<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" 
  xmlns="http://java.sun.com/xml/ns/javaee" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
  http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
  <!-- 添加監(jiān)聽器 TimerListener為自定義的類，見下方-->
  <listener >
   <listener-class>com.util.TimerListener</listener-class>
  </listener>

 <display-name></display-name> 
 <welcome-file-list>
  <welcome-file>index.jsp</welcome-file>
 </welcome-file-list>
</web-app>

package com.util;

import java.util.Timer;
import java.util.TimerTask;

/**
 * 1.定義一個(gè)任務(wù)對(duì)象
 *  JDK -- 任務(wù)對(duì)象需要繼承TimerTask
 *
 */
public class DataBackup extends TimerTask{

  @Override
  public void run() {
    //描述當(dāng)前任務(wù)需要執(zhí)行的任務(wù)內(nèi)容
    System.out.println("連接數(shù)據(jù)庫(kù)將表結(jié)和數(shù)據(jù)備份到本地的sql文件中");

  }

}

package com.util;

import java.util.Date;
import java.util.Timer;

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

public class TimerListener implements ServletContextListener{

  private static Timer timer;
  /**
   * 監(jiān)聽web容器關(guān)閉
   */
  @Override
  public void contextDestroyed(ServletContextEvent sce) {
    System.out.println("web容器關(guān)閉");
    timer.cancel();
  }

  /**
   * 監(jiān)聽web容器啟動(dòng)
   */
  @Override
  public void contextInitialized(ServletContextEvent sce) {
    System.out.println("web容器啟動(dòng)");
    /**
     * 準(zhǔn)備Timer計(jì)使器
     */
    timer = new Timer();
    System.out.println("計(jì)時(shí)器處于準(zhǔn)備工作,開始為任務(wù)調(diào)度分配時(shí)間和周期");
    //創(chuàng)建任務(wù)對(duì)象
    DataBackup backup = new DataBackup();
    //1 schedule(TimerTask task,Data time)
    //安排指定的任務(wù)在指定的時(shí)間開始執(zhí)行
    //月份要減一
    //timer.schedule(backup, new Date(115,8,10,9,54,0));

    //2 schedule(TimerTask task, Date firstTime, long period)
    // 安排指定的任務(wù)在指定的時(shí)間開始進(jìn)行重復(fù)的固定延遲執(zhí)行
    //timer.schedule(backup,new Date(115,8,10,10,0,0) ,2000 );

    //3schedule(TimerTask task, long delay) 
    //安排在指定延遲后執(zhí)行指定的任務(wù)。
    //timer.schedule(backup, 5000);

    //4 schedule(TimerTask task, long delay, long period) 
    //timer.schedule(backup, 5000, 2000);

    //5.每天早上9點(diǎn)出發(fā)一次任務(wù) 
    //timer.schedule(backup,new Date(115,8,11,9,0,0) ,24*60*60*1000);

    //6.每星期六的凌晨3點(diǎn)出發(fā)一次任務(wù) 
    //timer.schedule(backup, new Date(115,8,12,3,0,0),7*24*60*60*1000); 

  }

}