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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

   	
    
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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.OnlineListener
    
   

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+"/";%>              	
   	
   	
       	
   	
           
   
      HttpSessionListener方式监听Session：
    
    登陆：
        
        
   
  

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+"/";%>              	
   	
   	
       	
   	
           登陆成功  	  
您好：${username} [注销]
	当前在线用户：	
   
    	<%	    List onlineUserList = (List) application.getAttribute("onlineUserList");	    for (int i = 0; i < onlineUserList.size(); i++) {	    String onlineUsername = (String) onlineUserList.get(i);	%>	    
	<%	}	%>	
    
     
	              
<%=onlineUsername%>
	              
删除
	         
    
   
  

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+"/";%>              	
   	
   	
       	
   	
             
   
      HttpSessionBindingListener方式监听Session：
    
    登陆：
        
        
   
  

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
   
     sessionMap = (Map
    
     )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
     
      ();            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
   
     sessionMap = (Map
    
     )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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