Java中用Servlet容器實現程序監聽

2019-11-18 14:29:12

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分兩步走：（1）. 實現 javax.servlet.ServletContextListener 接口的兩個方法：contextInitialized()和contextDestroyed() contextInitialized()：當Servlet容器啟動時會執行 contextDestroyed()：當Servlet容器停止時會執行（2）. 在contextInitialized()中加入需要監聽的程序，并由 java.util.Timer 的 schedule() 方法來控制監聽程序執行的頻率

DEMO（這是我的一個短信回復監聽的程序原型，精簡了一下）

----------------------------------------------------------------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(); }}

將編譯好的class文件放入WEB-INF/classes中，最后別忘記了在Servlet容器中當前WEB應用的web.xml中加入監聽語句：

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

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