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Struts 2 Hello World Example

2015-09-15 14:04 561 查看
In this example, we show you how to create a hello world example in Struts 2.

The following libraries or tools are used :

Maven 3

Eclipse 3.7

Struts 2.3.1.2

1. Final project structure

Let review the final project structure of this tutorial, in case you get lost in later steps.



2. Struts2 dependencies

Use Maven to download the entire Struts2 dependencies. Add “
struts2-core
” in 
pom.xml
.

File : 
pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion>
<groupId>com.mkyong.common</groupId>
<artifactId>Struts2Example</artifactId>
<packaging>war</packaging>
<version>com.mkyong.common</version>
<name>Struts2Example Maven Webapp</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.struts</groupId>
<artifactId>struts2-core</artifactId>
<version>2.3.1.2</version>
</dependency>
</dependencies>
<build>
<finalName>Struts2Example</finalName>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.2</version>
<configuration>
<source>1.6</source>
<target>1.6</target>
</configuration>
</plugin>
</plugins>
</build>
</project>


3. Convert to Eclipse project

Compile and convert the to Eclipse web project in command prompt :

mvn eclipse:eclipse -Dwtpversion=2.0


Review the Eclipse 
.classpath
file, the following Struts2 dependencies are downloaded :

File : 
.classpath

<classpath>
<classpathentry kind="src" path="src/main/java" including="**/*.java"/>
<classpathentry kind="src" path="src/main/resources" excluding="**/*.java"/>
<classpathentry kind="output" path="target/classes"/>
<classpathentry kind="var" path="M2_REPO/asm/asm/3.3/asm-3.3.jar"/>
<classpathentry kind="var" path="M2_REPO/asm/asm-commons/3.3/asm-commons-3.3.jar"/>
<classpathentry kind="var" path
4000
="M2_REPO/asm/asm-tree/3.3/asm-tree-3.3.jar"/>
<classpathentry kind="var" path="M2_REPO/commons-fileupload/commons-fileupload/1.2.2/commons-fileupload-1.2.2.jar" />
<classpathentry kind="var" path="M2_REPO/commons-io/commons-io/2.0.1/commons-io-2.0.1.jar"/>
<classpathentry kind="var" path="M2_REPO/commons-lang/commons-lang/2.5/commons-lang-2.5.jar"/>
<classpathentry kind="var" path="M2_REPO/org/freemarker/freemarker/2.3.18/freemarker-2.3.18.jar"/>
<classpathentry kind="var" path="M2_REPO/javassist/javassist/3.11.0.GA/javassist-3.11.0.GA.jar"/>
<classpathentry kind="var" path="M2_REPO/junit/junit/3.8.1/junit-3.8.1.jar"/>
<classpathentry kind="var" path="M2_REPO/ognl/ognl/3.0.4/ognl-3.0.4.jar"/>
<classpathentry kind="var" path="M2_REPO/org/apache/struts/struts2-core/2.3.1.2/struts2-core-2.3.1.2.jar"/>
<classpathentry kind="lib" path="C:/Program Files/Java/jdk1.6.0_13/lib/tools.jar"/>
<classpathentry kind="var" path="M2_REPO/org/apache/struts/xwork/xwork-core/2.3.1.2/xwork-core-2.3.1.2.jar"/>
<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
</classpath>


4. JSP view pages

A JSP login page to use the Struts 2 tags to display username and password input fields and submit button.

Fie : 
login.jsp

<%@ page contentType="text/html; charset=UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags"%>
<html>
<head></head>
<body>
<h1>Struts 2 Hello World Example</h1>

<s:form action="Welcome">
<s:textfield name="username" label="Username" />
<s:password name="password" label="Password" />
<s:submit />
</s:form>

</body>
</html>


File : 
welcome_user.jsp
– A JSP view page to display a welcome message to user.

<%@ page contentType="text/html; charset=UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags"%>
<html>
<head></head>
<body>
<h1>Struts 2 Hello World Example</h1>

<h2>
Hello
<s:property value="username" />
</h2>

</body>
</html>


Both Struts 1 and Struts 2 has very similar UI tags syntax, just a little different in term of naming the HTML elements, for example :

Struts 1

<%@taglib uri="http://struts.apache.org/tags-html" prefix="html"%>
<html:form action="Welcome">
<html:text property="username"/>
</html:form>


Struts 2

<%@ taglib prefix="s" uri="/struts-tags" %>
<s:form action="Welcome">
<s:textfield name="username" label="Username"/>
</s:form>


5. Action, put all business logic here

A simple Struts2 Action class, it’s used to declared all the business logic inside.

File : 
WelcomeUserAction.java

package com.mkyong.user.action;

public class WelcomeUserAction{

private String username;

public String getUsername() {
return username;
}

public void setUsername(String username) {
this.username = username;
}

// all struts logic here
public String execute() {

return "SUCCESS";

}
}


In Struts2, the Action class is not required to implement any interface or extend any class, but it’s required to create an 
execute()
method to put all the business logic inside and return a 
String
value to tell user where to redirect.

Note

You may see some users implement the 
com.opensymphony.xwork2.Action
class, but it’s totally optional, because the 
com.opensymphony.xwork2.Action
is just provide some handy constant values only.

Note

Struts1’s Action class is required to extends the 
org.apache.struts.action.Action
. But Struts 2 Action class is optional, but you are still allow to implement the 
com.opensymphony.xwork2.Action
for some handy constant values or extends the 
com.opensymphony.xwork2.ActionSupport
for some common default Action implementation functions.

5. Struts configuration file

A Strut configuration file to link all stuff together. The xml file name must be “
struts.xml
”.

File : 
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>

<package name="user" namespace="/User" extends="struts-default">
<action name="Login">
<result>pages/login.jsp</result>
</action>
<action name="Welcome" class="com.mkyong.user.action.WelcomeUserAction">
<result name="SUCCESS">pages/welcome_user.jsp</result>
</action>
</package>

</struts>


Declare a 
package
and warp the 
action
classes inside, the 
action
classes are self-explanatory, but you may interest at following new tag :

package name=”user”


Just a 
package
name, don’t really care about it.

namespace=”/User”


It’s used to match the “
/User
” URL pattern.

Note

Actually, the Struts2 Namespaces is equivalent to Struts 1 multiple modules

3. 
extends=”struts-default”


It means the package is extends the 
struts-default
package components and interceptors, which is declared in the 
struts-default.xml
file, located at the root of the 
struts2-core.jar
file.

6. 
web.xml

Configure the Web Application Deployment Descriptor (
web.xml
) file to integrate Struts2 to your web project.

File 
web.xml

<!DOCTYPE web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
<display-name>Struts 2 Web Application</display-name>

<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>

</web-app>


7. Run it

In Struts2, you can access the action class directly with a suffix of 
.action
.

http://localhost:8080/Struts2Example/User/Login.action



http://localhost:8080/Struts2Example/User/Welcome.action



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