Step By Step Guide For Building A Simple Struts Application

03/26/2007

Step by Step Guide for building a simple Struts Application

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In this session, we will try to build a very simple Struts application step by step.

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Sang Shin [email protected] www.javapassion.com/j2ee Java™ Technology Evangelist Sun Microsystems, Inc. 2

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Sample App We are going to build

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Sample App ? ?

Keld Hansen's submit application Things to do – – – – –

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Creating ActionForm object Creating Action object Forwarding at either success or failure through configuration set in struts-config.xml file Input validation Internationalizaition

You can also build it using NetBeans 4

The sample application we are going to use and show is Keld Hansen's submit application. The source files and ant build.xml script can be found in the handson/homework material you can download from class website. This is a simple application but it uses most of Struts framework.

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Steps to follow

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Now let's take a look at the steps you will follow.

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Steps 1.Create development directory structure 2.Write web.xml 3.Write struts-config.xml 4.Write ActionForm classes 5.Write Action classes 6.Create ApplicationResource.properties 7.Write JSP pages 8.Build, deploy, and test the application 6

So this is the list of steps. Of course, you don't exactly follow these steps in sequence. In fact, it is expected that some of these steps will be reiterated.

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Step 1: Create Development Directory Structure

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The first step is to create development directory structure.

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Development Directory Structure ?

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Same development directory structure for any typical Web application Ant build script should be written accordingly If you are using NetBeans, the development directory structure is automatically created

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The source directory structure is the same directory structure we used for other Web application development under Java WSDP. Of course, the build.xml script should be written accordingly.

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Step 2: Write web.xml Deployment Descriptor

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Step 2 is to write web.xml file.

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web.xml ?

Same structure as any other Web application – –

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There are several Struts specific elements –

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ActionServlet is like any other servlet Servlet definition and mapping of ActionServlet needs to be specified in the web.xml

Location of Struts configuration file

Struts tag libraries could be defined 10

Because Struts application is a genuine Web application, it has to follow the same rules that any Web application has to follow. And one of them is the presence of web.xml deployment descriptor file. The web.xml file should define ActionServlet, which is the controller piece that is provided by the Struts framework, and its mapping with URI. As you will see in the example web.xml file in the following slide, there are several Struts specific initialization parameters. Also the Struts tag libraries also need to be declared.

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Example: web.xml 1 2 <web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> 3 <servlet> 4 <servlet-name>action 5 <servlet-class>org.apache.struts.action.ActionServlet 6 7 <param-name>config 8 <param-value>/WEB-INF/struts-config.xml 9 10 ... 11 12 <servlet-mapping> 13 <servlet-name>action 14 *.do 15 11

This is the continuation of the web.xml file. Here you see the declarations of Struts tag libraries.

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Step 3: Write struts-config.xml

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The next step is to write struts-config.xml

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struts-config.xml ?

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Identify required input forms and then define them as elements Identify required Action's and then define them as elements within element –

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make sure same value of name attribute of is used as the value of name attribute of element define if you want input validation

Decide view selection logic and specify them as element within element 13

(read theslide)

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struts-config.xml: 1 2 3 4 5 6 7 8 9 10 11 12

<struts-config>
name="submitForm" type="submit.SubmitForm"/>



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This is section of the struts-config.xml file. Here we define one element. The value of the name attribute of the element is the same as the value of name attribute of element in the following slide.

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struts-config.xml: 1

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This is an example of element.

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Step 4: Write ActionForm classes

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ActionForm Class ?

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Extend org.apache.struts.action.ActionForm class Decide set of properties that reflect the input form Write getter and setter methods for each property Write validate() method if input validation is desired

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Write ActionForm class 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

package submit; import javax.servlet.http.HttpServletRequest; import org.apache.struts.action.*; public final class SubmitForm extends ActionForm { /* Last Name */ private String lastName = "Hansen"; // default value public String getLastName() { return (this.lastName); } public void setLastName(String lastName) { this.lastName = lastName; } /* Address */ private String address = null; public String getAddress() { return (this.address); } public void setAddress(String address) { this.address = address; } ...

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Write validate() method 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

public final class SubmitForm extends ActionForm { ... public ActionErrors validate(ActionMapping mapping, HttpServletRequest request) { ... // Check for mandatory data ActionErrors errors = new ActionErrors(); if (lastName == null || lastName.equals("")) { errors.add("Last Name", new ActionError("error.lastName")); } if (address == null || address.equals("")) { errors.add("Address", new ActionError("error.address")); } if (sex == null || sex.equals("")) { errors.add("Sex", new ActionError("error.sex")); } if (age == null || age.equals("")) { errors.add("Age", new ActionError("error.age")); } return errors; } ..

19 a When this “LogonForm” is associated with controller, it will be passed to the controller whenever it’s service is requested by the user. JSP pages acting as the view for this LogonForm are automatically updated by Struts with the current values of the UserName and Password properties. If the user changes the properties via the JSP page, the LogonForm will automatically be updated by Struts But what if the user screws up and enters invalid data? ActionForms provide validation… Before an ActionForm object is passed to a controller for processing, a “validate” method can be implemented on the form which allows the form to belay processing until the user fixes invalid input as we will see on the next slide...

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Step 5: Write Action classes

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Action Classes ? ?

Extend org.apache.struts.action.Action class Handle the request –

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Decide what kind of server-side Model objects (EJB, JDO, etc.) can be invoked

Based on the outcome, select the next view

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Example: Action Class 1 package submit; 2 3 import javax.servlet.http.*; 4 import org.apache.struts.action.*; 5 6 public final class SubmitAction extends Action { 7 8 public ActionForward execute(ActionMapping mapping, 9 ActionForm form, 10 HttpServletRequest request, 11 HttpServletResponse response) { 12 13 SubmitForm f = (SubmitForm) form; // get the form bean 14 // and take the last name value 15 String lastName = f.getLastName(); 16 // Translate the name to upper case 17 //and save it in the request object 18 request.setAttribute("lastName", lastName.toUpperCase()); 19 20 // Forward control to the specified success target 21 return (mapping.findForward("success")); 22 } 23 }

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Step 6: Create ApplicationResource.properties and Configure web.xml accordingly

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Resource file ? ?

Create resource file for default locale Create resource files for other locales

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Example: ApplicationResource.properties 1 2 3 4 5 6 7

errors.header=

Validation Error(s)

errors.footer=

---

error.lastName=

Enter your last name error.address=

Enter your address error.sex=

Enter your sex error.age=

Enter your age

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Step 7: Write JSP pages

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JSP Pages ? ?

Write one JSP page for each view Use Struts tags for – –

Handing HTML input forms Writing out messages

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Example: submit.jsp 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

<%@ page language="java" %> <%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %> <%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %> <%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %>

Example Submit Page

Last Name:
Address:
Sex: Male Female
Married:
Age: 0-19 20-49 50-


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Example: submit.jsp 1 2 3 4 5 6 7 8 9 10 11 12 13

Hello young old

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Step 8: Build, Deploy, and Test Application

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Accessing Web Application

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Accessing Web Application

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Accessing Web Application

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Passion!

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