SchedulerServletContextListener.java example

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/*
 * cron4j - A pure Java cron-like scheduler
 * 
 * Copyright (C) 2007-2010 Carlo Pelliccia (www.sauronsoftware.it)
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License version
 * 2.1, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License 2.1 for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License version 2.1 along with this program.
 * If not, see <http://www.gnu.org/licenses/>.
 */
package com.sp2p.task;


import it.sauronsoftware.cron4j.Scheduler;
import it.sauronsoftware.cron4j.TaskCollector;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

import com.sp2p.constants.IConstants;

/**
 * This listener starts a scheduler bounded to the web application: the
 * scheduler is started when the application is started, and the scheduler is
 * stopped when the application is destroyed. The scheduler uses a custom
 * TaskCollector to retrieve, once a minute, its job list. Moreover the
 * scheduler is registered on the application context, in a attribute named
 * according to the value of the {@link Constants#SCHEDULER} constant.
 */
public class SchedulerServletContextListener implements ServletContextListener {

	public void contextInitialized(ServletContextEvent event) {
		ServletContext context = event.getServletContext();
		// 1. Creates the scheduler.
		Scheduler scheduler = new Scheduler();
		// 2. Registers a custom task collector.
		TaskCollector collector = new MyTaskCollector();
		scheduler.addTaskCollector(collector);
		// 3. Starts the scheduler.
		scheduler.start();
		// 4. Registers the scheduler.
		context.setAttribute(IConstants.SCHEDULER, scheduler);
	}

	public void contextDestroyed(ServletContextEvent event) {
		ServletContext context = event.getServletContext();
		// 1. Retrieves the scheduler from the context.
		Scheduler scheduler = (Scheduler) context.getAttribute(IConstants.SCHEDULER);
		// 2. Removes the scheduler from the context.
		context.removeAttribute(IConstants.SCHEDULER);
		// 3. Stops the scheduler.
		scheduler.stop();
	}
	
}