java session HttpSessionListener、HttpSessionBindingListener使用区别，实现在线人数统计以及踢出用户 -

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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>

httpSessionLogin.jsp:

<%@ 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");
%>

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");
%>

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