Listener - ServletContextListener Example

If You want to do something before application starts, then ServletContextListener is for you.

ServletContextListener is abstract interface provided as part of servler-api.jar which provides contextDestroyed and contextInitialized abstract method. One can create class which implements ServletContextListener and write implementation logic for example, logic that does something before web application starts.

AppContextListener Example :

package com.anuj.context;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

/**
 * 
 * @author Anuj
 *
 */
public class AppContextListener implements ServletContextListener{

 @Override
 public void contextDestroyed(ServletContextEvent event) {
  System.out.println("TODO something on ServletContextListener Destroyed");
 }

 @Override
 public void contextInitialized(ServletContextEvent event) {
  System.out.println("TODO something on ServletContextListener Initialized");
 }

}

Defining AppContextListener in web.xml deployment descriptor :

    com.anuj.context.AppContextListener

Output :

INFO: Initializing ProtocolHandler ["ajp-apr-8009"]

Aug 06, 2013 10:03:16 PM org.apache.catalina.startup.Catalina load

INFO: Initialization processed in 960 ms

Aug 06, 2013 10:03:16 PM org.apache.catalina.core.StandardService startInternal

INFO: Starting service Catalina

Aug 06, 2013 10:03:16 PM org.apache.catalina.core.StandardEngine startInternal

INFO: Starting Servlet Engine: Apache Tomcat/7.0.27

TODO something on ServletContextListener Initialized

Aug 06, 2013 10:03:16 PM org.apache.coyote.AbstractProtocol start

INFO: Starting ProtocolHandler ["http-apr-8080"]

Aug 06, 2013 10:03:16 PM org.apache.coyote.AbstractProtocol start

INFO: Starting ProtocolHandler ["ajp-apr-8009"]

Aug 06, 2013 10:03:16 PM org.apache.catalina.startup.Catalina start

INFO: Server startup in 238 ms