首先写个类:import javax.servlet.*; import javax.servlet.http.*; public class SessionCounter implements HttpSessionListener { private static int activeSessions = 0; public void sessionCreated(HttpSessionEvent se) { activeSessions++; } public void sessionDestroyed(HttpSessionEvent se) { if(activeSessions > 0) activeSessions--; } public static int getActiveSessions() { return activeSessions; } }然后配置web.xml<?xml version="1.0" encoding="UTF-8"?><web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">****************************************<!-- Listeners --> <listener> <listener-class> SessionCount.SessionCounter (注意此处)</listener-class> </listener>***************************************** </web-app>建个JSP测试:test.jsp<%@ page language="Java" contentType="text/html;charset=GBK"%><%@ page import="java.sql.*"%><%@ page import="SessionCount.SessionCounter" %> <html><head><meta http-equiv="Content-Type" content="text/html; charset=GBK"><title>无标题文档</title><body bgcolor="#FFFFFF"> 在线人数:<%=SessionCounter.getActiveSessions()%> </body> </html>
