Initial Requirement to Start
Before we starts with our first Hello World Struts 2 Example, we will need few tools.
- JDK 1.5 above (download)
- Tomcat 5.x above or any other container (Glassfish, JBoss, Websphere, Weblogic etc) (download)
- Eclipse 3.2.x above (download)
- Apache Struts2 JAR files:(download). Following are the list of JAR files required for this application.
- commons-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.
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 wizard screen.
After selecting Dynamic Web Project, press
Next.
Write the name of the project. For example
StrutsHelloWorld.
Once this is done, select the target runtime environment (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 not exists.
Login Application
Our
goal is to create a basic Struts2 application with a Login page. User
will enter login credential and if authenticated 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.
Mapping Struts2 in WEB.xml
As discussed in the previous article (
Introduction to Struts2),
the entry point of Struts2 application will be the Filter define in
deployment descriptor (web.xml). Hence we will define an entry of
org.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="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">
<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>
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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.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter
</filter-class>
</filter>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
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The Action Class
We
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 (this.username.equals("admin")
&& this.password.equals("admin123")) {
return "success";
} else {
return "error";
}
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
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Note
that, above action class contains two fields, username and password
which will hold the values from form and also contains an
execute() method that will authenticate the user. In this simple example, we are checking 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 required attributes and method.
The
execute()
method returns a String value which will determine the result page.
Also, in Struts2 the name of the method is not fixed. In this example we
have define method execute(). You may want to define a 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 which contains
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 be present in WEB-INF/classes
folders when the source is compiled. Thus we will create a source folder
called
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.
label.username= Username
label.password= Password
label.login= Login
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The JSP
We 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 welcome 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 | ViralPatel.net</title>
</head>
<body>
<h2>Struts 2 - Login Application</h2>
<s:actionerror />
<s:form action="login.action" method="post">
<s:textfield name="username" key="label.username" size="20" />
<s:password name="password" key="label.password" size="20" />
<s:submit method="execute" key="label.login" align="center" />
</s:form>
</body>
</html>
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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>
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Note
that we have used struts2 <s:> tag to render the textboxes and
labels. Struts2 comes with a powerful built-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 loaded from the classpath of the project. We will define struts.xml file in the
resources folder. Create file struts.xml in 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"
"http://struts.apache.org/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>
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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 returns success, 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 the resource bundle file that we created in above
steps. We just have to specify name of resource bundle file without
extension (ApplicationResources without .properties).
Our
LoginAction contains the method execute() which is the default method
getting called by Sturts2. If the name 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">
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Almost Done
We
are almost done with the application. You may want to run the
application now and see the result yourself. 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 -> Server and 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 wrong credential, she is redirected to Login page.
But no error message is displayed. User does not know what just
happened. A good application always show proper error messages to user.
So we must display an error 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:
label.username= Username
label.password= Password
label.login= Login
error.login= Invalid Username/Password. Please try again.
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Also
we need to add logic in LoginAction to add error message if user is not
authenticated. But there is one problem. Our error message is specified
in ApplicationResources.properties file. We must specify key
error.login in LoginAction and the message should be displayed on JSP
page.
For this we must implement
com.opensymphony.xwork2.TextProvider interface which provides method
getText().
This method returns String value from resource bundle file. We just
have to pass the key value as argument to getText() method. The
TextProvider interface defines several method that we must implement in
order to get hold on getText() method. But we don’t want to spoil our
code by adding all those 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 extend our 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 into it. 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 (this.username.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) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
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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
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