How to Iterate ArrayList in Struts2

Sandeep Bhandari

May. 17, 11 · Interview

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We will discuss how to iterate over a collection of String objects in Struts2 tag libraries and then a List of custom class objects. It looks as if iterating a list of string objects is easier than iterating over a list of custom class objects in Struts 2. But the reality is that iterating a list of custom class objects is also equally easier. By custom class we mean the User, Employee, Department, Products, Vehicles classes that are created in any web application.

Download Working Sample Here

Usually it happens that one needs to fetch a list of records from database/files and then display it in the JSP. The module requiring this functionality could be Search, Listing users/departments/products etc.

The basic flow of struts2 web application goes like:

The user initiates the request from one page. This request is received by the interceptor which further invokes the Struts2 action. The action class fetches the records and stores in a list. This list is available to the next JSP using the public getter method.

Please note that the public getter method for the List is mandatory.

Once the List has been populated by Struts2 action class, the JSP then iterates over this List and displays the corresponding information. In the days gone by, one would store the List as a session attribute and then access the list in JSP using the scriptlets to display appropriate output to the users.

Here is a Struts2 sample application to iterate one String and one custom class objects List.

Though we are using the Struts2 tag library to iterate the list but JSTL can also be used for iteration.

Also if you are going to use the code examples given below, use the following URL's to access the application:
http://localhost:8080//index.action

Iterate a Custom class ArrayList in Struts2

web.xml

<?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_2_5.xsd" version="2.5">
  <display-name></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>*.action</url-pattern>
  </filter-mapping>
</web-app>

struts.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN" "http://struts.apache.org/dtds/struts-2.1.dtd">
<struts>

<package name="default" extends="struts-default" >

    <action name="index">
        <result name="success">/home.jsp</result>
    </action>
    <action name="fetch" class="com.example.FetchAction">
        <result name="success">/success.jsp</result>
        <result name="failure">/failure.jsp</result>
    </action>

</package>

</struts>

home.jsp

<%@taglib uri="/struts-tags" prefix="s" %>

<html>
    <body>
        Enter a user name to get the documents uploaded by that user.
        <s:form name="fetch" theme="simple" action="fetch">
                Username <s:textfield name="username" />
                <s:submit value="Fetch Records" />
        </s:form>

        </body>
</html>

success.jsp

<%@taglib uri="/struts-tags" prefix="s" %>

<html>

    <body>
        Documents uploaded by the user are:</br>
        <s:iterator value="documents"><s:property value="name" /></br></s:iterator>
    </body>
</html>

failure.jsp

<%@taglib uri="/struts-tags" prefix="s" %>
<html>
    <body>
        <h3><s:property value="message" /></h3>  
    </body>
</html>

FileAction.java

package com.example;

import java.util.ArrayList;
import java.util.List;

public class FetchAction {

    private String username;
    private String message;
    private List documents = new ArrayList();
   
    public List getDocuments() {
        return documents;
    }
   
    public String getMessage() {
        return message;
    }
    public void setMessage(String message) {
        this.message = message;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
   
    public String execute() {
   
        if( username != null) {
            //logic to fetch the document list (say from database)
            Document d1 = new Document();
            d1.setName("user.doc");
            Document d2 = new Document();
            d2.setName("office.doc");
            Document d3 = new Document();
            d3.setName("transactions.doc");
           
            documents.add(d1);
            documents.add(d2);
            documents.add(d3);
           
            return "success";
        } else {
            message="Unable to fetch";
            return "failure";
        }
    }
}

Document.java

package com.example;

public class Document {

    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
  
  
}

Iterate String List in Struts2

The way to iterate the a String list is similar with the only difference that the action class FetchAction.java now populates the name of documents into an ArrayList of String objects.

The code zip file containing the iteration over an ArrayList of custom class object or bean can be downloaded at:
http://www.fileserve.com/file/QmrsJ7k

The URL to access this application will be:
http://localhost:8080/IteratorExample/index.action

The code zip file containing the iteration over an ArrayList of string class object or bean can be downloaded at:
http://www.fileserve.com/file/V2kXkfx

The URL to access this application will be:
http://localhost:8080/StringIteratorExample/index.action

From http://extreme-java.blogspot.com/2011/05/how-to-iterate-arraylist-in-struts2.html

Data structure Listing (computer) Web application Object (computer science)

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