javaweb之 HttpSessionListener
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>