WEB计时器的实现——Timer(转载)

Java定时器（java.util.Timer）有定时触发计划任务的功能，通过配置定时器的间隔时间，在某一间隔时间段之后会自动有规律的调用预先所安排的计划任务（java.util.TimerTask）。另外，由于我们希望当Web工程启动时，定时器能自动开始计时，在整个Web工程的生命期里，定时器能在每晚深夜触发一次报表计算引擎。因此定时器的存放位置也值得考查，不能简单的存在于单个Servlet或JavaBean中，必须能让定时器宿主的存活期为整个Web工程生命期，在工程启动时能自动加载运行。结合这两点，跟Servlet上下文有关的侦听器就最合适不过了，通过在工程的配置文件中加以合理配置，会在工程启动时自动运行，并在整个工程生命期中处于监听状态。

......下面就Servlet侦听器结合 Java定时器来讲述整个实现过程。要运用Servlet侦听器需要实现javax.servlet.ServletContextListener接口，同时实现它的contextInitialized(ServletContextEvent    event)和contextDestroyed(ServletContextEvent    event)两个接口函数。考虑定时器有个建立和销毁的过程，看了前面两个接口函数，就不容置疑的把建立的过程置入 contextInitialized，把销毁的过程置入contextDestroyed了。

 

 

package com.derek.servlet;

import javax.servlet.*;
import javax.servlet.http.*;
import com.derek.pub.TimerManager;
/**
 * 启动定时器的监听器
 * @author derek
 * @version 1.0
 */
public class TimerListener extends HttpServlet implements
        ServletContextListener {
    private TimerManager tm = null;
    //Notification that the web module is ready to process requests
    public void contextInitialized(ServletContextEvent sce) {
      int day,hour,min,sec;
      day = 26; hour = 16; min = 42; sec = 0;
      tm = new TimerManager(day,hour,min,sec);
    }

    //Notification that the servlet context is about to be shut down
    public void contextDestroyed(ServletContextEvent sce) {
       tm.destoryTimer();
    }
}

package com.derek.servlet;

import javax.servlet.*;
import javax.servlet.http.*;
import com.derek.pub.TimerManager;
/**
 * 启动定时器的监听器
 * @author derek
 * @version 1.0
 */
public class TimerListener extends HttpServlet implements
        ServletContextListener {
    private TimerManager tm = null;
    //Notification that the web module is ready to process requests
    public void contextInitialized(ServletContextEvent sce) {
      int day,hour,min,sec;      
      day = 26; hour = 16; min = 42; sec = 0;     
      tm = new TimerManager(day,hour,min,sec);
    }

    //Notification that the servlet context is about to be shut down
    public void contextDestroyed(ServletContextEvent sce) {
       tm.destoryTimer();
    }
}

 

 

 

package com.derek.pub;

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

/**
 * 定时器
 * @author derek
 * @version 1.0
 */
public class TimerManager {
    Timer t = null;
    public TimerManager(int day,int hour,int min,int sec) {
        time(day,hour,min,sec);
    }

    public void time(int day,int hour,int min,int sec){
    Calendar c = Calendar.getInstance();
    c.set(Calendar.DAY_OF_MONTH,day);
    c.set(Calendar.HOUR_OF_DAY,hour);
    c.set(Calendar.MINUTE,min);
    c.set(Calendar.SECOND,sec);
    Date date = c.getTime();
    System.out.println(c.getTime());
    t= new Timer();
    MyTask mt = new MyTask();
    t.schedule(mt,date);
    }
    public void destoryTimer(){
    t.cancel();
    }
}

 

 

package com.derek.pub;
import java.util.TimerTask;
/**
 * 计划任务代码
 * @author derek
 * @version 1.0
 */
public class MyTask extends TimerTask{
    public MyTask() {
    }
    /**
     * 任务块
     */
    public void run() {
        System.out.println("定时器RUN");
    }
}