Dinesh on Java: Annotations in Struts2 with an Example

We can achieve Zero Configuration in struts2 using java 5 annotations feature. Previously we normally configured struts.xml for all the configurations . The XML file wires up the action names (employee), with ActionSupport classes (EmployeeAction.java), and with the result to render back to the browser (success.jsp). Struts 2 provides an alternative to using XML to configure your application by using standard naming conventions and annotations for your action names, ActionSupport classes, and results.
We will use annotations in a small example and it is being developed in Eclipse.

Here we will take an example of Employee whose name, emailid, age and telephone would be captured using a simple page and we will put two validation to make sure that use always enter a name , a emailid and a telephone and age should be in between 18 and 65.

To start using annotations in your project, make sure you have included following jar files in your WebRoot/WEB-INF/lib folder:

struts2-convention-plugin-x.y.z.jar
asm-x.y.jar
asm-commons-x.y.jar
antlr-x.y.z.jar
commons-fileupload-x.y.z.jar
commons-io-x.y.z.jar
commons-lang-x.y.jar
commons-logging-x.y.z.jar
commons-logging-api-x.y.jar
freemarker-x.y.z.jar
javassist-.xy.z.GA
ognl-x.y.z.jar
struts2-core-x.y.z.jar
xwork-core.x.y.z.jar

Create main page:
Let us write main page JSP file employee.jsp, which will be used to collect Employee related information mentioned above.

<%@ page contentType="text/html; charset=UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags"%>
<html>
<head>
<title><s:property value="getText('global.form')" /> - Struts2 Demo | dineshonjava.com</title>
<s:head />
</head>
 
<body>
<h2><s:property value="getText('global.form')" /></h2>
 
<s:form action="employee" method="post" validate="true" >
    <s:textfield name="name" key="global.name" size="20"/>
    <s:textfield name="age" key="global.age" size="20" />
    <s:textfield name="email" key="global.email" size="20" />
    <s:textfield name="telephone" key="global.telephone" size="20" />
    <s:submit name="submit" key="global.submit" align="center" />
</s:form>

<s:url id="localeEN" namespace="/" action="locale" >
   <s:param name="request_locale" >en</s:param>
</s:url>
<s:url id="localeHN" namespace="/" action="locale" >
   <s:param name="request_locale" >hn</s:param>
</s:url>
<s:url id="localeES" namespace="/" action="locale" >
   <s:param name="request_locale" >es</s:param>
</s:url>
<s:url id="localezhCN" namespace="/" action="locale" >
   <s:param name="request_locale" >zh_CN</s:param>
</s:url>
<s:url id="localeDE" namespace="/" action="locale" >
   <s:param name="request_locale" >de</s:param>
</s:url>
<s:url id="localeFR" namespace="/" action="locale" >
   <s:param name="request_locale" >fr</s:param>
</s:url>
 
<s:a href="%{localeEN}" >English</s:a>
<s:a href="%{localeHN}" >Hindi</s:a>
<s:a href="%{localeES}" >Spanish</s:a>
<s:a href="%{localezhCN}" >Chinese</s:a>
<s:a href="%{localeDE}" >German</s:a>
<s:a href="%{localeFR}" >France</s:a>
</body>
</html>

Create Views:
We will use JSP file success.jsp which will be invoked in case defined action returns SUCCESS.

<%@ page contentType="text/html; charset=UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags"%>
<html>
<head>
<title><s:property value="getText('global.form')" /> - Struts2 Demo | dineshonjava.com</title>
</head>
 
<body>
    <h2><s:property value="getText('global.success')" />.</h2>
</body>
</html>

Create Action:
This is the place where annotation will be used. Let us re-define action class Employee with annotation, and then add a method called validate() as shown below in EmployeeAction.java file. Make sure that your action class extends the ActionSupport class, otherwise your validate method will not be executed.

package com.dineshonjava.struts2.action;

import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.Result;
import org.apache.struts2.convention.annotation.Results;

import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.validator.annotations.IntRangeFieldValidator;
import com.opensymphony.xwork2.validator.annotations.RequiredFieldValidator;

/**
 * @author Dinesh Rajput
 *
 */
@Results({
 @Result(name="success", location="/success.jsp"),
 @Result(name="input", location="/employee.jsp")
})
public class EmployeeAction extends ActionSupport {

 private static final long serialVersionUID = 1L;
 private String name;
    private Integer age;
    private String email;
    private String telephone;
    
    @Action(value="/employee")
    public String addEmployee() {
        return SUCCESS;
    }
    
    @RequiredFieldValidator( message = "The name is required" )
 public String getName() {
  return name;
 }
 public void setName(String name) {
  this.name = name;
 }
 
  @IntRangeFieldValidator(message = "Age must be in between 28 and 65",
             min = "18", max = "65")
 public Integer getAge() {
  return age;
 }
 public void setAge(Integer age) {
  this.age = age;
 }
 
 @RequiredFieldValidator( message = "The email is required" )
 public String getEmail() {
  return email;
 }
 public void setEmail(String email) {
  this.email = email;
 }
 
 @RequiredFieldValidator( message = "The phone is required" )
 public String getTelephone() {
  return telephone;
 }
 public void setTelephone(String telephone) {
  this.telephone = telephone;
 }
}

We have used few annotations in this example. Let me go through them one by one:

First, we have included the Results annotation. A Results annotation is a collection of results. Under the results annotation, we have two result annotations. The result annotations have the name that correspond to the outcome of the execute method. They also contain a location as to which view should be served corresponding to return value from addEmployee().
The next annotation is the Action annotation. This is used to decorate the addEmployee() method. The Action method also takes in a value which is the URL on which the action is invoked.
Finally, I have used two validation annotations. I have configured the required field validator on name field and the integer range validator on the age field. I have also specified a custom message for the validations.

Configuration Files:
We really do not need struts.xml configuration file, so let us remove this file and let us check the content of web.xml file:

<?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>Struts2I18N</display-name>
 <filter>
        <filter-name>struts2</filter-name>
        <filter-class>
            org.apache.struts2.dispatcher.FilterDispatcher
        </filter-class>
         <init-param>
          <param-name>struts.devMode</param-name>
          <param-value>true</param-value>
      </init-param>
      <init-param>
          <param-name>struts.custom.i18n.resources</param-name>
          <param-value>global</param-value>
      </init-param>
    </filter>
    <filter-mapping>
        <filter-name>struts2</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    <welcome-file-list>
        <welcome-file>employee.jsp</welcome-file>
    </welcome-file-list>
</web-app>

Now, right click on the project name and click Export > WAR File to create a War file. Then deploy this WAR in the Tomcat's webapps directory. Finally, start Tomcat server and try to access
URL http://localhost:8080/doj/employee.jsp.

This will give you following screen:

Employee error page because of validation fails

Employee page on success

Download Source Code
Struts2Annotation.zip

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