监听器

统计网站在线人数

package com.ding.listener;

import javax.servlet.ServletContext;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

/**
 * @Description 统计在线人数
 * @Author 丁帅帅
 * @Date 21/08/11 15:07
 * @Version 1.0
 */
@WebListener
public class OnlineListener implements HttpSessionListener {
    @Override
    public void sessionCreated(HttpSessionEvent Event) {
        ServletContext context =Event.getSession().getServletContext();
       // System.out.println(Event.getSession().getId());
        Integer onlineCount = (Integer) context.getAttribute("OnlineCount");
        if (onlineCount==null){
            onlineCount =new Integer(1);
        }else{
            //int count = onlineCount.intValue();
            onlineCount = onlineCount + 1;
        }
        context.setAttribute("OnlineCount", onlineCount);
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent event) {
        ServletContext context = event.getSession().getServletContext();
        Integer onlineCount = (Integer) context.getAttribute("OnlineCount");
        if (onlineCount == null) {
            onlineCount = new Integer(0);
        } else {
            int count = onlineCount.intValue();
            onlineCount = count - 1;
        }
        context.setAttribute("OnlineCount", onlineCount);

    }
}


<%--
  User: 丁帅帅
  Date: 21/08/11
  Time: 15:16
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>在线人数</title>
</head>
<body>
<h1>当前有 <span style="color: blue">
  ${OnlineCount}</span>
    人在线</h1>
</body>
</html>
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