這是管理類：

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import java.util.Calendar;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;
/**
 * Created by Administrator on 2017/9/29.
 */
public class TaskManager {
    /**
     * 開啟任務
     */
//預設時間間隔一天
 
private static long PERIOD_TIME = 24 * 60 * 60 * 1000;
Log log = LogFactory.getLog(TaskManager.class);
    public void startTask(TimerTask task, int dayInterval, int hour, int minute){
        PERIOD_TIME =  dayInterval * 24 * 60 * 60 * 1000;
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.HOUR_OF_DAY
 
, hour);
calendar.set(Calendar.MINUTE, minute);
calendar.set(Calendar.SECOND, 0);
//執行定時任務的時間
Date date=calendar.getTime();
//為了避免若容器啟動的時間晚於定時時間，在重啟容器的時候會立刻執行該任務
if (date.before(new Date())) {
            date = this.addDay(date, 1);
}
        Timer timer = new Timer();
//任務在指定的時間開始進行重複的固定延遲執行
timer.schedule(task,
 
date);
}
    // 增加或減少天數
public Date addDay(Date date, int num) {
        Calendar startDT = Calendar.getInstance();
startDT.setTime(date);
startDT.add(Calendar.DAY_OF_MONTH, num);
        return startDT.getTime();
}
}

這是監聽：

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
/**
 * Created by Administrator on 2017/9/29.
 */
public class RankTaskListener implements ServletContextListener {
    @Override
public void contextInitialized(ServletContextEvent servletContextEvent) {
        System.out.println("開啟監聽了.2點28準時啟動...........");String day="1";
String hour="14";
String minute="28";
        new TaskManager().startTask(new RankTask(),
Integer.parseInt(day), Integer.parseInt(hour), Integer.parseInt(minute));
}

    @Override
public void contextDestroyed(ServletContextEvent servletContextEvent) {

    }
}

這是定時任務：

importjava.util.TimerTask;
/**
 * Created by Administrator on 2017/9/29.
 */
public class RankTask extends TimerTask {
    @Override
public void run() {
        System.out.println("...............任務執行了.............");
}
}

web .xml配置監聽：

<listener>
  <listener-class>com.mytest.task.RankTaskListener</listener-class>
</listener>