A tutorial to show the use of the Struts 2’s ActionError and ActionMessage class.

1. ActionError – is used to send error feedback message to user – display via <s:actionerror/>.


<s:if test="hasActionErrors()">
   <div class="errors">
      <s:actionerror/>
   </div>
</s:if>

2. ActionMessage – is used to send information feedback message to user, display via <s:actionmessage/>.


<s:if test="hasActionMessages()">
   <div class="welcome">
      <s:actionmessage/>
   </div>
</s:if>

Here’s a simple login form, display the error message (actionerror) if the username is not equal to “mkyong”, otherwise redirect to another page and display the a welcome message (actionmessage). In addition, all the label and error messages are retrieve from the resource bundle (properties file).

1. Folder Structure

See this project structure

Struts 2 Login Folder Structure

2. Properties file

Two properties files to store the messages.

LoginAction.properties


#Welcome messages
welcome.hello = Hello

#error message
username.required = Username is required
password.required = Password is required

global.properties


#Global messages
global.username = Username
global.password = Password
global.submit = Submit
global.reset = Reset

3. Action

A classic action class, do a simple checking to make sure the username is equal to “mkyong”, and set the error message with addActionError() or successful message with addActionMessage().


package com.mkyong.user.action;

import com.opensymphony.xwork2.ActionSupport;

public class LoginAction extends ActionSupport{

	private String username;
	private String password;
	 
	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	public String getUsername() {
		return username;
	}

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

	//business logic
	public String execute() {

		return "SUCCESS";

	}

	//simple validation
	public void validate(){
		if("mkyong".equals(getUsername())){
			addActionMessage("You are valid user!");
		}else{
			addActionError("I don't know you, dont try to hack me!");
		}
	}
}

4. JSP View

Two simple JSP pages with css style to customize the error message.

login.jsp


<%@ page contentType="text/html; charset=UTF-8" %>
<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<head>

<style type="text/css">
.errors {
	background-color:#FFCCCC;
	border:1px solid #CC0000;
	width:400px;
	margin-bottom:8px;
}
.errors li{ 
	list-style: none; 
}
</style>

</head>

<body>
<h1>Struts 2 ActionError & ActionMessage Example</h1>

<s:if test="hasActionErrors()">
   <div class="errors">
      <s:actionerror/>
   </div>
</s:if>

<s:form action="validateUser">
	<s:textfield key="global.username" name="username"/>
	<s:password key="global.password" name="password"/>
	<s:submit key="global.submit" name="submit"/>
</s:form>

</body>
</html>

welcome.jsp


<%@ page contentType="text/html; charset=UTF-8" %>
<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<head>

<style type="text/css">
.welcome {
	background-color:#DDFFDD;
	border:1px solid #009900;
	width:200px;
}
.welcome li{ 
	list-style: none; 
}
</style>

</head>
<body>
<h1>Struts 2 Struts 2 ActionError & ActionMessage Example</h1>

<s:if test="hasActionMessages()">
   <div class="welcome">
      <s:actionmessage/>
   </div>
</s:if>

<h2>

<s:property value="getText('welcome.hello')" /> : 
<s:property value="username"/>

</h2>

</body>
</html>

5. struts.xml

Link all together.


<?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.custom.i18n.resources" value="global" />

  <package name="user" namespace="/user" extends="struts-default">
     <action name="login">
	 <result>pages/login.jsp</result>
     </action>
     <action name="validateUser" class="com.mkyong.user.action.LoginAction">
	 <result name="SUCCESS">pages/welcome.jsp</result>
	 <result name="input">pages/login.jsp</result>
     </action>
   </package>
	
</struts>
In Struts 2, the functionality and usage of ActionError & ActionMessage are quite similar with Struts 1.

6. Run it

http://localhost:8080/Struts2Example/user/login.action

Struts 2 ActionError 1

Username is invalid, display error message with <s:actionerror/>

Struts 2 ActionError 2

Username is valid, display welcome message <s:actionmessage/>

Struts 2 ActionError 3

Reference

  1. ValidationAware documentation