Creating a Struts-2 hello world application on eclipse

Hi,

This is a getting started tutorial for struts-2. Struts-2 is similar to struts-1 but there are certain changes in terms of functionality and syntax.
The main components needed to create the demo application are as follows:
1. Eclipse indigo.
2. Struts-2 distribution:- To download struts-2 distribution go to 'http://struts.apache.org/download.cgi#struts238-SNAPSHOT' and download 'Full Distribution:struts-2.3.7-all.zip (76mb) [PGP] [MD5] '
3. Tomcat 7.

That is all you need to create a struts application.

Application Structure: The demo application that we are going to create using struts-2 is a login application. The application will be having following components:
1. index.jsp
2. HelloWorld.jsp
3. error.jsp
4. HelloWorldAction.java

Now the application proceeds as follows:
1. When the application starts the user is presented with 'index.jsp' where the user enters username and password.
2. On submitting the 'index.jsp' page the request is directed to Action class which in our case is 'HelloWorldAction.java'.
3. 'HelloWorldAction.java' checks whether login data is valid or not. If login is valid then user is directed to 'HelloWorld.jsp' page else user is directed to 'error.jsp' page.


Getting Started:
With above grounds we will now start creating our application.

Steps:
1. Unzip the struts-2 binary that you downloaded above. You will get following files in the 'lib' folder of unzipped distribution (nearly 84 files will be there):

2. Create a dynamic web project in Eclipse J2EE Indigo.
3. Select following jar files from the unzipped distribution and paste them in the 'WebContent-> WEB-INF->lib' folder:
     a. asm-3.3.jar
     b. asm-commons-3.3.jar
     c. asm-tree-3.3.jar
     d. commons-fileupload-1.2.2.jar
     e. commons-io-2.0.1.jar
     f. commons-lang3-3.1.jar
     g. freemarker-2.3.19.jar
     h. javassist-3.11.0.GA.jar
     i. ognl-3.0.5.jar
     j. struts2-core-2.3.4.1.jar
     k. xwork-core-2.3.4.1.jar
4. The structure of your project will look like:

5. Notice all the files present under 'lib' folder.
6. Add three JSP files 'index.jsp', 'HelloWorld.jsp' and 'error.jsp' under the 'WebContent' folder.

7. Now create a package under src and name it 'rajeev.struts2.action'.
8. Add out action class 'HelloWorldAction.java' under the package 'rajeev.struts2.action' created above.
9. Add an XML file 'struts.xml' under the src folder.
10. The final project structure will look like:

We are done with adding the components to the project in eclipse. Now we need to add necessary code to these components.

Code Listings:
 Now we will be adding code to various components.

1. Action: Firstly we will be adding code to out action class which is 'HelloWorldAction.java'. Add following code:

package rajeev.struts2.action;

public class HelloWorldAction {

    private String name;
    private String pass;

       public String execute1() throws Exception {

           String result=null;
           if(name.equals("rajeev")  && pass.equals("password"))

           {

                   result="success";

           }

           else

           {

                  result="fail";

           }
          return result;
       }
      
       public String getName() {
          return name;
       }

       public void setName(String name) {
          this.name = name;
       }

    public String getPass() {
        return pass;
    }

    public void setPass(String pass) {
        this.pass = pass;
    }
}

The action class is a simple class that doesn't extends any other class. It has two string parameters to hold the User Name and Password given by the user and a method 'execute1()' that holds the logic to check whether the login is valid or not.

2. web.xml: Following code snipped is needed to be added to web.xml of your web application:
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>struts</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
 
  <filter>
    <filter-name>struts2</filter-name>
    <filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class>
</filter>

<filter-mapping>
   <filter-name>struts2</filter-name>
   <url-pattern>/*</url-pattern>
</filter-mapping>

</web-app>

The code highlighted in yellow is the extra code that tells your web application that it is using struts2.


3. struts.xml: Next we need to update 'struts.xml' with following code:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
   "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
   "http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<constant name="struts.devMode" value="true" />
   <package name="default" extends="struts-default">
    
      <action name="hello"
            class="rajeev.struts2.action.HelloWorldAction"
            method="execute1" >
            <result name="success">/HelloWorld.jsp</result>
            <result name="fail">/error.jsp</result>
      </action>
   </package>
</struts>
Here the lines highlighted in yellow specify the action declaration rest is struts specific code. Now in the <action> tag we have following attributes with following meaning:
      a. name    // specifies the name with which the action will be accessed.
      b. class    // specifies the class that will act as action.
      c. method   // specifies the method that must be executed when the action executes.
next we have two <result> tags. These tags define which view will be displayed depending on the value returned from the 'execute1()' method of the action. If 'execute1()' returns "success" then 'HelloWorld.jsp' page will be displayed, if 'execute1()' method of the action returns "fail" then 'error.jsp' page will be displayed.

4. View(jsp files): now we need to add these code segments to the three jsp files:

    index.jsp
    <%@ page language="java" contentType="text/html; charset=ISO-8859-1"
   pageEncoding="ISO-8859-1"%>
<%@ taglib prefix="s" uri="/struts-tags"%>
   <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Hello World</title>
</head>
<body>
   <h1>Hello World From Struts2</h1>
   <form action="hello" method="post">     
      User Name: <input type="text" name="name"/> <br>
      Password: <input type="text" name="pass" /><br>
      <input type="submit" value="Say Hello"/>
   </form>
</body>
</html>
Here the 'action' attribute tells to which action class the request should be directed. In our case the request will be directed to 'hello' action that maps to 'rajeev.struts2.action.HelloWorldAction' in struts.xml above. Here the 'name' attribute of the HTML form will be automatically mapped to the 'name' attribute of 'HelloWorldAction.java' and 'pass' attribute of the HTML form will be automatically mapped with the 'pass' attribute of 'HelloWorldAction.java'.

HelloWorld.jsp
<%@ page contentType="text/html; charset=UTF-8" %>
<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<head>
<title>Hello World</title>
</head>
<body>
   <h2>HelloWorld.jsp</h2><br><br>
   Hello World, <s:property value="name"/>
</body>
</html>
Here the highlighted segment is the code related to struts-2 rest is HTML. Here the 'value' attribute will be mapped to the 'name' attribute of the 'HelloWorldAction.java'.

error.jsp
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<h2>HelloWorld.jsp</h2><br><br>
Error in login.
</body>
</html>
This jsp file is a simple HTML file with no struts-2 specific code.

Execution:
Now we are done with configuring and creating our application. To execute the application right click on the project in the Project Explorer in eclipse and run as 'Run On Server', after the server starts running you will be displayed with index.jsp file.

if you enter correct User Name and Password then you will get 'HelloWorld.jsp' page:

However if the credentials entered are wrong then 'error.jsp' page will be displayed:

I hope this tutorial will help as a start up tutorial for struts-2 application.
Feel free to submit your queries and suggestions.

Thanks.