Download this example – Struts-Logic-Present-NotPresent-Example.zip

Struts <logic:present> tag is used to check the given object or property is present or exists in the current request; while the <logic:notPresent> is doing the opposite way.

Here’s an example to show the use of the <logic:present> and <logic:notPresent>.

User.java – An user class contains a url property.

package com.mkyong.common;
 
public class User{
 
	String url;
 
	public String getUrl() {
		return url;
	}
 
	public void setUrl(String url) {
		this.url = url;
	} 
}

LogicExampleAction.java – Initial the User object and set the url property and store it into the request session.

package com.mkyong.common.action;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
 
import com.mkyong.common.User;
 
public class LogicExampleAction extends Action{
 
	public ActionForward execute(ActionMapping mapping,ActionForm form,
		HttpServletRequest request,HttpServletResponse response) 
        throws Exception {
 
		User user = new User();
		user.setUrl("http://www.mkyong.com");
 
		request.setAttribute("user", user);
 
	    return mapping.findForward("success");
	}
 
}

LogicExample.jsp

<%@taglib uri="http://struts.apache.org/tags-bean" prefix="bean"%>
<%@taglib uri="http://struts.apache.org/tags-logic" prefix="logic"%>
<html>
<head>
</head>
<body>
 
<h2>Struts - &lt;logic:present&gt; & &lt;logic:notPresent&gt;</h2>
 
<logic:present name="user">
	User object is exists.
</logic:present>
<logic:notPresent name="user">
	User object does not exists.
</logic:notPresent>
 
<br/></br/>
 
<logic:present name="abc">
	Abc object is exists.
</logic:present>
<logic:notPresent name="abc">
	Abc object does not exists.
</logic:notPresent>
 
<br/></br/>
 
<logic:present name="user" property="url">
	User object, url property is exists.
</logic:present>
<logic:notPresent name="user" property="url">
	User object, url property does not exists.
</logic:notPresent>
 
<br/></br/>
 
<logic:present name="user" property="email">
	User object, email property is exists.
</logic:present>
<logic:notPresent name="user" property="email">
	User object, email property does not exists.
</logic:notPresent>
 
 
</body>
</html>

struts-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts-config PUBLIC 
"-//Apache Software Foundation//DTD Struts Configuration 1.3//EN" 
"http://jakarta.apache.org/struts/dtds/struts-config_1_3.dtd">
 
<struts-config>
 
	<action-mappings>
 
	 	<action
			path="/LogicTest"
			type="com.mkyong.common.action.LogicExampleAction"
			>
 
			<forward name="success" path="/pages/LogicExample.jsp"/>
 
		</action>
 
	</action-mappings>
 
</struts-config>

Result

http://localhost:8080/StrutsExample/LogicTest.do

Struts-logic-present-notpresent-example
Struts - <logic:present> & <logic:notPresent>
User object is exists.
 
Abc object does not exists.
 
User object, url property is exists.
 
User object, email property does not exists.
Any Java questions or problems? please post at this JavaNullPointer.com forum, see you there ~
[ Read More ] You can find more similar articles at Struts 1.x Tutorials