a simple way to share a single Session object across multiple ServletContexts? How can I share data between two different web applications? How can I pass data from a servlet running in one context (webapp) to a servlet running in another context? Can two web applications (servlet contexts) share the same session object?

I don't get it ... why can't two web applications share a session? Author: Gary Bisaga (http://www.jguru.com/guru/viewbio.jsp?EID=580782), Dec 11, 2001 Ok, I officially don't get it. There seem to be two problems here: •

•

It looks like "crossContext" allows you to get the ServletContext. According to the servlet docs, "There is one context per 'web application' per Java Virtual Machine." This would appear to be a server-wide piece of information, not tied to the particular browser's session. If this does have anything to do with the browser's session, I don't understand why this should be disabled for "security purposes." What's insecure about

two web applications on my own server, both of which I wrote, accessing the same user session information? We're trying to set up a group of related but somewhat independent applications that all want to be able to share the same user session information (user id, language choice, etc.) and don't really want to put them all in the same WAR file. And I don't see why I should have to. If anybody has an answer to these questions I'd be grateful. Re: I don't get it ... why can't two web applications share a session? Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 11, 2003 > What's insecure about two web applications on my own server, both of > which I wrote, accessing the same user session information? Nothing! But some people run other people's webapps on their server (think ISPs, or commercial/third-party webapps). The crossContext attribute is there for you to tell Tomcat, "Yes, it's OK, I know what I'm doing." Re: I don't get it ... why can't two web applications share a session? Author: Vijay Arunkumar (http://www.jguru.com/guru/viewbio.jsp?EID=1055450), Feb 10, 2003 SECURITY, isnt just related to hackers... Also implies the issue of ISOLATION. Lets say your WEBAPP-ONE uses session variables to track logical steps or whatever. And one of the variables is called FOO. Now if there is a WEBAPPTWO using a session variable FOO also, both will overwrite each other, if the same client is accessing both applications at same time... which we all do. SESSION ISOLATION is very important, since the person developing WEBAPPTWO doesnt necessarily know what variable names WEBAPP-ONE is using. SAMPLE SCENARIO: The most common scenario where session conflict will introduce security problems is when access rights are stored in session variables. Lets say user 1 has access level 5 for WA1, and access level 10 for WA2. (Access Levels are arbitrary numbers i am using and not part of the JSP or Servlet spec). User logs into WA1 which creates a session variable SV_ACC_LEVEL and stores 5. now all pages hide CLASSIFIED info based on this level. Now, user logs into WA2, (hmmmm... using SV_ACC_LEVEL again, i suppose), now user goes back to WA1. Aahaah! Now the user has level 10 access to both WA1 and WA2. Many huge corporations groups all there "Supposed to be Isolated" Apps under the same WEB-APP context. Including the place where i am working at... and it took a lot of effort for me to explain to my managers the problems of not using seperate web-apps. And when I demoed this point by simply writing a jsp page that set up certain session vars for logiging into classified apps, and obviously demoed a log in when i am supposed to be denied access, it hit em.

So, .... before i go too deep into hacking and lose my mind over this matter, let me just state my point. SHARED SESSIONS is a HUUUGE SECURITY RISK. Can i setup Tomcat to run inside the web server process itself (on Netscape/IIS?), instead of running it as a separate process. Do there something available i can use or do i have to write my own JNI code for this? Location: http://www.jguru.com/faq/view.jsp?EID=520057 Created: Oct 14, 2001 Modified: 2001-10-18 12:10:28.738 Author: Davanum Srinivas (http://www.jguru.com/guru/viewbio.jsp?EID=2011) Yes. The dirty work has already been done for you. More information can be found at TOMCAT - In-Process HowTo. Comments and alternative answers

Use JspISAPI for it Author: Akash Kava (http://www.jguru.com/guru/viewbio.jsp?EID=1135160), Jan 2, 2004 Well the solution is here... http://jspisapi.neurospeech.com , we had similar problem and trying to find solution but too complex method of tomcat's documentation lead us to develop our own solution called JspISAPI. The details of installation is given in the website. It has features: 1) eliminate 8080 port from urls 2) redunce load on tomcat as images and other resources are handled by IIS 3) support http keep alive for jsp and servlets 4) easy setup for SSL by IIS, no hassle for setting up SSL for tomcat - Akash Kava How to return a value from a servlet to a JSP? Location: http://www.jguru.com/faq/view.jsp?EID=524336 Created: Oct 18, 2001 Author: Shahram Khorsand (http://www.jguru.com/guru/viewbio.jsp?EID=3357) Question originally posed by hassan hassan (http://www.jguru.com/guru/viewbio.jsp?EID=519522 There are couple of ways to do this. 1. You can put the information you like in a HTTPSession object. This object is created for you and stays with the user during the time they are in the site. This is done like this: 2. HttpSession s = request.getSession(true); 3. s.setAttribute("returnVal", callMethod());

The first row creates the session if there are no sessions. Next row sets the value you like in to the session object. Remember that in the JSP page you have to cast this object back to whatever object it is. All "things" in a session object are stored as java.lang.Objects. here is how that is done inside the JSP page: myObject = (myObject) session.getAttribute("returnVal");

4. The other way of doing this is to put the value in the request object. It is similar to the previous example, only it is the request object. Here is how that is done: 5. RequestDispatcher rd = getServletContext().getRequestDispatcher("/yourjsppage.jsp"); 6. request.setAttribute("myObject", getMyObject()); rd.forward(request, response); The first row gets the requestDispatcher, the second line adds your object to the request object and the last line forwards the request. In the JSP page you use the "request" object like this: myObject = (myObject)request.getAttribute("myObject"); Comments and alternative answers

How to return a value from a servlet to a JSP? Author: Lee Jeffrey (http://www.jguru.com/guru/viewbio.jsp?EID=563988), Nov 27, 2001 Hi, I tried the methods you wrote but I am always returned with the following error: 1. ......: Cannot resolve symbol symbol :method getServletContext() location: class.mips.Report.Ui.ReportAction RequestDispatcher rd = getServletContext().getRequestDispatcher("/test1.jsp") Re: How to return a value from a servlet to a JSP? Author: Sergi Pérez (http://www.jguru.com/guru/viewbio.jsp?EID=724738), Jan 20, 2002 You must use the JSDK2.1 or higher. If you must use the 2.0 try to use the method: resp.sendRedirect("page.jsp"); When using URLConnection to upload an object from applet to servlet, the servlet's doGet method is never executed. Why? Location: http://www.jguru.com/faq/view.jsp?EID=524345 Created: Oct 18, 2001 Author: Ana Narvaez (http://www.jguru.com/guru/viewbio.jsp?EID=231092) Question originally posed by leo lee (http://www.jguru.com/guru/viewbio.jsp?EID=477092

URL url=new URL("http://localhost:8080/servlet/ServerServlet?Action=3"); URLConnection servletConnection=url.openConnection(); servletConnection.setDoInput(true); servletConnection.setDoOutput(true); servletConnection.setUseCaches (false); servletConnection.setDefaultUseCaches (false); servletConnection.setRequestProperty ("Content-Type", "application/octet-stream"); ObjectOutputStream outputToServlet = new ObjectOutputStream(servletConnection.getOutputStream()); outputToServlet.writeObject("asdfa"); outputToServlet.flush(); outputToServlet.close(); I had the same problem and I resolved it reading the response from the servlet. You can do: ..... outputToServlet.writeObject("asdfa"); outputToServlet.flush(); outputToServlet.close();

//and now read from the servlet int code = servletConnection.getResponseCode();

//or you can read the header. String header = servletConnection.getHeaderField(0);

//or you can obtain de inputstream InputStream in = servletConnection.getInputStream();

I Hope this helps you Comments and alternative answers

Don't reinvent the wheel. Author: Christopher Bowland (http://www.jguru.com/guru/viewbio.jsp?EID=217833), Oct 18, 2001 You might want to take a look at the work that Jason Hunter did at http://www.servlets.com/cos/index.html. The HttpMessage class provides exactly what you are seeking and I know from personal experience that servlets handling its request will process the doGet() or doPost() as appropriate.

When using URLConnection to upload an object from first servlet to second servlet, the doGet method of second Servlet is never executed. Why Author: Rajagopalan Subramanian (http://www.jguru.com/guru/viewbio.jsp?EID=989686), Aug 29, 2002 We have implemented the same code u have specified. But the actual scenario is Reading an object ( may be a plain document , XML Document...) in First Servlet which is in First Webserver and pass it to Second servlet which is in Second WebServer. And how this object is to be accepted in Second servlet ( may be in doGet method) and display it in its original format. We are getting the same problem of doget() of the second servlet not getting executed. And what should be the coding for reading the passed object from first servlet. After HttpSession.invalidate() is called I expect the next getSession call should return a new session with a different session id. However, it returns the same sessionid ??? Location: http://www.jguru.com/faq/view.jsp?EID=524347 Created: Oct 18, 2001 Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985) Question originally posed by Prabodh Navare (http://www.jguru.com/guru/viewbio.jsp?EID=440669 I believe that the new session will be generated on next request by the client, not immediately after the invalidate. Comments and alternative answers

New session Author: Subrahmanyam Allamaraju (http://www.jguru.com/guru/viewbio.jsp?EID=265492), Oct 18, 2001 That's true. In case you want to establish a new session within the same request, try using send-redirect to the same servlet. This way, the container gets a chance to establish a new session. When downloading a PDF document that is less than 8000 bytes long, the document is downloaded but is not displayed. How can I fix this? Location: http://www.jguru.com/faq/view.jsp?EID=524472 Created: Oct 18, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Alan Taylor (http://www.jguru.com/guru/viewbio.jsp?EID=447303 I've had a similar problem before when I'm sending a PDF that I'm generate. The problem seems to happen when the PDF file is smaller than the buffer size of the response object (8K by default). We've solved the problem with a little help from the buglist of Microsoft IE knowledge base. Setting the Content-Length in the response object, shoud do the trick. Working code:

byte[] data = ...; response.setContentType("application/pdf"); response.setContentLength(data.length); BufferedWriter out = new BufferedWriter(new OutputStreamWriter(response.getOutputStream())); out.write(data); out.flush(); out.close(); For more discussion, see these two threads in the Servlets FAQ and the JSP FAQ. Comments and alternative answers

serving static pdf files with tomcat Author: Hartmut Bernecker (http://www.jguru.com/guru/viewbio.jsp?EID=424953), Apr 10, 2002 I have the same problem when sending a PDF that I don't generate. If I do the same with IIS 5 the PDF is actually displayed. When having a look to the HTTP headers You will see that: HTTP/1.1 200 OK Server: Microsoft-IIS/5.0 Connection: close Date: Wed, 10 Apr 2002 20:20:57 GMT Content-Type: application/pdf Accept-Ranges: bytes Last-Modified: Tue, 05 Sep 2000 10:51:39 GMT ETag: "802fb1442717c01:d91" Content-Length: 91853 HTTP/1.1 200 OK Content-Type: application/pdf Content-Length: 91853 Date: Wed, 10 Apr 2002 20:23:00 GMT Server: Apache Tomcat/4.0.3 (HTTP/1.1 Connector) Last-Modified: Tue, 05 Sep 2000 10:51:39 GMT ETag: "91853-968151099000"

That seems to be o.k, but as a matter of fact it isn't. What do you suggest????? How do I play a sound on the server from inside a servlet? The Java Sound API doesn't seem to work. Location: http://www.jguru.com/faq/view.jsp?EID=524475 Created: Oct 18, 2001 Author: Jitendra Mehta (http://www.jguru.com/guru/viewbio.jsp?EID=64025) Question originally posed by Jitendra Mehta (http://www.jguru.com/guru/viewbio.jsp?EID=64025 [More Q: I am trying to use java sound API in my servlet based application. One of the subclass in my 'playSound.class' extends thread. I am loading audioClip inside this thread, which is not working. It doesn't raise any error. If I skip the thread and load clip directly, it works fine.]

I changed my servlet to implement 'SingleThreadModel' and my code worked! Now I don't know if implementing 'SingleThreadModel' will hamper performance of my application. I am using only one servlet which is mounted when web server starts. Below is my 'playSound' class. package moore.mifc.system; import java.applet.AudioClip; import java.applet.*; import javax.swing.*; import java.awt.*; import java.awt.event.*; import java.net.URL; import java.net.MalformedURLException; import java.awt.GridBagLayout; import moore.mifc.system.*; public class playSound { SoundList soundList; String login = "login.wav"; String logout = "logout.wav"; String menu = "menu.wav"; String ready = "systemReady.wav"; String unknown = "unknown.wav"; String chosenFile; String status; static private final Log logSound = new Log ("logSound"); AudioClip onceClip, loopClip; URL codeBase; boolean looping = false; public playSound() { startLoadingSounds(); }

void startLoadingSounds() { //Start asynchronous sound loading. try { codeBase = new URL("file:\\mifc\\res\\") ; } catch (MalformedURLException e) { logSound.out(e.getMessage()); } soundList = new SoundList(codeBase); soundList.startLoading(login); soundList.startLoading(ready); soundList.startLoading(unknown); }

public void stop() { onceClip.stop(); if (looping) { loopClip.stop(); } } public void start() { if (looping) { loopClip.loop(); } }

//Cut short the one-time sound. //Stop the sound loop.

//Restart the sound loop.

public void play( String what) { if (what.equalsIgnoreCase("login") ) { //based on time play greetings.. onceClip = soundList.getClip("login.wav"); if (onceClip == null) { logSound.out("Sound " + "login" + " not loaded yet."); return; } stop(); onceClip.play(); return;

//Play it once.

} else if( what.equalsIgnoreCase("ready") ) { onceClip = soundList.getClip("systemReady.wav"); if (onceClip == null) { logSound.out("Sound " + "ready" + " not loaded yet."); } stop(); //Play it once. onceClip.play(); return; } else if( what.equalsIgnoreCase("unknown") ) { onceClip = soundList.getClip("unknown.wav"); if (onceClip == null) { logSound.out("Sound " + "logout" + " not loaded yet."); } stop(); onceClip.play();

//Play it once.

return; } return; } class SoundList extends java.util.Hashtable { JApplet applet; URL baseURL, completeURL; public SoundList(URL baseURL) { super(5); //Initialize Hashtable with capacity of 5 entries. logSound.out( "baseURL*******"+baseURL); this.baseURL = baseURL; } public void startLoading(String relativeURL) { /* uncomment this only if soundLoader class doesn't work... try { completeURL = new URL(baseURL, relativeURL); logSound.out( "completeURL*******"+completeURL); } catch (MalformedURLException e){ logSound.out("SoundLoader:"+e.getMessage()); } AudioClip audioClip = Applet.newAudioClip(completeURL); soundList.putClip(audioClip, relativeURL); **/ }

new SoundLoader(this, baseURL, relativeURL);

public AudioClip getClip(String relativeURL) { logSound.out( "relativeURL*******"+relativeURL); }

return (AudioClip)get(relativeURL);

public void putClip(AudioClip clip, String relativeURL) { put(relativeURL, clip); } }

//This guy doesn't work if my servlet does NOT implement interface 'SingleThreadModel' class SoundLoader extends Thread { SoundList soundList; URL completeURL; String relativeURL; public SoundLoader(SoundList soundList,URL baseURL, String relativeURL) { this.soundList = soundList;

try { completeURL = new URL(baseURL, relativeURL); } catch (MalformedURLException e){ } this.relativeURL = relativeURL; setPriority(MIN_PRIORITY); this.start();

} public void run() { AudioClip audioClip = Applet.newAudioClip(completeURL); soundList.putClip(audioClip, relativeURL); } } }

How can I call a servlet from a regular Java application? Location: http://www.jguru.com/faq/view.jsp?EID=524479 Created: Oct 18, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Annar Innad (http://www.jguru.com/guru/viewbio.jsp?EID=522486 See How can my applet communicate with my servlet? Comments and alternative answers

Applet Servlet communication Author: Stuart Woodward (http://www.jguru.com/guru/viewbio.jsp?EID=129604), Oct 21, 2001 You could subclass your servlet from HttpServlet and POST to it. You might also want to look at an RPC protocol like SOAP before reinventing the wheel. Alternatively, you could also develop your own Socket based protocol to communicate with the servlet. Can we capture clickstreams using servlets? Location: http://www.jguru.com/faq/view.jsp?EID=524483 Created: Oct 18, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Raj Kumar (http://www.jguru.com/guru/viewbio.jsp?EID=454402 To capture clickstreams generally you need a browser-side plugin like Alexa. That's *way* out of the realm of servlets. To track click streams inside your site, check the Referer HTTP field (to see where people came from before hitting your site). Once they're in your site, you can make every servlet-generated page log its name and the username to your database. But there's no simple way to "turn clickstream recording on" or whatever.

Comments and alternative answers

The new servlet 2.3 specification allows you to easily write a click-stream filter. Author: mindaugas idzelis (http://www.jguru.com/guru/viewbio.jsp?EID=128502), Nov 1, 2001 With the new servlet 2.3 specification, it IS possible to see the clickstreams of people on your site. This is implemented using a filter. There are "ready-made" filters that you can just plug in and they will work. For a detailed overview please go to http://www.javaworld.com/javaworld/jw-06-2001/jw-0622-filters.html Also, http://www.orionsupport.com/clickstream/ http://www.opensymphony.com/clickstream/ How do I set session timeouts of greater than 30 minutes? Location: http://www.jguru.com/faq/view.jsp?EID=525564 Created: Oct 19, 2001 Author: Janko Harej (http://www.jguru.com/guru/viewbio.jsp?EID=280966) Question originally posed by Joji Daniel (http://www.jguru.com/guru/viewbio.jsp?EID=503188 Tomcat session keeps expiring in spite of entries in web.xml to the effect of <session-config> <session-timeout>60 (where the number indicates the time in minutes) While this works fine for small time values, for large values the session dies out well before the given time value. Is there a way around this?? The documentation talks of HttpSession.getMaxInactiveInterval() using which the session timeout can be set. Has anyone tinkered with this?? Appreciate some help very much. Answer: I've included this in my JSP page: session.setMaxInactiveInterval(600); Comments and alternative answers

session timeouts Author: Nick Furiak (http://www.jguru.com/guru/viewbio.jsp?EID=431833), Feb 26, 2002 I think the session.setMaxInactiveInterval(time) requires that you enter the interval in milliseconds. Re: session timeouts

Author: fresh guy (http://www.jguru.com/guru/viewbio.jsp?EID=1032778), May 9, 2003

hai friends,

Iam working on email system for which iam using 1. tomcat4.0.4 2. Javamail api 3. servlets

I need the sessiontimeout for 4 hours. I already set in my servlets as

session.setMaxInactiveInterval(14400);

as well as in web.xml file as

<session-config> <session-timeout>240

Eventhough i set in both ways my session is expiring after 30 mins(the default sessiontimeout for tomcat)

Please, let me know how i could achieve 4 hours for my sessiontimeout.

I'll will be thankful to them who responds me quickly as this is too urgent.

thanks.

How can I modify a Request object before passing it to another servlet? Location: http://www.jguru.com/faq/view.jsp?EID=528234 Created: Oct 23, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Patrick Timmins (http://www.jguru.com/guru/viewbio.jsp?EID=427817 2.3 Servlets, doFilter(), and Request Headers If you've ever done NSAPI, you know that it gives you full access to the web server's processing of a request. One of the neat things it lets you do is modify/insert request headers. For example, you could look for a specific cookie in the request, and if it's there, insert an authorization header into the request, and then pass this modified request on to the rest of the web-server's normal processing (most importantly for this particular example, the authentication phase). Are there any classes out there that let you do this sort of thing? It doesn't appear to me that the standard 2.3 doFilter() chaining scenario will work, as I can only manipulate the response headers. I'm thinking of developing something myself using lwj (libwww-java: http://lwj.sourceforge.net/.). Any advice/ideas about going down this road? Thanks! You can do something like this in Servlets 2.3 by subclassing HttpRequestWrapper. See the Servlet 2.3 spec for more details. Comments and alternative answers

Modifying http parameters in request. Author: Roger Hand (http://www.jguru.com/guru/viewbio.jsp?EID=292314), Oct 24, 2001 This may not fit exactly into what you're trying to do, but thought it might help . . .

If manipulating http headers and parameters at the http stream level would work for you, then see my comment Here's a servlet wrapper that makes it easy in the topic Can I call a CGI script from a servlet?. What is a session? What is the difference between session and cookie? Location: http://www.jguru.com/faq/view.jsp?EID=528741 Created: Oct 24, 2001 Author: Bozidar Dangubic (http://www.jguru.com/guru/viewbio.jsp?EID=433955) Question originally posed by sabu vs PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=476248 [See the topic Servlets: Sessions and the question How do I use Session Tracking? -Alex] A session is an object associated with a client connection to the server. it has the ability to carry information related to the client. since http is a connectionless protocol, developers need an ability to "remember" what the client of the application did during the visit to the page. a great example of the need and use of session is a infamous shopping cart. as users browse through products they are interested in, they add products they want to buy to the 'shopping cart' this information needs to be stored somewhere so that when users decides to check-out and purchase the products, the system knows all the products client wants to purchase. so 'shopping cart' is stored in the session which drags along on each client invocation to the server until session expires. the way server handles session is server-specific. the specification does not specify exact implementation of the session. some web servers may use cookies, some may use something else. but overall, it is up to the implementer to decide how this is done. the difference between session and a cookie is two-fold. 1) session should work regardless of the settings on the client browser. even if users decide to forbid the cookie (through browser settings) session still works. there is no way to disable sessions from the client browser. 2) session and cookies differ in type and amount of information they are capable of storing. javax.servlet.http.Cookie class has a setValue() method that accepts Strings. javax.servlet.http.HttpSession has a setAttribute() method which takes a String to denote the name and java.lang.Object which means that HttpSession is capable of storing any java object. Cookie can only store String objects. Comments and alternative answers

I am Sorry Author: Rotti Sowmindra (http://www.jguru.com/guru/viewbio.jsp?EID=487648), Dec 30, 2001 I am sorry to say that if we diable cookies in the client browsers we cant user sessions too.Because the basic funda with sessions is they use cookies to store the reference to the value of the session.It means a session creates a cookie on the client side which

has reference to its value in the server where as a cookie directly stores the value in the client's side. I would like to be proven wrong Regards Sowmindra Re: I am Sorry Author: Kumar KMK (http://www.jguru.com/guru/viewbio.jsp?EID=716239), Jan 10, 2002 If you disable cookies servlet container may use urlrewriting for session management in effect you cant disable sessions by disabling cokies. Re[2]: I am Sorry Author: Tuan Sau-Wern (http://www.jguru.com/guru/viewbio.jsp?EID=437561), Oct 14, 2002 What Rotti says is correct. You still need to enable cookies at the client side to have sessions working. Re[3]: I am Sorry Author: neal ravindran (http://www.jguru.com/guru/viewbio.jsp?EID=17737), Dec 23, 2003 Hmmm..I thought it could still be(ie with cookies disabled at client) encapsulated in the header part and the browser could read it. Wrong? Do I have to synchronize read-only access to a text file? Location: http://www.jguru.com/faq/view.jsp?EID=531243 Created: Oct 26, 2001 Modified: 2001-10-27 08:18:32.688 Author: Bozidar Dangubic (http://www.jguru.com/guru/viewbio.jsp?EID=433955) Question originally posed by Tony Fagan (http://www.jguru.com/guru/viewbio.jsp?EID=226421 My servlet reads the contents of a text file which I access using a File object. What issues are involved when this file is read concurrently by several different threads? Do I have to synchronize access to the file, or does it not matter when access is read-only? Should not matter if the file is only for reading. Make sure that you close the file when you are done using it. Comments and alternative answers

Do I have to synchronize read-only access to a text file? Author: Serge Borodai (http://www.jguru.com/guru/viewbio.jsp?EID=1135393), Dec 22, 2003 So, I have to synchronize read-only access to a text file? Can I place my classes somewhere other than inside WEB-INF? Location: http://www.jguru.com/faq/view.jsp?EID=536258 Created: Nov 1, 2001 Modified: 2002-04-19 05:36:14.822 Author: Alessandro A. Garbagnati

(http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by S R (http://www.jguru.com/guru/viewbio.jsp?EID=530361 Sun's specifications for Servlet define only the WEB-INF/classes and WEB-INF/lib directories in order to make the web application portable. If you are not interested in portability, you can still put all your classes into the CLASSPATH environment variable. The startup script for Tomcat 3.2.x should automatically add that classpath to the one used by Tomcat, while, with version 4.0.x and 3.3.x, you definitely need to make a small change in the startup script to add the CLASSPATH environment to the one that is generated by the script to esecute Tomcat. The only issue is that the classes/jars you've added will be available to all the web applications running under that instance. [Also, they may conflict with other library JARs. XML parsers are notorious for this problem. -Alex C] Comments and alternative answers

Classes outside WEB-INF\classes Author: Subrahmanyam Allamaraju (http://www.jguru.com/guru/viewbio.jsp?EID=265492), Nov 1, 2001 Portability may not be a concern. In addition to the fact that such classes will be available to all applications running under that container (since such classes will be loaded by the classloader loading the the container runtime itself), you will not have the ability to undeploy and deploy such classes dynamically.

Re: Classes outside WEB-INF\classes Author: Maheedhar Pullakhandam (http://www.jguru.com/guru/viewbio.jsp?EID=544002), Nov 9, 2001 There is certain overhead in keeping the classes in WEB-INF\Classes. Container verifies any change made to the concerned class file, before passing every request to a servlet, which may amount to certain lag in response time. If the efficiency is so concerned, classes should be added to WEB-INF\Classes during development and to CLASSPATH while shipping the product. Re: Re: Classes outside WEB-INF\classes Author: Subrahmanyam Allamaraju (http://www.jguru.com/guru/viewbio.jsp?EID=265492), Nov 10, 2001 Most contaienrs let you specify the interval for checking changes. I think you

may even turn off this. I'm not sure how much overhead it involves, but this does not outweigh the advantages of scoping classes under /WEB-INF/classes and /WEB-INF/lib directories.

EAR files? Author: Pete Halverson (http://www.jguru.com/guru/viewbio.jsp?EID=537495), Nov 2, 2001 a J2EE Enterprise Application Archive (an .ear file) allows a web app (.war file) to be packaged with any dependent libraries (.jars), including third-party class libraries as well as EJB client stub jars, e.g. something like webapps/webapp.war ejbs/ejb-client.jar xerces.jar xalan.jar

If you declare all your .jar dependencies in the .war's JAR manifest (*not* web.xml), the container is supposed to make those classes available in addition to /WEB-INF/lib and /WEB-INF/classes. But support for EARs is still limited. JBoss handles them (and if you're running tomcat inside of JBoss, it seems to work as expected), but I don't know who else does. pch small change Author: bill weaver (http://www.jguru.com/guru/viewbio.jsp?EID=575360), Dec 12, 2001 you say "while, with version 4.0, you definitely need to make a small change in the startup script to add the CLASSPATH environment to the one that is generated by the script to esecute Tomcat." what is the "small change" you mention and to what file (i'm a newbie to apache/tomcat and all things java and am having lots of problems locating servlets) many thanks classes outside WEB-INF Author: Martin Ober (http://www.jguru.com/guru/viewbio.jsp?EID=120947), Mar 26, 2002 I have an application that runs standalone and on multiple webapps with separate databases. I also have different versions of the application running on my server, so the setting of the CLASSPATH doesn't work at all. Using WebappClassLoader.addRepository() could be a solution ??? Another very simple way: write a little class that copies the jars and resources from a specified source to your WEB-INF directory and call it on initializing your context.

NOT FINE BUT WORKS ;-) Use a Manfifest for the jars with Version-Infos. bye Re: classes outside WEB-INF Author: Todd Stark (http://www.jguru.com/guru/viewbio.jsp?EID=1056632), Feb 14, 2003 Hi, I am trying to reference jar files and classes outside the WEB-INF. I would like to add my CLASSPATH so that when the JSP page is compiled the necessary jars are available. Do you have some sample code and steps of how to use WebappClassLoader.addRepository() or have you found a better way of doing this? Thanks CLASSPATH and Tomcat 3.3.1 Author: simmo uk (http://www.jguru.com/guru/viewbio.jsp?EID=845358), Apr 19, 2002 There is a particular problem when for example you are using ZIP files, or when the CLASSPATH is used to store other resources (eg. properties files) not loaded by the class loaders. I can't seem to get system properties org.apache.tomcat.apps.classpath or org.apache.tomcat.common.classpath to work either...

Is it a good idea to declare your connection object globally, open the connection in init and close it on destroy? Or is it better to just open and close it all in a doGet or doPost each time a thread request the servlet? Location: http://www.jguru.com/faq/view.jsp?EID=538678 Created: Nov 4, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by brett haas (http://www.jguru.com/guru/viewbio.jsp?EID=538610 Globally. Definitely. It can take upwards of 10 seconds or even several minutes to open a DB connection (depending on your sever and drivers). See How do I access a database from my servlet or JSP?... and the topic Servlets:Databases Comments and alternative answers

Disagree Author: Bozidar Dangubic (http://www.jguru.com/guru/viewbio.jsp?EID=433955), Nov 5, 2001

This solution leaves connections open for the life of the JSP page. If you have 200300 JSP pages (not unusual at all for medium-size projects) you would have to have 200-300 connections open just to serve JSPs. and although you will save some time if you keep the connections in JSPs open, it is a pretty bad design and wastes a lot of resource. connection pooling is the way to go. create a pool of connections for the JSPs to use and get the connection from the pool. resources can be used optimally with this approach and performance will be about the same (with some tweaking based on load). Re: Disagree Author: brett haas (http://www.jguru.com/guru/viewbio.jsp?EID=538610), Nov 5, 2001 What if the portion of the site (or project) only has about 20-30 pages which actually make an connection to a database. Would it be better than just to leave open the connection and allow them to be shared for all threads? Connection handling Author: Subrahmanyam Allamaraju (http://www.jguru.com/guru/viewbio.jsp?EID=265492), Nov 5, 2001 Here is the correct approach: • •

Get the connection when required and close it immediately after use. Do this within the doXXX() methods. Configure your J2EE container for connection pooling.

Why? Here are the reasons. Firstly, you **should** not keep connections as instance variables - this would not work under multiple threads (which happens all the time with servlets/JSPs). There is an example about this in one of my papers published in JDJ Mar 2000 issue. Most J2EE containers provide connection pooling (i.e, implement the JDBC2 connection handling SPI). This takes care of the connection overhead, and transperantly pools connection objects. Re: Connection handling Author: brett haas (http://www.jguru.com/guru/viewbio.jsp?EID=538610), Nov 6, 2001 I ran 4 separate test today, using two different schools of thought on using a connection object. I created two servlets, and created 25 near simultaneous threads to each servlet. Each servlet made a call to a database to display 198 records using the stored procedure which is at the very bottom of this message.

The first one was declaring the connection object inside of a doGet() method and closing it before the end of the method. The avg load of each page was: 13519 ms (local connection) The second one was declaring the connection object globalling and intializing it once in init(). The avg load of each page was: 7337 ms (global connection) Neither of these test used connection pooling. And I called System.gc in the finally block after getting the load time for the current thread. By these results, I would have to assume that global connection is your better option, if you are not going to use connection pooling. CREATE Procedure sp_GetAllArticles As SELECT

// text

id, // int cat, // varchar(25) title, // varchar(100) byline, //varchar(20) left(convert(varchar(1000), body), charindex('. ', convert(varchar(1000), body), 500) as body

FROM

article ORDER BY cat, title ASC

Re: Re: Connection handling Author: Subrahmanyam Allamaraju (http://www.jguru.com/guru/viewbio.jsp?EID=265492), Nov 6, 2001 Assuming that you're getting connections in the init() method, and that your servlet does not implement the SingleThreadModel interface, here is how can things can go wrong. Let's say there are two hits T1 and T2 (almost concurrently) to this servlet, and that there are three database related tasks (D1, D2 and D3). Here is one hypothetical scenario: • •

T1 does D1 (the transaction begins here). T1 does D2.

• • • • •

T2 does D1. T2 roles back T2 ends T1 does D3 T1 ends.

How many transactions do you see? You will see two, with the first rolled back. The second transaction starts after the first rolls back. So, the second transaction includes D3 only. As you see, this is incomplete. The poing is that, transactions get mixed up since both the threads are operating on a single connection object. I hope this explains why multiple threads should not share the same connection. This is precisely what happens in the case of servlets. For performance sake, you SHOULD consider pooling. It is unrealistic to test without pooling. Re: Re: Re: Connection handling Author: brett haas (http://www.jguru.com/guru/viewbio.jsp?EID=538610), Nov 7, 2001 I DEFINITELY believe you. You should also use a form of connection pooling. I was just giving some information on a simple test I performed, which only had one database interaction. I have a quick question for you, which is not directly related to this topic. I am displaying results from a database, one of the fields is a "Text"; field which contains content that was written in Microsoft word. When it is displayed to the clients browser any ‘ or “ is converted into a question mark. I know Java uses Unicode(utf-16), is there a what to change the code to different set just for this servlet? Of course there is always the brute force way, and do a char replacement on that content, but that is not such an elegant solution. Thanks in advance for your help. Alternative - Connection Pool in Tomcat Author: Norman Hanson (http://www.jguru.com/guru/viewbio.jsp?EID=462048), Dec 7, 2001 Not every has or wants a J2EE Server. You may want to consider using a connection pool created on startup, then just grabbing a connection from the pool in your jsps. I found a nice simple pool package from ww.bitmechanic.com then wrote a servlet with just an init method, load-on-startup in the web.xml and viola, connection pooling with tomcat. import import import import

javax.servlet.*; javax.servlet.http.*; java.io.*; com.bitmechanic.sql.*;

import java.sql.*; public class StartupConnectionPoolServlet extends HttpServlet { private private private private private private private private private

static static static static static static static static static

String String String String String String String String String

ALIAS URL DRIVER USERNAME PASSWORD MAXCONN IDLE CHECKOUT DEBUG

private private private private private private private private private

String dbAlias; String dbDriver; String dbUrl; String dbUsername; String dbPassword; int dbMaxConnections; int dbIdleTimeout; int dbCheckoutTimeout; boolean debug = true;

= = = = = = = = =

"alias"; "jdbc.url"; "jdbc.driver"; "jdbc.username"; "jdbc.password"; "jdbc.max.connections"; "jdbc.idle.timeout"; "jdbc.checkout.timeout"; "debug";

public void init() throws ServletException { try { ConnectionPoolManager poolMgr = null; // see if the application already has a connection pool manager attached to it if ( getServletContext().getAttribute("connectionPoolManager") != null) { poolMgr = (ConnectionPoolManager)(getServletContext().getAttribute("connectionPoolManager")); } else { poolMgr = new ConnectionPoolManager(120); } ConnectionPool pool= null; if (getConnectionInfo() ) { //DriverManager.registerDriver((Driver)(Class.forNa me(dbDriver))); - " + dbAlias); dbUsername, dbPassword, dbCheckoutTimeout);

if( debug) System.out.println("adding alias to mgr poolMgr.addAlias(dbAlias, dbDriver, dbUrl, dbMaxConnections, dbIdleTimeout, if( debug) System.out.println("setting pool on

session - " + dbAlias);

poolMgr );

pool = poolMgr.getPool( dbAlias ); getServletContext().setAttribute( dbAlias, pool);

} getServletContext().setAttribute( "connectionPoolManager",

if (debug) System.out.println("****** end StartupConnectionPoolServlet - debug true ******"); } catch (Exception e) { e.printStackTrace(); throw new ServletException(e); } } private boolean getConnectionInfo() { debug = Boolean.valueOf(getInitParameter(DEBUG)).booleanValue(); dbAlias = getInitParameter(ALIAS); boolean connection = (dbAlias != null)?true:false; if (connection) { dbDriver = getInitParameter(DRIVER); dbUrl = getInitParameter(URL); dbUsername = getInitParameter(USERNAME); dbPassword = getInitParameter(PASSWORD); dbMaxConnections = Integer.parseInt(getInitParameter(MAXCONN)); dbIdleTimeout = Integer.parseInt(getInitParameter(IDLE)); dbCheckoutTimeout = Integer.parseInt(getInitParameter(CHECKOUT)); if (debug) { System.out.println("****** StartupConnectionPoolServlet - debug true ******"); System.out.println("get attributes for pool - " + dbAlias); System.out.println( dbDriver); System.out.println( dbUrl); System.out.println( dbUsername); System.out.println( dbPassword); System.out.println( dbMaxConnections); System.out.println( dbIdleTimeout); System.out.println( dbCheckoutTimeout); } } return connection; } }

then in jsp...

/* get a connection from the pool with the given alias */

ConnectionPool pool= (ConnectionPool)getServletContext().getAttribute("myConnection"); Connection conn = pool.getConnection(); ... /* for completeness */ /* return the connection to the pool */ pool.returnConnection((PooledConnection)conn);

you need to define the servlet in your web.xml, define the paramters for your connection and set loadon-startup also to support multiple pools, just have multiple entries in your web.xml, but using the same servletclass --norm Re: Alternative - Connection Pool in Tomcat Author: Joost Schouten (http://www.jguru.com/guru/viewbio.jsp?EID=581960), Feb 1, 2002 Hi, I'm not sure if this thread is still alive, but I'll give it a try anyway. I'm in the prosses of setting up a pool, and used your advice. But I don't understand the following part of the StartupConnectionPoolServlet. if (getConnectionInfo() ) {

//DriverManager.registerDriver((Dr

iver)(Class.forName(dbDriver)));

if( debug) System.out.println("adding alias to mgr - " + dbAlias); poolMgr.addAlias(dbAlias, dbDriver, dbUrl, dbUsername, dbPassword, dbMaxConnections, dbIdleTimeout, dbCheckoutTimeout); if( debug) System.out.println("setting pool on session - " + dbAlias); pool = poolMgr.getPool( dbAlias ); getServletContext().setAttribute( dbAlias, pool); }

I don't understand why the addAlias() and getPool() methods are both used within a debug block. These methods seem pretty essencial to me. Esspecially with the registerDriver commented. I'm not an expert yet, and cannot figure out how I should reconfigure this servlet to make it work for me. Can you shine your light on the matter? Thanks, Joost Re[2]: Alternative - Connection Pool in Tomcat Author: Norman Hanson

(http://www.jguru.com/guru/viewbio.jsp?EID=462048), Feb 1, 2002 they are not. the if debug is a oneliner, look closely, no {}. --norm Re[3]: Alternative - Connection Pool in Tomcat Author: Joost Schouten (http://www.jguru.com/guru/viewbio.jsp?EID=581960), Feb 1, 2002 Oops! sorry for bugging you. But now I relize that the problem lies somewhere else. Thanks for your reply, Joost

Re: Alternative - Connection Pool in Tomcat Author: Joost Schouten (http://www.jguru.com/guru/viewbio.jsp?EID=581960), Feb 2, 2002 Hi, I think I'm really close to making my pool work. However. From my dbConnect Bean I call the fo method:

pool = (ConnectionPool)StartupConnectionPoolServlet.getServletContext().getAttribute("rbd

And during compilation I'm presented with the following error: non-static method getServletContext() cannot be referenced from a static context

If I only knew what it meant? What am I doing wrong? Thanks, Joost Re[2]: Alternative - Connection Pool in Tomcat Author: Norman Hanson (http://www.jguru.com/guru/viewbio.jsp?EID=462048), Feb 3, 2002 you are really making this harder than it ought be. the servlet code i posted will compile. then as a stated before simply define the db pool paramaters in the web.xml for a <servlet> hmmm, maybe like this.

<servlet> <servlet-name>startConnectionPoolForMyDb <servletclass>com.path.to.my.servlet.StartupConnectionPoolServlet <param-name>debug <param-value>false

<param-name>alias

<param-value>mydbpool

<param-name>jdbc.driver <paramvalue>com.sybase.jdbc2.jdbc.SybDriver

<param-name>jdbc.url <paramvalue>jdbc:sybase:Tds:myhost:myport/mydatabase

<param-name>jdbc.username <param-value>myusername

<param-name>jdbc.password <param-value>mypassword

<param-name>jdbc.max.connections <param-value>10

<param-name>jdbc.idle.timeout <param-value>120

<param-name>jdbc.checkout.timeout <param-value>120

Re[3]: Alternative - Connection Pool in Tomcat Author: Norman Hanson (http://www.jguru.com/guru/viewbio.jsp?EID=462048), Feb 3, 2002 then to get a connection from the pool... <%@ page import="com.bitmechanic.sql.*, java.sql.*,java.util.*" %> <% ConnectionPool pool= (ConnectionPool)getServletContext().getAttribute("whatevermyalaiswas"); Connection conn = pool.getConnection(); /* use your connection for this or that then for completness... */ /* return the connection to the pool */ pool.returnConnection((PooledConnection)conn); %>

why create a new bean? you can put any Object in the servlet context. Re[4]: Alternative - Connection Pool in Tomcat

Author: Joost Schouten (http://www.jguru.com/guru/viewbio.jsp?EID=581960), Feb 4, 2002 Thanks for your help. By looking at your code I found out that I should ommit the servletname when using the getServletContext() method. It's all working fine now. I'm using this one bean to communicate with my database. Just so I keep my JSP pages clean. Cheers, Joost Re[5]: Alternative - Connection Pool in Tomcat Author: MAHABOOB PASHA (http://www.jguru.com/guru/viewbio.jsp?EID=740395), Jun 3, 2002 Hi Joost Schouten, I am also using the JSP page and bean id "cargo" is using for the Database connection(This is Corba Connection not JDBC). Please could you advise me how can go about this. I am also using the Tomcat4.0.1 with apache server. Please could you send me the sample changes in Tomcat/Servlet/JSP. My email id is [email protected]. Thanks again. <jsp:useBean id="cargo" class="Track.TrackTransaction" scope="session" /> Regards, Mahaboob Pasha Re[6]: Alternative - Connection Pool in Tomcat Author: Joost Schouten (http://www.jguru.com/guru/viewbio.jsp?EID=581960), Jun 4, 2002 Hi, I'm not quite sure what you are asking for. what do you have working so far, and what is not working? Also I'm not familiar with COBRA. maybe it's a good idea to also reply to one of the guys above, since they have way more experiance than I do. But I'll see what I can mean for you. cheers, Joost. Re[3]: Alternative - Connection Pool in Tomcat Author: ad joyce (http://www.jguru.com/guru/viewbio.jsp?EID=921197), Jul 22, 2002 I have placed the parameters into web.xml but when i try to make a connection it cannot find the class so i wondering where should

project.StartupConnectionPoolServlet be located <servletClass>project.StartupConnectionPoolServlet any help would be appreciated Re[4]: Alternative - Connection Pool in Tomcat Author: Norman Hanson (http://www.jguru.com/guru/viewbio.jsp?EID=462048), Jul 22, 2002 if you don't know where to put servlets you need to back up and start with a simpler example, but i'll answer anyway. given... <servlet-class> com.mypackage.servlet.BlahServlet your class (.class file) should be compiled into mywebapp/WEBINF/classes/com/mypackage/servlet/BlahServlet.class if its jarred up the the jar file should be in WEB-INF/lib --norm Re: Alternative - Connection Pool in Tomcat Author: MAHABOOB PASHA (http://www.jguru.com/guru/viewbio.jsp?EID=740395), May 31, 2002 Hi Norman Hanson, Thanks for your ver good information for connection pooling in tomcat. I am using a JSP with bean name like <jsp:useBean id="cargo" scope="session" class="Track.Tracking" /> The bean cargo will take care all the connection using the corba object conection. In this case how can I implement your code in my application. How can I define Alise,URL, DRIVER, USER NAME, PASSWORD, MAX CONNECTION, IDLE, CHECK OUT, DEBUG. Please advise me. Everybody suggesting to go for J2EE BUT I need to do it only in tomcat. Thanks again. Regards, Mahaboob Pasha Re[2]: Alternative - Connection Pool in Tomcat Author: Norman Hanson (http://www.jguru.com/guru/viewbio.jsp?EID=462048), Jun 1, 2002 look up in the thread to my posting on Norman Hanson, Feb 3, 2002 the params are defined in the web.xml. hope this helps --norm « previous

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Is there any way to change/set owner of a file that is uploaded, before it's saved to the filesystem? Location: http://www.jguru.com/faq/view.jsp?EID=543979 Created: Nov 9, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Henrik Bengtsson (http://www.jguru.com/guru/viewbio.jsp?EID=536810

No, but once it's written you can spawn a "chown" using Runtime.exec. It's up to your OS whether it will let you do that, however. Search the Servlets and Tomcat FAQs on "user permissions" and the like for more help. How to get the values of the variables in a different session? Location: http://www.jguru.com/faq/view.jsp?EID=559280 Created: Nov 23, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by rakesh sa (http://www.jguru.com/guru/viewbio.jsp?EID=545976 Short answer: you can't, at least not directly. However, you can share data across sessions on your own by using the "application context." See also • • • •

Is there any way to retrieve all of the active session ids on a server? The HttpSessionContext interface used to provide methods to do this, but has since been deprecated in the 2.1 API. How can I find out the number of live sessions within my servlet engine using either JSP or servlets? How can I join a session with a given sessionId without using cookies? Assume I get the session from the HttpSessionContext passing the session Id. What is the difference between request attributes, session attributes, and ServletContext attributes?

Is access to ServletContext and Session attributes thread safe? Location: http://www.jguru.com/faq/view.jsp?EID=567276 Created: Nov 29, 2001 Author: Ryan Breidenbach (http://www.jguru.com/guru/viewbio.jsp?EID=45212) Question originally posed by Tal Golan (http://www.jguru.com/guru/viewbio.jsp?EID=512887 For example, is the following code thread safe? public void setServletAttr( String theAttr, String theValue ) { getServletContext().setAttribute( theAttr, theValue ); } public void setSessionAttr( HttpServletRequest request, String theAttr, String theValue ) { request.getSession().setAttribute( theAttr, theValue ); } Thanks. This has been killing me! ---------------------------------------Since both ServletContext and HttpSession are interfaces, how thread-safe they are depends on their implementations.

That said, I wouldn't think that you would have to worry about this issue much. Since HttpSession objects are unique to each user, you probably won't be accessing any of these with more than one thread at the same time. As for ServletContext objects - nearly all the methods are read methods. And since the only objects you will be putting in the ServletContext are application wide in scope, you will probably want to put these in at the apps startup anyway and read them from that point on. BTW, it appears that both of these implementation in Tomcat 3.2.2 have no sychronization. Hope this helps. Comments and alternative answers

Is access to ServletContext and Session attributes thread safe? Author: Mark Kauffman (http://www.jguru.com/guru/viewbio.jsp?EID=1007647), Oct 3, 2002 So how is it typically implemented? I want to use the ServletContext for caching data I get from a backend DB. This means the named object (a data bean) will change during run-time and the code reading the data bean should not be interrupted by some code setting the data bean. How can administrator invalidate sessions other than his own? Location: http://www.jguru.com/faq/view.jsp?EID=567278 Created: Nov 29, 2001 Author: Kevin Schaaf (http://www.jguru.com/guru/viewbio.jsp?EID=466729) Question originally posed by Betsy Zelinger (http://www.jguru.com/guru/viewbio.jsp?EID=432122 I know that HttpSessionContext is deprecated with no replacement, but is there a work-around if an administrator wants to be able to delete sessions? I can get him a list of the sessions open, but can't find a way to invalidate them... cannot find any way to get a handle on a session other than the getSession method of HttpRequest, which of couse will be the administrator's own... is this just impossible now? -------------------------------If you're using a Servlet 2.3 container, create a HttpSessionListener that puts each new Session object in a Collection on sessionCreated() and takes it out on sessionDestroyed(). Your administrator user can retrieve that Collection (you would probably want store it in the Application Context), and do things with the Sessions like list them, invalidate them, etc. I have got this error when I tried to access the Tomcat welcome page at http://localhost:8080 using Tomcat 4.0. Starting service Tomcat-Standalone Apache Tomcat/4.0.1 Starting service Tomcat-Apache

Apache Tomcat/4.0.1 java.lang.NoSuchMethodError at org.apache.catalina.connector.ResponseStream.flush(ResponseStream.java: 244) at java.io.OutputStreamWriter.flush(OutputStreamWriter.java:245) at java.io.PrintWriter.flush(PrintWriter.java:120) at org.apache.catalina.connector.ResponseWriter.flush(ResponseWriter.java: 125) at org.apache.catalina.connector.ResponseBase.finishResponse(ResponseBase. java:481) at org.apache.catalina.connector.HttpResponseBase.finishResponse(HttpRespo nseBase.java:229) at org.apache.catalina.connector.http.HttpResponseImpl.finishResponse(Http ResponseImpl.java:288) at org.apache.catalina.connector.http.HttpProcessor.process(HttpProcessor. java:1038) at org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor.java :1106) at java.lang.Thread.run(Thread.java:484) The server starts up fine. The error comes up when I access the welcome page. All my other JSP codes residing in Tomcat cannot be access as a result of this problem.

I have tried to reinstall the entire Tomcat Server and JDK 1.3 to ensure that everything is the default setting but the problem still persists. This problem came all of a sudden. There was no problem at all in the first place.

Location: http://www.jguru.com/faq/view.jsp?EID=568095 Created: Nov 30, 2001 Author: Perry Tew (http://www.jguru.com/guru/viewbio.jsp?EID=60814) Question originally posed by Sad Guy (http://www.jguru.com/guru/viewbio.jsp?EID=547265 This is caused by mismatched versions of jars used by Tomcat. I've encountered this error before when I've done upgraded tomcat and failed to remove old jars from my classpath ( like servlet.jar, etc). It happens when tomcat attempts to call a new method that is not found in older jars. If you download a fresh version of tomcat and copy over your existing jars, you should sync up your system. A better idea would be to download a fresh version of tomcat and just use that version completely. How can I suppress the parameters from displaying in the URL? For instance, if I pass in a password, I don't want it to show up in the address bar. Location: http://www.jguru.com/faq/view.jsp?EID=586493 Created: Dec 16, 2001

Author: Mathias Neuhaus (http://www.jguru.com/guru/viewbio.jsp?EID=131203) Question originally posed by Radhe Yanamandra (http://www.jguru.com/guru/viewbio.jsp?EID=579307 Simply use POST method for submitting the form instead of GET. Note there's no way to suppress parameters when using GET; that's the way the parameters are passed - as part of the URL, which the browser displays. Oh, may be there is a way... Use a REDIRECT to tell the browser to fetch another page (you'll have to "remember" the parameters from the first request though!). Comments and alternative answers

Alex Author: Alexandros Kotsiras (http://www.jguru.com/guru/viewbio.jsp?EID=397266), Dec 21, 2001 You can always use a dummy frame, this is a frame with zero size and include all your pages in a frameset. This way there is no query string in the url, but a savvy user can easily find the url that hits the data page without the frameset Re: How to prevent display in the url. Author: Rommel Sharma (http://www.jguru.com/guru/viewbio.jsp?EID=234085), Dec 22, 2001 One easy solution is use HttpSession object to maintain the values in a session. Do not use the GET method. Use POST. The advantage of taking the values in a session is that you dont have to set and unset the values each time while going from one page to another. All values stored in the session will persist for the entire browsing session. To create the session: HttpSession session = request.getSession(true); session.putValue("PASWD", password); In subsequent pages: (In fact direct access to pages can be prevented if the user is not logged in by verifying if the session value is null or not) HttpSession session = request.getSession(false); String passwd = (String)session.getValue("PASWD"); For other things ... Author: Gary Bisaga (http://www.jguru.com/guru/viewbio.jsp?EID=757704), Feb 13, 2002 For things other than passwords, it may not be practical to use HTTP POST fields. For example, some piece of page display state that is not a field on the form. You could store these on the session, of course, but there may be reasons you don't

want to do that. For example, sometimes you want to pass forward a parameter that is specific to the page being displayed. These kinds of parameters you don't want to put on the HTTP session, and for this reason: if the user goes past this page into another page that sets the parameter to something else, then backs up using his browser "back" button and refreshes the page, you will have the later value, not the correct page-specific value. For these cases, you can use a URL encryption algorithm. Take a look at many financial sites and you'll see a URL that looks something like: http://foo.com?876sdf=SDS987987SDF

They are encrypting the URL parameters to pass some "secret" information. It's a little more work of course, since you have to decrypt them on the way out. But it can be a handy mechanism. What are the steps that I need to follow to deploy my servlet in WebLogic 6.1? Location: http://www.jguru.com/faq/view.jsp?EID=586701 Created: Dec 17, 2001 Author: Samiul Karim (http://www.jguru.com/guru/viewbio.jsp?EID=523694) Question originally posed by Saravanan Devaji Rao (http://www.jguru.com/guru/viewbio.jsp?EID=383486 1. Create a folder with any name of ur choice (say MyAssignment). 2. Create inside this the structure reqd. as per Servlet 2.2 API viz. MyAssignment | --WEB-INF | --classes 3. Place ur HTML,JSP files in MyAssignment folder(or any folder inside it but outside WEB-INF folder). 4. Place your compiled servlet class file inside classes folder (or any folder inside it. Just use packages in that case). 5. Place the web.xml and weblogic.xml files in the WEB-INF folder. 6. Edit web.xml to read as: <web-app> My Web Assignment <servlet> <servlet-name>CounterServlet <servlet-class>CounterServlet

<servlet-mapping> <servlet-name>CounterServlet /CounterServlet/* 7. Copy the entire structure and place it inside the applications folder of Weblogic. 8. Deploy the web-app (see docs). 9. You can now access the servlet as: http://127.0.0.1:7001/MyAssignment/CounterServlet" [You can also cd to your project directory ("MyAssignment") and use jar, as jar cf ../myassignment.war * Then use the WebLogic deploy tool inside the console to deploy the WAR (the console is available in http://localhost:7001/console/ -A] Comments and alternative answers

Deploying a simple servlet in weblogic 7.0 Author: puneet jain (http://www.jguru.com/guru/viewbio.jsp?EID=1088585), May 27, 2003 hi i have followed the directory structure and put my application named "WebApp" in the application dire domain . i am accessing succes.. the static files that is html but i am not able to access the srvlet inside the directory. every time i access it it thros the following error stating that the classes not founnd in the classp classes is the server talking about thouhg i havesset the classpath ?? THE ERROR IT THROWS IS THIS ********************************* <May 28, 2003 12:09:54 PM IST> <Error> <101250> <[ServletContext(id=1642082,name=WebApp,context-path=)]: Servlet class myclasses.Gservlet for servl not be loaded because a class on which it depends was not found in t he classpath D:\bea\user_projects\Applicationdomain\applications\WebApp;D:\bea\user_projects\Applicationdomain\a ons\WebApp\WEB-INF\classes. java.lang.NoClassDefFoundError: myclasses/Gservlet (wrong name: Gs 28, 2003 12:09:54 PM IST> <Error> <101018> <[ServletContext(id=1642082,name=WebApp, Servlet f ailed with ServletException javax.servlet.ServletException: [ServletContext(id=1642082,name=WebApp,context-path=)]: Servlet class myclasses.Gservlet for servlet not be loaded because a class on which it depends was not found in the classpath D:\bea\user _projects\Applicationdomain\applications\WebApp;D:\bea\user_projects\Applicationdomain\applications INF\class es. java.lang.NoClassDefFoundError: myclasses/Gservlet (wrong name: Gservlet) at weblogic.servlet.internal.ServletStubImpl.prepareServlet(ServletStubImpl.java:791) at weblogic.servlet.internal.ServletStubImpl.getServlet(ServletStubImpl.java:517) at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:351) at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:306) at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.ja weblogic.security.service.SecurityServiceManager.runAs(SecurityServiceManager.java:744) at weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:3086) at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:2544) at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:153) at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:134) > ****************** please help me pu

In some web.xml I find DOCTYPE reference of "web-app_2_2.dtd",(in Weblogic 5.1 example) in others, of "web-app_2.2.dtd" (in java pet store). What is the difference between the two DTDs? Location: http://www.jguru.com/faq/view.jsp?EID=586710 Created: Dec 17, 2001 Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985) Question originally posed by vikrant jain (http://www.jguru.com/guru/viewbio.jsp?EID=502452 I believe that web-app_2.2.dtd is misspelled and you can verify it at this page: J2EETM — DTDs. Both are aivable at Sun' site: • •

http://java.sun.com/j2ee/dtds/web-app_2_2.dtd http://java.sun.com/j2ee/dtds/web-app_2.2.dtd

Maybe this is to prevent errors for misspelled web.xml like the one that you found. I've made a diff between them and contents are identical, so no problem may occur, but it's better to make things right. HttpUtils.parseQueryString is deprecated. What should we use instead ? Location: http://www.jguru.com/faq/view.jsp?EID=587251 Created: Dec 17, 2001 Author: Bozidar Dangubic (http://www.jguru.com/guru/viewbio.jsp?EID=433955) Question originally posed by sam pitroda (http://www.jguru.com/guru/viewbio.jsp?EID=476938 Use getParameterMap() in HttpServletRequest. Comments and alternative answers

seems wrong Author: shan fu (http://www.jguru.com/guru/viewbio.jsp?EID=241378), Apr 9, 2002 show refer to HttpServletRequestWrapper Re: seems wrong Author: Garp Garp (http://www.jguru.com/guru/viewbio.jsp?EID=1071362), Apr 12, 2003 This does not handle case where request has nothing to do with string being parsed. What should we do in these cases? How do i find out whether a request to a particular servlet is coming from another servlet or, if it is coming from a user request? Location: http://www.jguru.com/faq/view.jsp?EID=594117 Created: Dec 22, 2001 Author: Christopher Schultz (http://www.jguru.com/guru/viewbio.jsp?EID=138382) Question originally posed by jayashree viswanathan (http://www.jguru.com/guru/viewbio.jsp?EID=589873

[While it is tempting to use request.getRemoteHost, this will not work.] The getRemoteHost should always return a foreign IP address. The only reason you might get the local host as your IP from getRemoteHost is if your servlet actually made an HTTP request to another servlet. To answer the original question, you can use a standard way to notify servlets further-down the 'forward-chain' that they have been forwarded-to by placing an object in the request 'attributes'. Each action can check this attribute against, say, null, and if it is non-null, then it can assume that it was a forward from another servlet, not an original request from a client's browser. -chris When two or more people are using my servlet, why does everyone see the data for the person who has logged in latest? Location: http://www.jguru.com/faq/view.jsp?EID=594540 Created: Dec 23, 2001 Author: Norman Hanson (http://www.jguru.com/guru/viewbio.jsp?EID=462048) Question originally posed by Gajanan Koparde (http://www.jguru.com/guru/viewbio.jsp?EID=592587 [It's probably because you're using instance variables to store data. Instance variables are dangerous in a servlet. Use session attributes instead. -Alex] If you still want your servlet multithreaded, try creating the data Object in one request (doGet), add the data Object to the users session, then forward to the second servlet where you pick up the object. // in first servlet doGet... HttpSession session = request.getSession(); session.setAttribute(dataBeanId, dataBean ); ... RequestDispatcher rd = request.getRequestDispatcher("servlet2uri"); rd.forward(request, response); // in the second servlet doGet... HttpSession session = request.getSession(); dataBean = (DataBean)session.getAttribute( dataBeanId ); Is it better to have lots of methods to my servlet, or to keep the code inside the doGet or doPost method? Location: http://www.jguru.com/faq/view.jsp?EID=594560 Created: Dec 23, 2001 Author: Ryan Breidenbach (http://www.jguru.com/guru/viewbio.jsp?EID=45212) Question originally posed by Stephen Ward (http://www.jguru.com/guru/viewbio.jsp?EID=560878 There are probably two questions here: Can you put all your code in the doXXX method(s) and Should you put all you code in the doXXX method(s). As for the first part - yes, you can put all the code in your servlets. However, you need to be aware of a couple of things. First, this obviously limits your servlet to a

specific task. This is fine if this is what you are wanting. Also, know that servlets are not thread-safe unless it explicity implements SingleThreadModel, so you don't want any unsychronized access to a class-scoped attribute. In fact, you are probably best not using any "non-constant" class-scoped attribute. You are safer creating attributes at the method level and passing them as parameters. As for your question of how you return a ResultSet from a public void doXXX method - you can't. Instead, you would probably place this object in the request/session as so: ... ResultSet rs = loadData(); req.getSession().setAttribute("resultSet", rs); ... Now the object can be retrieved from the request/session by another servlet of JSP. Now, for the second part - should you do all the work in the servlet class. Well, this depends. If you application is fairly simple, you can get away with this because you won't have that much code to maintain. However, once your application becomes somewhat complex, you probably want to employ the Front Controller Pattern. Basically, this is a single servlet that intercepts all application requests and forwards them to other classes to be processed. This pattern has several advantages: • • •

Your application is very extensible. To add another piece of functionality, you simply create a class to encapsulates this fucntionality - your servlet code remains unchanged. Single point of entry to your site. Since all requests go throught the same servlet, you have one place for error-handling, logging, etc. Decouples application code from web interface. Since classes independant of your servlet our handling the processing, they can be reused by other non-web components.

For more on this pattern and other J2EE patterns, go to Sun's J2EE Patterns Catalog. Hope this helps. [Make sure to also read the forum thread where this question was posed for more advice. -Alex] Comments and alternative answers

Is it better to have lots of methods to my servlet, or to keep the code inside the doGet or doPost method? Author: shivangi gupta (http://www.jguru.com/guru/viewbio.jsp?EID=762763), Feb 18, 2002 According to me keeping a code inside doGet() /doPost() is best idea . Because in this way we can follow the oops concepts by encapsulating things without showing what's going on. if we define whole methods outside it will lead to low cohesion which is bad practice Re: Is it better to have lots of methods to my servlet, or to keep the code

inside the doGet or doPost method? Author: Sushil Srivastava (http://www.jguru.com/guru/viewbio.jsp?EID=744298), Feb 21, 2002 I would recommend logically splitting your servlet class into methods rather than putting everyting within one method. Putting everyting in one method smells of structural programming.For e.g not much point in adding database related connection into doPost. How do I set a System Property and access it from a Servlet? Location: http://www.jguru.com/faq/view.jsp?EID=594561 Created: Dec 23, 2001 Author: Dane Foster (http://www.jguru.com/guru/viewbio.jsp?EID=224441) Question originally posed by Muhammad Asif (http://www.jguru.com/guru/viewbio.jsp?EID=301509 I am using JAXP for parsing xml documents. With JAXP we specify the parser to use in system property named "javax.xml.parsers.SAXParserFactory". The related function createXMLReader() automatically takes this value from system. Now the purpose of this approach is to make your code portable across different vendor for parsers. How can i specify a system property out side the servlet so that createXMLReader() can get it on its own...thus true vendor independence can be obtained??? --------------------------------Answer: Most servlet engines allows you to pass parameters to the VM when its starting. Find out how your servlet engine does this and pass:

-Djavax. xml.parsers.SAXParserFactory=qualified.name.of.parserfactory [This will probably be in the servlet container's startup script. E.g. for Tomcat this will be either tomcat.sh, tomcat.bat, catalina.sh, or catalina.bat. For WebLogic it is startWebLogic.bat. Etc... -Alex] Comments and alternative answers

Alternative solution Author: Giles Paterson (http://www.jguru.com/guru/viewbio.jsp?EID=806029), Mar 21, 2002 JAXP looks in the following places when trying to locate a factory: 1) It uses the value of the system property (e.g. javax.xml.parsers.SAXParserFactory) 2) It looks in the JRE/lib/jaxp.properties file

3) It uses a JAR file service provider to look in a file called METAINF/services/javax.xml.parsers.SAXParserFactory

4) It uses the default instance. For a truly neutral configuration method, option 3 is your best bet. It is the method I use, and it works flawlessly. As I make use of SAX, DOM and Transformers, I have three files in the METAINF/services directory: javax.xml.parsers.SAXParserFactory javax.xml.parsers.DocumentBuilderFactory javax.xml.transform.TransformerFactory

each of these files contain a single line, specifying the appropriate implementation class to use. Re: Alternative solution Author: Leos Literak (http://www.jguru.com/guru/viewbio.jsp?EID=910037), Oct 1, 2004 And do you have generic solution? E.g. when I want to setup custom log4j for each context? Or to have my own system property to be set for each context? If I set it in container startup script, it will be shared across all contexts. But I want to have different value in each context :-( Is it achievable via System.properties? Do servlet containers support such use case? I read the section on Filters and the spec seems to be silent on some issues... Can you clarify? Location: http://www.jguru.com/faq/view.jsp?EID=594562 Created: Dec 23, 2001 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Taruvai Subramaniam (http://www.jguru.com/guru/viewbio.jsp?EID=23676

1. Can a filter attach new objects to the request without having to create a request wrapper. I have no need to override any methods in request just make available some objects downstream to other filters and the servlet. 2. What happens when a filter throws an exception other than UnavailableException. Does the container continue to go on. I mean is my only choice to have a catch block and not do a doFilter in it or does an exception automatically halt the processing down the filter chain and the servlet. 3. I have an authentication filter and I want to do a mapping to /* so that all requests pass thro' authentication. However I need to add some extra filters to servlets by name. Is this possible.? 4. Is there any way to create a filter chain on the fly? I have to string together a number of reusable components. But which ones I use will depend on some parameters in the URL.

-------------------------------------------Answer: Let me try to give you some answers or, better, the way I interpret the specs. 1) Yes, I definitely think so. You have both the request and response objects and so you should be able to attach objects in the request scope with setAttribute(String, Object). 2) I think that the better way to discover that is to try. Personally I think that for the scenario you have described, the servlet container will get the exception halting the process. 3-4) Yes, you should be able to achieve what you need, maybe trying to create some kind of filter factory and chain the created filter to the one you need. It looks like an interesting thing to try... As soon I have some free time, I'm going to try it myself. Our servlet program needs to read an image file (*.jpg or gif) and create thumnail files. Is there any program available I can use ? Location: http://www.jguru.com/faq/view.jsp?EID=594565 Created: Dec 23, 2001 Author: Denis Navarre (http://www.jguru.com/guru/viewbio.jsp?EID=495283) Question originally posed by Jason Peng (http://www.jguru.com/guru/viewbio.jsp?EID=533294 Try these links: http://java.sun.com/products/jimi/ http://rsb.info.nih.gov/ij/ Java Advanced Imaging You'll find how to read and write some image formats. How to apply some effects. And if I remember well, you can save the image with different sizes. Comments and alternative answers

JPEG thumbnails Author: Mathias Neuhaus (http://www.jguru.com/guru/viewbio.jsp?EID=131203), Jan 8, 2002 I used the Independend JPEG group's JPEG-library via JNI for this. The decompress-function has a parameter to extract every 2nd, 4th or 8th pixel. Just compress the resulting bitmap to a new JPEG and return that as a byte [] to the Java-program. Pretty fast, no fiddling with Images and the IJGs implementation can easily be replaced by Intel's JPEG-library.

ImageMagick Author: Fredric Palmgren (http://www.jguru.com/guru/viewbio.jsp?EID=1092794), Mar 31, 2004 What about imageMagick (http://www.imagemagick.org/) do anyone has any experiances with it? How to check for the validation of a Unix login username and password from Java? Location: http://www.jguru.com/faq/view.jsp?EID=594578 Created: Dec 23, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Kady Ny (http://www.jguru.com/guru/viewbio.jsp?EID=512473 See http://cscene.org/CS4/CS4-04.html for a JNI tutorial with source code which verifies a user's password. Comments and alternative answers

How to check for the validation of a Unix login username and password from Java? Author: Omindra Rana (http://www.jguru.com/guru/viewbio.jsp?EID=1164665), Jun 6, 2005 just open the password file from the root directory and fetch data(login and password) from that file. But u must have root permission for that. Omindra Rana Is it possible to make calls to C or C++ methods from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=594580 Created: Dec 23, 2001 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by David Leonard (http://www.jguru.com/guru/viewbio.jsp?EID=555596 Yes, but you have to use JNI. See the JNI FAQ for help on using JNI. Also, see your servlet engine's documentation for help on how to set up the environment (environment variables, where to place the library files, etc.) so JNI will be able to work inside the servlet container. Comments and alternative answers

Then How if i wanna call some java methods from a C or C++??? Author: Jia Li (http://www.jguru.com/guru/viewbio.jsp?EID=581971), Jul 9, 2002 Thanx! Calling java Methods Author: Madhan Iyer Vasudevan

(http://www.jguru.com/guru/viewbio.jsp?EID=985437), Aug 19, 2002 U CAN USE JNI TO CALL METHODS AND FIELDS IN JAVA. REFER SUN DOCUMETATION ON JNI_>METHOD AND FIELS ACCESSORS How do I pass some servlet variable to javascript? Location: http://www.jguru.com/faq/view.jsp?EID=715231 Created: Jan 9, 2002 Author: Shirish Bathe (http://www.jguru.com/guru/viewbio.jsp?EID=550801) Question originally posed by Dewi Sumatra (http://www.jguru.com/guru/viewbio.jsp?EID=712005 I embedded the javascript code in the servlet such as: out.println("<scriptlanguage=\"JavaScript\" >"); out.println(" <servlet-mapping> <servlet-name>MyApp / <servlet-mapping> <servlet-name>default /images <servlet-mapping> <servlet-name>jsp /private/*.jsp

Needless to say, this doesn't work the way I expected it to. Everything is served by the servlet. Per Re[2]: Servlet URL patterns Author: j wishnie (http://www.jguru.com/guru/viewbio.jsp?EID=897786), Jul 9, 2002 I have a similar configuration with Tomcat 4.0.4/Linux and it seems to work fine. Here are the differences between your config and mine: 1. In the images mapping you are using the incorrect url-pattern. You have: /images

But that is mapping only the SPECIFIC path "/images" to default. You need: /images/*

Which will map EVERYTHING under /images to the default servlet. 2. JSP mapping

When Tomcat matches a url-pattern it seems to eat up all the paths that match so that given your url-pattern of "/private/*.jsp", the following would happen: User requests "http://example.org/private/foo.jsp", tomcat matches the urlpattern and knows to use the JSP servlet BUT the file-path it gives the servlet appears to be "foo.jsp" NOT "/private/foo.jsp" A quick&dirty way to solve this is to make your url-pattern: "*.jsp" Now that JSP servlet will match _any file_ ending in .jsp and pass in the appropriate full path. So "http://example.org/private/foo.jsp" gets handed to the JSP servlet as "/private/foo.jsp" My specific config is as follows: <servlet-mapping> <servlet-name>Main / <servlet-mapping> <servlet-name>default *.html <servlet-mapping> <servlet-name>default *.js <servlet-mapping> <servlet-name>default *.css <servlet-mapping> <servlet-name>jsp *.jsp

In order to run Struts, do I need to install a servlet container such as Tomcat? Location: http://www.jguru.com/faq/view.jsp?EID=771298 Created: Feb 25, 2002 Author: Aron Tunzi (http://www.jguru.com/guru/viewbio.jsp?EID=446077) Question originally posed by Nguyen van Tin (http://www.jguru.com/guru/viewbio.jsp?EID=761500 Yes, you must! See the installation requirement for Struts: http://jakarta.apache.org/struts/userGuide/installation.html Request parameter How to find whether a parameter exists in the request object? Location: http://www.jguru.com/faq/view.jsp?EID=771300 Created: Feb 25, 2002 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Unnikrishnan Nair (http://www.jguru.com/guru/viewbio.jsp?EID=432032 boolean hasFoo = !(request.getParameter("foo") == null || request.getParameter("foo").equals("")); Tom Paris adds: boolean hasParameter = request.getParameterMap().contains(theParameter); (which works in Servlet 2.3+) Comments and alternative answers

Code comment.. Author: Fredric Palmgren (http://www.jguru.com/guru/viewbio.jsp?EID=1092794), Mar 31, 2004 It seems like the right code would be: boolean containsKey = request.getParameterMap().containsKey(param);

It would also be possible to ask for a value of the supplied key(param) using boolean containsKey = request.getParameterMap().containsValue(param);

How do i get the name of the file from a file upload form? Location: http://www.jguru.com/faq/view.jsp?EID=771302 Created: Feb 25, 2002 Author: sachin thukral (http://www.jguru.com/guru/viewbio.jsp?EID=573922) Question originally posed by ken lo (http://www.jguru.com/guru/viewbio.jsp?EID=589625 Using Jason Hunter's O'reilly Servlet package, if you pass some parameter as query String or hidden variable,then only by using Vectors I was getting parameters which was passed from the previous page. Since in multipart forms Request.getPararmeter does not work.

But it is possible to get filename of the file which is uploded (I suppose this is your requirement). Using iws.getWorkingDirectory will give you the current working directory. Now using the following you can get the filename,just try the last one as well to get the requested parameter(I'm not sure for the last line) MultipartRequest multi = new MultipartRequest(request, basedir, iSize);

Enumeration files = multi.getFileNames(); String strText = multi.getParameter("txtLink"); Now easily you can enumerate through the file names. Comments and alternative answers

Jakarta Commons FileUpload Bean Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Feb 15, 2003 The Jakarta Commons FileUpload Bean provides this feature and more! It's a great solution to the annoyingly long-standing problem of servlet file upload. I put my JAR file inside WEB-INF/lib, but my classes are not getting found. However, when i unzipped classes into WEB-INF/classes/, it works. What's up? Location: http://www.jguru.com/faq/view.jsp?EID=771307 Created: Feb 25, 2002 Author: Luigi Viggiano (http://www.jguru.com/guru/viewbio.jsp?EID=101985) Question originally posed by ko ko (http://www.jguru.com/guru/viewbio.jsp?EID=764398 Some old versions of Tomcat do not include WEB-INF/lib/*.jar in WebApp classpath. You may handle it updating to a newer version of tomcat or (as you did) unpacking jars into WEB-INF/classes/. [Get the latest version of Tomcat (currently 4.0.2) from http://jakarta.apache.org -Alex] Comments and alternative answers

Tomcat & jarfiles... Author: May Thomas (http://www.jguru.com/guru/viewbio.jsp?EID=757571), Feb 25, 2002 Put your jarfile into $TOMCAT_HOME/common/lib. Tomcat should find them there. Re: Tomcat & jarfiles... Author: Ryan Breidenbach (http://www.jguru.com/guru/viewbio.jsp?EID=45212), Feb 26, 2002 Just be careful about what JAR files you put under $TOMCAT_HOME/common/lib. These libraries become available to all web applications and can lead to some nasty classpath problems. Make sure you only

place JARs here that you know will be needed by all your applications, and that all of these applications will need the same version of that JAR. zip file will not be loaded Author: Guizhong Chen (http://www.jguru.com/guru/viewbio.jsp?EID=772849), Feb 26, 2002 Classes in WEB-INF/lib/*.zip files will not be loaded. It is the behavior in Tomcat4.0.2. Unzip zip files and jar them into jar files in WEB-INF/lib. Re: zip file will not be loaded Author: Karri Salli (http://www.jguru.com/guru/viewbio.jsp?EID=781982), Mar 4, 2002 I got the same problem, the only JAR file on the classpath is bootstrap.jar. Re: zip file will not be loaded Author: prem Gogineni (http://www.jguru.com/guru/viewbio.jsp?EID=853193), Apr 24, 2002 I got it working by just renaming oracles *.zip to *.jar Re[2]: zip file will not be loaded Author: Feng Ji (http://www.jguru.com/guru/viewbio.jsp?EID=1013740), Oct 17, 2002 Hi there, Which directory you put your oracle file in? I got the similiar problem. The oracle driver cannot be found in my JSP application. I use tomcat-4.1 under unix. my email is [email protected] many thanks, Feng Ji Re[2]: zip file will not be loaded Author: Sunil Bhadauriya (http://www.jguru.com/guru/viewbio.jsp?EID=1242137), May 2, 2005 Exactly, I did the same, and it worked for me. I wanted use classes12.zip-the file containing oracle driver. There was no lib folder in my web application, deployed in Tomcat.I simply created a lib folder in my WEB-INF folder, kept the classes12.zip in this folder, renamed classes12.zip to classes12.jar and my application was able to connect to the intended database and was fetching data successfully. Thanks. Similar Problem Author: Brendan Richards (http://www.jguru.com/guru/viewbio.jsp?EID=773717), Feb 27, 2002 I'm getting a similar problem attempting to run cocoon2 on Tomcat 4.0.2. None of lib files in webapps/cocoon2/WEB-INF/lib are being found. If I copy all the jar files to $CATALINA_HOME/common/lib, the application works fine but I definately don't want a large pile of application-specific jars in the common

directory. I've already tried explicitly adding a context for the application in $CATALINA_HOME/conf/server.xml any more suggestions? Tomcat 4.0.2 & jar files problem Author: Davide B. (http://www.jguru.com/guru/viewbio.jsp?EID=780374), Mar 4, 2002 My jar files under WEB-INF/lib are not found. Tomcat version is 4.0.2. These lines are from the server log: 2002-03-04 11:15:11 WebappLoader[/lutest]: Deploying class repositories to work directory D:\jakarta-tomcat\dist\work\localhost\lutest 2002-03-04 11:15:11 WebappLoader[/lutest]: Deploy JAR /WEB-INF/lib/crimson.jar to e:\Progetti\lutest\WEB-INF\lib\crimson.jar 2002-03-04 11:15:11 ContextConfig[/lutest]: Scanning library JAR files 2002-03-04 11:15:11 ContextConfig[/lutest]: tldConfigJar(/WEBINF/lib/crimson.jar): java.io.IOException: Impossibile trovare il percorso specificato (Impossibile trovare il percorso specificato -> Could not find specified path) Where do I go wrong ? David Re: Tomcat 4.0.2 & jar files problem Author: hitesh shah (http://www.jguru.com/guru/viewbio.jsp?EID=874279), May 10, 2002 I think this is a bug in tomcat 4+. see the link, http://www.mail-archive.com/[email protected]/msg24405.html thanks, How to force Tomcat to use your classes Author: Sergio Almeida (http://www.jguru.com/guru/viewbio.jsp?EID=1194460), Aug 20, 2004 It's a drastic approach, but worked for me. I'm a beginer at JSP, but I have a good background in ASP what makes things a little easier for me and I'm a Java programmer ( up to now, for hobby - PLEASE HIRE ME IF YOU HAVE AN OFFICE IN BRAZIL - ;) and I have made some interesting things with Java2, for example a Visual Program to build Applications in Java Swing -

Inspired in VB and Delphi, but much simpler... Let's go for the solution: "This hint is for Windows users, under Linux I haven't tested it, so there's no warranty. At least it can serve as a guideline..." Add to your machine CLASSPATH the following code: %CATALINA_HOME%\work\Catalina\[name of the host]\_ As I'm using the localhost (127.0.0.1), it ended up as: %CATALINA_HOME%\work\Catalina\localhost\_ Below this directory, resides the package org.apache.jsp That's the secret: Every JSP that you run is exported to this package as a java file, then it's compiled. Add as the first line of the java source codes that you want to use the following string: package org.apache.jsp; Now compile your adapted sources inside this directory: %CATALINA_HOME%\work\Catalina\localhost\_\org\apache\jsp Now, when you call JSP pages, Tom kitty (I find Tomcat's logo very nice!) has the class files in an accessible area to link to the new compilations. I love open source and I knew a say that I liked very much:"The future is open". I have a free upload component that I made for ASP programmers at http://www.amorpositivo.com/download/index.asp Just a problem: Everything is in Portuguese, as I am a Brazilian. Good look and comment it back! Sergio Almeida Re: How to force Tomcat to use your classes Author: ravi kanth (http://www.jguru.com/guru/viewbio.jsp?EID=318820), Mar 18, 2005 By default, the jar files in the lib folder are not on the build classpath. The example build.xml provided with Tomcat installation indicates that. You have to modify the build.xml file for your web application to put the lib

folder on the compilation classpath. You can do this by addding these:

lines in the build.xml file for your web application. This XML element should be added in <path id="compile.classpath"> element. I have tested this with Tomcat 5.0. I have been trying to find a way not only to get the user certificate info - i.e. Authentication via DigitalID, but also to have a digest of the request, signed by the client (Web Browser Only - not the Applet/Application case) or something like that, so I can proove to a 3rd party that the user with the specific certificate has issued the specific request. Is it at all possible? Location: http://www.jguru.com/faq/view.jsp?EID=776825 Created: Feb 28, 2002 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Alexander Radev (http://www.jguru.com/guru/viewbio.jsp?EID=769532 That's an interesting question. I'm pretty sure the answer is "no," at least not without hacking the server. The request *is* signed by the client, effectively, but (a) since it's SSL, what's signed is not the request itself, but the symmetric key used to encrypt the request before it's sent, and (b) the Servlet spec doesn't expose any of the mechanics of the SSL transaction anyway -- it just hands you an alreadyauthorized Principal. Can we use the constructor, instead of init(), to initialize servlet? Location: http://www.jguru.com/faq/view.jsp?EID=776892 Created: Feb 28, 2002 Author: Chandra Patni (http://www.jguru.com/guru/viewbio.jsp?EID=33585) Question originally posed by P SK (http://www.jguru.com/guru/viewbio.jsp?EID=748577 No you can't. It's the container who manages the lifecycle of the sevlet not you. Also, you must call super.init() for init() to work properly. Comments and alternative answers

Sure you can Author: Christopher St. John (http://www.jguru.com/guru/viewbio.jsp?EID=778908), Mar 1, 2002 Yes, of course you can use the constructor instead of init(). There's nothing to stop you. But you shouldn't. The original reason for init() was that ancient versions of Java couldn't dynamically invoke constructors with arguments, so there was no way to give the constructur a ServletConfig. That no longer applies, but servlet containers still

will only call your no-arg constructor. So you won't have access to a ServletConfig or ServletContext. Plus, all the other servlet programmers are going to expect your init code to be in init(). Why confuse them? Re: Sure you can Author: Sheikh Azad (http://www.jguru.com/guru/viewbio.jsp?EID=967553), Aug 4, 2002 can use constructor only if you are intantiating your servlet class.it is not must to call super.init(config) you can hold your config at your own without calling super.init(config). java Author: kojma fer (http://www.jguru.com/guru/viewbio.jsp?EID=1032159), Nov 29, 2002 whats the difference between webserver and application server? why ejb programes run in application server only why not in web server? how will u handle multiple resultset objects? Re: java Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Nov 30, 2002 See What are all the different kinds of servers? (Such as Web Servers, Application Servers, etc) no constructor in servlet Author: shaik kalesha (http://www.jguru.com/guru/viewbio.jsp?EID=1102933), Sep 10, 2003 the reason for not using constrctor in servlet is we can't write constructors in interfaces Does Jserv support the following methods from Servlet spec 2.2? 1. javax.servlet.http.HttpServletRequest: method getSession 2. javax.servlet.http.HttpSession: method setAttribute 3. javax.servlet.ServletContext: method getRequestDispatcher

Location: http://www.jguru.com/faq/view.jsp?EID=777589 Created: Feb 28, 2002 Author: Chandra Patni (http://www.jguru.com/guru/viewbio.jsp?EID=33585) Question originally posed by Nigel Smith (http://www.jguru.com/guru/viewbio.jsp?EID=458605 [or are these methods new to the servlet API since 2.0, as this appears to be the latest version that JServ supports? My problem is that I have developed in using Tomcat 4.0.1 (and hence servlet 2.3), and now have been given an Oracle server which seems to use Jserv as the servlet engine. The above methods cannot be found. Any ideas on how to get around this?. Please!]

For JServ, you can ues the following methods. 1. javax.servlet.http.HttpServletRequest: method getSession(true) 2. javax.servlet.http.HttpSession: method putValue(String str, Object o); 3. javax.servlet.ServletContext: method getRequestDispatcher This method is supported by JSPs but not by servlets in JServ. It's weird but don't ask me why. How do I run a servlet from command-line mode? Location: http://www.jguru.com/faq/view.jsp?EID=777592 Created: Feb 28, 2002 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by maha devan (http://www.jguru.com/guru/viewbio.jsp?EID=463184 Once you install your servlet inside a servlet container like Tomcat, you can fetch the results of the servlet by using a command-line tool like wget or curl (or write your own HTTP client -- it's not very difficult). You can also use a tool like ServletUnit (part of HTTPUnit) that's a "bare-bones" onthe-spot servlet runner. Be warned, though; it doesn't implement all the features. Why is my servlet called twice from a JavaScript button? Location: http://www.jguru.com/faq/view.jsp?EID=777595 Created: Feb 28, 2002 Author: Bozidar Dangubic (http://www.jguru.com/guru/viewbio.jsp?EID=433955) Question originally posed by Arvind S (http://www.jguru.com/guru/viewbio.jsp?EID=585871 Do you submit the form from the javascript? This can happen if you are calling the javascript function which does document.formName.submit() but the form itself also has an action attribute. Therefore, the form actually gets submitted twice. If you are submitting the page from the javascript, remove the action attribute from the form tag. Comments and alternative answers

Submit from Javascript Author: Igor Dikhtyaruk (http://www.jguru.com/guru/viewbio.jsp?EID=860508), May 2, 2002 How about if I need an action attribute to specify mapping (servlet URL)? for example: <script language="JavaScript"> function submitRequest() { document.runReport.submit();

} Re: Submit from Javascript Author: kamalanathan vijatt (http://www.jguru.com/guru/viewbio.jsp?EID=833101), May 2, 2002 sir u have mentioned that Action attribute should not be used . Then, how i will map my destination URLfrom the Javascript funtion.

Re[2]: Submit from Javascript Author: DD DD (http://www.jguru.com/guru/viewbio.jsp?EID=865851), May 4, 2002 document.form.action=target just before submitting form in javascript. Why is my servlet is called twice. Author: Rajkumar Murugesan (http://www.jguru.com/guru/viewbio.jsp?EID=521246), May 15, 2002 As said by Bozidar Dangubic, if in the form we have a submit button and write a Script to submit, we land up sending two request. Again.. If we use Image as an input type and provide an onclick action then also the request will sent twice [even though Action attribute is not set in the form, but set in the Script]. To avoid this we can have the Input type tag outside the form tag. By this we can ensure only the Script submit() sends the request. Re: Why is my servlet is called twice. Author: Scott Yaung (http://www.jguru.com/guru/viewbio.jsp?EID=915592), Jul 1, 2002 you can try add an hidden value like beensubmit in the form, before submit the form in javascript , you can check it. another way to do it is not add a click even handler in your img button, just use onsubmit() event handler, and return a true when the all the form fileds are well filled, return a false, if any fields can not match your request. like this

...... function checkb4send() { if (...document.form1.fields are well filled...) {return true;} return false;

}

Facing the same problem with websphere 4.0 Author: Dhanesh Choudhary (http://www.jguru.com/guru/viewbio.jsp?EID=1089617), May 30, 2003 I have coded my jsps in the same way as it was suggested. I donot have more than one action parameter in my jsp. But wherever I submit a page to servlet It is called always called twice. I sending hidden parameter to servlet, first time it works well but since it is calling twice second time it goes with null. and servlet throw null pointer exception. Not able to understand why it is happening. Same thing is working fine with weblogic. . Here is the sample code I am using <SCRIPT language="JavaScript"> function getPage(choice) { document.view_search_result.eventID.value=choice; document.view_search_result.submit(); }

Why is my servlet called twice from a JavaScript button? Author: Hubert Carvallo (http://www.jguru.com/guru/viewbio.jsp?EID=1250033), Jun 23, 2005 If you have a javascript function which does document.formName.submit() and a form that has a submit button when you click on submit the form will be submitted twice. A simple way to avoid that it is to change the type of the submit button from "submit" to "button" then only the javascript function will submit the form. Is possible to subdir webapps directory? Location: http://www.jguru.com/faq/view.jsp?EID=779619 Created: Mar 3, 2002 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Peter Burgstaller (http://www.jguru.com/guru/viewbio.jsp?EID=763476 Additional info: I'd like to organize my webapps in subdirectories of the tomcat/webapps/ directory. I have right now a setup like: /tomcat/webapps//application The problem that I have is that those applications are not started automatically upon tomcat startup. I do have the tags in my individual web.xml files but it doesn't seem to do anything. Unfortunately, this structure can't really work. Tomcat, in fact, consider all the subdirectories under the webapps directory as default contexts. In this case it considers all the directories as contexts and looks for the WEB-INF/web.xml for each of them. So, in your design, Tomcat considers the client's directories (and not their subdirectories) as web applications.

You can organize all your applications using that structure, but do not use the webapps directory (use any other location) and you have to define all the context manually in the server.xml, or just put all the applications in the webapps directory. Why request.getRemoteUser() returns NULL ? Location: http://www.jguru.com/faq/view.jsp?EID=842151 Created: Apr 17, 2002 Author: Mikkel Bruun (http://www.jguru.com/guru/viewbio.jsp?EID=771030) Question originally posed by Muhammad Asif (http://www.jguru.com/guru/viewbio.jsp?EID=301509 As specified by the documentation, this method returns the login of the user making this request, if the user has been authenticated, or null if the user has not been authenticated. The authentication, in this case, is the http authentication. Comments and alternative answers

How does one go about authenticating so that getRemoteUser() does not return null? Author: John Corro (http://www.jguru.com/guru/viewbio.jsp?EID=271751), Apr 23, 2002 How does one go about authenticating so that getRemoteUser() does not return null? Re: How does one go about authenticating so that getRemoteUser() does not return null? Author: Gerard Fernandes (http://www.jguru.com/guru/viewbio.jsp?EID=903300), Jun 4, 2002 You set up a Realm - See the Tomcat documentation for Realms and use that for authentication. The default Realm in Tomcat is the Memory Realm where users and administrators can be configured. Only a User with "manager" role assigned can access the Tomcat Management application. Re: How does one go about authenticating so that getRemoteUser() does not return null? Author: Joachim Aschoff (http://www.jguru.com/guru/viewbio.jsp?EID=904224), Jun 5, 2002 If you use Tomcat with IIS as web server, it is possible to get the login name of the client by using getRemoteUser, if the client is running windows. In the IIS management console, go to the properties of the virtual directory "jakarta", select the security tab and press edit. Uncheck anonymous access and check integrated windows authentification. (How to configure IIS with tomcat is described somewhere else ...). Calling getRemoteUser now returns the clients windows login name. Joachim Re[2]: How does one go about authenticating so that getRemoteUser() does not return null? Author: YAC YAC (http://www.jguru.com/guru/viewbio.jsp?EID=949856), Jul 15, 2002

hello I have a problem with TOMCAT 4.O with IIS server, the OS is WINDOWS NT 4 I am making an upload from the client to the server. in the server IIS where I installed TOMCAT and the OS is WINDOWS 2000, all thing are ok and the upload works but in the server IIS where I installed TOMCAT and the OS is WINDOWS NT 4, it doesn't work. have you any idea about this problem or how I can to know all right that have the TOMCAT USER or any idea about this thank you yac [email protected] Re[2]: How does one go about authenticating so that getRemoteUser() does not return null? Author: robert luo (http://www.jguru.com/guru/viewbio.jsp?EID=953211), Jul 17, 2002 Hi Joachim Aschoff, Your message is great. What if I am using Apache with Tomcat as webserver? I would like to get remote user's profile, such as the machine/domainname and user role to determine if the client is accessible to the secured page (an intranet application). Your help is greatly appreciated. Robert Re[3]: How does one go about authenticating so that getRemoteUser() does not return null? Author: Joachim Aschoff (http://www.jguru.com/guru/viewbio.jsp?EID=904224), Jul 18, 2002 Sorry Robert, I only tried it with IIS as web server. Maybe somebody else can help. Re[3]: How does one go about authenticating so that getRemoteUser() does not return null? Author: rondari shabang (http://www.jguru.com/guru/viewbio.jsp?EID=1018536), Oct 28, 2002 You can use getRemoteUser() on tomcat hooked on to APache by doing the following - I use mod_webapp as the apache/tomcat connector (dont know if the others work) - I use apache 2 and tomcat 4.2.12 - in Apache's httpd.conf, configure mod_webapp by adding lines like this: LoadModule webapp_module /opt/apache/modules/mod_webapp.so WebAppConnection conn warp localhost:8008 WebAppDeploy webappName conn /someOtherName/ WebAppInfo info

- the trick is to make sure that your servlet URL has restrictions defined in the httpd.conf file. Something like this: AuthName "MainRealm" AuthType Basic

AuthUserFile /opt/apache/users require valid-user

- now go to your servlet URL .http://localhost/someOtherName/...... you will get a native browesr login popup and getRemoteUser() will return the proper user on every request that is below that URL Re[3]: How does one go about authenticating so that getRemoteUser() does not return null? Author: Alain Chiorboli (http://www.jguru.com/guru/viewbio.jsp?EID=1155141), Mar 17, 2004 I've the same problem with Apache 1.3.28 / Tomcat 5.0.19 and mod_jk 1.2.5. After long searches on the net I finally found how to do this. Update the connector configuration in the server.xml file: By setting the tomcatAuthentication="false" for the AJP1.3 connector now the getRemoteUser return the user authenticated through Apache! Re[2]: How does one go about authenticating so that getRemoteUser() does not return null? Author: Arthur Simberg (http://www.jguru.com/guru/viewbio.jsp?EID=1025501), Nov 14, 2002 I can't setup Tomcat & IIS. Method getRemoteUser() returns null. I've tried almost everything. Please help me. Re[2]: How does one go about authenticating so that getRemoteUser() does not return null? Author: aris javier (http://www.jguru.com/guru/viewbio.jsp?EID=1196565), Aug 31, 2004 Hello! i'm using Tomcat with IIS.. i followed this steps.. i went to the properites of virtual directory "ces", selected the security tab and press edit... unchecked anonymous access and checked windows authentication... but still, calling getRemoteUser returns null... =| what else did you do? please help! aris Re: How does one go about authenticating so that getRemoteUser() does not return null for websphere and weblogic? Author: vivek kamble (http://www.jguru.com/guru/viewbio.jsp?EID=1138420), Jan 12, 2004 Re: How does one go about authenticating so that getRemoteUser() does not return null for websphere and weblogic? request.getRemoteUser() = null Author: Ar Ja (http://www.jguru.com/guru/viewbio.jsp?EID=1158024), Mar 27, 2004 I am using Tomcat Server3.3, even though I configured server.xml file like

File upload and login using IIS6 and Tomcat5. There are problems related to file upload (POST) when using JK2.04 and there is a patch for it. Author: Terje Christensen (http://www.jguru.com/guru/viewbio.jsp?EID=1212259), Nov 22, 2004 http://www.odindata.no/infopot/tomcat_iis_errors.htm How to get Tomcat and IIS to work.for file uploading and login There are several pages on how to get Tomcat and IIS working. But I have (unfortunately) found some undocumented problems. I have used several weeks to figure out the reason and how to solve these problems and I think that my findings are useful for others. Terje (terchris2hotmail.com) My case is Tomcat 5.024 and IIS6 running on Windows 2003 server standard edition. (Java 1.5 is used) If you need to have users logging in to your app and file upload then you can read on. INTRO When using IIS6 and Tomcat5 you need a connector that enables IIS to forward requests to .jsp and servlets to Tomcat. You have to my knowledge 3 connectors to choose from JK – the first connector JK2 – A newer and better, faster version of JK jspISAPI – a commercial connector DEVELOPMENT STATUS ON THE CONNECTORS: JK The JK connector is the oldest one and Apache Jakarta (makers of Tomcat) and on the Tomcat connectors page they suggest to use JK2 instead of JK. JK2 The newest connector for Tomcat from Apache Jakarta project. Latest official version is JK2.04. The connector is as of 14. November no longer supported. jspISAPI A commercial connector developed by www.jspisapi.com. The connector is maintained and supported. Latest news After JK2 development was shut down it seems that functionality from JK2 will be ported to JK. But this has not happened yet. BUGS IN THE CONNECTORS: Unfortunately there are bugs in the connectors. The bugs are not permanent and occur when there is many users or high load on your app. JK I did not test this connector since the Tomcat connectors page encourages use of JK2 over JK. JK2 File upload (PUT) does not work 100% using JK2.04 I have situations where users on fast lines (LAN) can upload, but users on slow lines cannot upload at all. Users that have good speed can upload most of the time. See “JK2 upload bug” for full description of the bug. This problem has been corrected in JK2, but the patch is not officially released. Unfortunately the patch creates another problem when displaying pages. The display problem is not permanent and you will need some load on your sever to experience it. jspISAPI jspisapi does not support getting user logged in by request.getRemoteUser() so you must rewrite your app to use request.getHeader("IIS-REMOTE-USER") The request.getHeader("IIS-REMOTE-USER") works on XP version of IIS and is reported to work on Windows Server 2003 web edition. But sadly it does not work on Windows Server 2003 standard edition. The jspISAPI is smart and removes the load of serving static content from Tomcat so I tried to use jspISAPI on sites that do not require login. But after running jspISAPI for a while I saw that jspISAPI did not serve pages anymore. I could verify that the problem was not in Tomcat by accessing the page on port 8080. I did not test file upload using jspISAPI because of the above problems. The jspISAPI is a promising connector, but the bugs must be sorted out before it can be used. HOW I SOLVED THE PROBLEMS I found that the JK2 connector was the best. The official JK2.04 has no problems displaying pages. I use this on public sites. I use the JK2.04 patch on sites that require login. It can do file upload. The site that requires file upload and login does not have a high load.

Therefore I don’t get the display page errors on this site. If you need file upload (POST) on pages that has high load. Then you can continue the search for a solution. If you find it then please inform me terchris2hotmail.com HOW TO INSTALL JK2 I found the documentation for installing and setting up the connectors hard to understand. Now that I have spent a lot of time on this I see that what was hard to understand was all the manual steps and the mixing of how to install JK and JK2. The simplest way to install JK2 is to download the Shiftomat JK2 installer. It sets up the JK2 for you. To get authentication working you must add these lines in \conf\jk2.properties request.tomcatAuthentication=false request.registerRequests=false REFERED LINKS Tomcat connectors page http://jakarta.apache.org/tomcat/connectors-doc/jk2/index.html JK2 upload bug http://issues.apache.org/bugzilla/show_bug.cgi?id=15278 JK2 upload patch http://jakarta.apache.org/~mturk/isapi_redirector2.zip JK2 is officially unsupported message http://jakarta.apache.org/~mturk/docs/ Shoftomat JK2 installer http://www.shiftomat.com/opensource/ THE LINKS I GATHERED WHILE TRYING TO SOLVE THE PROBLEM http://wiki.apache.org/jakarta-tomcat/Tomcat_2fLinks http://jakarta.apache.org/tomcat/tomcat-4.1-doc/config/jk.html http://www.unlimitedftp.ca/support/resources/tomcat-iis.html http://cephas.net/blog/2004/06/25/getting_iis_5x_tomcat_5x_to_play_nice.html http://www.jguru.com/faq/view.jsp?EID=842151 http://www.junlu.com/msg/107129.html http://www.rit.edu/~ack5504/tomcat-iis6howto/narantugs-sengee-guide.html http://jakarta.apache.org/tomcat/connectorsdoc/jk2/index.html http://jakarta.apache.org/~mturk/docs/ http://www.jguru.com/forums/view.jsp?EID=741701 http://servlets.com/cos/faq.html http://www.servlets.com/jservlet2/examples/ch04/index.html#ex04_21 http://www.servlets.com/soapbox/bugs.html METADATA FOR SEARCH ENGINES JK, JK2, Tomcat, IIS, Connector, Upload, unexpected end of part, java.io.IOException: Stream closed, POST, Multipart, request.getRemoteUser(),com.oreilly.servlet, ParamPart, MultipartParser What is a "javax.servlet.ServletException: Broken pipe" exception? Location: http://www.jguru.com/faq/view.jsp?EID=994194 Created: Sep 4, 2002 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by David Howie (http://www.jguru.com/guru/viewbio.jsp?EID=494945 Is this when the user aborts the process by clicking the browser's stop button, or navigating to another link? At what point in the process is this exception thrown, when the servlet attempts to send the response back to the browser?

Yes, it happens when the user clicks stop, or logs off, or otherwise prematurely aborts the connection. It's nothing to worry about. It's a normal part of life on the Web. Comments and alternative answers

broken pipe exception Author: sudarshan prasad (http://www.jguru.com/guru/viewbio.jsp?EID=1041572), Dec 29, 2002 I had this problem sometime back. My servlet used to call a stored proc.after the call there used to be this error immediately. the problem was that there were cursors declared in the stored proc which were not opened( because they were opened conditionally) and the java program expected the resultset which it did not get. Open all the declared cursors and this must solve the problem How can an HttpSessionListener comunicate directly to an user web browser that his session has been destroyed by server web.xml "timeout" parameter? Location: http://www.jguru.com/faq/view.jsp?EID=994198 Created: Sep 4, 2002 Author: Lasse Koskela (http://www.jguru.com/guru/viewbio.jsp?EID=573277) Question originally posed by JL JLCHIP (http://www.jguru.com/guru/viewbio.jsp?EID=305597 It can't. The request-response nature of the HTTP protocol prevents us from sending "push" data to the browser. When the HttpSessionListener.sessionDestroyed() method is called by the container, the session is already dead (the actual HttpSession object is alive, though). If the browser sends a request just before that moment (session still alive), the session timeout is renewed. If the browser sends a request just after that moment (session already dead), we cannot recognize the relation between "the session that was killed about 48 seconds ago" and the incoming request (which doesn't have an existing session, yet). In a servlet, are the method variables are shared between several threads or not? Location: http://www.jguru.com/faq/view.jsp?EID=994203 Created: Sep 4, 2002 Author: Luc-André Essiambre (http://www.jguru.com/guru/viewbio.jsp?EID=430486) Question originally posed by Harry Angel (http://www.jguru.com/guru/viewbio.jsp?EID=993284 Variables declared in methods are never shared, whether these methods are static or not... [However, session variables are shared, and instance variables *may* be shared (or may not, which means you shouldn't use them) - Alex] Comments and alternative answers

confusion!!

Author: Harry Angel (http://www.jguru.com/guru/viewbio.jsp?EID=993284), Sep 5, 2002 "Variables declared in methods are never shared" "session variables are shared" "instance variables *may* be shared (or may not, which means you shouldn't use them)" There is much confusion! Who really knows java & servlet?? Re: confusion!! Author: Jegadisan Sankar Kumar (http://www.jguru.com/guru/viewbio.jsp?EID=992176), Sep 5, 2002 I am not sure why you find this confusing. It is quite simple actually. public final class SomeServlet extends HttpServlet { private int instanceVariable; public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { int localVariable; HttpSession session = request.getSession(); String sessionVariable = session.getAttribute("SomeAttribute"); } }

Taking the above code block as an example, the instanceVariable will be available to any thread that makes use of the servlet. If you are just using the variable for reading, and not for any modifications, then it should be fine. You can also declare the variable as static if you wanna, and it would still be acceptable to all threads that are executing the doGet method of the servlet. The localVariable is created for each and every single thread. This is the same for pretty much all the programming languages I have ever encountered (If anyone has seen something else, please do correct me). Each thread usually has it's own memory space, and they will allocate memory for the variable and store it within their own memory space. As for the sessionVariable, this variable is available to any servlet to which the User visits. So, if the User were to visit another servlet, regardless of the thread coz each request will spawn it's own thread, the session variable will be available to the servlet. Hope that explains, or clarifies your doubts. Regards Jega

Re[2]: confusion!! Author: Jegadisan Sankar Kumar (http://www.jguru.com/guru/viewbio.jsp?EID=992176), Sep 5, 2002 Oh yeah, just to make sure I provide you with the complete picture. When i said the instanceVariable is available to any thread executing within the doGet method, I was assuming that the Serlvet Engine only had one instance of the SomeServlet in it's context. If the Servlet Container had 2 instances of SomeServlet running, there would be 2 different versions of the instanceVariable. One for each instance of the SomeServlet within the context of the Servlet Engine. If you want the instanceVariable to be shared among any and all possible instances of the SomeServlet, you should declare it as static. If for example you declared a variable like private static int staticVariable above or below the instance variable declaration, then this staticVariable will be the same for all the instances of SomeServlet that exists within the Servlet Engine. Just wanted to make sure I gave you all the info, and didn't leave you with a misconception. Regards Jega Re[3]: confusion!! Author: Christopher Koenigsberg (http://www.jguru.com/guru/viewbio.jsp?EID=722897), Sep 5, 2002 Another possible clarification of terminology is that an "Instance Variable" (the general Object Oriented term) is also often called a "Member Field", in Java-specific parlance.

Re: confusion!! Author: vikram shahi (http://www.jguru.com/guru/viewbio.jsp?EID=1020223), Oct 31, 2002 Hey ... only the service method is used as a part of multi threads accross users. Any variables created inside that, will have multiple copies, with values specific to the users using it. Instance variables are not shared. And yes, set the variables and their values as attributes in the HttpSession. And share it with as many servlets u want, in the SAME session. Anybody correct me if i am wrong... Clarficiations Author: Samer Naser (http://www.jguru.com/guru/viewbio.jsp?EID=1022799), Nov

7, 2002 1- Static objects are always shared, there is one instance per application (i.e. process). All threads within the process access the same instance. 2- Member variables within a servlet are available to multiple threads, but only one thread at a time. This is because threads reuse a servlet, but do not use it at the same time! Re: Clarficiations Author: Rasmus Pedersen (http://www.jguru.com/guru/viewbio.jsp?EID=1007915), Nov 12, 2002 Does that mean that each thread in a sense creates its own "copy" of the doPost method found in the single servlet instance? This "copy" has the effect that each thread does not have to worry about simultanious access to variables only in the scope of the doPost method? Re: Clarficiations Author: Steven Zacharias (http://www.jguru.com/guru/viewbio.jsp?EID=1020313), Nov 12, 2002 This is because threads reuse a servlet, but do not use it at the same time! That's not true, is it? In general, isn't there one instantiated object of a particular servlet, and isn't it quite possible (even likely under any kind of load) that the server's threads concurrently use that object? In other words, wouldn't the following servlet pseudo-code frequently print out differences under load? class Silly { java.util.ArrayList al_ = new java.util.ArrayList() ; public ... doGet(...) { // ...add a timestamp to the array long lTimestamp1 = System.currentTimeMillis() ; al_.add(new Long(lTimestamp1)) ; // ...do some stuff that takes a bit of time so we cant test the concurrency situation (blah, blah, blah) // ...(vainly?) attempt to retrieve the timestamp we set before long lTimestamp2 = (Long) al_.get(al_.size()-1) ; if(lTimestamp2 != lTimestamp1) { System.out.println("The timestamp we set was " + lTimestamp + ", the one we retrieved was" + lTimestamp2) ; } }

Re: Clarficiations

Author: Sandip Chitale (http://www.jguru.com/guru/viewbio.jsp?EID=14537), Nov 19, 2002 Well, in case of Java, ClassLoaders can make the static fields non-shared. How to send a SMS or MMS from a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=1019760 Created: Oct 30, 2002 Author: Lasse Koskela (http://www.jguru.com/guru/viewbio.jsp?EID=573277) Question originally posed by Surapun Assaratt (http://www.jguru.com/guru/viewbio.jsp?EID=975585 There is no standard way for this. If you've studied the infrastructure for SMS (or MMS) messaging, you would've noticed that there needs to be a gateway for sending the SMS (or MMS). The API with which you ask the gateway to send a message depends on the gateway vendor. I'm not aware of an open-source SMS gateway, but you'll find some commercial products with Google. Oops. Actually there is one that I know of: www.kannel.org Comments and alternative answers

Java SMS API Author: Markus Eriksson (http://www.jguru.com/guru/viewbio.jsp?EID=1029113), Nov 22, 2002 If you want to send SMS:es from Java I would suggest that you look at some of the Java SMS libraries that is available. For example: http://smsj.sourceforge.net/ http://www.sourceforge.net/projects/smsj [Yes, I'm the developer of that library :)] Maintaining database state across session I have a servlet, which when called from a web page calls a PL/SQL procedure that updates certain records in the database. After which the servlet redirects the user to another Web page. Only if the user Submits from this page, do I need to COMMIT the UPDATES done in the stored procedure. How can I ensure this? Location: http://www.jguru.com/faq/view.jsp?EID=1019764 Created: Oct 30, 2002 Author: Eugene Kuleshov (http://www.jguru.com/guru/viewbio.jsp?EID=442441) Question originally posed by Arun Iyer (http://www.jguru.com/guru/viewbio.jsp?EID=1018788 [You could store the Connection object somewhere, but that's] not a very good approach anyway.

You better show a confirmation dialog before sending anything to server. You may also put everything within a session (or hidden fields if you hate sessions) and do the real update only on real confirmation. What is a "Distributed Web Application"? Location: http://www.jguru.com/faq/view.jsp?EID=1021034 Created: Nov 3, 2002 Author: Lasse Koskela (http://www.jguru.com/guru/viewbio.jsp?EID=573277) Question originally posed by sabu vs PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=476248 Usually the word "distributed" refers to the system being composed of physically separate parts where different logic is performed in different places. A typical distributed web application is such that there is one "web server", which hosts the View and Controller parts of the MVC pattern and a separate (or several) "app server", which hosts the EJBs acting as the Model of the MVC pattern. The advantage of this approach is the flexibility of the infrastructure. You can scale the hardware only for the EJB layer if you want, you can locate the web server closer to your enterprise network's edge while leaving the app server behind more firewalls. [See the discussion forum thread for some interesting further discussion. -A] I've recently installed j2sdk1.4.1, having previously been developing in jdk1.2.1 and my old code is not compiling as it can't find packages javax.servlet.* and javax.servlet.http.*. How can I fix this? Location: http://www.jguru.com/faq/view.jsp?EID=1027648 Created: Nov 19, 2002 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Rahul Rohatgi (http://www.jguru.com/guru/viewbio.jsp?EID=852923 The package javax.servlet is not in the standard J2SE libraries. It's included in j2ee.jar or servlet.jar. You can find these by downloading J2EE or Tomcat respectively. (Tomcat is probably what you want -- it's a lot lighter.) Then add the JAR to your classpath and you're all set. See How do I set my CLASSPATH for servlets? How do I map a JSP using web.xml and RequestDispatcher? Location: http://www.jguru.com/faq/view.jsp?EID=1027649 Created: Nov 19, 2002 Author: Abhinav Srivastava (http://www.jguru.com/guru/viewbio.jsp?EID=981434) Question originally posed by Abhinav Srivastava (http://www.jguru.com/guru/viewbio.jsp?EID=981434

It is not mandatory for JSPs to be registered in the web.xml but it is sometimes done; the <servlet-class> tag being replaced by the <jsp-file> tag (and others remaining the same). e.g <jsp-file>/index.jsp And thus you can give a JSP an alias. Now when you want to forward to a servlet that doesn't have a url-mapping in the web.xml, you use getNamedDispathcer(servlet-name) else it should be the urlpattern when you are using getRequestDispatcher(path). This is what I have understood of it. The more hazy part is that even JSPs are compiled into servlets at runtime. But these servlets are accessible without specifying any url-pattern. How do I access an Init Parameter set in web.xml from a JavaBean? Location: http://www.jguru.com/faq/view.jsp?EID=1027650 Created: Nov 19, 2002 Author: Bozidar Dangubic (http://www.jguru.com/guru/viewbio.jsp?EID=433955) Question originally posed by Lee KF (http://www.jguru.com/guru/viewbio.jsp?EID=768959 You must get the init-param from servlet and load it into the bean, either defining a set method or passing it into the constructor. The init-param tag is for init parameters for the servlets and JSP and not for JavaBeans. They have other ways to load parameters (such as properties files and things like that). How can I make Apache/Tomcat notice that my servlet changed, without having to restart it? Location: http://www.jguru.com/faq/view.jsp?EID=1027658 Created: Nov 19, 2002 Author: Shelleen Qian (http://www.jguru.com/guru/viewbio.jsp?EID=1021730) Question originally posed by Venkat Rangachari (http://www.jguru.com/guru/viewbio.jsp?EID=1026229 You need to turn on Servlet Reloading on your Tomcat. [While the below works, for Tomcat 4 another answer is simply to add the attribute reloadable="true" to the Context element for that webapp. Sometimes you don't want all contexts to be reloadable. -Alex] To turn on servlet reloading, edit install_dir/conf/server.xml and add a DefaultContext subelement to the main Service element and supply true for the reloadable attribute. The easiest way to do this is to find the following comment: and insert the following line just below it:

Be sure to make a backup copy of server.xml before making the above change. Comments and alternative answers

See also Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3), Jan 12, 2003 Restarting Tomcat after rebuilding a servlet Modifying server.xml for automatically reloading class files Author: Rommel Sharma (http://www.jguru.com/guru/viewbio.jsp?EID=1006127), Jan 14, 2003 In addition, in case you wish to specify reloading after a certain interval add the following attributes also to the server.xml: By default reload takes place every 15 seconds. The above object should be placed withing the Context element of your web-application. Rommel Sharma

Re: Modifying server.xml for automatically reloading class files Author: Brian Kaplan (http://www.jguru.com/guru/viewbio.jsp?EID=1110555), Aug 24, 2003 I have tried everything and still cannot get the file to reload... the server.xml entry is:

I am running Tomcat 4.1.27 & J2SDK 1.4.2 on a Win 98SE box. When I run java, I tweak the java it the dos window message: Aug 24, 2003 12:47:53 PM org.apache.jk.server.JkMain start INFO: J time=50/770 config=C:\tomcat-4.1.27\conf\jk2.properties WebappClassLoader: Resource '/WEBINF/classes/PageTwo.class' was modified; Date is now: Sun Aug 24 12:50:12 CDT 2003 Was: Sun 11:52:32 CDT 2003 javax.servlet.ServletException: Wrapper cannot find servlet class PageTwo or depends on at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:891) a org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:668) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPip at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPip at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2416) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180) at

org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPip at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPip at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPip at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPip at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:223) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:601) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Pr at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:565) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:619) at java.lang.Thread.run(Thread.java:534) root cause java.lang.ClassNotFoundException: PageTwo at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1444) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1289) at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:885) at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:668) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPip at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPip at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2416) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPip at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPip at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPip at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174) at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPip at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:223) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:601) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Pr at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:565) at

org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:619) at java.lang.Thread.run(Thread.java:534) I refresh the page again and now get this error: HTTP Statu page2 is currently unavailable type Status report message Servlet page2 is currently unavailable de requested service (Servlet page2 is currently unavailable) is not currently available. I hope someon figure this out. Brian java beans reloading Author: Tushar Kapila (http://www.jguru.com/guru/viewbio.jsp?EID=1059392), Feb 22, 2003 this did not work for common java beans in install_foler//common/classes how do i set tomcat to scan and reload these? Re: java beans reloading Author: Hilke Heremans (http://www.jguru.com/guru/viewbio.jsp?EID=1070504), Mar 27, 2003 A 'trick' you can use for Java Beans (I realize it's not the cleanest thing to do, but it does work).. 1) Delete the class file 2) Try to access the class file directly (by referring to it via your browser, might also work if you try to run the app that depends on it, I don't remember) 3) Tomcat will realize it's gone and throw an exception 4) Copy over a newer version of the .class 5) Reload Similar problem with Tomcat 5.5.7 Author: Gautam Singh (http://www.jguru.com/guru/viewbio.jsp?EID=1237364), Aug 26, 2005 I also want to turn on the auto reloading for tomcat 5.5.7. But could not find the comment ''in server.xml. Where should I place the following line '' In order to find the proper URL to which to submit forms, I need to manually set the context name in every URL, using somthing like:

But this seems like a round about way to go for something so simple. Am I missing something here?

Location: http://www.jguru.com/faq/view.jsp?EID=1027662 Created: Nov 19, 2002

Author: Roger Hand (http://www.jguru.com/guru/viewbio.jsp?EID=292314) Question originally posed by Taylor Sabine (http://www.jguru.com/guru/viewbio.jsp?EID=1026487 [Short answer: No, unfortunately you need to actively make your URLs "contextaware". Some frameworks make this easier for you, but I end up doing something like you described. -Alex] You can avoid a lot of the base path problems by having your forms submit to a jsp page, and having that jsp page forward to the servlet. So your form submission avoids all path problems: I started by making a dummy jsp page that did nothing but forwarded, but now I put the forwarding action at the top of the jsp page with the form ... there's a small bit of code that checks to see if the query includes the form variables from a form submission. It the query vars (or, actually, a single "marker" var - see example below) are there we forward to the servlet for processing. If not we display the page with the form, ready to be filled in. Since the browser sees the return url as being in the same dir as the original form jsp page, all image links, etc., work correctly even though it's the servlet that's doing all the work and then forwarding to the result page. (Of course if you do a redirect you avoid the path problems too but you burn an extra trip to the browser.) Of course this really just offloads the problem you bring up of the path to the servlet ... instead of the problem being in the action tag in the jsp code that forwards to the servlet. To make my code portable I use something similar to the method you suggest: if ("true".equals(request.getParameter("_saveNew"))) { String urlForward = pageContext.getServletContext() + "com.mycompany.editinfo.BeanSaveServlet"; %> <jsp:forward page="<%= urlForward %>"/> <% return; } //if saving data /* We have no data to save; show the form. */ ... How do I redirect from a servlet in one context to a servlet in another? Specifically I'd like to know how to share objects between contexts. Location: http://www.jguru.com/faq/view.jsp?EID=1028275 Created: Nov 20, 2002 Author: Michael Dean (http://www.jguru.com/guru/viewbio.jsp?EID=805382) Question originally posed by Bryan Dollery PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=963590 If you're trying to do a redirection (i.e. response.sendRedirect(String)), it requires an absolute URI (including the context path). If you don't know the context path, you're out of luck. :(

If you're trying to forward, you need to get a ServletContext reference pointing to the other context, then get a RequestDispatcher from that other context. Once again, you'll need to know the context path. To get a reference pointing to the other context, just call getContext(String uripath) on the ServletContext reference for your context. The uripath should be a String specifying the context path of another web application in the container. Note, however, that in many cases, you will receive null references--even if you specify a valid context path. In most servlet containers, a context (web application) must explicitly allow other contexts access to its ServletContext. For example, in Tomcat, the crossContext attribute of the Context element of server.xml must be set to true to allow other contexts to access this context. The Servlet specification recommends this behavior for "security conscious" environments. See also: •

Can two web applications (servlet contexts) share the same session object? (which also has links to many other places it's answered)

Comments and alternative answers

response.sendRedirect(String) Author: Andrew Postoyanets (http://www.jguru.com/guru/viewbio.jsp?EID=343575), Nov 22, 2002 response.sendRedirect(String) works fine with relative URLs as of Servlet API 2.2 See J2EE 1.2.1 API Specification for HttpServletResponse.sendRedirect(java.lang.String)

This method can accept relative URLs; the servlet container will convert the relative URL to an absolute URL before sending the response to the client. Re: response.sendRedirect(String) Author: Michael Dean (http://www.jguru.com/guru/viewbio.jsp?EID=805382), Dec 4, 2002 OK, let me rephrase my first sentance: Although the sendRedirect(String) method of the HttpServletResponse interface accepts relative URL's, a URL that does not start with a "/" is interpreted as relative to the current context and a URL that starts with a "/" is interpreted as relative to the container root (this was changed in Servlets 2.3--in previous versions the spec was ambiguous, so there is no guarantee as to which way your servlet container implemented it--in which case you need to use an absolute URL to achieve portability). Therefore, to redirect a request to a servlet in another context (which was the original question), you will need either an absolute URL or

a container-relative URL (which is an absolute URL without the protocol and domain information), and, therefore, you will need to know the context path of the other web application. (Although you could use a request-relative URL that "backs out" of the current context with "../" (repeated as necessary), using an absolute- or container-relative URL would be a far more clear and concise means of expressing the information.) I thought the shorter version presented the information more clearly, but the longer version is technically more correct. :)

Sending object from servlet on one machine to JSP on another machine Author: Vishal Rodge (http://www.jguru.com/guru/viewbio.jsp?EID=1038665), Dec 17, 2002 I want to send certain information from servlet running on one server to JSP on another server. i do not want to send that info as a FLAT FILE nor i want to send it through URL rewriting. can anybody suggest me a solution to this vishal Can destroy() be called from inside the service() method of my servlet? Location: http://www.jguru.com/faq/view.jsp?EID=1029043 Created: Nov 21, 2002 Modified: 2002-11-22 11:45:19.872 Author: Andrew Postoyanets (http://www.jguru.com/guru/viewbio.jsp?EID=343575) Question originally posed by rajesh [missing] (http://www.jguru.com/guru/viewbio.jsp?EID=1028350 destroy() is a servlet life-cycle method called by servlet container to kill the instance of the servlet. The answer to your question is "Yes". You can call destroy() from within the service(). It will do whatever logic you have in destroy() (cleanup, remove attributes, etc.) but it won't "unload" the servlet instance itself. You do not manage the life cycle of servlets in the program; the servlet engine does. [Alex adds:] On the other hand, if the question is, "Is it possible that the servlet container will call destroy() while the servlet is still processing a request inside service() on a different thread?" then the answer is also yes, but it's a degenerate case. The servlet container is required to wait a reasonable amount of time for current requests to finish processing. So if your request is not totally lagging, it should work out fine. If you're spending more than a few seconds processing a request, that's a UI problem that you should try to work out first.

Check the servlet spec for more details. BTW, destroy() does not imply garbage collection. The instance may live on in memory long after destroy() is called. How can I call the get method of a servlet automatically, when a *different* HTML page is loaded? Location: http://www.jguru.com/faq/view.jsp?EID=1030392 Created: Nov 25, 2002 Author: Michael Dean (http://www.jguru.com/guru/viewbio.jsp?EID=805382) Question originally posed by sriram rangaraj (http://www.jguru.com/guru/viewbio.jsp?EID=1020819 [I thought of using a image on the html page and sending the request to the servlet for the image.] The image will work if the user enables images in his/her browser. Other solutions (JavaScript, link pre-fetching, servlet receiving requests for Cascading Style Sheets, etc.) all have similar "failure modes." To use an image, just use a tag like:

And return a tiny image (i.e. a 0-pixel image). (P.S. The spyware thing is a joke. :) The only way to ensure that the servlet gets called, though, is to make all clients request the servlet directly (and have the servlet serve the appropriate HTML page). This will work if you don't have external pages (i.e. not yours) pointing directly to the HTML page... However, the Servlets 2.3 specification (i.e. the current one) has added a new feature which you could use. It allows you to define Servlet Filters--which provide a "controller-like" functionality to your web application. With a filter, you can intercept and pre-process requests and/or intercept and post-process responses to any web content on your server (i.e. Servlets, JSP's, HTML, images, CGI's, SSI's, etc.). You can even refuse requests and responses. Since it's all done on the web server, clientside configuration cannot be used to defeat this mechanism. This is the functionality you want. [Another poster suggests using an IFRAME] Comments and alternative answers

META HTTP-EQUIV="refresh" CONTENT="5; URL=http://host:port/servlet/YourServlet" Author: preveeth ott (http://www.jguru.com/guru/viewbio.jsp?EID=1037194), Dec 12, 2002 try using this in your html page

'<META HTTP-EQUIV="refresh" CONTENT="5; URL=http://host:port/servlet/YourServlet"> ' after 5 seconds your servlet will be called. Incase your html page is generated from a servlet u could as well use the below statement res.setHeader("Refresh", "5; URL=http://host:port/servlet/YourServlet"); Re: META HTTP-EQUIV="refresh" CONTENT="5; URL=http://host:port/servlet/YourServlet" Author: shashidhar kache (http://www.jguru.com/guru/viewbio.jsp?EID=1215318), Dec 8, 2004 res.setHeader("Refresh", "5; URL=http://host:port/servlet/YourServlet"); This does not refresh the html page through servlet. i am trying tor refresh same page from servlet handler. Am i doing anything wrong. Shashi What is the best way to generate a universally unique object ID? Do I need to use an external resource like a file or database, or can I do it all in memory? Location: http://www.jguru.com/faq/view.jsp?EID=1030397 Created: Nov 25, 2002 Modified: 2003-02-28 08:01:34.258 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Andy Brown (http://www.jguru.com/guru/viewbio.jsp?EID=1027054 [I need to generate unique id's that will be used for node 'ID' attribute values within XML documents. This id must be unique system-wide. The generator must be available to a number of servlets that add various node structures to my XML docs as a service. What is the best way to tackle this? The 'possible' ways I can see: • • •

Keep the maximum ID value in a flat-file where the service would read it upon start-up and increment it. Upon shutdown or failure, it would write the latest max id to the file. Calculate the max id by searching the XML itself. This will be tougher since XML requires an alpha-numeric value (not strictly numeric). Use a database (MySQL) with a two-field table where one field is the incremental counter.

I just have this feeling that none of the above are the most efficient ways of doing this. Regards, -Andy] There is an additional way to do that that doesn't rely on an external file (or database) like the one you have presentred. If has been presented in the EJB Design

Patterns book, written by Floyd Marinescu, and available in a pdf format for free from the given link. The suggested solution is based on the UUID for EJB pattern, that comes out from this question: How can universally unique primary keys can be generated in menory without requiring a database or a singleton? Without enetring in the specifics (you can fully check out the pattern by reading the appropriate chapter), the solution is to generate a 32 digit key, encoded in hexadecimal composed as follows: 1: Unique down to the millisecond. Digits 1-8 are are the hex encoded lower 32 bits of the System.currentTimeMillis() call. 2: Unique across a cluster. Digits 9-16 are the encoded representation of the 32 bit integer of the underlying IP address. 3: Unique down to the object in a JVM. Digits 17-24 are the hex representation of the call to System.identityHashCode(), which is guaranteed to return distinct integers for distinct objects within a JVM. 4: Unique within an object within a millisecond. Finally digits 25-32 represent a random 32 bit integer generated on every method call using the cryptographically strong java.security.SecureRandom class. [See also the following FAQs: • • • •

I need to generate a GUID and have seen suggestions about using an RMI server but nothing about how to actually generate the GUID itself. What is the best way to provide a unique identifier as a primary key that will work in a database independent manner? I'm looking for functionality similar to Oracle's proprietary MY_SEQ.NEXTVAL. How do I automatically generate primary keys? and the original thread: What is the best way to implement a system-wide object ID generator?

- Alex Chaffee] Comments and alternative answers

Random class Author: P Manchanda (http://www.jguru.com/guru/viewbio.jsp?EID=344357), Feb 28, 2003 Hi, Try using the java.util.Random class to generate random numbers that can be used as IDs. Re: Random class

Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727), Feb 28, 2003 Hi, java.util.Random will generate random numbers, not unique numbers. Re[2]: Random class Author: Prashanth Nandavanam (http://www.jguru.com/guru/viewbio.jsp?EID=818802), Apr 24, 2003 Look at the JUG class by Tatu Saloranta: http://www.doomdark.org/doomdark/proj/jug/index.html It is based on the IETF UUID drafts, and works wonderfully. Re: Random class Author: Nathan Ciliberto (http://www.jguru.com/guru/viewbio.jsp?EID=1139136), Jan 14, 2004 You can also use some built-in java classes: java.rmi.server.UID or java.rmi.dgc.VMID

I'm guessing the UID class is the one you want though. (BTW,you don't need to use rmi nor know anything about rmi to use these classes) -Nathan Making it Faster Author: Kimbo Mundy (http://www.jguru.com/guru/viewbio.jsp?EID=1120338), Oct 8, 2003 It seems to me that you could speed up the algorithm above by modifying step #4. Instead of computing the random number every time, just compute it the first time, and then increment it after that. 2 different JVMs should still just have a 1 in 4 billion chance of overlap. Re: Making it Faster Author: Scott Carlson (http://www.jguru.com/guru/viewbio.jsp?EID=1085622), Oct 8, 2003 There are two reasons to use the random number instead of incrementing your last. 1. The number would be predictable and, depending on what this is used for, you could be opening up a potential security issue. This is why ProcessIDs are randomized on some OSes (AIX for one). 2. You must synchronize on that counter to guarantee that your number isn't reused. Your random number generator need not be synchronized, (though its implementation may be). There are Three possible ways Author: Narayana Prasad (http://www.jguru.com/guru/viewbio.jsp?EID=1142103), Jan 29, 2004

1) If ur using Oracle You can create a sequence ,by which u can generate unique primary key or universal primary key. 2) U can generate by using random nunmbers but u may have to check the range and check for unique id. ie random number generate 0.0 to 1.0 u may have to make some logic which suits ur unique id 3) Set the maximum value into an XML file and read that file at the time of loding ur application from xml . thanks and regards prasad UUID and Random IDs Author: Wesley Theobalds (http://www.jguru.com/guru/viewbio.jsp?EID=1165144), Apr 22, 2004 Hi, I've just finished implementing the Sequence Block pattern a la Marinescu using a Session bean and an entity bean representing the sequence, and its working well. Using a UUID makes life harder for any Data analysis further down the line, having to enter a 32 bit number for the key for any ad hoc SQL queries you may need to write, and I've often found it helpful to have an incremental key as it indicates when the record was created in the absence of a timestamp. hashcode isn't unique Author: x x (http://www.jguru.com/guru/viewbio.jsp?EID=1174058), May 27, 2004 > System.identityHashCode(), which is guaranteed to return > distinct integers for distinct objects within a JVM. Sorry, but it isn't true. See http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4990451 Tomas Millisecond overlap Author: Thomas Paré (http://www.jguru.com/guru/viewbio.jsp?EID=1238395), Apr 14, 2005 Thanks for the very interesting pointer on 'Ejb design patterns'. I've read the implementation details and found something troublesome. In step 1 : "Unique down to the millisecond. Digits 1-8 are are the hex encoded lower 32 bits of the System.currentTimeMillis() call". Only the lower 32 bits of time are considered, which makes the uniqueness of that part only valuable for a period of 50 days. Looks like a serious issue.

How to get international unicode characters from a a form input field/servlet parameter into a string? Location: http://www.jguru.com/faq/view.jsp?EID=1030399 Created: Nov 25, 2002 Author: charief gael (http://www.jguru.com/guru/viewbio.jsp?EID=1005789) Question originally posed by Martin Kultermann (http://www.jguru.com/guru/viewbio.jsp?EID=520941

[ I have a servlet based app that generates and processes HTML forms. I would like to support mutiple languages/character sets that will be stored in unicode UTF-8 in the database. I am setting the following tags, for example: <meta content="text/html; charset=Shift_JIS" http-equiv="Content-Type"> and
String myparam = request.getParameter("myparamname"); if (myparam != null) myparam = new String(myparam.getBytes"8859_1"),"UTF8");

Comments and alternative answers

How to get international unicode characters from a a form input field/servlet parameter into a string? Author: Arthur Tang (http://www.jguru.com/guru/viewbio.jsp?EID=34155), Dec 13, 2002 myparam.getBytes("8859_1") will definitely kill double byte string if page encoding is not 8859_x or latins. I found that all of the big 3 browsers(IE,NS/M,O) have very poor support of sending encoding information of their request. So you will not get the encoding anyway from the request. I took the approach of setting the uniform encoding, such as utf-8, to all pages in your app (and hope the users do not change the browser's encoding between pages, fortunately most of user do not know what it is and won't change it), or page before

submit. So, the request's encoding will be as you specified (utf-8). AND, most important is to set the request char encoding (setCharacterEncoding()) to 'your' encoding (utf-8) before you get the parameter (getParameter). This will interpret the submitted request in utf-8. Otherwise, the getParameter will split the double byte chars into some string cannot interpret again. This work for any langauages, mixed language on the same page, or even mixed language on a form field (as long as the user can type it in).

JSP and UTF8 is simple Author: dom sir (http://www.jguru.com/guru/viewbio.jsp?EID=1135191), Dec 21, 2003 I don't know way many people suggest things like the following "myparam = new String(myparam.getBytes"8859_1"),"UTF8");" You don't have to do that all you need is putting the following on top of your JSPs <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=UTF-8"> <%@ page pageEncoding="UTF-8" %> <%@ page language="java" contentType="text/html;charset=UTF-8" %> Re: JSP and UTF8 is simple Author: june Quin (http://www.jguru.com/guru/viewbio.jsp?EID=579553), Jan 29, 2004 HI, The reason is all of the settings you mentioned don't solve the problem. I tried those and after getting a double byte character value using request.getParameter("name") and print out the value, the value is corrupted, but if I do what many people suggested, the value is not corrupted. Reading non-Latin form data from forms on UTF-8 pages Author: Malcolm McMahon (http://www.jguru.com/guru/viewbio.jsp?EID=1151003), Mar 3, 2004 I've found for myself the approach. parm = new String(param.getBytes("ASCII"), "UTF-8");

I'm uneasy using it however, because sooner or later a version of Tomcat or some other servlet engine is going to fix the problem and do the stream to string conversion based on the character set specified in the headers of the message from the browser. When that happens existing applications with this code are going to screw up a treat.

Non-Latin form data Author: Malcolm McMahon (http://www.jguru.com/guru/viewbio.jsp?EID=1151003),

Mar 3, 2004 Just tried it another way and it seems to work (at least for a UTF-8 form). if(request.getCharacterEncoding() == null) request.setCharacterEncoding("UTF-8"); address = request.getParameter("address");

This has successfully input Greek text without the need for explicit conversion and should be more future-proof (since it doesn't depend on the servlet engine not doing the translation automatically.) Re: Non-Latin form data Author: K Fl (http://www.jguru.com/guru/viewbio.jsp?EID=1256922), Aug 6, 2005 And just make sure you set the method="post" in your form declaration! GETs do not seem to work with non-latin character sets. K Can an Application Scope Variable be clustered? Location: http://www.jguru.com/faq/view.jsp?EID=1031015 Created: Nov 26, 2002 Author: John P Jensen (http://www.jguru.com/guru/viewbio.jsp?EID=985825) Question originally posed by ashok ayengar (http://www.jguru.com/guru/viewbio.jsp?EID=137446 [ For example I want to load some settings when the application starts and i keep that object in the application scope so that any part of the application can use that information. Now if the environment is clusterd will this Object available across the clustered application?]

No, an object saved with 'application scope' (Saved in the ServletContext) is not truly global. As per Servlet 2.2 spec: 4.3.1 Context Attributes in a Distributed Container Context attributes exist locally to the VM in which they were created and placed. This prevents the ServletContext from being used as a distributed shared memory store. If information needs to be shared between servlets running in a distributed environment, that information should be placed into a session, a database or set in an Enterprise JavaBean. Oh.. By the way... If the data is doesnt change often (like a city-zipcode table) there is no problem using application scope. Just initialize it when your Container starts up! The fun starts when your servlet begins to update the Object. An update to a Context done by a Servlet in Container A is not propagated to the Context in Container B!

Personally I wouldnt use the the ServletContext as a parking place for global variables - I see it as a place for holding information relevant for the application infrastructure (paths, datasource names etc) - not for the application logic. I would place the data as a static instance variable on the servlet! Comments and alternative answers

Can an Application Scope Variable be clustered? Static vs Application scope Author: ras ras (http://www.jguru.com/guru/viewbio.jsp?EID=1184726), Jul 8, 2004 .... Personally I wouldnt use the the ServletContext as a parking place for global variables - I see it as a place for holding information relevant for the application infrastructure (paths, datasource names etc) - not for the application logic. I would place the data as a static instance variable on the servlet! ... Is there a reason not to store data that "doesn't change often" in an application scope variable? How is it different from storing it in a static variable defined in a servlet? In a "production environment", I believe a servlet (and hence the static variable) exists until the webapp is restarted. IMHO, the advantages of storing in a static variable is "lazyloading". But if the data is static and small, say "US states", and if a large number of web pages require "US states", you could retrieve this data from the DB and store it in application scope at webapp start-up time since: 1) the data-set is small 2) US states don't change (added/deleted/updated) often The key to remember is "what works for you may not work for others" :) How to find the parent directory of a servlet? Location: http://www.jguru.com/faq/view.jsp?EID=1031016 Created: Nov 26, 2002 Author: Gerrit Goetsch (http://www.jguru.com/guru/viewbio.jsp?EID=992616) Question originally posed by Shanthi Natarajan (http://www.jguru.com/guru/viewbio.jsp?EID=141300 try this.. to get the URL java.net.URL url; try { url = new java.net.URL(new java.net.URL(req.getRequestURL ().toString()),"../"); } catch (java.net.MalformedURLException e) { // catch the exception .... } or this to get the real path String path = new java.io.File(getServletContext().getRealPath("")).getParent(); Why does cookie.getMaxAge() always return -1 (regardless of real expiry)? Location: http://www.jguru.com/faq/view.jsp?EID=1033944

Created: Dec 4, 2002 Author: Hitoshi Gosen (http://www.jguru.com/guru/viewbio.jsp?EID=1027729) Question originally posed by Garrett Smith (http://www.jguru.com/guru/viewbio.jsp?EID=733867 By default, the maxAge is set to a negative number. You should set the maximum age with setMaxAge(int seconds) with a positive number to set your own expiry right after creating the cookie. Use getMaxAge() right after setting the expiry, because once the cookie itself is set to the client browser, the getMaxAge() doesn't perform like the way you are intending. Comments and alternative answers

Cookie max age Author: Petru Curticapean (http://www.jguru.com/guru/viewbio.jsp?EID=995730), Dec 5, 2002 Depending on application server and configuration, cookies can be generated automatically by servlet engine. In such case you can control the max age trough configuration. For example in IBM Websphere you can set (trough Admin Console) the max age in the Session Manager. Not just maxAge, Domain and path also returns default value Author: Avani Shah (http://www.jguru.com/guru/viewbio.jsp?EID=28330), Jul 23, 2003 Not just maxAge, Domain and path also returns default value for a cookie irrespective of they being set when they were created in the previous request on the server... so once they return from the client browser (netscape or IE) only name value pair returns... is it webserver dependent? How can I keep track of how may times my servlet is called? Location: http://www.jguru.com/faq/view.jsp?EID=1033951 Created: Dec 4, 2002 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Robert Taylor (http://www.jguru.com/guru/viewbio.jsp?EID=1006063 See How do I implement a hit counter in Servlets or JSP? for a definitive answer. How can I access an NNTP newsgroup using JSP or Servlets? Location: http://www.jguru.com/faq/view.jsp?EID=1033959 Created: Dec 4, 2002 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by wu min (http://www.jguru.com/guru/viewbio.jsp?EID=910820 Your servlet must know how to speak NNTP, or call a library that does. There are NNTP implementation in the following packages:

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JavaMail: See the JavaMail:NNTP FAQ subtopic.

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Jakarta Commons Sandbox.

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Jakarta James mail server

You may also find the NNTP specifications enlightening. See RFC 977 and RFC 2980. I'd like to dynamically generate a PHP file from a servlet, then have Apache execute it. Is this possible? Setting the Content-type does not seem to help. Location: http://www.jguru.com/faq/view.jsp?EID=1035740 Created: Dec 9, 2002 Author: Alex Chaffee (http://www.jguru.com/guru/viewbio.jsp?EID=3) Question originally posed by Dima Gutzeit (http://www.jguru.com/guru/viewbio.jsp?EID=1011859 [I am working with Apache 2 with Tomcat 4.1. I am integrating some system that was built with servlets, with some PHP project. What I need to do is generate PHP files from servlets. Problem is that after generating the files , Apache does not parse it as PHP files , which is not good :-). I;ve tryed to change the pageContent of HTTPResponse to "text/plain" - Nope. "text/html" - presents the files as HTML without the PHP part , it simpoy ignores it. I've even tryed setting it to "application/x-httpd-php" , in this case after clicking on link it saves me the file on my computer (Apache does not understand the file type. ] Answer: You need to write the PHP files to your server's disk drive, in the htdocs directory. Then send a browser redirect to the URL corresponding to the file you just wrote. The client will then ask the server for that file; Apache will notice the PHP file on its disk and execute the PHP interpreter on it. There's no way to get Apache to invoke the PHP interpreter directly on pages output by Tomcat. It happens too late in the dispatching game. How to suppress the URL shown in the address bar? No matter what page the customer is on, I want to just show http://sitename.com and no JSP page name. Location: http://www.jguru.com/faq/view.jsp?EID=1035749 Created: Dec 9, 2002 Author: Brian Glodde (http://www.jguru.com/guru/viewbio.jsp?EID=313271) Question originally posed by Edison T (http://www.jguru.com/guru/viewbio.jsp?EID=1004270 Try using a hidden frame, similar to this:

Then all querystrings will be hidden, the address bar will display only where the default document is located. [However, Michael Dean warns:] And the user cannot bookmark any pages. And the browser's history list will contain a bunch of identical names (meaning it's extremely difficult to find a specific page from the list under the Back button--browse a few pages in the frames version of the API javadoc to see). And a user opening a link in a new window (i.e. right-click, "Open Link in New Window") or bookmarking a link (i.e. right-click, "Bookmark This Link") will get only part of the page--possibly losing a navigation bar or a title frame (or, if all content is in the "content" frame, will see the page and its location in the location bar--thereby getting around your desired behavior). And when a new window is opened or a link accessed directly via a bookmark, the user may get strange behavior due to target attributes of the a (anchor) element. And ... But if you really want to create a difficult to use web application (or, more likely, your boss is telling you to do so), go ahead--you won't be the only one. :) Remember, the reason that the web is so popular is because the user controls the experience. Therefore, any time you ask, "How do I remove some capability provided by HTTP and/or HTML?" Abraham Lincoln answered the question best, "You can fool some of the people all of the time, and all of the people some of the time, but you can not fool all of the people all of the time." Being able to display one address in the location bar while displaying a page from another "anonymous" location without any way for the user to identify the "misdirection" would be a huge security problem. HTTP/HTML make the location available to the user so he/she can potentially make informed decisions about whether to submit information. [See also: • •

How can I suppress the parameters from displaying in the URL? For instance, if I pass in a password, I don't want it to show up in the address bar. Why do Frames suck?

- Alex] Comments and alternative answers

Could you give me small example in detail? Author: cathy HAN (http://www.jguru.com/guru/viewbio.jsp?EID=1070144), Mar 26, 2003 I don't understand this every well, but I think this is a great idea to solve this problem, could you give me a more detail example? thanks. Cathy How to notify the user to save data before the session expires? Then if the user does not respond, then save the data. Location: http://www.jguru.com/faq/view.jsp?EID=1035755 Created: Dec 9, 2002

Author: raj subramani (http://www.jguru.com/guru/viewbio.jsp?EID=576334) Question originally posed by Subbareddy Kalakota (http://www.jguru.com/guru/viewbio.jsp?EID=1017528 If you are going to save the data even if the user does not repond, then why not save it right at the beginning anyway? Cheers -raj [See also the original forum thread Is there a way to detect when the session has expired, so that we can send a redirect to a login page? ] Comments and alternative answers

Regarding Session Expire Author: Madhav Lonari (http://www.jguru.com/guru/viewbio.jsp?EID=1036985), Dec 12, 2002 This can be achieved with the HttpSessionBindingListener interface If the session is going to expire the ,valueUnbound(HttpSessionBindingEvent event) method of this interface get called provided this interface is implemented to valid concrete class and object of this class is bounded with this binding listener Why do I get the error: SAX parser fatal error: External entity not found: "http://java.sun.com/dtd/web-app_2_3.dtd"? Location: http://www.jguru.com/faq/view.jsp?EID=1037581 Created: Dec 13, 2002 Author: Benoit Quintin (http://www.jguru.com/guru/viewbio.jsp?EID=394478) Question originally posed by Manos Batsis (http://www.jguru.com/guru/viewbio.jsp?EID=984102 [This happens because Sun's Web site is down, so the servlet engine can't find the remote copy of the web.xml DTD at that URL.] Well, you can download the dtd and point the document reference inside web.xml to the local copy, I suppose. [You can also "inline" the DTD by replacing the reference with the literal text of the DTD. See this web.xml file for an example. Finally, you could attempt to turn off DTD validation in the XML parser, but not all servlet engines allow you to configure the XML parser they use to parse web.xml.

-Alex] When a first request is made to a servlets the init() method is called for the first time and after that the threads will serve the subsequent requests. What will happen when 2 requests are made to a servlet at the same time immediately after the server has restarted? Location: http://www.jguru.com/faq/view.jsp?EID=1041360 Created: Dec 27, 2002 Author: Stephen McConnell (http://www.jguru.com/guru/viewbio.jsp?EID=248618) Question originally posed by anil reddy (http://www.jguru.com/guru/viewbio.jsp?EID=505941 The App server will queue up the requests. Then, they will be processed with the first one (the App server decides) calling the init method and the second waiting until it's finished to throw the processing thread. At least that's how I understand it. Stephen McConnell Comments and alternative answers

init method() Author: bitap kalita (http://www.jguru.com/guru/viewbio.jsp?EID=1222505), Jan 21, 2005 The init() method is called when the server start if you specify that servlet should be loaded on start up(which is the normal practice).So,when the request arrives the servlet is already ready waiting for you. What is the maximum length of the data we can send through the get() method? Location: http://www.jguru.com/faq/view.jsp?EID=1041361 Created: Dec 27, 2002 Author: Stephen McConnell (http://www.jguru.com/guru/viewbio.jsp?EID=248618) Question originally posed by Augustine Dsilva (http://www.jguru.com/guru/viewbio.jsp?EID=1032362 It is dependent upon the browser and server, however in RFC 2068 it states Servers should be cautious about depending on URI lengths above 255 bytes, because some older client or proxy implementations may not properly support these lengths. Since the GET method packs all it's information into the URI, yo shouldn't work with a URI (that is internet address plus data) of > 255 bytes. Read the RFC (Request for Comment). It's dry, but has a lot of info in it and helps you learn the history of the Internet. The RFCs are a compilation of all the documents and communications which helped set the standards and lay the foundation for the internet. They also contain information on upcoming standards.

Hope this Helps Stephen McConnell Comments and alternative answers

Question Author: Ugo Posada Zabala (http://www.jguru.com/guru/viewbio.jsp?EID=1040388), Dec 30, 2002 Does that mean that the full resource must not excede 255 bytes, for instance, if a file we want to read is stored in http://www.hellobeautifuljavaworld.com.wa/publications/tutorials/beginners/march/2002/... or whatever, the full address lenght must be less than 255 or otherwise it wont be possible to access it? That means that the website admins must be careful in where do they store the data. Why shouldn't we make the service() method synchronized? Location: http://www.jguru.com/faq/view.jsp?EID=1041533 Created: Dec 28, 2002 Author: Michael Dean (http://www.jguru.com/guru/viewbio.jsp?EID=805382) Question originally posed by anil reddy (http://www.jguru.com/guru/viewbio.jsp?EID=505941 [Full question: When we implement singlethreadmodel it means that only one thread can access the service method at a time.now my question is ,why can't we achieve the same thing my making the service() method synchronized. theory says that we shouldn't synchronize the service method. but what will happen if we do so,except from the performance problem?] Assume that you write a servlet and synchronize the service(...) (or any of the doXXX(...) methods or any method you call from any of these methods). Once you deploy the servlet, the servlet container receives ten "near-simultaneous" requests for the servlet. Upon receipt of the first request, the servlet container kicks off a thread and sends it on its way (i.e. starts it executing the service(...) method). Unbeknownst to the servlet container, the thread executing in the service(...) method "locks the door" behind it (holds the lock for the servlet object). Not knowing any better, the servlet container starts the other nine threads and assumes they are happily executing the service(...) method. In reality, each of the nine other threads finds the object (the servlet instance) locked, so they go into a "wait" state. Meanwhile, the first thread finishes executing the service(...) method, so it releases the lock on the servlet instance. One of the other threads--not necessarily the second thread, so we'll say the eighth thread--awakens to find the servlet's lock

available, so it requests the lock and starts processing the service(...) method. Meanwhile, the servlet container may be receiving other requests. It's possible that when the eighth thread (which was the second to execute the service(...) method) finishes, the thirty-fifth thread grabs the lock. With this approach each thread has an "equal" probability of being the next allowed to execute the service(...) method. It's complete anarchy--every thread for itself. About this time, the person who sent the second request is calling you to say that your application is down. :) And, if you really want things to get complex, try synchronizing the service(...) method and the doXXX(...) methods... So what does the servlet container do? It provides queueing and prioritization (generally first-in-first-out) of requests. Some servlet containers instantiate multiple servlet objects (and maintain a servlet pool--remember that synchronizing a method locks the object (or instance), not the method, so multiple threads can execute the same method in different instances) to handle multiple simultaneous requests. (Note that this means that you may need to synchronize access of static members.) Others (like Tomcat, IIRC) provide as little support for SingleThreadModel servlets as is required by the servlet specification (they don't waste time creating object pools) since using SingleThreadModel is a "cop out." Keep reading, I'll explain why... :) Implementing the interface often gives developers a false sense of security when it comes to multi-threaded programming. For example, regardless of whether your servlet implements SingleThreadModel or not, you still need to consider synchronization problems with static members, HttpSession attributes, ServletContext attributes, and any other classes outside the scope of the servlet (i.e. JavaBeans, support classes, etc.). So, what do you do if you're not sure whether your servlet is thread-safe? Your best bet is to talk with other developers who have more experience in multi-threaded programming (someone who's been doing it for 30 years is a good beginner ;). Also, do all you can to learn about the topic. IBM's DeveloperWorks website has a lot of articles on multi-threaded programming, including Understand that for instance methods, synchronized locks obj..., Threading lightly, Part 1: Synchronization is not the enemy (and parts 2 and 3), and many, many more. Also, check out some of their tutorials, like Introduction to Java threads. Best of luck, and have fun with threads. How do I keep Tomcat 4.1.x from persisting Session Objects? Location: http://www.jguru.com/faq/view.jsp?EID=1041534 Created: Dec 28, 2002 Author: Brendan Patterson (http://www.jguru.com/guru/viewbio.jsp?EID=999118) Question originally posed by Nathan Christiansen (http://www.jguru.com/guru/viewbio.jsp?EID=1039297 [Full question:

I have an application that I am migrating to a clustered environment with multiple Tomcat 4.1.x servers. I am in the process of changing the persistent session data to another format. I am inclined to persist the limited data we have in a cookie rather than use a session server and persisting the data in a central database. What I need to know is how to make Tomcat not persist the session object between requests and not send back the jsessionid cookie. ] This is a bit of a hack, but it's encapsulated and could work. Set up a filter to run incoming requests past a JSP that with page directive <%@ page session="false" %>. There are probably other ways. Or you can dig through Tomcat's source code to figure out the mechanism by which this page directive deactivates sessions. Good luck! There is an HttpSessionBindingListener for changes to the session. Is there anything similar for changes of ServletContext? Location: http://www.jguru.com/faq/view.jsp?EID=1041535 Created: Dec 28, 2002 Author: G M (http://www.jguru.com/guru/viewbio.jsp?EID=802175) Question originally posed by guru prasanth PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=847725 Yes, as of Servlet Spec 2.3. See javax.servlet.ServletContextListener, javax.servlet.ServletContextAttributeListener. How can I access a configuration and/or log.properties file (stored under WEB-INF) in a web application? Location: http://www.jguru.com/faq/view.jsp?EID=1041791 Created: Dec 30, 2002 Author: Charles Cuozzo (http://www.jguru.com/guru/viewbio.jsp?EID=3774) Question originally posed by Charles Cuozzo PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=3774 I place the log.properties and the appconfig.xml file in the WEB-INF/classes directory. (appconfig.xml is the other configuration file I spoke of.) I get the locations as a URL object using the following code: String logFile = getInitParameter("logger"); // or just logFile = "log.properties" URL logurl = this.getClass().getResource("/" + logFile); if(logurl != null) { PropertyConfigurator.configure(logurl);

} else { System.out.println("log.properties not found!!"); } I do pretty much the same thing to get my appconfig.xml file read in and parsed. I simply convert the URL into a string format and use that to parse the XML. When using a dispatcher and calling .forward(), will doGet() or doPost() be called in the target servlet? Location: http://www.jguru.com/faq/view.jsp?EID=1041792 Created: Dec 30, 2002 Author: Eelco Cramer (http://www.jguru.com/guru/viewbio.jsp?EID=200853) Question originally posed by Simon Kelly (http://www.jguru.com/guru/viewbio.jsp?EID=1036030 The RequestDispatcher will call the servlet's service method. If your servlet extends javax.servlet.http.HttpServlet the same 'do' method will be called automatically by the service method, depending on the method used the original request. Comments and alternative answers

When using a dispatcher and calling .forward(), will doGet() or doPost() be called in the target servlet? Author: Kotra Mallikanand (http://www.jguru.com/guru/viewbio.jsp?EID=1176065), Jun 3, 2004 could you please elaborate on this point a little further. Re: When using a dispatcher and calling .forward(), will doGet() or doPost() be called in the target servlet? Author: Satish Rapalli (http://www.jguru.com/guru/viewbio.jsp?EID=1233969), Mar 21, 2005 No, We can not enter directly into the doPost() of any servlet class,except through a form which uses method = post. When calling .forwarding or .include the target servlet class must have doGet() method to accept this request. Re[2]: When using a dispatcher and calling .forward(), will doGet() or doPost() be called in the target servlet? Author: Eelco Cramer (http://www.jguru.com/guru/viewbio.jsp?EID=200853), Apr 14, 2005 No. Just to be sure I tested this with Tomcat 5.5. If I foward the request like this: getServletContext().getRequestDispatcher("/printing").forward(request, response);

The forward will use the request method from the orginal request. How to do a simple session timeout? Location: http://www.jguru.com/faq/view.jsp?EID=1044373

Created: Jan 8, 2003 Author: Christopher Schultz (http://www.jguru.com/guru/viewbio.jsp?EID=138382) Question originally posed by Patrick Wardhana (http://www.jguru.com/guru/viewbio.jsp?EID=1042019 In WEB-INF/web.xml, use the following incantation: <webapp> . . <session-config> <session-timeout>30</session-timeout> minutes --> </session-config> . . </webapp>

<!-- 30

It's one of the last sub-elements of <webapp>. Check the DTD if you're unsure. See also: • • •

•

How close is the actual session timeout period to the specified timeout period? How can you set the session timeout in tomcat higher? How can an HttpSessionListener comunicate directly to an user web browser that his session has been destroyed by server web.xml "timeout" parameter? Is there a way to detect when the session has expired, so that we can send a redirect to a login page? How can I prevent the expiration of a Session?

•

How do I set session timeouts of greater than 30 minutes?

•

Comments and alternative answers

using invalidate() Author: sridhar Tirumala (http://www.jguru.com/guru/viewbio.jsp?EID=1139770), Jan 18, 2004 I hope u can timeout the session with help of invalidate()method .But if u want timeout specific session id then simply use removeAttribute(java.lang.String name) based on getLastAccessedTime() ("Returns the last time the client sent a request associated with this session ") How to deploy and run a simple servlet on websphere? Location: http://www.jguru.com/faq/view.jsp?EID=1044409 Created: Jan 8, 2003 Author: Subbareddy Kalakota (http://www.jguru.com/guru/viewbio.jsp?EID=1017528) Question originally posed by new user (http://www.jguru.com/guru/viewbio.jsp?EID=999934 If you are new to websphere, it seems to be strange at least initially,to deploy the simple servlet. One way you can do is you need to generate a war file. For this you

can use Application Assembly Tool that ships with websphere, it is simple if you use this tool, it walks you throwgh the steps to create a war file, and you can start a websphere console from "first steps" and you can deploy the file you created . And you can access your servlet by http://localhost:8090/your_web_application_context/servlet_url_mapping This is very high level to get started, you can find more info in "infocenter" at ibm.com. You really need to do some research. Comments and alternative answers

Not complex Author: Manjunatha Prasad (http://www.jguru.com/guru/viewbio.jsp?EID=1220641), Jan 11, 2005 This task is not at all complex. Just open web.xml and change the Servlet and Servlet mapping configuration. Keep you servlet in the WEB-INF/classes followed by your package name. Restart your system. Thanks, Manju How can I set parameters in a JSP, something equivalent to setAttribute on a request object? That is, I need to do setParameter in order to read it as getParameter in the servlet. Location: http://www.jguru.com/faq/view.jsp?EID=1044746 Created: Jan 9, 2003 Author: Michael Dean (http://www.jguru.com/guru/viewbio.jsp?EID=805382) Question originally posed by Rita Vepa (http://www.jguru.com/guru/viewbio.jsp?EID=1016597 [One solution is: I am assuming you're referring to "intercepting" a request, then checking/modifying the values. If so, have a look at one of the newer features of the Servlet API, Filters. ] Although that's a very elegant solution, it may be overkill. There are a couple of simple solutions available. The more elegant approach using Filters, however, could make for a much more reuasable, maintainable, and robust architecture. I couldn't tell exactly what you are trying to do, but here are some options. My guess is that you want Case 1, but just in case... Case 1: An HTTP request is submitted to a servlet. From this servlet, you are dispatching a request to another (third-party) servlet that needs a parameter that is not included in the request. You can add a parameter to the request by "appending" it to the URL. For example: RequestDispatcher dispatcher = request.getRequestDispatcher("/servlet/some.ThirdPartyServlet" + "?" + "param_name=" + "somevalue"); dispatcher.forward(request, response);

Just be careful to run the parameters through the java.net.URLEncoder.encode(String, String) method if there's a possibility that the values contain "illegal" characters. Case 2: An HTTP request is submitted to a JSP that is forwarding (or including) a request to a (third-party) servlet. You would like to "add" parameters to the request when received by the JSP. Do so with the <jsp:param ... > tag. <jsp:forward page="/servlet/some.ThirdPartyServlet" > <jsp:param name="param_name" value="somevalue" /> Note that the value of the value attribute may be a request time expression (i.e. <jsp:param name="param_name" value="<%= request.getAttribute("someAttributeWithAValidToString") %>" />. Here the JSP translator should take care of encoding "illegal" characters in the value. Case 3: You have an HTML form that submits directly to a (third-party) servlet, but you do not want the user to see some fields (i.e. you want to keep the form simple). Use "hidden" form fields: If you want a dynamic value, you can create the HTML form with a JSP. Here, the browser "packages up" the form values, so you don't want to run the values through java.net.URLEncoder.encode(String, String). Case 4: You want call the third-party servlet directly from HTML without using a form. Append the required parameters to the URL: Clickable Text Here again, if using a JSP to create "dynamic" links, make sure you properly encode the characters in the URL with java.net.URLEncoder.encode(String, String). Comments and alternative answers

How can I set parameters in JSP? Author: Scott Andrews (http://www.jguru.com/guru/viewbio.jsp?EID=1188219), Jul 23, 2004 I have the same issue, but the answers provided do not address the question, as I understand it. I have a JSP page which contains a form that is "self submitting", meaning the action on the form calls the same JSP page again. After a submit, I want the JSP to process the parameters and change their values. Just like there is a request.getParameter, I'm

looking for a setParameter method. When the page reloads, I want the a new value set for the parameter. Lets say I have a form field called preditor_id, with a value of "Gator". When the form is submitted to my "preditor.jsp" code, I want to get the preditor_id parameter, use the value that was submitted, say "Gator", and reload the form with a new value set for the preditor_id parameter, say "shark". I know I can simply write out the new value "shark" as an input type: - but that's not what I'm talking about. What I want to know is - how do I change the value of the parameter sent back in the request header? How do I do that? Re: How can I set parameters in JSP? Author: Rishi Venkatarama (http://www.jguru.com/guru/viewbio.jsp?EID=1193458), Aug 16, 2004 When the form is being submitted, you can use javascript to add parameters "dynamically" as the form is beign submitted. function addMenuContextParam (form,paramValue) { if (document.getElementById) { var input = document.createElement('INPUT'); if (document.all) { // what follows should work // with NN6 but doesn't in M14 input.type = 'HIDDEN'; input.name = 'SOME_NAME'; input.value = paramValue; } else if (document.getElementById) { // so here is the // NN6 workaround input.setAttribute('type', 'HIDDEN'); input.setAttribute('name', 'SOME_NAME'); input.setAttribute('value', paramValue); } form.appendChild(input); } }

hope this helps. Rishi I too need to a logical response.setParameter Author: Greg Marsh (http://www.jguru.com/guru/viewbio.jsp?EID=1255498), Jul 28, 2005 I currently have a login page that uses a form to pass a username and password. The receipent of the post is a hardware box that I cannot change. I can add the parameters on the URL and it works just fine. But then the username and password are shown in

the address line of the browser. I would like ot simulate what a form does but from code rather than from form. It is enough that it does not show in the address line -- I don't need better security. It seems like there must be some way to write parameters into the stream going back to the browser, but I haven't found it! How could I use NTLM Authentication to authenticate via Windows NT Authentication for a servlet based intranet-application ? Location: http://www.jguru.com/faq/view.jsp?EID=1045412 Created: Jan 11, 2003 Author: Chad Skeeters (http://www.jguru.com/guru/viewbio.jsp?EID=976796) Question originally posed by Manfred Regele PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=230192 [There was a great discussion of this at http://www.jguru.com/faq/viewquestion.jsp?EID=393110 The code below seems to be the final solution, but I recommend reading the thread to make sure, especially since there was much discussion about making it not take 40 seconds to return. Also, you apparently have to do it during each doPost call??? Not sure what that means, since you can't call sendError during each doPost... Maybe you just have to set the WWW-Authenticate header each time. Brett Knights also recommends: The easy way is to use Apache and mod_ntlm. Then req.getRemoteUser() returns the logged in user's name. You can use Apache directives to limit access to servlet urls. I have used this with JServ and Tomcat. -Alex]

String auth = request.getHeader("Authorization"); if (auth == null) { response.setStatus(response.SC_UNAUTHORIZED); response.setHeader("WWW-Authenticate", "NTLM"); response.flushBuffer(); return; } if (auth.startsWith("NTLM ")) { byte[] msg = new sun.misc.BASE64Decoder().decodeBuffer(auth.substring(5)); int off = 0, length, offset; if (msg[8] == 1) { byte z = 0; byte[] msg1 = {(byte)'N', (byte)'T', (byte)'L', (byte)'M', (byte)'S', (byte)'S', (byte)'P',

z,(byte)2, z, z, z, z, z, z, z,(byte)40, z, z, z, (byte)1, (byte)130, z, z,z, (byte)2, (byte)2, (byte)2, z, z, z, z, z, z, z, z, z, z, z, z}; response.setHeader("WWW-Authenticate", "NTLM " + new sun.misc.BASE64Encoder().encodeBuffer(msg1)); response.sendError(response.SC_UNAUTHORIZED); return; } else if (msg[8] == 3) { off = 30; length = msg[off+17]*256 + msg[off+16]; offset = msg[off+19]*256 + msg[off+18]; String remoteHost = new String(msg, offset, length); length = msg[off+1]*256 + msg[off]; offset = msg[off+3]*256 + msg[off+2]; String domain = new String(msg, offset, length); length = msg[off+9]*256 + msg[off+8]; offset = msg[off+11]*256 + msg[off+10]; String username = new String(msg, offset, length); out.println("Username:"+username+"
"); out.println("RemoteHost:"+remoteHost+"
"); out.println("Domain:"+domain+"
"); } } Comments and alternative answers

NT Authentication using servlets Author: P N (http://www.jguru.com/guru/viewbio.jsp?EID=1054248), Feb 6, 2003 This code is fine except that when I tried, it does not pop up the username/password (authentication) box in the browser, although it does manage to get the required data, decode it and prints the username, remote host and domain. Any idea why it is behaving in this manner? Re: NT Authentication using servlets Author: Jon Peccarelli (http://www.jguru.com/guru/viewbio.jsp?EID=1057547), Feb 17, 2003 Because it is using NTLM authenication. It is a "silent" authentication with your current NT credentials. If this fails, you will get a login box (i.e. you are in a different domain then the servers you are trying to access and there is not a trust setup). You only get the login box all of the time using clear text authentication. Re[2]: NT Authentication using servlets

Author: Maggie Chau (http://www.jguru.com/guru/viewbio.jsp?EID=1064841), Mar 10, 2003 I tried this coding, however I keep getting the Login box. I'm in the same domain where I try to logon. Can you pls help me out. Thanks. Maggie Re: NT Authentication using servlets Author: Abhay Kumar (http://www.jguru.com/guru/viewbio.jsp?EID=1145500), Feb 11, 2004 Hello, I am using the same code as given in this thread. I am having a problem, I am not able to use the POST method for sending data from a JSP to an servlet. Please help Regards Abhay Re[2]: NT Authentication using servlets Author: Dave Jarvis (http://www.jguru.com/guru/viewbio.jsp?EID=1154253), Mar 15, 2004 Hi i have exactly the same problem "I am not able to use the POST method for sending data from a JSP " when using NTLM Authentication. What was the solution please ? Thanks Dave Re[2]: NT Authentication using servlets Author: Anup Vijayaraghavan (http://www.jguru.com/guru/viewbio.jsp?EID=1177514), Jun 9, 2004 Did you get a solution for not being able to use POST in forms with mod_ntlm. We are having the same problem with our intranet. Thanks in advance ... Anup Re: NT Authentication using servlets Author: Akash Kava (http://www.jguru.com/guru/viewbio.jsp?EID=1135160), Feb 25, 2004 Hi, We made one product which we used for some other purpose but fortunately it also gave solution of your problem as well. By using JspISAPI you can enable NTLM authentication for tomcat applications. http://jspisapi.neurospeech.com - Akash Kava Experience with trying to use NTLM Author: Frederik Heick (http://www.jguru.com/guru/viewbio.jsp?EID=886161), Mar 27, 2003 I have made some serious attempts to implements NTLM, using to code mentioned. It wont work with Windows 95, no matter what I did. But in my firm we still have

some WS that uses it, hmmmm. Secondly, it has to be in every doPost method, not great. Thirdly, i tried to pack the code in a FilterChain, but couldnt make the forward,import etc stuff work. So i gave up, and made a simple Ms IIS server, with one asp page witch redirects the username & domain back to me. A very sad,bad hack, but it works. Tech specs: J2EE = Weblogic Server 6.1 sp1 OS = Unix TRU64 Re: Experience with trying to use NTLM Author: Robert McKenzie (http://www.jguru.com/guru/viewbio.jsp?EID=1079571), Apr 27, 2003 If you trim the encoded string it should take care of the 40 sec. delay. There are a lot of garbage bytes at the end of that string. Since HTTP sees two carriage returns as the end of the headers, the rest of the headers after WWW-Authenticate are put in the body of the message and the browser gets confused. This includes content-length, encoding, type, etc. Modified code line below. response.setHeader("WWW-Authenticate", "NTLM " + new sun.misc.BASE64Encoder().encodeBuffer(msg1).trim());

Re: Experience with trying to use NTLM Author: Babu Kopparam (http://www.jguru.com/guru/viewbio.jsp?EID=1196844), Sep 2, 2004 Hi! Frederik, I am trying to achieve the same using asp page hosted on IIS. I am using the following code : This is login asp file <% dim UserName dim authlogin UserName = request.ServerVariables("LOGON_USER") authlogin = request.ServerVariables("AUTH_LOGIN") response.write("

Logged in user is " & UserName) response.write(" Login in auth is " & authlogin) response.write(" ") %> Finished executing the asp file. This is not giving me any user id hint logged in. Any help is highly appreciated. -Babu.

Re: Experience with trying to use NTLM Author: joan cao (http://www.jguru.com/guru/viewbio.jsp?EID=1257118), Aug 8, 2005 How did you make it work, can you tell me, I'd like to do the same way as you do. Thanks Joan This is incorrect... Author: Eric Glass (http://www.jguru.com/guru/viewbio.jsp?EID=1088764), May 28, 2003 The above code performs IDENTIFICATION, not AUTHENTICATION. A user can easily set their IE preferences to prompt for a password, enter ANY username and password, and enter the system. Also, NTLM is a negotiated authentication protocol; any hard-coded values are bound to fail, as the client and server use flags to negotiate supported capabilities. The posted code, for example, specifies the following flags: Negotiate Unicode (0x00000001) Always Sign (0x00008000) Negotiate NTLM (0x00000200)

This will fail on Windows 95/98 clients, since they don't support Unicode (should send Negotiate OEM (0x00000002)). The open-source jCIFS library provides exactly the functionality mentioned (namely, HTTP NTLM authentication against a domain for servlets): http://jcifs.samba.org

The newest versions can be found at: http://users.erols.com/mballen/jcifs Eric Re: Can NTLM communicate with active directories using a servlet? Author: Edward Castellarin (http://www.jguru.com/guru/viewbio.jsp?EID=1149996), Feb 28, 2004 Can the NTLM communicate with the windows LDAP (active directories) from a Servlet or JSP program? Re[2]: Can NTLM communicate with active directories using a servlet? Author: Brian Compton (http://www.jguru.com/guru/viewbio.jsp?EID=111701), Mar 2, 2004 Well, once you have authenticated via NTLM you can get the users logon name and query the domain's active directory to get more information about that person. I use the jfcis package to enable the NTLM.

You can do the querying of active directory with JNDI API. The following code does what you need, but the down side is that you have to pass in security credintials to the active directory to create a connection before you can search against it. (Microsoft's site has documented the steps to take to allow anonymous access to the active directory.) try {

// retrieve the authenticated user's logon name String userName = request.getRemoteUser(); String DOMAIN_NAME = "domain"; String DOMAIN_CONTROLER = "domaincontroller"; Hashtable env = new Hashtable(); env.put(Context.SECURITY_AUTHENTICATION,"simple"); // TODO: change to a user on your domain! String activeDirUser = DOMAIN_NAME + "\\user"; String activeDirPassword = "cleartextpassword!";

env.put(Context.SECURITY_PRINCIPAL, activeDirUser); env.put(Context.SECURITY_CREDENTIALS, activeDirPassword);

String host = DOMAIN_CONTROLER; // A Domain Controller Server String port = "389"; // Active Dir Port String url = new String("ldap://"+host+":"+port); env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory"); env.put(Context.PROVIDER_URL,url); System.out.println("Connecting to " +url); DirContext ctx; ctx = new InitialDirContext(env); SearchControls ctls = new SearchControls(); ctls.setCountLimit(1); ctls.setReturningObjFlag(false); ctls.setSearchScope(SearchControls.SUBTREE_SCOPE); String userLogon = userName.substring(DOMAIN_NAME.length() +1); System.out.println(userLogon); String filter = "(&(objectCategory=User)(cn="+ userLogon +"))"; NamingEnumeration n= ctx.search("DC="+ DOMAIN_NAME +",DC=COM", filter, ctls); System.out.println(" Attributes .... "); while (n.hasMoreElements()) { System.out.println(n.next()); } ctx.close(); } catch (Exception e) { System.out.println("Exception = "+ e); }

You will see that the users active directory information is spit out to the console. It will be up to you to retrieve the relevant information. Please help What is this error ?? where my i wrong Author: Rajesh Francis (http://www.jguru.com/guru/viewbio.jsp?EID=1157367), Mar 25, 2004 Please help >> What is this error ?? where my i wrong. I just want to retireve the User Name from the Active Directory using JNDI and Tomcat 3.3 Problem getting attribute: javax.naming.InvalidNameException: cn=Woods, Anthony (HQ), ou=Silverdale, ou=sews-e: [LDAP: error code

34 - 0000208F: NameErr: DSID-031001B6, problem 2006 (BAD_NAME), data 8350, best match of: 'cn=Woods, Anthony (HQ), ou=Silverdale, ou=sews-e,dc=sews-e,dc=com' ]; remaining name 'cn=Woods, Anthony , ou=Silverdale, ou=sews-e' My code try { env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory"); env.put(Context.PROVIDER_URL, "ldap://ukhqits002/dc=sewse,dc=com"); } catch(Exception ex) { out.print("erroe in first para-----"+ex); } try { // Create the initial directory context DirContext ctx = new InitialDirContext(env); //String userLogon = userName.substring(DOMAIN_NAME.length() +1); //System.out.println(userLogon); // Ask for all attributes of the object Attributes attrs = ctx.getAttributes("cn=francir, ou=Silverdale, ou=sewse"); // Find the surname ("sn") and print it out.println("sn: " + attrs.get("sn").get()); // Close the context when we're done ctx.close(); } catch (NamingException e) { out.println("Problem getting attribute: " + e); } Your advice is highly appreciated. Rajesh Entering worng user id. Author: Selvapandian Gurunathan (http://www.jguru.com/guru/viewbio.jsp?EID=1025470), Aug 31, 2003 If the user enters wrong user id in the pop up i am getting the wrong user id. HOw to avoid showing the pop-up? Re: Entering worng user id. Author: Jaya Selvan (http://www.jguru.com/guru/viewbio.jsp?EID=1199885), Sep 18, 2004 Hi i'm facing the same problem.Can u suggest me if u have come across any valid solutions. Thanks in advance. Problem using the above code on Web sphere running SSL Author: Altaf Malik (http://www.jguru.com/guru/viewbio.jsp?EID=1113901), Sep 8, 2003 The above mentioned code is not running on Websphere running SSL. When it tries to send type2 message to client, the browser says, invalid response from the server. can anyone suggest any better solution or changes in this code???? I really need it immediately. Altaf Malik

How to save the authenticated user info to a java Bean Author: joan cao (http://www.jguru.com/guru/viewbio.jsp?EID=1257118), Aug 8, 2005 I used the code to get userID and password, but I need to save the ID and password in a session bean which can be shared among pages. Do you know how to do that with the code. Any help is greatly appreciated. Thanks Joan NTLM Hash password Author: Sherjeel Ghouse (http://www.jguru.com/guru/viewbio.jsp?EID=1260744), Sep 2, 2005 Is there a way to get NTLM hash password with this code. Otherwise, how would i authenticate a user against a domain like Active Directory using JNDI/LDAP. « previous

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How do I use HttpServletRequest.getHeaderNames() to get the names of the headers of the HTTP request? Location: http://www.jguru.com/faq/view.jsp?EID=1045427 Created: Jan 11, 2003 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Chris Marks (http://www.jguru.com/guru/viewbio.jsp?EID=1007132 Well, it is that simple, this is java basics, and is based on the simple exanple that is provided in the Java API Documentation, for java.util.Enumeration. I strongly suggestion to read it when you have some time. for (Enumeration enum=request.getHeaderNames(); enum.hasMoreElements();) { String headerName = (String)enum.nextElement(); System.out.println("Name = " + headerName); } Remember, that HttpServletRequest is an interface, so you don't have to worry about the implementation, otherwise if you decide to switch to another Servlet Container, then you will not be able to do that... That's why they are called interfaces. What is the role of the controller in MVC architecture? Location: http://www.jguru.com/faq/view.jsp?EID=1045434 Created: Jan 11, 2003 Author: Lasse Koskela (http://www.jguru.com/guru/viewbio.jsp?EID=573277)

Question originally posed by sabu vs PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=476248 The role of controller is to dictate what to do behind the scenes and what to display in the view next. 1. 2. 3. 4.

Controller Controller Controller Controller

receives a request decides the requested activities based on request parameters delegates tasks to be performed based on the request parameters delegates the next view to be shown

There must be a lot better explanations for the controller's responsibilities, but at least I tried... As it comes to choosing between a JSP and a servlet for the controller implementation, servlet is the obvious choice as JSPs are designed for simplifying generating dynamic responses primarily (mixing HTML and logic). [See also: What is the best way of implementing a web application that uses JSP, servlet and EJB technologies all together following a Model View Controller (MVC) architecture? what is the role of controller in MVC architecture ] How should I configure JBuilder7 to work on servlets? Location: http://www.jguru.com/faq/view.jsp?EID=1045506 Created: Jan 12, 2003 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Krystof Malak (http://www.jguru.com/guru/viewbio.jsp?EID=1001958 JBuilder doesn't really need of any additional setup for working with Servlets. Just create a new Project and creare a new Web Application. Then when you want to create a new file, just select "servlet" from the WEB tag of the File|New popup. How can I read parameters from a multipart/form-data upload form? Location: http://www.jguru.com/faq/view.jsp?EID=1045507 Created: Jan 12, 2003 Author: Sean Sullivan (http://www.jguru.com/guru/viewbio.jsp?EID=203382) Question originally posed by Sean Sullivan (http://www.jguru.com/guru/viewbio.jsp?EID=203382 [That is, given the form: What is your name?
What file are you sending? <INPUT TYPE=FILE NAME=secretDocument>

I cannot read the submitter using request.getParameter("submitter") (it returns null). ] Situation: javax.servlet.HttpServletRequest.getParameter(String) returns null when the ContentType is multipart/form-data Solutions: Solution A: 1. download http://www.servlets.com/cos/index.html 2. invoke getParameters() on com.oreilly.servlet.MultipartRequest Solution B: 1. download http://jakarta.apache.org/commons/sandbox/fileupload/ 2. invoke readHeaders() in org.apache.commons.fileupload.MultipartStream Solution C: 1. download http://users.boone.net/wbrameld/multipartformdata/ 2. invoke getParameter on com.bigfoot.bugar.servlet.http.MultipartFormData Solution D: Use Struts. Struts 1.1 handles this automatically. Comments and alternative answers

Use MultiPartRequest Author: Pazhanikanthan Periasamy (http://www.jguru.com/guru/viewbio.jsp?EID=230166), Apr 9, 2003 Use Oreilley's MultiPartRequest Reusable class for this condition Example for multi part request Author: srinivas kandagatla (http://www.jguru.com/guru/viewbio.jsp?EID=1150943), Mar 2, 2004 /* * DemoParserUploadServlet.java * * Example servlet to handle file uploads using MultipartParser for * decoding the incoming multipart/form-data stream */ import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import com.oreilly.servlet.multipart.*; public class DemoParserUploadServlet extends HttpServlet { private File dir; public void init(ServletConfig config) throws ServletException { super.init(config); // Read the uploadDir from the servlet parameters String dirName; //= config.getInitParameter("uploadDir"); dirName="C:\\Program Files\\Apache Group\\Tomcat 4.1\\webapps\\examples\\WEBINF\\classes\\cal"; //if (dirName == null) { // throw new ServletException("Please supply uploadDir parameter"); //} dir = new File(dirName); if (! dir.isDirectory())

{ throw new ServletException("Supplied uploadDir " + dirName + " is invalid"); } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter out = response.getWriter(); response.setContentType("text/plain"); out.println("Demo Parser Upload Servlet"); if(false) { try { MultipartParser mp = new MultipartParser(request, 1*1024*1024); // 10MB Part part; while ((part = mp.readNextPart()) != null) { String name = part.getName(); if (part.isParam()) { // it's a parameter part ParamPart paramPart = (ParamPart) part; String value = paramPart.getStringValue(); out.println("param; name=" + name + ", value=" + value); } else if (part.isFile()) { // it's a file part FilePart filePart = (FilePart) part; String fileName = filePart.getFileName(); if (fileName != null) { // the part actually contained a file long size = filePart.writeTo(dir); out.println("file; name=" + name + "; filename=" + fileName + ", filePath=" + filePart.getFilePath() + ", content type=" + filePart.getContentType() + ", size=" + size); } else { // the field did not contain a file out.println("file; name=" + name + "; EMPTY"); } out.flush(); } } } catch (IOException lEx) { this.getServletContext().log(lEx, "error reading or saving file"); } } CommandProcessor cp=new CommandProcessor(); cp.process(request,response); HttpSession session=request.getSession(); String fname=(String)session.getAttribute("FILENAME"); out.println("returned from cp"+fname); } } Re: Example for multi part request Author: srinivas kandagatla (http://www.jguru.com/guru/viewbio.jsp?EID=1150943), Mar 2, 2004 <META NAME="GENERATOR" Content="Microsoft Visual Studio 6.0"> <TITLE> /* * DemoParserUploadServlet.java * * Example servlet to handle file uploads using MultipartParser for * decoding the incoming multipart/form-data stream */ import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import com.oreilly.servlet.multipart.*; public class DemoParserUploadServlet extends HttpServlet { private File dir; public void init(ServletConfig config) throws ServletException { super.init(config); // Read the uploadDir from the servlet parameters String dirName; //= config.getInitParameter("uploadDir"); dirName="C:\\Program Files\\Apache Group\\Tomcat 4.1\\webapps\\examples\\WEB-INF\\classes\\cal"; //if (dirName == null) {

// throw new ServletException("Please supply uploadDir parameter"); //} dir = new File(dirName); if (! dir.isDirectory()) { throw new ServletException("Supplied uploadDir " + dirName + " is invalid"); } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter out = response.getWriter(); response.setContentType("text/plain"); out.println("Demo Parser Upload Servlet"); if(false) { try { MultipartParser mp = new MultipartParser(request, 1*1024*1024); // 10MB Part part; while ((part = mp.readNextPart()) != null) { String name = part.getName(); if (part.isParam()) { // it's a parameter part ParamPart paramPart = (ParamPart) part; String value = paramPart.getStringValue(); out.println("param; name=" + name + ", value=" + value); } else if (part.isFile()) { // it's a file part FilePart filePart = (FilePart) part; String fileName = filePart.getFileName(); if (fileName != null) { // the part actually contained a file long size = filePart.writeTo(dir); out.println("file; name=" + name + "; filename=" + fileName + ", filePath=" + filePart.getFilePath() + ", content type=" + filePart.getContentType() + ", size=" + size); } else { // the field did not contain a file out.println("file; name=" + name + "; EMPTY");

}

}

out.flush();

} } catch (IOException lEx) { this.getServletContext().log(lEx, "error reading or saving file"); } } CommandProcessor cp=new CommandProcessor(); cp.process(request,response); HttpSession session=request.getSession(); String fname=(String)session.getAttribute("FILENAME"); out.println("returned from cp"+fname); } }

How can I read parameters from a multipart/form-data upload form using "http://jakarta.apache.org/commons/fileupload/" library? Author: Dharmanand Singh (http://www.jguru.com/guru/viewbio.jsp?EID=1207306), Oct 26, 2004 > Solution B: > 1. download > http://jakarta.apache.org/commons/sandbox/fileupload/ > 2. invoke readHeaders() in > org.apache.commons.fileupload.MultipartStream The Solution B as given by my dear friend is a bit hectic and a bit complex :( We can try the following solution which I found much simpler (at least in usage). 1. Download one of the versions of UploadFile from http://jakarta.apache.org/commons/fileupload/ 2. Invoke parseRequest(request) on org.apache.commons.fileupload.FileUploadBase which returns list of org.apache.commons.fileupload.FileItem objects. 3. Invoke isFormField() on each of the FileItem objects. This determines whether the file item is a form paramater or stream of uploaded file. 4. Invoke getFieldName() to get parameter name and getString() to get parameter value on FileItem if it's a form parameter. Invoke write(java.io.File) on FileItem to save the uploaded file stream to a file if the FileItem is not a form parameter.

From a servlet, how do I access files and directories on the client's file system? Location: http://www.jguru.com/faq/view.jsp?EID=1045509

Created: Jan 12, 2003 Modified: 2003-01-25 19:22:20.915 Author: Erik Runia (http://www.jguru.com/guru/viewbio.jsp?EID=585265) Question originally posed by john varghese (http://www.jguru.com/guru/viewbio.jsp?EID=997638 You cannot access the client's directory structure using a web application (jsp, servlet, javascript, html) because of security issues. You may need to look into an applet or other client based application, instead of server based. [See also Files:Downloading subtopic] [It's not simply a security issue -- it's more basic than that. The servlet runs on the server; it can only send and receive data to the client via HTTP. HTTP only allows simple file transfer operations -- no arbitrary remote access. -A] Comments and alternative answers

re Author: Massimiliano Ragazzi (http://www.jguru.com/guru/viewbio.jsp?EID=945577), Feb 17, 2003 The only way to access file or directory is applet, but if it's not authenticated i can only read and not write Re: re Author: umair rahim (http://www.jguru.com/guru/viewbio.jsp?EID=1212152), Jan 17, 2005 you can use ListFiles() method with file path as a parameter ..... n you can activate this method against some specifice text using querey string ..... e.g, if (quereystring=="file path") f.listFiles("file path") it would be stored as an array Re[2]: re Author: bitap kalita (http://www.jguru.com/guru/viewbio.jsp?EID=1222505), Jan 21, 2005 This "file path" has to be that of the server not client machine.As the first answer says you cannot access client machine. Re[3]: re Author: Rajesh Kumar (http://www.jguru.com/guru/viewbio.jsp?EID=1222672), Feb 7, 2005 Hai people, Then is it possible to upload files from client side like what yahoomail do? Thanks in advance

How do I execute a servlet from the command line, or from Unix shell program or Windows BAT file? Location: http://www.jguru.com/faq/view.jsp?EID=1063884 Created: Mar 6, 2003 Author: Christopher Koenigsberg (http://www.jguru.com/guru/viewbio.jsp?EID=722897) Question originally posed by rupali kandarkar (http://www.jguru.com/guru/viewbio.jsp?EID=1051696 Of course as with any Java class, you could put a "main" method in your class that extends HttpServlet, so you could run it (the main(), not the doGet/doPut/service()) from a command line. But it wouldn't have the whole server infrastructure set up for it, with the request, session, response, etc. (which is why you couldn't call the doGet/doPut/service, unless you have a good "mock object" test scaffolding set up). Or are you saying that you have some utility classes & methods that might be useful to run, standalone in a command line situation (e.g. calling them from main()), as well as from inside a servlet (e.g. calling them from doGet/doPut/service)? In that case, perhaps you would want to make a Jar file with just the utility classes, and an application with main() that uses the Jar file, and also a web application WAR file that uses the Jar file too (in its WEB-INF/lib). How do you create a browser cookie that persists to a different domain? Location: http://www.jguru.com/faq/view.jsp?EID=1063895 Created: Mar 6, 2003 Author: Jeff Hubbach (http://www.jguru.com/guru/viewbio.jsp?EID=504430) Question originally posed by Eric Cho (http://www.jguru.com/guru/viewbio.jsp?EID=1051283 I have server1 and server2(12.23.34.45). Note: I have no control over server2 and it's a cgi server. Server1 creates a request to server2. In response, server2 feeds back an html page with the headers I display the html to the browser via the OutputStream. Also I obtain the response headers and attempt to relay it back to the browser. Here is the relay cookie I'm attempting to create for the next request Note: USER1 is obtained from server2's response

Cookie aCookie1 = new Cookie("_user", USER1); aCookie1.setDomain("12.23.34.45"); //to server2 aCookie1.setPath("/cgi-bin/"); response.addCookie(aCookie1); The next request will be towards server2 but for some reason the cookie doesn't exist in the request even though I created one for that domain on the response before it.

Please don't ask why I'm going through all this trouble of relaying back and forth between 2 servers. I realize a simple POST method from the browser/html would work just fine, but that couldn't be in this case. ----------------------------Look at section 4.3.2 of RFC 2109, linked below. It states that a cookie is rejected if the following is true: - The value for the request-host does not domain-match the Domain attribute. What that means is that you can't set a cookie for a different domain than is being accessed. NOTE: you _can_ set a cookie that will get sent to all subdomains, ie www.foo.com and secure.foo.com, but you _can't_ set a cookie on a page requested from foo.com to be sent to a server in the bar.com domain. http://www.ietf.org/rfc/rfc2109.txt Comments and alternative answers

How do you create a browser cookie that persists to a different domain? Author: tech tech (http://www.jguru.com/guru/viewbio.jsp?EID=809635), Mar 6, 2003 Totally right. And also think in terms of security. Say one user is surfing bank site ( say bank.com) and the bank site puts a cookie with some user info in it. Now the same user is surfing on say foo.com and now if the foo.com application had an access to the bank.com cookie, then foo.com will be rich in no time :-). They can access all secure / non secure, confidential info of all the cookies of that user. So u see, it is absoultely NOT ACCEPTABLE for one domain to share cookies of other one. Solution!.....hopefully Author: Eric Cho (http://www.jguru.com/guru/viewbio.jsp?EID=1051283), Mar 12, 2003 Thanks Jeff, That actually helped me a lot. What I'm going to do now is put server1 and server2 behind a proxy and funnel the requests in through that. So, both servers will have the same domain and thus, the cookie persists! Hopefully it works. Re: Solution!.....hopefully Author: Manivasakam Ramaswamy (http://www.jguru.com/guru/viewbio.jsp?EID=1092515), Jun 10, 2003 Hi Eric Cho, I would like to know how you achieved the task because i am also in deep trouble.

I will be grateful if I get the sample code for the same.

thanks. mani.

Re[2]: Solution!.....hopefully Author: Eric Cho (http://www.jguru.com/guru/viewbio.jsp?EID=1051283), Jun 17, 2003 Mani, It's the same code as I originally had posted. Except, make sure both servers are under the same domain. That is the only way I could make the cookie persist. So what we had done was put a proxy in front of both with the domain of abc.com. But all requests going to the URI of /x/y/z/* goto server 1 and all requests goint to URI /a/* go to server 2. So now you have to make sure all your links accomodate this. I believe this handy work with the proxy is called 'reverse proxying'. Hopefully this helps. Eric Re[3]: Solution!.....hopefully Author: Magdi Ahmed (http://www.jguru.com/guru/viewbio.jsp?EID=316472), Dec 17, 2003 Actually, you didn't need to do all that proxy stuff... just set the DNS for both servers to be different hosts of the same domain name, so box01.yourdomain.com and box02.yourdomain.com If you did it that way, both servers would see cookies set to a domain of '.yourdomain.com' Cookie domains and path are set to define the scope of access Author: Frank Nimphius (http://www.jguru.com/guru/viewbio.jsp?EID=1139332), Jan 15, 2004 The problem in your request is that you are trying to push a cookie information from one domain to another. if you know that you want to use cookies to exchange information between applications of different servers, you can define the cookie domain to the one for the second server when setting it to teh client Browser. Redirect to an application that is hosted by the second server and have this application accessing the cookie. Using cookies may not be the best solution of integrating applications with each other, but its works. Frank Re: Cookie domains and path are set to define the scope of access Author: A L (http://www.jguru.com/guru/viewbio.jsp?EID=1250267), Jun 24, 2005 I tried to set the cookie domain to the second server and redirect the page to that domain. It won't work. The cookies are not created or are not accessible from the second domain. How can we find out the number of ServletContext currently active in a servlet container? Location: http://www.jguru.com/faq/view.jsp?EID=1063899 Created: Mar 6, 2003

Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Ashutosh Satyam (http://www.jguru.com/guru/viewbio.jsp?EID=1063699 Hi, No, there are no references in the specifications for that. As far as I know there is nothing available for that, especially if you need something that is portable or not server specific. If you have the source code of the server, it is probably trivial (well, depend how documented is the code) to write something, otherwise you need to find alternative solution (like reading and analizing the server configuration files). But, again, this would be a server specific solution. Comments and alternative answers

Servlet Context Author: Sushil Chatrani (http://www.jguru.com/guru/viewbio.jsp?EID=1148988), Aug 27, 2004 U can use HttpServletContextListener to keep track of number of servletContext Initialized. All the listeners will use the factory using singleton pattern to get the instance of a controller class to update the count of the servlet context. Does anyone know if there is a way to check the size of a file (a picture in my case) that the user can upload from a form *BEFORE* the file is uploaded? Location: http://www.jguru.com/faq/view.jsp?EID=1074628 Created: Apr 8, 2003 Author: Matan Amir (http://www.jguru.com/guru/viewbio.jsp?EID=1010674) Question originally posed by Jerome Iffrig (http://www.jguru.com/guru/viewbio.jsp?EID=977875 I know that it is possible to check the size of the file on the server side once it has been completly uploaded by the user, but this is not ideal (e.g. I can always delete the file from the server if it is too big, but it would have been uploaded in teh first place, which I would like to avoid). If this question is not directly Servlet/JAVA related, maybe the answer is Javascript??? ----One obvious solution is to check the HTTP content-length of the file POST request and cancel the upload if it's too big (throw a ServletException for example). The problem is that I think IE doesn't care if the server has stopped receiving the file and continues to upload it anyway. Hope that helps.

About the Javascript...there *is* a trick I have used to check the file size of a file, but it requires the user to load it locally. You basically create a new Image object with that file name the same way you do with image pre-loaders and check the size property of the Image object. I have used it to get file sizes of images and audio files, but it should work with other types as well. If I remember right, the Image object loading is asynchronous, so you might need to define an onload function that will be called when the file is actually loaded. I do think, though, that providing a server-side check is preferable. Comments and alternative answers

I think we can do before we upload a file Author: rajesh khanna (http://www.jguru.com/guru/viewbio.jsp?EID=1172410), Mar 31, 2005 we have

which is used to upload. we can get the size of file by using request.getContentLength() you can get a good example from sun.com. we can also do using java script we can use the File class for mozilla and an active Control for IE.(but I think the server side validation is better). thank u. How can we add file upload utility in a program Author: Jyotsna Sharma (http://www.jguru.com/guru/viewbio.jsp?EID=1249491), Jun 21, 2005 Hi, I am making some application in which i want add file upload for the users.Plz tell me the way to do it through ftp protocol or other. I have a Servlet and a Servlet Filter that is supposed to apply an xsl to it. The transformation appears to work, I get back a transformed document, but it appears (in IE) as if IE thinks its an HTML document (i.e., you see the , etc tags). Viewing source, and saving as an HTML file will display correctly. How can I correctly set the Content Type of the response? Location: http://www.jguru.com/faq/view.jsp?EID=1074630 Created: Apr 8, 2003 Author: Vincent Fischer (http://www.jguru.com/guru/viewbio.jsp?EID=1035285) Question originally posed by Vincent Fischer (http://www.jguru.com/guru/viewbio.jsp?EID=1035285 I figured this out. Many thanks go out to Matan Amir for pointing me in the right direction. I used Ethereal (I couldn't get tcptrace to work), to verify that in fact the content type was "text/xml", instead of "text/html". So, I finally figured out that instead of: response.setContentType("text/html"); I wrote: wrapper.setContentType("text/html");

I'm guessing the reason is because the response and request objects in the Filter cannot be modified... So instead, I made the changes to the wrapper. Of course, if I'd set my servlet to send the response as "text/html" this would work too, but the purpose of the assignment was to change the contentType... [See http://www.jguru.com/forums/view.jsp?EID=1072839 for the source code and more discussion. -Alex] [Todo: add "Filters" category; add this to it] I want to exclude a certain file, "*/SlideMenu.js", from a filter. Can I do it? Location: http://www.jguru.com/faq/view.jsp?EID=1074633 Created: Apr 8, 2003 Author: Eelco Cramer (http://www.jguru.com/guru/viewbio.jsp?EID=200853) Question originally posed by Garrett Smith (http://www.jguru.com/guru/viewbio.jsp?EID=745187

GZIPFilter

*.jsp

GZIPFilter

*.js

In the example above, I have a fictitious tag "exclude-pattern" that would exclude */SlideMenu.js from the filter mapping. What is the proper way to do it? -----------There is no way to exclude files from an url-pattern. You could change your mapping strategy or change the extension of the file you want to exclude (not so nice). You could configure your filter to not process certain files. Good luck. What's difference between Servlet/JSP session and EJB session? Location: http://www.jguru.com/faq/view.jsp?EID=1082544 Created: May 7, 2003 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by guru prasanth PREMIUM (http://www.jguru.com/guru/viewbio.jsp?EID=847725 From a logical point of view, a Servlet/JSP session is similar to an EJB session. Using a session, in fact, a client can connect to a server and maintain his state. But, is important to understand, that the session is maintained in different ways and, in theory, for different scopes.

A session in a Servlet, is maintained by the Servlet Container through the HttpSession object, that is acquired through the request object. You cannot really instantiate a new HttpSession object, and it doesn't contains any business logic, but is more of a place where to store objects. A session in EJB is maintained using the SessionBeans. You design beans that can contain business logic, and that can be used by the clients. You have two different session beans: Stateful and Stateless. The first one is somehow connected with a single client. It maintains the state for that client, can be used only by that client and when the client "dies" then the session bean is "lost". A Stateless Session Bean doesn't maintain any state and there is no guarantee that the same client will use the same stateless bean, even for two calls one after the other. The lifecycle of a Stateless Session EJB is slightly different from the one of a Stateful Session EJB. Is EJB Container's responsability to take care of knowing exactly how to track each session and redirect the request from a client to the correct instance of a Session Bean. The way this is done is vendor dependant, and is part of the contract. Comments and alternative answers

which will be of high performance,maintaining the session in http/jsp or EJB. Author: munish kumar (http://www.jguru.com/guru/viewbio.jsp?EID=1101096), Jul 14, 2003 if we simply have to place the objects required in session , then which will be faster.As we have to implement the scrolling in the pages.I think that accessing the object from http/jsp session will be faster then the EJB session. Am i right pls let me know. Thanks. Munish Re: which will be of high performance,maintaining the session in http/jsp or EJB. Author: Nanda Kumar (http://www.jguru.com/guru/viewbio.jsp?EID=1116828), Sep 22, 2003 Hi, I have one question regarding this... If Httpsession Object is Expired, what will happen Stateless or Stateful session bean ??? Any idea. Thanks in advance, Nanda Re[2]: If Httpsession Object is Expired, what will happen Stateless or Stateful session bean Author: Sergey Pomytkin (http://www.jguru.com/guru/viewbio.jsp?EID=1045816), Oct 29, 2003 With Stateless - nothing, once it done with your method invocation it's don't care about you. About satefull it’s up to particular app sever implementation/configuration .. Chances are if you hold reference to it in httpsession and it’s get expired (= user will never be able to release this EJB) server eventually will recycle this instance Re[2]: which will be of high performance,maintaining the session in

http/jsp or EJB. Author: Ram V.L.T (http://www.jguru.com/guru/viewbio.jsp?EID=449849), Jun 28, 2004 If Httpsession is expired irrespective of the type of the bean all the references stored in the Httpsession will be lost. Re: which will be of high performance,maintaining the session in http/jsp or EJB. Author: Murthy VVVS (http://www.jguru.com/guru/viewbio.jsp?EID=1243697), May 11, 2005 It is more of design issue rather than performance. The concept/scope of both HTTPSession and EJB Session Bean are different from each other. What if ? Author: rachna chadha (http://www.jguru.com/guru/viewbio.jsp?EID=1077370), Oct 8, 2003 I have seen that many times JSP session is still there but session bean's session expires ? Is there any way to manage this problem ? Re: What if ? Author: Bill Schnellinger (http://www.jguru.com/guru/viewbio.jsp?EID=1120424), Oct 8, 2003 you have to match the <session-timeout> in your web.xml with the statefull session timeout parameter in your application servers xml file. For example, weblogic-ejb-jar.xml has a <stateful-session-descriptor> <stateful-session-cache> <max-beans-in-cache>100 0

entry. In JBoss you will have to look at standardjboss.xml and http://www.jboss.org/j2ee/dtd/jboss_3_0.dtd and for others, you will have to look at that containers documentation to see how to set that. hope that helps An Alternative Description Author: vimarsh vasavada (http://www.jguru.com/guru/viewbio.jsp?EID=972756), Oct 8, 2003 The earlier explaination has cleared my clouds.Representing in different way .

Container View Point : 1. Servlet Container A HttpServlet.service() represents a client thread. A logical session is maintaied per such different client threads.The container manages the association rather then the Servlet.Hence Servlet from the pool of servlet instances are reusable for different threads and can be swaped in between client threads.This is why Servlet Instance variable are not thread-safe. 2. EJB Container : Stateful Session Bean. The Stateful Session Bean LOGICALLY is a "client thread with State".This thread can be Activated/Passivated as per the situation.But during this activation/passivation essentially the state is saved plus anything else instructed by the bean developer in respective methods. In other words the state mangement control is available to Bean developer also.This is what missing in servlet.In other words for Stateful Session Bean instance variable are thread safe. Designers Perspective : 1. Servlet Helps the session management but the servlet developer needs to invoke SessionManagement API to read/write. Right candidate for UserInfo,AuthInfo etc. 2.SFB A well designed component for the stateful processes. An object state is automaticaly managed by container.Threadsaftey is guranteed.Developer need not to bother.Right candidate for Order/Shopping Process. Performance wise it is a FEELING that SFB are slower then simple http sessions.Hence needs to be used with care. which is the best way to pass the value from one screen to another either hiddenor session Author: lekoria martin (http://www.jguru.com/guru/viewbio.jsp?EID=1124801), Oct 30, 2003 According to theory concept says, session is best way to pass the the value from one screen to another since there is no limitation in session. what i feel is if u keep so many data in session will it affect the network. all the session is going to be in memory in application server only know. pls suggest me when to use hidden, cookie,

session. Re: which is the best way to pass the value from one screen to another either hiddenor session Author: Kimbo Mundy (http://www.jguru.com/guru/viewbio.jsp?EID=1120338), Nov 15, 2003 Perhaps it's obvious, but don't forget about the simplest way of passing state: For small bits of data, like the page # in a list of search results, just use a parameter in the URL. Re[2]: which is the best way to pass the value from one screen to another either hiddenor session Author: sridhar Tirumala (http://www.jguru.com/guru/viewbio.jsp?EID=1139770), Jan 18, 2004 URL rewriting gives moderate performance because the data has to pass between the client and server for every request but there is a limitation on amount of data that can pass through URL rewriting. It gives moderate performance because of overhead involved on the network for passing data on every request. But session object mechanism gives better performance because it stores the session data in memory and reduces overhead on network. Only session id will be passed between client and server. But it does not scale well up on increasing session data and concurrent users because of increase in memory overhead and also increase in overhead on garbage collection. There choosing the session mechanism out of one of the above approaches not only depends on performance but also depends on scaling and security factor . The best approach to maintain a balance between performance, scalability and security. Mixture of session mechanism and Hidden fields gives both performance and scalability. By putting secure data in session and non secure data in hidden fields you can achieve better security Re[3]: which is the best way to pass the value from one screen to another either hiddenor session Author: Bill Bruns (http://www.jguru.com/guru/viewbio.jsp?EID=1150451), Mar 1, 2004 Isn't it true that there are circumstances where the session variables cannot be used? In other words, that some items must be passed by means of URL rewriting because they are being changed by javaScript code instead of JSP code. The difference is that javaScript executes on the client but JSP exectues on the server. For example, consider a page that asks if the user is a man or a woman, and has a dropdown list that changes depending on if a man or a woman is choosing (clothing types: blouse versus shirt). The dropdown list might only change at the client, not at the server. But the session variables only

exist at the server. In this case, the data can only be passed by URL parameters. Unless someone knows of a way to use javaScript to change items at the server, without using parameter passing (aka, URL rewriting)? Bill Re[4]: which is the best way to pass the value from one screen to another either hiddenor session Author: Shrinivas Vadavadagi (http://www.jguru.com/guru/viewbio.jsp?EID=1170700), May 17, 2004 You can give the same name in the form, so that you can recognise what the user has selected. Hence what ever you can do in URL rewriting can be done through the session management. But there is a limitation in this as this is no scalable. One study suggests that one can store upto 3K of data in the session after whicg there will be drop in the performance. Hence should store the data in the session which are necessary and clear the session data, if not necessary. Re[5]: which is the best way to pass the value from one screen to another either hiddenor session Author: sathish kumar (http://www.jguru.com/guru/viewbio.jsp?EID=1185907), Jul 18, 2004 i AM ACCEPTING ANY FIVE DIFFERENCE BETWEEN THEM.PLEASE IF ANY ONE FOR THIS... Tomcat 4.x and /servlet/ mapping. Location: http://www.jguru.com/faq/view.jsp?EID=1105228 Created: Jul 31, 2003 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) With Tomcat 3.x, by default the servlet container was set up to allow invoking a servet through a common mapping under the /servlet/ directory. A servlet could be accessed by simply using an url like this one: http://[domain]:[port]/[context]/servlet/[servlet full qualified name]. The mapping was set inside the web application descriptor (web.xml), located under $TOMCAT_HOME/conf. With Tomcat 4.x the Jakarta developers have decided to stop allowing this by default. The <servlet-mapping> tag that sets this mapping up, has been commented inside the default web application descriptor (web.xml), located under $CATALINA_HOME/conf:

A developer can simply map all the servlet inside the web application descriptor of its own web application (that is highly suggested), or simply uncomment that mapping (that is highly discouraged). It is important to notice that the /servlet/ isn't part of Servlet 2.3 specifications so there are no guarantee that the container will support that. So, if the developer decides to uncomment that mapping, the application will loose portabiliy. Comments and alternative answers

Tomcat 4.x and /servlet/ mapping. In http://[domain]:[port]/[context]/servlet/[servlet full qualified name].What is context in this url? Author: Nataraj CV (http://www.jguru.com/guru/viewbio.jsp?EID=1221732), Jan 19, 2005 Please clarify ASAP, Thanks in advance. Cross Site Scripting (XSS) with Jakarta Tomcat. Location: http://www.jguru.com/faq/view.jsp?EID=1105229 Created: Jul 31, 2003 Author: Alessandro A. Garbagnati (http://www.jguru.com/guru/viewbio.jsp?EID=32727) Question originally posed by Michael Murphy (http://www.jguru.com/guru/viewbio.jsp?EID=1090804 Hi, The XSS vulnerability has been found at the time Tomcat 4.0.3 has been released (and 4.1.2 was in beta). The problem was connected to the fact that it was possible to run some specific classes simply using the /servlet/ mapping. The Jakarta group that is working on Tomcat has immediately found a solution to the problem. The simple, but working solution, was to comment the /servlet/ mapping from the default web application descriptor (web.xml), located under the $TOMCAT_HOME/conf. This has been done sinc 4.1.3 beta. A developer can still uncomment the /servlet/ mapping, but on a standard installation, that mapping is not available. Personal note: To be honest, I think that this is also a good choice for writing clearer web application. What is GlassFish? Location: http://www.jguru.com/faq/view.jsp?EID=1255621 Created: Jul 29, 2005 Author: John Zukowski (http://www.jguru.com/guru/viewbio.jsp?EID=7) The GlassFish Project is Sun's open source application server project. Found at https://glassfish.dev.java.net/, you can participate in the development of the latest

version of Sun's Java System Application Server PE 9.0. It is based on Java Enterprise Edition 5.

Servlets Faq From Jguru

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Error log this session:

Look out

Today's Message:

One: "+one[0]+"

Two: "+two[0]+"

Three: "+three[0]+"

Cookie Information

Cookie Information

Cookies in Session

Session Information

Sample Web Application Directory Structure

Long Task

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Current

Status

Waiting...

Done

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Done

Waiting...

Done

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Servlets Faq From Jguru

Overview

More details

Error log this session:

Look out

Today's Message:

One: "+one[0]+"

Two: "+two[0]+"

Three: "+three[0]+"

Cookie Information

Cookie Information

Cookies in Session

Session Information

Sample Web Application Directory Structure

Long Task Page

Current Status

Waiting...

Done

Waiting...

Done

Waiting...

Done

Download in Progress

Please wait.

Actual Page is being displayed

Waiting...

Hello World Applet

This is the Source Servlet

Target's output

Related Documents

Servlets Faq From Jguru

Collections Faq From Jguru

Serialization Faq From Jguru

Threads Faq From Jguru

Transactions Faq From Jguru

Struts Faq From Jguru

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Page

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