Struts 2 merge tag is useful for merging the two lists into one object. This is very helpful when you have two different list of objects and then you need to merge them and use it in your JSP page. Merge tag has nested param element to take the multiple list objects in each line. You can add more than one param element and as many as you want. All the lists will be merged and assigned to one variables which is given in the var attribute of merge tag. I have used the iterate tag example to demonstrate this example.
1. Create Data Bean
Create a UserDetails.java class for storing the user details.
package javabeat.net.struts2;
public class UserDetails {
private String name;
private String city;
public UserDetails(String... args){
this.name = args[0];
this.city = args[1];
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
}
2. Create Struts 2 Action
Create a Struts 2 action class with two different list objects and pass it to the JSP page.
package javabeat.net.struts2;
import java.util.ArrayList;
public class Struts2Iteration {
private ArrayList<UserDetails> users;
private ArrayList<UserDetails> admins;
public ArrayList<UserDetails> getAdmins() {
return admins;
}
public void setAdmins(ArrayList<UserDetails> admins) {
this.admins = admins;
}
public ArrayList<UserDetails> getUsers() {
return users;
}
public void setUsers(ArrayList<UserDetails> users) {
this.users = users;
}
public String execute(){
users = new ArrayList<UserDetails>();
users.add(new UserDetails("Name 1","City 1"));
users.add(new UserDetails("Name 2","City 2"));
admins = new ArrayList<UserDetails>();
admins.add(new UserDetails("Admin 1","City 1"));
admins.add(new UserDetails("Admin 2","City 2"));
return "success";
}
}
3. Merge Tag Example
See the below code, we are using s:merge tage to merge two lists. Later it is displayed using the s:iterator tag.
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%@ taglib prefix="s" uri="/struts-tags"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Struts 2 Merge Example</title>
</head>
<body>
<B>Struts 2 Merge Example</B>
<form action="iterationexample">
<s:merge var="allusers">
<s:param value="users"/> ,
<s:param value="admins"/><br/>
</s:merge>
<s:iterator value="allusers">
<s:property value="name"/> ,
<s:property value="city"/><br/>
</s:iterator>
</form>
</body>
</html>
4. Struts.xml configurations
Create struts.xml configuration file.
<?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.devMode" value="true" /> <package name="tags" extends="struts-default"> <action name="iterationexample" class="javabeat.net.struts2.Struts2Iteration" method="execute"> <result name="success">/index.jsp</result> </action> </package> </struts>
5. Run the application
If you access the application http://localhost:8080/Struts2App/iterationexample.action. You would see the following output in your screen.
Struts 2 Iterator Tag Example