HttpSessionListener

实现一个***的接口；（有n种）

先附上代码吧
//OnlineCountListener
package com.kuang.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session
public class OnlineCountListener implements HttpSessionListener {
    //创建session监听：看你的一举一动
    //一旦创建session就会触发一次这个事件！

    public void sessionCreated(HttpSessionEvent se) {
        ServletContext servletContext = se.getSession().getServletContext();
        Integer onlineCount = (Integer) servletContext.getAttribute("OnlineCount");
        if (onlineCount == null){
            onlineCount = new Integer(1);
        }else {
            int count = onlineCount.intValue();
            onlineCount = new Integer(count+1);
        }
        servletContext.setAttribute("OnlineCount",onlineCount);
    }

    public void sessionDestroyed(HttpSessionEvent se) {
        ServletContext servletContext = se.getSession().getServletContext();
        Integer onlineCount = (Integer) servletContext.getAttribute("OnlineCount");
        if (onlineCount == null){
            onlineCount = new Integer(1);
        }else {
            int count = onlineCount.intValue();
            onlineCount = new Integer(count-1);
        }
        servletContext.setAttribute("OnlineCount",onlineCount);
    }
}
//index.jsp

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

//web.xml

    <!--注册***-->
<listener>
        <listener-class>com.kuang.listener.OnlineCountListener</listener-class>
</listener>
javaweb之 HttpSessionListener

HttpSessionListener

实现一个***的接口；（有n种）
