package com.caizhen.listener;
import javax.servlet.ServletContext;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
@WebListener
public class OnlineListener implements HttpSessionListener {
private int count = 0;
public OnlineListener() {
}
public void sessionCreated(HttpSessionEvent se) {
count++;
ServletContext context = se.getSession().getServletContext();
context.setAttribute("count", new Integer(count));
}
public void sessionDestroyed(HttpSessionEvent se) {
count--;
ServletContext context = se.getSession().getServletContext();
context.setAttribute("count", new Integer(count));
}
}运用了servlet监听器，将conur存在context里
<listener>
<listener-class>com.caizhen.listener.OnlineListener</listener-class>
</listener>在web.xml配置监听器
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Insert title here</title>
</head>
<body>
当前在线人数<%=application.getAttribute("count") %></br>
<a href="<%=response.encodeRedirectUrl("logout.jsp") %>">退出登陆</a>
</body>
</html>获取count
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Insert title here</title>
</head>
<body>
<%session.invalidate(); %>
当前在线人数<%=application.getAttribute("count") %>
<p>你已经退出本系统</p>
</body>
</html>使session对象失效
运行项目即可