javaee starts the scheduled task when the task scheduler starts in the listener

TestContextServletListener

package com.yyy.listener;

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

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

import com.yyy.schedule.MyTimeTask;

/**
 * Application Lifecycle Listener implementation class TestContextServletListener
 *
 */
@WebListener
public class TestContextServletListener implements ServletContextListener {
    
    

    /**
     * Default constructor. 
     */
    public TestContextServletListener() {
    
    
        // TODO Auto-generated constructor stub
    }

	/**
     * @see ServletContextListener#contextDestroyed(ServletContextEvent)
     */
    public void contextDestroyed(ServletContextEvent arg0)  {
    
     
         // TODO Auto-generated method stub
    }

	/**
     * @see ServletContextListener#contextInitialized(ServletContextEvent)
     */
    public void contextInitialized(ServletContextEvent arg0)  {
    
     
         // TODO Auto-generated method stub
    	//创建一个定时器对象  
		Timer timer=new Timer();
		
		//从当前时间开始 每隔1秒钟调用一次任务,每次执行时间为上一次任务开始起向后推一个period间隔
		//timer.scheduleAtFixedRate(new MyTimeTask(), new Date(), 1000);
		//timer.schedule(new MyTimeTask(), new Date(), 1000);
		
		//延时指定的时间 执行任务
		//timer.schedule(new MyTimeTask(), 60*1000);
	
		//在指定的时间执行某个任务
		try {
    
    
			timer.schedule(new MyTimeTask(), new SimpleDateFormat("HH:mm:ss").parse("20:00:00"),24*3600*1000);
		} catch (ParseException e) {
    
    
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
    }
	
}

MyTimeTask

package com.yyy.schedule;

import java.text.SimpleDateFormat;
import java.util.TimerTask;

public class MyTimeTask extends TimerTask {
    
    

	//重写run方法
		@Override
		public void run() {
    
    
			// TODO Auto-generated method stub
			
			System.out.println("当前任务的执行时间为:"+new SimpleDateFormat("HH:mm:ss").format(this.scheduledExecutionTime()));
			
			try {
    
    
				Thread.sleep(2000);
			} catch (InterruptedException e) {
    
    
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			
		}
}