首页布局：index.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <%@ page import="java.util.*" %> <%@ page import="com.hanqi.model.*" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> 当前在线人数: <%=application.getAttribute("userCount") %> <hr> 在线用户列表:<br> <% List<User> userList = (List<User>)application.getAttribute("userList"); if(userList!=null) { for(User u : userList) { out.print(u+"<br>"); } } %> </body> </html>
创建用户信息：User
package com.hanqi.model; import java.text.SimpleDateFormat; import java.util.Date; public class User { private String sessionid; private Date firstTime; public String getSessionid() { return sessionid; } public void setSessionid(String sessionid) { this.sessionid = sessionid; } public Date getFirstTime() { return firstTime; } public void setFirstTime(Date firstTime) { this.firstTime = firstTime; } @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + ((firstTime == null) ? 0 : firstTime.hashCode()); result = prime * result + ((sessionid == null) ? 0 : sessionid.hashCode()); return result; } @Override public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false; if (getClass() != obj.getClass()) return false; User other = (User) obj; if (firstTime == null) { if (other.firstTime != null) return false; } else if (!firstTime.equals(other.firstTime)) return false; if (sessionid == null) { if (other.sessionid != null) return false; } else if (!sessionid.equals(other.sessionid)) return false; return true; } @Override public String toString() { return "User [sessionid=" + sessionid + ", 最近登录时间=" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(firstTime) + "]"; } }
编写监听器：TestSessionListener
package com.hanqi.listener; import java.util.ArrayList; import java.util.Date; import java.util.Iterator; import javax.servlet.annotation.WebListener; import javax.servlet.http.HttpSession; import javax.servlet.http.HttpSessionEvent; import javax.servlet.http.HttpSessionListener; import com.hanqi.model.User; /** * Application Lifecycle Listener implementation class TestSessionListener * */ @WebListener public class TestSessionListener implements HttpSessionListener { private int userCount; private ArrayList<User> userList; /** * Default constructor. */ public TestSessionListener() { // TODO Auto-generated constructor stub } /** * @see HttpSessionListener#sessionCreated(HttpSessionEvent) */ public void sessionCreated(HttpSessionEvent sessionEvent) { userCount++; if(userList==null) { userList = new ArrayList<User>(); } HttpSession session = sessionEvent.getSession(); String sessionid = session.getId(); long stime = session.getCreationTime(); if(!checkUsersSession(sessionid, userList)) { User u = new User(); u.setFirstTime(new Date(stime)); u.setSessionid(sessionid); userList.add(u); } session.getServletContext().setAttribute("userCount", userCount); session.getServletContext().setAttribute("userList", userList); } private boolean checkUsersSession(String sessionid, ArrayList<User> userList2) { for(User u : userList2) { if(u.getSessionid().equals(sessionid)) { return true; } } return false; } /** * @see HttpSessionListener#sessionDestroyed(HttpSessionEvent) */ public void sessionDestroyed(HttpSessionEvent sessionEvent) { userCount--; HttpSession session = sessionEvent.getSession(); String sessionid = session.getId(); System.out.println(sessionid + "的用户下线"); if(checkUsersSession(sessionid, userList)) { Iterator<User> iter = userList.iterator(); while(iter.hasNext()) { User u = iter.next(); if(u.getSessionid().equals(sessionid)) { iter.remove(); } } } session.getServletContext().setAttribute("userCount", userCount); session.getServletContext().setAttribute("userList", userList); } }
在web.xml文件中注册监听器
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<listener> <listener-class>com.hanqi.listener.TestSessionListener</listener-class> </listener> <session-config> <session-timeout>1</session-timeout> </session-config> </web-app>