监听器模拟用户在线

　　由于会话管理机制的原因，用户需在不同的浏览器上进行登录。 期间可以访问onlineservlet查询在线用户列表。

　　　设置监听器：

package com.listener;

import java.util.LinkedList;
import java.util.List;

import javax.faces.application.Application;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
@WebListener
public class OnlineListener implements HttpSessionListener,
        HttpSessionAttributeListener, ServletContextListener {
     private  ServletContext application;
    @Override
    public void contextInitialized(ServletContextEvent arg0) {
        //上下文启动时创建list放进application用来存放在线用户列表
        List<String> list = new LinkedList<>();
         application  = arg0.getServletContext();
         application.setAttribute("online",list);
    }

    @Override
    public void attributeAdded(HttpSessionBindingEvent arg0) {
        //session属性添加时调用   将登陆的用户名存进list
        String name = (String) arg0.getSession().getAttribute("name");
        List<String> list =(List<String>)application.getAttribute("online");
        list.add(name);
        application.setAttribute("online",list);
    }
    @Override
    public void sessionDestroyed(HttpSessionEvent arg0) {
        //session 结束时调用 将下线的用户从list中去除
        System.out.println("session destroyed");
        List<String> list = (List<String>)application.getAttribute("online");
        String name =(String) arg0.getSession().getAttribute("name");
        list.remove(name);
        application.setAttribute("online",list);
    }
        @Override
    public void sessionCreated(HttpSessionEvent arg0) 
        {}
        @Override
    public void attributeRemoved(HttpSessionBindingEvent arg0) {}
        @Override
    public void attributeReplaced(HttpSessionBindingEvent arg0) {}
        @Override
    public void contextDestroyed(ServletContextEvent arg0) {}
}

登录serlet：

package com.servlet;

import java.io.IOException;

import javax.jms.Session;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
@WebServlet(name="loginservlet",urlPatterns="/loginservlet")
/**
 * 用户的登陆
 * @author Administrator
 *
 */
public class LoginServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
            String name = req.getParameter("name");
            HttpSession session =  req.getSession();
            if(null!=name){
            session.setAttribute("name",name);
            resp.sendRedirect("main.jsp");
            }
    }
    

}

下线servlet：

package com.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.faces.application.Application;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet(name="logoutservlet",urlPatterns="/logoutservlet")
/**
 * 用户的下线
 * @author Administrator
 *
 */
public class LogoutServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        req.setCharacterEncoding("utf8");
        resp.setCharacterEncoding("utf8");
        resp.setContentType("text/html;charset=UTF-8");
        req.getSession().invalidate();//会话销毁
        PrintWriter out = resp.getWriter();
        
        out.println("在线用户:");
        List<String> list = (List)getServletContext().getAttribute("online");
        for (String s : list) {
            out.println(s);
        }
    }

}

在线用户查询servlet：

package com.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet(name="onlineservlet",urlPatterns="/onlineservlet")
/**
 * 通过访问可以查询在线用户名单
 * @author Administrator
 *
 */
public class OnlineServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        resp.setContentType("text/html;charset=UTF-8");
        PrintWriter out = resp.getWriter();
        out.println("在线用户:");
        List<String> list = (List)getServletContext().getAttribute("online");
        for (String s : list) {
            out.println(s);
        }
    }

}

登录界面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>
  <form action="loginservlet" method="postggi">
  <center>
      name:<input type="text" name="name"><br>
      <input type="submit" value="load..">
      </center>
  </form>
  </body>
</html>

登录后主界面：

<%@ 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>main</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>
          <center>
          <form action="logoutservlet" method="post">
                <%
                    String name = (String)session.getAttribute("name");
                 %> 
                 <%=name %>欢迎登录
                 <br><input type="submit" value="注销">
         </form>
         </center>
  </body>
</html>