Tutorial_Create Struts 2 Application in Eclipse

Things We NeedBefore we starts with our first Hello World Struts 2 Example, we will need few tools.

1. JDK 1.5 above (download)

2. Tomcat 5.x above or any other container (Glassfish, JBoss, Websphere, Weblogic etc) (download)

3. Eclipse 3.2.x above (download)

4. Apache Struts2 JAR files:(download). Following are the list of JAR files required for this mons-logging-1.0.4.jar

freemarker-2.3.8.jar

ognl-2.6.11.jar

struts2-core-2.0.12.jar

xwork-2.0.6.jar

Note that depending on the current version of Struts2, the version number of above jar files may change.Our Goal

Our goal is to create a basic Struts2 application with a Login page. User will enter login credential and ifauthenticated successfully she will be redirected to a Welcome page which will display message ”Howdy,<username>…!“. If user is not authenticated, she will be redirected back to the login page.

Getting Started

Let us start with our first Struts2 based application.

Open Eclipse and goto File -> New -> Project and select Dynamic Web Project in the New Project wizardscreen.

After selecting Dynamic Web Project, press

Next.

Write the name of the project. For example StrutsHelloWorld. Once this is done, select the target runtimeenvironment (e.g. Apache Tomcat v6.0). This is to run the project inside Eclipse environment. After this

press Finish.

Once the project is created, you can see its structure in Project Explorer.

Now copy all the required JAR files in WebContent -> WEB-INF -> lib folder. Create this folder if it does notexists.

Mapping Struts2 in WEB.xml

As discussed in the previous article (Introduction to Struts2), the entry point of Struts2 application will be theFilter define in deployment descriptor (web.xml). Hence we will define an entry

oforg.apache.struts2.dispatcher.FilterDispatcher class in web.xml.

Open web.xml file which is under WEB-INF folder and copy paste following code.

<?xml version="1.0" encoding="UTF-8"?><web-app id="WebApp_9" version="2.4" xmlns="/xml/ns/j2ee" xmlns:xsi="/2001/XMLSchema-instance" xsi:schemaLocation="/xml/ns/j2ee /xml/ns/j2ee/web- <display-name>Struts2 Application</display-name>

<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><welcome-file-list><welcome-file>Login.jsp</welcome-file></welcome-file-list></web-app>

The above code in web.xml will map Struts2 filter with url/*. The default url mapping for struts2 application will be/*.action. Also note that we have define Login.jsp as welcome file. Note: The FilterDispatcher filter is deprecated since Struts version 2.1.3. If you are using latest version of Struts2 (> 2.1.3) use StrutsPrepareAndExecuteFilter class instead.<filter><filter-name>struts2</filter-name><filter-class>org.apache.struts2.dis

patcher.ng.filter.StrutsPrepareAndExecuteFilter</</filter><filter-mapping><filter-name>struts2</filter-name><url-pattern>/*</url-pattern></filter-mapping>

The Action ClassWe will need an Action class that will authenticate our user and holds the value for username and password. For this we will create a package net.viralpatel.struts2 in the source folder. This package will contain the action file.

Create a class called LoginAction in net.viralpatel.struts2 package with following content. package net.viralpatel.struts2; public class LoginAction{ private String username; private String password; public String execute(){ if (ername.equals("admin")&& this.password.equals("admin123")){ return"success";} else{ return"error";

} } public String getUsername() { return username; } public void setUsername(String username) { ername = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; }}

Note that, above action class contains two fields, username and password which will hold the values fromform and also contains an execute() method that will authenticate the user. In this simple example, we arechecking if username is admin and password is admin123.

Also note that unlike Action class in Struts1, Struts2 action class is a simple POJO class with requiredattributes and method.

The execute() method returns a String value which will determine the result page. Also, in Struts2 thename of the method is not fixed. In this example we have define method execute(). You may want to definea method authenticate() instead.

The ResourceBundle

ResourceBundle is very useful Java entity that helps in putting the static content away from the source file.Most of the application define a resource bundle file such as ApplicationResources.properties file whichcontains static messages such as Username or Password and include this with the application.

ResourceBundle comes handy when we want to add Internationalization (I18N) support to an application.We will define an ApplicationResources.properties file for our application. This property file should bepresent in WEB-INF/classes folders when the source is compiled. Thus we will create a source foldercalled resources and put the ApplicationResources.properties file in it.

To create a source folder, right click on your project in Project Explorer and select New -> Source Folder.

Specify folder name resources and press Finish. Create a file ApplicationResources.properties under resources folder.

Copy following content in ApplicationResources.properties. ername= Username label.password= Password label.login= Login

The JSPWe will create two JSP files to render the output to user. Login.jsp will be the starting point of our application which will contain a simple login form with username and password. On successful authentication, user will be redirected to Welcome.jsp which will display a simple welcom

e message. Create two JSP files Login.jsp and Welcome.jsp in WebContent folder of your project. Copy following content into it.

Login.jsp<%@ page contentType="text/html; charset=UTF-8"%><%@ taglib prefix="s" uri="/struts-tags"%><html><head><title>Struts 2 - Login Application| </title></head><body><h2>Struts 2 - Login Application</h2><s:actionerror/><s:form action="login.action" method="post"><s:textfield name="username" key="ername" size="20"/><s:password name="password" key="label.password" size="20"/><s:submit method="execute" key="label.login" align="center"/>

</s:form></body></html>

Welcome.jsp

<%@ page contentType="text/html; charset=UTF-8"%><%@ taglib prefix="s" uri="/struts-tags"%><html><head><title>Welcome</title></head> <body> <h2>Howdy, <s:property value="username" />...!</h2></body></html>

Note that we have used struts2 <s:> tag to render the textboxes and labels. Struts2 comes with a powerfulbuilt-in tag library to render UI elements more efficiently.

The struts.xml file

Struts2 reads the configuration and class definition from an xml file called struts.xml. This file is loadedfrom the classpath of the project. We will define struts.xml file in the resources folder. Create file struts.xmlin resources folder.

Copy following content into struts.xml.

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN" "/dtds/struts-2.0.dtd"> <struts> <constant name="struts.enable.DynamicMethodInvocation" value="false" /> <constant name="struts.devMode" value="false" /> <constant name="struts.custom.i18n.resources" value="ApplicationResources" /> <package name="default" extends="struts-default" namespace="/"> <action name="login" class="net.viralpatel.struts2.LoginAction"> <result name="success">Welcome.jsp</result> <result name="error">Login.jsp</result> </action> </package></struts>

Note that in above configuration file, we have defined Login action of our application. Two result paths are

mapped with LoginAction depending on the outcome of execute() method. If execute() method returnssuccess, user will be redirected to Welcome.jsp else to Login.jsp.

Also note that a constant is specified with name struts.custom.i18n.resources. This constant specify theresource bundle file that we created in above steps. We just have to specify name of resource bundle filewithout extension (ApplicationResources without .properties).

Our LoginAction contains the method execute() which is the default method getting called by Sturts2. If thename of method is different, e.g. authenticate(); then we should specify the method name in<action> tag.<action name="login" method="authenticate" class="net.viralpatel.struts2.LoginAction">

Almost Done

We are almost done with the application. You may want to run the application now and see the resultyourself. I assume you have already configured Tomcat in eclipse. All you need to do:

Open Server view from Windows -> Show View -> Server. Right click in this view and select New -> Serverand add your server details.

To run the project, right click on Project name from Project Explorer and select Run as -> Run on Server(Shortcut: Alt+Shift+X, R)

But there is one small problem. Our application runs perfectly fine at this point. But when user enters wrongcredential, she is redirected to Login page. But no error message is displayed. User does not know whatjust happened. A good application always show proper error messages to user. So we must display anerror message Invalid Username/Password. Please try again when user authentication is failed.

Final Touch

To add this functionality first we will add the error message in our ResourceBundle file.

Open ApplicationResources.properties and add an entry for error.login in it. The final

ApplicationResources.properties will look like:

ername= Usernamelabel.password= Passwordlabel.login= Loginerror.login= Invalid Username/Password. Please try again.

Also we need to add logic in LoginAction to add error message if user is not authenticated. But there is oneproblem. Our error message is specified in ApplicationResources.properties file. We must specify keyerror.login in LoginAction and the message should be displayed on JSP page.

For this we must implement com.opensymphony.xwork2.TextProvider interface which provides

methodgetText(). This method returns String value from resource bundle file. We just have to pass thekey value as argument to getText() method. The TextProvider interface defines several method that wemust implement in order to get hold on getText() method. But we don’t want to spoil our code by adding allthose methods which we do not intend to use. There is a good way of dealing with this problem.

Struts2 comes with a very useful class com.opensymphony.xwork2.ActionSupport. We just have to extendour LoginAction class with this class and directly use methods such as getText(), addActionErrors() etc.

Thus we will extend the LoginAction class with ActionSupport class and add the logic for error reporting intoit. The final code in LoginAction must look like:

package net.viralpatel.struts2; import com.opensymphony.xwork2.ActionSupport; public class LoginAction extends ActionSupport { private String username; private String password; public String execute() { if (ername.equals("admin") && this.password.equals("admin123")) { return "success"; } else { addActionError(getText("error.login")); return "error"; } } public String getUsername() { return username; } public void setUsername(String username) { ername = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; }}

And that’s it. Our first Hello World Struts2 Application is now ready.

That’s All Folks

Execute the application in Eclipse and run it in your favorite browser.

Login page

Welcome page

Login page with error

Download Source Code

Source Code without JAR files (9 KB)

Source Code with JAR files (3 MB)

Moving On

Now that we have created our first webapp using Struts2 framework, we know how the request flows inStruts2. We also know the use of struts.xml and properties file. In this application we implemented a

preliminary form of validation. In next part we will learn more about Validation Framework in Struts2 andimplement it in our example.

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