java web 定时器

JAVA WEB定时器,定时器的启动一般随web server的启动而启动,一般有两种方法.

方法一：在web.xml里配置一个Servlet，继承HttpServlet，并设置其随web server的启动而启动。然后在该Servlet的init()方法里启动定时器，在destory()方法里销毁定时器。

方法二：在web.xml里配置一个Listener，继承ServletContextListener，然后在该Listener的初始化方法里启动定时器，在其销毁的方法朝左销毁定时器。

在servlet中启动定时器

一，继承HttpServlet的写法：

1，Servlet

import java.io.IOException;
import java.util.Timer;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.lang.StringUtils;

public class ConvergeDataServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    private Timer timer1 = null;

    private Task task1;

    /**
      * Constructor of the object.
      */
    public ConvergeDataServlet() {
        super();
     }

    /**
      * Destruction of the servlet.
      */
    public void destroy() {
        super.destroy();
        if(timer1!=null){
             timer1.cancel();
         }
     }


    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

     }


    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
         doGet(request, response);
     }

    // init方法启动定时器
    public void init() throws ServletException {

         ServletContext context = getServletContext();

        // (true为用定时间刷新缓存)
         String startTask = getInitParameter("startTask");

        // 定时刷新时间(分钟)
         Long delay = Long.parseLong(getInitParameter("delay"));

        // 启动定时器
        if(startTask.equals("true")){
             timer1 = new Timer(true);
             task1 = new Task(context);
             timer1.schedule(task1, delay * 60 * 1000, delay * 60 * 1000);
         }
     }
}

2，任务

2. import java.util.TimerTask;   
4.   
5. import javax.servlet.ServletContext;   
6.   
7. public class Task extends TimerTask{   
8.   
9.     private ServletContext context;   
10.        
11.     private static boolean isRunning = true;   
12.        
13.     public Task(ServletContext context){   
14.         this.context = context;   
15.      }   
16.        
17.            
18.     @Override  
19.     public void run() {   
20.         if(isRunning){   
21.              
22.          }   
23.      }   
24.   
25. }   

3，web.xml中的配置

< servlet >
     < servlet-name >taskservlet< / servlet-name >
    < servlet-class >com.task< /servlet-class >
    < init-param >
    < param-name >startTask< /param-name >
    < param-value >true< /param-value >
    < /init-param >
    < init-param >
    < param-name >intervalTime< /param-name >
    < param-value >1< /param-value >
    < /init-param >
    < load-on-startup >300< /load-on-startup >
< /servlet >

二，继承ServletContextListener

1，定时器

/**
*
*/
package com.annlee.website.util;

import java.util.Timer;

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

/**
* @author Administrator 定时器
*/
public class TimerListener implements ServletContextListener {

private Timer timer;
private AnnleeTimerTask task;

public void contextDestroyed(ServletContextEvent arg0) {
   timer.cancel();
   System.out.println("定时器已销毁");
}

public void contextInitialized(ServletContextEvent event) {

   timer = new java.util.Timer(true);
   task = new AnnleeTimerTask(event.getServletContext());
   System.out.println("定时器已启动");
   timer.schedule(task, 0, 60 * 1000);
   System.out.println("已经添加任务调度表");
}

}

2，任务

package com.annlee.website.util;

import java.util.Calendar;
import java.util.TimerTask;

import javax.servlet.ServletContext;

import com.annlee.website.model.service.member.UsmAccessDataService;

/**
* 定时器的任务
*/
public class AnnleeTimerTask extends TimerTask {

private ServletContext context;
    private static boolean isRunning = false;
    private static boolean flag = true;
    private static final int C_SCHEDULE_HOUR = 0;
    private UsmAccessDataService accessDataService;
  
    public AnnleeTimerTask(ServletContext context){
     this.context = context;
    }

    public void run() {
    accessDataService = new UsmAccessDataService();
        Calendar cal = Calendar.getInstance();
        if (!isRunning) {
            if (C_SCHEDULE_HOUR == cal.get(Calendar.HOUR_OF_DAY) && flag) {
                isRunning = true;
            //    accessDataService.SendHttpByMonth(0,0, 0);
                System.out.println("正在执行任务");
                isRunning = false;
                flag = false;
                context.log("指定任务执行结束");
            }
        } else {
            context.log("上一次任务执行还未结束");
        }
        if(C_SCHEDULE_HOUR != cal.get(Calendar.HOUR_OF_DAY)){
            flag = true;
        }
      }

}

3，web.xml中的配置

  
    com.annlee.website.util.TimerListener