Configuring Web Servers And Web Applications

Configuring web servers and web applications

Configuring web servers and web applications

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Server configuration vs. application configuration • A web server may run several web application • Server configuration – Affects all web application running on the server – Port number – Reference to username/password database

• Application configuration – – – – – –

Affects only one web application Welcome files Mapping of Servlet names Pages to handle errors Setting session timeout Securing the web application Configuring web servers and web applications

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Server configuration • No standard – Different web servers are configured in different ways

• Tomcat – Configuration described in the file server.xml – TOMCAT_DIR/conf/server.xml • C:\Program Files\netbeans-5.5\enterprise3\apache-tomcat5.5.17\conf\server.xml – Used if you run Tomcat outside NetBeans

• C:\Documents and Settings\anders\.netbeans\5.5\apachetomcat-5.5.17_base\conf\server.xml – Used if you run Tomcat inside NetBeans Configuring web servers and web applications

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Web application configuration • Standard – All Java enabled web servers should do it the same way

• Configuration described in the file WEBINF/web.xml • C:\andersb\wspj\login\web\WEB-INF\web.xml • C:\Program Files\netbeans-5.5\enterprise3\apachetomcat-5.5.17\webapps\VerySimple\WEB-INF\web.xml

Configuring web servers and web applications

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The structure of web.xml • The file web.xml is an XML file – Elements are tagged – The structure of the file is described in a DTD (Document Type Definition) file • • • •

It’s not free format! Names on elements Sub-elements Sequence of elements

• Web.xml can be edited – Using any text editor • Easy to make mistakes

– Using NetBeans • NetBeans guides you Configuring web servers and web applications

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Editing web.xml with NetBeans

Configuring web servers and web applications

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Assigning names to URLs • Servlets are Java classes – First letter in the Servlet name should be capital – Servlet class should be in a Java package

• Problem – URL will look like …/package/ServletName • Package name is ugly • Capital letter

• Solution – Assign the Servlet a virtual name in web.xml – <servlet> <servlet-name>virtualname <servlet-class>package.ClassName – NetBeans does this when you create a new Servlet Configuring web servers and web applications

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Custom URLs • Sometimes you want to make a virtual URL for a Servlet (or JSP) – Usually shorter than the original URL – <servlet-mapping> <servlet-name>virtualname /someurl – NetBeans does this when you create a new Servlet Configuring web servers and web applications

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Remapping the /servlet URL pattern • Sometimes you don’t want users to call Servlets directly – Only through custom URLs – Make a special Servlet to say “sorry, no entrance” – Redirect all request for /servlet/* to this special Servlet – OH Listing 5.5 (page 290), web.xml, disabling the invoker servlet. Configuring web servers and web applications

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Initialization parameters • Servlets (and JSP) may need initialization parameters – – – –

Usually read and used in the init() method The init() method is executed ONCE. The doGet() method is executed at each request Initialization parameters are (name, value) pair

• Example – OH Listing 5.7 InitServlet.java – OH Listing 5.8 web.xml, initialization parameters

Configuring web servers and web applications

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Welcome pages • If a URL does not refer to a file – http://laerer.rhs.dk/andersb/ – Which file to send in the response?

• Web application holds a prioritized list of welcome files – Typically: index.html, index.jsp, etc. – <welcome-file-list> – <welcome-file>index.jsp – <welcome-file>index.html – Configuring web servers and web applications

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Pages to handle errors • Two types of errors – HTTP status codes (not 2xx) • Called error codes in the Java terminology

– Java exceptions • No caught by the Servlets

• Errors can be caught and special pages send as response – Like a global try block – OH Listing 5.13 + 5.14, page 307 – OH Listing 5.17 + 5.18, page 310 Configuring web servers and web applications

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Session timeout • When a session has been inactive for some time it should be deleted – To save memory in the server machine – <session-config> – <session-timeout> – 30 – – – Time unit is minutes Configuring web servers and web applications

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Deployment • The file web.xml is called – “Web application deployment descriptor”

• Deployment – Military: Inserting material and people into a battle – Application: Moving software into a new environment • Moving a web application into a new web server

Configuring web servers and web applications

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Deploying a web application • When you build a web application you produce a WAR file – WAR: Web Application Archive • JAR: Java Application Archive

– Zip file holding class files, web.xml, images, etc. But not conf/server.xml

• WAR files can be moved to other servers – Put in the SERVER_HOME/webapps catalog Configuring web servers and web applications

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