JSF 2 PostConstructApplicationEvent and PreDestroyApplicationEvent example

By mkyong | Updated: November 14, 2010

Viewed: 15,800

Tags: jsf2

Since JSF 2.0, you can register javax.faces.event.PostConstructApplicationEvent and javax.faces.event.PreDestroyApplicationEvent system event to manipulate the JSF application life cycle.

1. PostConstructApplicationEvent – Perform a custom post-configuration after application has started.
2. PreDestroyApplicationEvent – Perform a custom cleanup task before application is about to be shut down.

The following example shows you how to create a PostConstructApplicationEvent and PreDestroyApplicationEvent system event in JSF 2.0.

1. Implements SystemEventListener

Create a class which implements javax.faces.event.SystemEventListener, and override the processEvent() and isListenerForSource() methods for your custom post-configuration and clean up task.

package com.mkyong;

import javax.faces.application.Application;
import javax.faces.event.AbortProcessingException;
import javax.faces.event.PostConstructApplicationEvent;
import javax.faces.event.PreDestroyApplicationEvent;
import javax.faces.event.SystemEvent;
import javax.faces.event.SystemEventListener;

public class FacesAppListener implements SystemEventListener{

  @Override
  public void processEvent(SystemEvent event) throws AbortProcessingException {

	if(event instanceof PostConstructApplicationEvent){
		System.out.println("PostConstructApplicationEvent is Called");
	}
		
	if(event instanceof PreDestroyApplicationEvent){
		System.out.println("PreDestroyApplicationEvent is Called");
	}
		
  }

  @Override
  public boolean isListenerForSource(Object source) {
	//only for Application
	return (source instanceof Application);
		
  }	

}

2. Register System Events

Register both PostConstructApplicationEvent and PreDestroyApplicationEvent system event in faces-config.xml file like this :

faces-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<faces-config
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    http://java.sun.com/xml/ns/javaee/web-facesconfig_2_0.xsd"
    version="2.0">
    <application>
    	
    	<!-- Application is started -->
    	<system-event-listener>
		<system-event-listener-class>
			com.mkyong.FacesAppListener
		</system-event-listener-class>
		<system-event-class>
			javax.faces.event.PostConstructApplicationEvent
		</system-event-class>    					
    	</system-event-listener> 	 
    	
    	<!-- Before Application is shut down -->
    	<system-event-listener>
		<system-event-listener-class>
			com.mkyong.FacesAppListener
		</system-event-listener-class>
		<system-event-class>
			javax.faces.event.PreDestroyApplicationEvent
		</system-event-class>    					
    	</system-event-listener> 	 
    	
    </application>
</faces-config>

3. Demo

Run your JSF application. The processEvent() method is executed after your JSF application is started, see figure below :

Download Source Code

Reference

1. JSF 2 PostConstructApplicationEvent JavaDoc
2. JSF 2 PreDestroyApplicationEvent JavaDoc