Java中用Servlet容器实现程序监听-JSP教程,Java技巧及代码

分两步走：（1）. 实现 javax.servlet.servletcontextlistener 接口的两个方法：contextinitialized()和contextdestroyed() contextinitialized()：当servlet容器启动时会执行 contextdestroyed()：当servlet容器停止时会执行（2）. 在contextinitialized()中加入需要监听的程序，并由 java.util.timer 的 schedule() 方法来控制监听程序执行的频率

demo（这是我的一个短信回复监听的程序原型，精简了一下）

—————————————————————-replylistener.java—————————————————————-

package com.hanweb.jcms;

import javax.servlet.*;

public class replylistener implements servletcontextlistener {  private replytimer rt = null;  public void contextinitialized(servletcontextevent event) {    string status = "[sys] sms reply listener start .";    event.getservletcontext().log(status);    system.out.println(status);

    rt = new replytimer(1);    rt.start();  }

  public void contextdestroyed(servletcontextevent event) {    string status = "[sys] sms reply listener stop .";    event.getservletcontext().log(status);    system.out.println(status);

    if (rt != null) {      rt.stop();    }  }}

—————————————————————-replytimer.java—————————————————————-

package com.hanweb.jcms;

import java.util.*;

public class replytimer {  private final timer timer = new timer();  private final int min;

  public replytimer(int minutes) {    min = minutes;  }

  public void start() {    date date = new date();    timer.schedule(new replytask(), date, min * 60 * 1000);  }

  public void stop() {    timer.cancel();  }}

—————————————————————-replytask.java—————————————————————-

package com.hanweb.jcms;

import java.util.*;

public class replytask extends timertask {  public void dosomething() {    system.out.println("[sys] sms reply listener running ");  }

  public void run() {    dosomething();  }}

将编译好的class文件放入web-inf/classes中，最后别忘记了在servlet容器中当前web应用的web.xml中加入监听语句：

 <listener> <listener-class>com.hanweb.jcms.replylistener</listener-class> </listener>