HttpSessionListener, HttpSessionAttributeListener的用法 .

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Listener

以下是一个统计在线会话数的功能，并且让超时的自动销毁

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
	http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
	<listener>
		<listener-class>
			org.xiosu.listener.onlineListener
		</listener-class>
	</listener>


	<!--默认的会话超时时间间隔，以分钟为单位  -->
	<session-config>
		<session-timeout>1</session-timeout>
	</session-config>
	<welcome-file-list>
		<welcome-file>index.jsp</welcome-file>
	</welcome-file-list>

</web-app>

onlineListener.java

package org.xiosu.listener;

import java.util.ArrayList;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class onlineListener implements HttpSessionListener,
		HttpSessionAttributeListener {
	// 参数
	ServletContext sc;

	ArrayList list = new ArrayList();

	// 新建一个session时触发此操作
	public void sessionCreated(HttpSessionEvent se) {
		sc = se.getSession().getServletContext();
		System.out.println("新建一个session");
	}

	// 销毁一个session时触发此操作
	public void sessionDestroyed(HttpSessionEvent se) {
		System.out.println("销毁一个session");
		if (!list.isEmpty()) {
			list.remove((String) se.getSession().getAttribute("userName"));
			sc.setAttribute("list", list);
		}
	}

	// 在session中添加对象时触发此操作，在list中添加一个对象
	public void attributeAdded(HttpSessionBindingEvent sbe) {
		list.add((String) sbe.getValue());
		System.out.println(sbe.getValue());
		sc.setAttribute("list", list);
	}

	// 修改、删除session中添加对象时触发此操作
	public void attributeRemoved(HttpSessionBindingEvent arg0) {
		
		System.out.println("5555555");
	}

	public void attributeReplaced(HttpSessionBindingEvent arg0) {
		System.out.println("77777777");
	}
}

index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
	String path = request.getContextPath();
	String basePath = request.getScheme() + "://"
			+ request.getServerName() + ":" + request.getServerPort()
			+ path + "/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
	<head>
		<base href="<%=basePath%>">

		<title>My JSP 'index.jsp' starting page</title>
		<meta http-equiv="pragma" content="no-cache">
		<meta http-equiv="cache-control" content="no-cache">
		<meta http-equiv="expires" content="0">
		<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
		<meta http-equiv="description" content="This is my page">
		<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->
	</head>

	<body>
		<%
			session = request.getSession(false);

			if (session != null)
				session.invalidate();
		%>
		<form action="isOnline.jsp" method="post">
			用户名：
			<input type="text" name="uName" />
			<input type="submit" value="上线">
	</body>
</html>

isOnline.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'isOnline.jsp' starting page</title>
    
	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">    
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->

  </head>
  
  <body>
    <%

session=request.getSession();

session.setAttribute("userName",request.getParameter("uName"));

response.sendRedirect("showOnline.jsp");
%>
  </body>
</html>

showOnline.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
	<head>
		<base href="<%=basePath%>">

		<title>My JSP 'showOnline.jsp' starting page</title>

		<meta http-equiv="pragma" content="no-cache">
		<meta http-equiv="cache-control" content="no-cache">
		<meta http-equiv="expires" content="0">
		<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
		<meta http-equiv="description" content="This is my page">
		<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->

	</head>

	<body>
		<%
ArrayList showList=(ArrayList)(getServletContext().getAttribute("list"));
out.print("在线人数 "+showList.size()+"<br>");
for(int i=0;i<showList.size();i++){
out.print(showList.get(i)+"在线"+"<br>");
}
%>
		<br>
		<a href="index.jsp">退出</a>
	</body>
</html>

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