jsp 实现在线人数统计

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="https://java.sun.com/xml/ns/j2ee"

xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="https://java.sun.com/xml/ns/j2ee

https://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>