Struts 2 Subset tag example

Download It – Struts2-Subset-Tag-Example.zip

Struts 2 subset tag is used to output a subset or portion of an iterator elements. In this tutorials, you will create a “numbers” list, contains 10 elements (from 1 to 10), and use the subset tag “start & count” attribute and decider method to output a subset of an iterator (list).

1. Action

An Action class to populate elements into a list, and a decider method to filter the element to display.

If the decider method return a “true” means display this value; otherwise ignore it. You can do whatever filter logic here.

SubsetTagAction.java

package com.mkyong.common.action;
 
import java.util.ArrayList;
import java.util.List;
 
import org.apache.struts2.util.SubsetIteratorFilter.Decider;
import com.opensymphony.xwork2.ActionSupport;
 
public class SubsetTagAction extends ActionSupport{
 
	private List<String> numbers = new ArrayList<String>();
 
	public String execute() {
 
		numbers.add("Number 1");
		numbers.add("Number 2");
		numbers.add("Number 3");
		numbers.add("Number 4");
		numbers.add("Number 5");
		numbers.add("Number 6");
		numbers.add("Number 7");
		numbers.add("Number 8");
		numbers.add("Number 9");
		numbers.add("Number 10");
 
		return SUCCESS;
	}
 
	public List<String> getNumbers() {
		return numbers;
	}
 
	public void setNumbers(List<String> numbers) {
		this.numbers = numbers;
	}
 
	public Decider getNumberDecider() {
	     return new Decider() {
	         public boolean decide(Object obj) throws Exception {
	             String number = ((String)obj).toString();
 
	             if(("Number 7").equals(number)){
	            	 return true;//display it
	             }else{
	            	 return false;//ignore
	             }
	         }
	     };
	}	
}

2. Subset tag example

A JSP page to show the use of subset tag to output a subset of an iterator.

The “start” and “count” attribute in the subset tag is start from 0 , which means <s:subset source=”numbers” start=”1″ count=”5″> will extract the element from #2 to #6.

subset.jsp

<%@ taglib prefix="s" uri="/struts-tags" %>
 <html>
<head>
</head>
 
<body>
<h1>Struts 2 Subset tag example</h1>
 
<table border="1px" cellpadding="8px">
<tr valign="top">
<td>
1. Display all numbers.
<ol>
<s:subset source="numbers">
   <s:iterator>
      	<li><s:property /></li>
   </s:iterator>
</s:subset>
</ol>
</td>
 
<td>
2. Display numbers , from #2 to #6
<ol>
<s:subset source="numbers" start="1" count="5">
   <s:iterator>
      	<li><s:property /></li>
   </s:iterator>
</s:subset>
</ol>
</td>
 
<td>
3. Display numbers 7 only, with decider
<ol>
<s:subset source="numbers" decider="numberDecider">
   <s:iterator>
     	<li><s:property /></li>
   </s:iterator>
</s:subset>
</ol>
</td>
</tr>
</table>
 
</body>
</html>

3. struts.xml

Link it ~

<?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="default" namespace="/" extends="struts-default">
		<action name="subsetTagAction" 
			class="com.mkyong.common.action.SubsetTagAction" >
			<result name="success">pages/subset.jsp</result>
		</action>
	</package>
</struts>