javaweb中实现在线人数统计

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session并不是浏览器关闭时销毁的，而是在session失效的时候销毁下列代码就是监测session创建、销毁

package com.my.count;import javax.servlet.http.*;public class SessionCounter implements HttpSessionListener {    private static int activeSessions = 0;    //session创建时执行    public void sessionCreated(HttpSessionEvent se) {        activeSessions++;    }    //session销毁时执行    public void sessionDestroyed(HttpSessionEvent se) {        if (activeSessions > 0)            activeSessions--;    }    //获取活动的session个数(在线人数)    public static int getActiveSessions() {        return activeSessions;    }}

接下来就是配置web.xml

<listener>      <listener-class>          com.my.count.SessionCounter  //这里是包名加类名      </listener-class>  </listener>

接下来就可以在jsp页面中使用

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%><%@ page import="com.my.count.SessionCounter"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <base href="<%=basePath%>">        <title>My JSP 'ApplicationTest.jsp' starting page</title>        <meta http-equiv="pragma" content="no-cache">    <meta http-equiv="cache-control" content="no-cache">    <meta http-equiv="expires" content="0">        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">    <meta http-equiv="description" content="This is my page">    <!--    <link rel="stylesheet" type="text/css" href="styles.css">    -->  </head>    <body>        在线人数为：<%=SessionCounter.getActiveSessions() %>  </body></html>

不用jsp页面写成接口代码如下:

package com.wangyun.web.controllers;import javax.servlet.http.HttpSessionEvent;import javax.servlet.http.HttpSessionListener;public class SessionCounter implements HttpSessionListener {     static int activeSessions = 0;    //session创建时执行    public void sessionCreated(HttpSessionEvent se) {        activeSessions++;    }    //session销毁时执行    public void sessionDestroyed(HttpSessionEvent se) {        if (activeSessions > 0)            activeSessions--;    }    //获取活动的session个数(在线人数)    public static int getActiveSessions() {        return activeSessions;    }}

   /**   * 在线用户人数   * @throws IOException    * @throws ServletException    */      @RequestMapping(value="user_online", method=RequestMethod.POST, produces="text/json;charset=utf-8")  @ResponseBody  public Object user_online() throws ServletException, IOException {  JSONObject data = new JSONObject();  int number=SessionCounter.activeSessions;  data.put("msg",number);  return data.toString();      }

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