HttpsessionListener 实现在线人数统计

最近在学servlet jsp,用的林信良先生的 jsp&servlet 这本书,在第五章有道在线人数统计的课后题完成,做一次记录.

实际效果:

一:用户类:

 package cc.openhome.controler;

 public class User {
     private String name;
     private String sessionId;
     private String ip;
     private String firstTime;
     private String userAgent;
     public User(){

     }

     public String getName() {
         return name;
     }

     public String getIp() {
         return ip;
     }

     public String getSessionId() {
         return sessionId;
     }

     public String getFirstTime() {
         return firstTime;
     }

     public String getUserAgent() {
         return userAgent;
     }

     public void setUserAgent(String userAgent) {
         this.userAgent = userAgent;
     }

     public void setName(String name) {
         this.name = name;
     }

     public void setFirstTime(String firstTime) {
         this.firstTime = firstTime;
     }

     public void setIp(String ip) {
         this.ip = ip;
     }

     public void setSessionId(String sessionId) {
         this.sessionId = sessionId;
     }

 }

public class User

二:登录页面:

 package cc.openhome.controler;

 import javax.servlet.ServletException;
 import javax.servlet.annotation.WebServlet;
 import javax.servlet.http.Cookie;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import java.io.IOException;
 import java.text.SimpleDateFormat;
 import java.util.*;

 @WebServlet("/login.do")
 public class Login extends HttpServlet {

    private ArrayList<User> ulist;
    private Map<String,String> users;
    public Login(){
        users = new HashMap<String,String>();
        users.put("liming","123456");
        users.put("小猪","123456");
        users.put("小林","123456");
    }

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

         req.setCharacterEncoding("UTF-8");
         String uname = req.getParameter("user");
         String pssd = req.getParameter("pwd");

         String page = "login.html";

         if (users.containsKey(uname) && users.get(uname).equals(pssd)) {
             req.getSession().setAttribute("uname", uname);
             String sessionId = req.getSession().getId();
             ArrayList<User> ulist = (ArrayList<User>) getServletContext().getAttribute("ulist");
             if(ulist == null){
                 ulist = new ArrayList<User>();
                 getServletContext().setAttribute("ulist",ulist);
             }
             User u = new User();
             u.setSessionId(sessionId);
             u.setName(uname);
             u.setIp(req.getRemoteAddr());
             SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd hh:MM:ss");
             u.setFirstTime(df.format(new Date()));
             u.setUserAgent(req.getHeader("user-agent"));
             ulist.add(u);
             page = "welcome.view";
         }
         resp.sendRedirect(page);
     }
 }

三:统计在线人数:

 package cc.openhome.controler;

 import javax.servlet.ServletContext;
 import javax.servlet.annotation.WebListener;
 import javax.servlet.http.HttpSession;
 import javax.servlet.http.HttpSessionEvent;
 import javax.servlet.http.HttpSessionListener;
 import java.util.List;

 @WebListener
 public class OnlineUserCounter implements HttpSessionListener {
     private static int counter;

     public static int getCounter(){
         return counter;
     }

     @Override
     public void sessionCreated(HttpSessionEvent se) {
         System.out.println("新建session: "+se.getSession().getId());

     }

     @Override
     public void sessionDestroyed(HttpSessionEvent se) {
         HttpSession session = se.getSession();
         ServletContext application = session.getServletContext();
         String username = (String) session.getAttribute("username");

         List ulist = (List)
                 application.getAttribute("ulist");
         ulist.remove(username);
         System.out.println(username+"已经退出!");

     }
 }

四:登录成功页面显示

 package cc.openhome.view;

 import cc.openhome.controler.User;
 import cc.openhome.controler.OnlineUserCounter;
 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;
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;

 @WebServlet("/welcome.view")
 public class Welcome extends HttpServlet {
     @Override
     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

         resp.setContentType("text/html;charset=UTF-8");
         PrintWriter out = resp.getWriter();
         HttpSession session = req.getSession(false);
         out.println("<!DOCTYPE HTML PUBLIC '-//W3C//DTD HTML 4.01'" +
                 "Transitional//EN");
         out.println("<html>");
         out.println("<head>");
         out.println("<title>欢迎</title>");
         out.println("</head>");
         out.println("<body>");

         ArrayList<User> ul = (ArrayList <User>) getServletContext().getAttribute("ulist");
         out.println("<h1> 目前在线人数 "+ ul.size() +"人</h1>");
             Iterator<User> it = ul.iterator();
             while (it.hasNext()){
                 User u = it.next();
                 out.println("<h4>id: "+ u.getSessionId() +" </h4>");
                 out.println("<h4>用户: "+ u.getName()+" </h4>");
                 out.println("<h4>ip: "+ u.getIp() +" </h4>");
                 out.println("<h4>访问时间: "+ u.getFirstTime() +" </h4>");
                 out.println("<h4>浏览器信息: "+ u.getUserAgent() +" </h4>");
                 out.println("<br>");
             }

         out.println("</body>");
         out.println("</html>");
         out.close();

         }
 }

五:登录的前端页面:

 <!DOCTYPE html>
 <html lang="en">
 <head>
     <meta charset="UTF-8">
     <title>登录</title>
 </head>
 <body>
 <form action="login.do" method="post">
     用户名: <input type="text" name="user"><br>
     密码:  <input type="password" name="pwd"><br>
     提交: <input type= "submit">
 </form>
 </body>
 </html>

longin.html

六:实际效果:

七:总结

1.httpsessionListener 工作机制

2,ArrayList 使用

八:不足之处:

1页面展示用的是:在servlet中用的html,还没有学习jsp.

2.已知问题:同一个用户同时登录,重新显示为一新用户,后面再改

参考资料:

http://www.cnblogs.com/shencheng/archive/2011/01/07/1930227.html

https://blog.csdn.net/su20145104009/article/details/53217201

本人菜鸟一枚,如有问题请大神不吝赐教!