java session HttpSessionListener、HttpSessionBindingListener使用區別，實如今線人數統計以及踢出用戶

時間 2019-12-06

標籤 java session httpsessionlistener httpsessionbindinglistener 使用區別如今線人統計以及踢出用戶欄目 Java 简体版

原文原文鏈接

java web項目中管理session的時候，除了在web.xml文件中設置過期時間html

<session-config>
 <session-timeout>2</session-timeout>
</session-config>

xxx分鐘，還能夠經過 HttpSessionListener 接口或HttpSessionBindingListener接口來實現對session的監控，經過監聽session的新建和銷燬來控制

實現HttpSessionListener接口：java

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();
        // 取得登陸的用戶名
        String username = (String) session.getAttribute("username");
        // 從在線列表中刪除用戶名
        List onlineUserList = (List) application.getAttribute("onlineUserList");
        onlineUserList.remove(username);
        System.out.println(username+"已經退出！");
	}
}

後要在web.xml中配置監聽接口配置：web

<listener>
	<listener-class>listener.OnlineListener</listener-class>
</listener>

當用戶首次訪問網站頁面的時候，框架就會生成一個sessionID這時執行listener.OnlineListener.sessionCreated()方法，執行操做，不是對單個session與用戶的是對整個全局的session的操做session

項目其餘文件代碼：
index.jspapp

<%@ 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方式監聽Session：<br/>
    登錄：<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");
	// 取得登陸的用戶名
	String username = request.getParameter("username");
	// 把用戶名保存進session
	System.out.println("jspsession:" + session.getId());
	session.setAttribute("username", username);
	session.setAttribute("onlineUserList", new OnlineListener(username));
	
	System.out.println("用戶："+username+" 登錄成功");
	// 把用戶名放入在線列表
	List onlineUserList = (List) application.getAttribute("onlineUserList");
	// 第一次使用前，須要初始化
	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>
  登錄成功
  
	  <h3>您好：${username} [<a href="logout.jsp">註銷</a>]</h3>
	當前在線用戶：
	<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%>">刪除</a></td>
	    </tr>
	<%
	}
	%>
	</table>
  </body>
</html>

而HttpSessionBindingListener運用時不用在web.xml中配置，HttpSessionBindingListener雖然叫作監聽器，但使用方法與HttpSessionListener徹底不一樣。咱們實際看一下它是如何使用的。新建類OnlineUserBindingListener，實現HttpSessionBindingListener接口，構造方法傳入username參數，HttpSessionBindingListener內有兩個方法valueBound(HttpSessionBindingEvent event)和valueUnbound(HttpSessionBindingEvent event)，前者爲數據綁定，後者爲取消綁定所謂對session進行數據綁定，就是調用session.setAttribute()把HttpSessionBindingListener保存進session中框架

index.jspjsp

<%@ 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方式監聽Session：<br/>
    登錄：<input id="username" name="username"/>
    <input type="submit"/>
    </form>
  </body>
</html>

sessionBindingLogin.jsp:網站

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@page import="listener.OnlineBindingListener"%>
<%
	request.setCharacterEncoding("UTF-8");
	// 取得登陸的用戶名
	String username = request.getParameter("username");
	// 把用戶名放入在線列表
    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("建立Session:"+session.getId());
        System.out.println("username:"+username);
        
        session.setAttribute("username", username);
        
        ServletContext application = session.getServletContext();
        // 把用戶名放入在線列表
        List onlineUserList = (List) application.getAttribute("onlineUserList");
        Map<String, HttpSession> sessionMap = (Map<String, HttpSession>)application.getAttribute("sessionMap");
        // 第一次使用前，須要初始化
        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();
 
        // 從在線列表中刪除用戶名
        List onlineUserList = (List) application.getAttribute("onlineUserList");
        onlineUserList.remove(this.username);
        System.out.println("Session實效:"+session.getId());
        System.out.println(this.username + "退出。");
 
    }

}

把某人踢出登錄狀態：

deleteUser.jspui

<%@ page language="java" import="java.util.*,javax.servlet.*" pageEncoding="UTF-8"%>
<%
	request.setCharacterEncoding("UTF-8");
	// 取得登陸的用戶名
	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");
%>