java session HttpSessionListener、HttpSessionBindingListener使用区别，实现在线人数统计以及踢出用户
java web项目中管理session的时候，除了在web.xml文件中设置过时时间
<session-config>
<session-timeout>2</session-timeout>
</session-config>xxx分钟，还可以通过
HttpSessionListener
接口或HttpSessionBindingListener接口来实现对session的监控，通过监听session的新建和销毁来控制
实现HttpSessionListener接口：
package listener;
import java.util.List;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
public class OnlineListener implements HttpSessionListener {
public void sessionCreated(HttpSessionEvent event) {
System.out.println("新建session:" + event.getSession().getId());
}
public void sessionDestroyed(HttpSessionEvent event) {
HttpSession session = event.getSession();
ServletContext application = session.getServletContext();
// 取得登录的用户名
String username = (String) session.getAttribute("username");
// 从在线列表中删除用户名
List onlineUserList = (List) application.getAttribute("onlineUserList");
onlineUserList.remove(username);
System.out.println(username+"已经退出！");
}
}
后要在web.xml中配置监听接口配置：
<listener> <listener-class>listener.OnlineListener</listener-class> </listener>
当用户首次访问网站页面的时候，框架就会生成一个sessionID这时执行listener.OnlineListener.sessionCreated()方法，执行操作，不是对单个session与用户的是对整个全局的session的操作
项目其他文件代码：
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">
</head>
<body>
<form action="httpSessionLogin.jsp" method="get">
HttpSessionListener方式监听Session：<br/>
登陆：<input id="username" name="username"/>
<input type="submit"/>
</form>
</body>
</html>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@page import="listener.OnlineListener"%>
<%
request.setCharacterEncoding("UTF-8");
// 取得登录的用户名
String username = request.getParameter("username");
// 把用户名保存进session
System.out.println("jspsession:" + session.getId());
session.setAttribute("username", username);
session.setAttribute("onlineUserList", new OnlineListener(username));
System.out.println("用户："+username+" 登陆成功");
// 把用户名放入在线列表
List onlineUserList = (List) application.getAttribute("onlineUserList");
// 第一次使用前，需要初始化
if (onlineUserList == null) {
onlineUserList = new ArrayList();
application.setAttribute("onlineUserList", onlineUserList);
}
onlineUserList.add(username);
// 成功
response.sendRedirect("result.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">
</head>
<body>
登陆成功
<h3>您好：${username} [<a href="logout.jsp">注销</a>]</h3>
当前在线用户：
<table>
<%
List onlineUserList = (List) application.getAttribute("onlineUserList");
for (int i = 0; i < onlineUserList.size(); i++) {
String onlineUsername = (String) onlineUserList.get(i);
%>
<tr>
<td><%=onlineUsername%></td>
<td><a href="deleteUser.jsp?username=<%=onlineUsername%>">删除</a></td>
</tr>
<%
}
%>
</table>
</body>
</html>
而HttpSessionBindingListener运用时不用在web.xml中配置，HttpSessionBindingListener虽然叫做监听器，但使用方法与HttpSessionListener完全不同。我们实际看一下它是如何使用的。新建类OnlineUserBindingListener，实现HttpSessionBindingListener接口，构造方法传入username参数，HttpSessionBindingListener内有两个方法valueBound(HttpSessionBindingEvent event)和valueUnbound(HttpSessionBindingEvent event)，前者为数据绑定，后者为取消绑定所谓对session进行数据绑定，就是调用session.setAttribute()把HttpSessionBindingListener保存进session中
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">
</head>
<body>
<form action="sessionBindingLogin.jsp" method="get">
HttpSessionBindingListener方式监听Session：<br/>
登陆：<input id="username" name="username"/>
<input type="submit"/>
</form>
</body>
</html>
sessionBindingLogin.jsp:
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@page import="listener.OnlineBindingListener"%>
<%
request.setCharacterEncoding("UTF-8");
// 取得登录的用户名
String username = request.getParameter("username");
// 把用户名放入在线列表
session.setAttribute("onlineUserBindingListener", new OnlineBindingListener(username));
// 成功
response.sendRedirect("result.jsp");
%>
package listener;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;
public class OnlineBindingListener implements HttpSessionBindingListener {
String username;
public OnlineBindingListener(String username){
this.username=username;
}
public void valueBound(HttpSessionBindingEvent event) {
HttpSession session = event.getSession();
System.out.println("创建Session:"+session.getId());
System.out.println("username:"+username);
session.setAttribute("username", username);
ServletContext application = session.getServletContext();
// 把用户名放入在线列表
List onlineUserList = (List) application.getAttribute("onlineUserList");
Map<String, HttpSession> sessionMap = (Map<String, HttpSession>)application.getAttribute("sessionMap");
// 第一次使用前，需要初始化
if (onlineUserList == null) {
onlineUserList = new ArrayList();
application.setAttribute("onlineUserList", onlineUserList);
}
if (sessionMap == null) {
sessionMap = new HashMap<String, HttpSession>();
application.setAttribute("sessionMap", sessionMap);
}
onlineUserList.add(this.username);
sessionMap.put(username, session);
}
public void valueUnbound(HttpSessionBindingEvent event) {
HttpSession session = event.getSession();
ServletContext application = session.getServletContext();
// 从在线列表中删除用户名
List onlineUserList = (List) application.getAttribute("onlineUserList");
onlineUserList.remove(this.username);
System.out.println("Session实效:"+session.getId());
System.out.println(this.username + "退出。");
}
}
把某人踢出登陆状态：
deleteUser.jsp
<%@ page language="java" import="java.util.*,javax.servlet.*" pageEncoding="UTF-8"%>
<%
request.setCharacterEncoding("UTF-8");
// 取得登录的用户名
String username = request.getParameter("username");
System.out.println(username);
Map<String, HttpSession> sessionMap = (Map<String, HttpSession>)application.getAttribute("sessionMap");
HttpSession otherSession = (HttpSession)sessionMap.get(username);
//otherSession.removeAttribute("username");
otherSession.invalidate();
sessionMap.remove(username);
// 成功
response.sendRedirect("result.jsp");
%>