J2EE实现计划任务

一、建立监听类

package com.cjx;
import java.util.Calendar;
import java.util.Timer;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.http.HttpServlet;
public class DBListener extends HttpServlet implements ServletContextListener {
	private static final long serialVersionUID = 1L;
	/** 间隔时间 */
	private static final long interval = 24 * 60 * 60 * 1000;
	/** 开始时间 */
	private static final int hours = 9;
	private static final int minutes = 37;
	private static final int seconds = 45;
	/** 定时器 */
	private static Timer timer;
	public void contextDestroyed(ServletContextEvent arg0) {
		System.out.println("监听任务停止！");
		timer.cancel();
	}
	public void contextInitialized(ServletContextEvent arg0) {
		if (timer == null) {
			System.out.println("监听任务启动！");
			Calendar calendar = Calendar.getInstance();
			calendar.set(Calendar.HOUR_OF_DAY, hours);
			calendar.set(Calendar.MINUTE, minutes);
			calendar.set(Calendar.SECOND, seconds);
			timer = new Timer("DataBaseListener");
			timer.schedule(new DataBaseTask(), calendar.getTime(), interval);
		}
	}
}

二、建立操作任务

package com.cjx;
import java.util.TimerTask;
public class DataBaseTask extends TimerTask {
	private static boolean running = false;
	public void run() {
		if (!running) {
			running = true;
			/** 任务开始 */
			System.out.println("更新数据库操作！");
			/** 任务完成 */
			running = false;
		} else {
			System.out.println("任务执行中！");
		}
	}
}

三、配置web.xml文件

<?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" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
    <listener>
        <listener-class> com.cjx.DBListener </listener-class>
    </listener>
</web-app>

四、也可以直接建一个应用

import java.util.Timer;
import java.util.TimerTask;
public class Test {
    public static void main(String[] args) {
        Timer timer = new Timer();
        timer.schedule(new MyTimerTask(),0, 1000);
		//Date date= new Date(107,05,21,00,01,10);
        //timer.schedule(new MyTimerTask(),date,5000);
    }
}
class MyTimerTask extends TimerTask {
    public void run() {
        System.out.println("现在的时间是:"+System.currentTimeMillis());
    }
}