一.java.util.timer类(一般不用它)
首先在web.xml中配置listener监听器

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" 
	xmlns="http://java.sun.com/xml/ns/j2ee" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
	http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>

  
  <!-- 可以用来启动schelduledExcutorsService 或 timer -->   
    <listener>
  	<listener-class>com.timer.TimerListener</listener-class>
  </listener>
   
</web-app>

然后在com.timer包下创建TimerListener.java

package com.timer;

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

import com.scheldule.SchelduCall;

import java.util.*;


public class TimerListener implements ServletContextListener {
	private Timer timer;
	
	public TimerListener(){
		System.out.println("执行TimerListener构造函数");
	}
	
	public void contextDestroyed(ServletContextEvent arg0) {
		System.out.println("destory listener");
		timer.cancel();

	}

	
	public void contextInitialized(ServletContextEvent arg0) {
		System.out.println("init listener");
	    timer = new Timer();                //可以使用timer
		timer.schedule(new TopicTask(), 0, 20*1000);    //服务器启动时就执行一次
		new SchelduCall().scheldul();      //可以调用scheldul()方法
	
	}

}

?任务类：topicTask.java

package com.timer;

import java.util.*;

public class TopicTask extends TimerTask{

	public void run() {
		System.out.println("task:"+new Date());
	}

}

?然后启动服务器就能循环执行任务了。

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二.使用类java.util.concurrent.ScheduledExecutorService;

首先建立SchedulCall.java

package com.scheldule;

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;

public class SchelduCall {
	private final ScheduledExecutorService scheduler = 
	       Executors.newScheduledThreadPool(1);
	
	public static void main(String[] args) throws Exception{
		new SchelduCall().scheldul();
	}
	
	public void  scheldul(){
		        final Runnable beeper = new Runnable() {
		                public void run() { System.out.println("beep"); }
		            };
		        final ScheduledFuture<?> beeperHandle = 
		            scheduler.scheduleAtFixedRate(beeper, 5, 7, TimeUnit.SECONDS);   //过五秒后开始执行，然后循环7秒执行一次
		        scheduler.schedule(new Runnable() {        //第27秒后执行
		                public void run() { 
		                	beeperHandle.cancel(true);
		                	System.out.println("stop");
		                }
		            }, 27, TimeUnit.SECONDS);
		        //scheduler.shutdown();
    }
		 
}

然后再TimerListener中调用即可

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三.自然要属任务调度框架quartz

1.首先在web.xml文件中加入 如下内容（根据自己情况设定）

在web.xml中添加QuartzInitializerServlet，Quartz为能够在web应用中使用，提供了一个QuartzInitializerServlet和一个QuartzInitializerListener，用于在加载web应用时，对quartz进行初始化。

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<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" 
	xmlns="http://java.sun.com/xml/ns/j2ee" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
	http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  
  <!-- 使用监听器初始化quartz -->
  <!-- <context-param>
		<param-name>config-file</param-name>
		<param-value>/quartz.properties</param-value>
	</context-param>
	
	<context-param>
		<param-name>shutdown-on-unload</param-name>
		<param-value>true</param-value>
	<