session並不是瀏覽器關閉時銷毀的，而是在session失效的時候銷毀下列代碼就是監測session創建、銷毀
package com.my.count; import javax.servlet.http.*; public class SessionCounter implements HttpSessionListener { private static int activeSessions = 0; //session創建時執行 public void sessionCreated(HttpSessionEvent se) { activeSessions++; } //session銷毀時執行 public void sessionDestroyed(HttpSessionEvent se) { if (activeSessions > 0) activeSessions--; } //獲取活動的session個數(在線人數) public static int getActiveSessions() { return activeSessions; } }
接下來就是配置web.xml
<listener> <listener-class> com.my.count.SessionCounter //這里是包名加類名 </listener-class> </listener>
接下來就可以在jsp頁面中使用
<%@ 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> 在線人數為：<%=SessionCounter.getActiveSessions() %> </body> </html>