<?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>test.timer.TimerListener</listener-class>
    </listener>

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

package test.timer;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Timer;

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

public class TimerListener implements ServletContextListener {

    @SuppressWarnings("unused")
    private ServletContext servletContext = null;
    private Timer timer = null;

    /**
     * 开始执行
     */
    @Override
    public void contextInitialized(ServletContextEvent e) {
        e.getServletContext().log("init !");
        timer = new Timer(true);
        // 获得当天的日期
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd ");
        Date date = new Date();
        // 定义开始时间字符串
        String timeStr = "12:00:00";
        timeStr = sdf.format(date) + timeStr;
        // 获得当天的指定时间的date对象
        sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
        try {
            date = sdf.parse(timeStr);
        } catch (ParseException e1) {
            e1.printStackTrace();
        }

        // 判断今天的执行时间是否已经过去，如果过去则改为明天
        if (date.getTime() < System.currentTimeMillis()) {
            date = new Date(date.getTime() + 24 * 60 * 60 * 1000);
        }

        timer.schedule(new TestTimer(), date, 24*60*60 * 1000);

    }

    /**
     * 销毁
     */
    @Override
    public void contextDestroyed(ServletContextEvent e) {
        timer.cancel();
        e.getServletContext().log("destroyed");
    }
}