JavaWeb_listener

Y1_King

于 2022-04-17 13:40:18 发布

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文章标签： intellij-idea java

本文链接：https://blog.youkuaiyun.com/king_xbstudy/article/details/124228593

本文介绍如何在Java Web应用中使用监听器（OnlineCountListener）实时统计并显示网站的在线用户数量，通过HttpSessionListener接口管理session创建和销毁事件来更新计数。

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JavaWeb_listener

1.web.xml

<listener>
            <listener-class>com.king.listener.OnlineCountListener</listener-class>
        </listener>

2.OnlineCountListener.java

在这里插入代码片package com.king.listener;

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

//统计网站在线人数：统计seesion
public class OnlineCountListener implements HttpSessionListener {

    //创建session监听
    public void sessionCreated(HttpSessionEvent httpSessionEvent) {
        ServletContext ctx = httpSessionEvent.getSession().getServletContext();
        Integer onlineCount = (Integer) ctx.getAttribute("OnlineCount");
        if (onlineCount==null){
            onlineCount = new Integer(1);
        }else {
            int count = onlineCount.intValue();
            onlineCount = new Integer(count+1);
        }
        ctx.setAttribute("OnlineCount",onlineCount);
    }


    //销毁session监听
    public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
        ServletContext ctx = httpSessionEvent.getSession().getServletContext();
        Integer onlineCount = (Integer) ctx.getAttribute("OnlineCount");
        if (onlineCount==null){
            onlineCount = new Integer(1);
        }else {
            int count = onlineCount.intValue();
            onlineCount = new Integer(count-1);
        }
        ctx.setAttribute("OnlineCount",onlineCount);
    }

}

3.index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  <h1>当前有<span style="color: blue"><%=this.getServletConfig().getServletContext().getAttribute("OnlineCount")%></span>人在线</h1>
  </body>
</html>