This example will show you how to run Running Infinite TimerTask in Java Servlet.
For achieving this we can initialize TimerTask inside ServletContextListener and schedule it for a certain time period. ServletContextListener is used to, make your code run before your web application started. For more understanding on ServletContextListener, refer my post on ServletContextListener Example in Servlet.
Following example explains how to implement the ServletContextListener
1) Create a class and implement the ServletContextListener interface
package com.javatechig;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
public class AppContextListener implements ServletContextListener {
@Override
public void contextDestroyed(ServletContextEvent arg0) {
// Your code here
System.out.println("HelloWorld Listener has been shutdown");
}
@Override
public void contextInitialized(ServletContextEvent servletContextEvent) {
// Your code here
System.out.println("HelloWorld Listener initialized.");
TimerTask vodTimer = new VodTimerTask();
Timer timer = new Timer();
timer.schedule(vodTimer, 1000, (2 * 1000));
}
class VodTimerTask extends TimerTask {
@Override
public void run() {
System.out.println("TimerTask " + new Date().toString());
}
}
}
2) Configure deployment descriptor
Just add the listener tag and listener-class tag with the class path, as shown in the example.
< ?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" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0"> <display -name>HelloServlet</display> <servlet> </servlet><servlet -name>HelloServlet</servlet> <servlet -class>com.javatechig.HelloServlet</servlet> <servlet -mapping> </servlet><servlet -name>HelloServlet</servlet> <url -pattern>/HelloServlet</url> <listener> </listener><listener -class>com.javatechig.AppContextListener</listener> </web>
3) Start Tomcat and deploy your application
You will see the output in the console
Jun 13, 2014 3:52:25 PM org.apache.catalina.core.AprLifecycleListener init Jun 13, 2014 3:52:27 PM org.apache.catalina.core.ApplicationContext log INFO: No Spring WebApplicationInitializer types detected on classpath HelloWorld Listener initialized. Jun 13, 2014 3:52:27 PM org.apache.coyote.AbstractProtocol start INFO: Starting ProtocolHandler ["http-bio-8080"] Jun 13, 2014 3:52:27 PM org.apache.coyote.AbstractProtocol start INFO: Starting ProtocolHandler ["ajp-bio-8009"] Jun 13, 2014 3:52:27 PM org.apache.catalina.startup.Catalina start INFO: Server startup in 1787 ms TimerTask Fri Jun 13 15:52:28 BST 2014 TimerTask Fri Jun 13 15:52:30 BST 2014 TimerTask Fri Jun 13 15:52:32 BST 2014 TimerTask Fri Jun 13 15:52:34 BST 2014 TimerTask Fri Jun 13 15:52:36 BST 2014
