javaWeb定时器

//这是我的定时器类，用来定时执行某段任务；

package com.my.time;

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

public class BugXmlTimer  {
   public   Timer timer;
 
  
   public void timerStart(){
       timer = new Timer();
       Date datetime=new Date();
       Date midnightDate=new Date();

       SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd");
       SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
      
    try {
               
        midnightDate = sdf2.parse(sdf1.format(datetime)+" 23:00:00");
    } catch (ParseException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
       
        long in=midnightDate.getTime()-datetime.getTime();
  
        System.out.println("before task");
//立刻执行，然后每隔30s执行一次
        timer.schedule(new BugXmlTimerTask(), 0,30000);
       
     
   }
  
   public void timerStop(){
       if(timer!=null)
          timer.cancel();
   }
  
   public static void main(String[] args){
        BugXmlTimer myTimer=new BugXmlTimer();
       

            // TODO Auto-generated method stub
        myTimer.timerStart();
       
   }
}

//这是执行任务的类，即每隔一段时间要做的事情在这里

package com.my.time;

import java.util.TimerTask;

 

public class BugXmlTimerTask extends TimerTask {
    @Override
    public void run() {
           System.out.print("run task");
     }
}
//以下是出发定时操作的类，该类继承了ServletContextListener

public class MyTimerListener implements ServletContextListener {
    private BugXmlTimer  mytimer = new BugXmlTimer  ();
    public void contextInitialized(ServletContextEvent event) {
        mytimer.timerStart();
    }

    public void contextDestroyed(ServletContextEvent event) {
        mytimer.timerStop();
    }
}

然后在web.xml里部署一下，即可在程序启动后运行定时器了！

 <listener>
        <listener-class>com.my.time.MyTimerListener </listener-class>
 </listener>