1 package com.mvc.test; 2 3 import javax.servlet.ServletException; 4 import javax.servlet.annotation.WebServlet; 5 import javax.servlet.http.HttpServlet; 6 import javax.servlet.http.HttpServletRequest; 7 import javax.servlet.http.HttpServletResponse; 8 import java.io.IOException; 9 import java.io.PrintWriter; 10 import java.util.HashSet; 11 import java.util.Set; 12 13 /** 14 * 用户是否登录，使用全局方法 15 * 16 * @author liuwenlong 17 * @create 2020-09-09 09:23:23 18 */ 19 @SuppressWarnings("all") 20 @WebServlet(urlPatterns = "/login") 21 public class Application_Test extends HttpServlet { 22 23 24 @Override 25 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 26 resp.setContentType("text/html;charset=UTF-8"); 27 PrintWriter out = resp.getWriter(); 28 String user = req.getParameter("user"); 29 if (user == null) { 30 out.print("无效的用户或者密码！"); 31 return; 32 } 33 String key = "islogin_" + user; 34 String islogin = (String) req.getServletContext().getAttribute(key); 35 if (islogin == null) { 36 if ("zs".equals(user) || "ls".equals(user)) { 37 req.getServletContext().setAttribute(key + "id", req.getSession().getId());//记录SessionID 38 req.getSession().setAttribute("islogin", user); 39 req.getServletContext().setAttribute(key + "_t", System.currentTimeMillis());//记录时间 40 41 out.print("成功"); 42 } else { 43 out.print("无效的账号或者密码"); 44 } 45 } else { 46 out.print("您已经登录..."); 47 } 48 } 49 50 //发心跳，接收新的心跳，如果关闭浏览器，就接收不到新的心跳，时间就会超时 51 @Override 52 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 53 resp.setContentType("text/html;charset=UTF-8"); 54 PrintWriter out = resp.getWriter(); 55 String user = req.getParameter("user");//取出用户 56 String key = "islogin_" + user;//这个用户，然后设置这个用户的时间，重新刷新时间 57 String id = (String) req.getServletContext().getAttribute(key + "id"); 58 String id2 = req.getSession().getId(); 59 60 req.getServletContext().setAttribute(key + "_t", System.currentTimeMillis());//记录时间 61 if (id != id2) { 62 req.getSession().setAttribute("islogin", "notlogin"); 63 out.print(user + "已经在设备" + id + "登录"); 64 } else { 65 out.print("OK"); 66 } 67 } 68 }
JSP页面：
1 <%@ page contentType="text/html;charset=UTF-8" language="java" %> 2 <html> 3 <head> 4 <title>首页</title> 5 <script type="text/javascript" src="static/js/jquery-3.3.1.min.js"></script> 6 </head> 7 <body> 8 9 <font color="red" id="ts"></font> 10 11 </body> 12 13 <script type="text/javascript"> 14 var inter = null; 15 16 function heart() { 17 var islogin = "${sessionScope.islogin}"; 18 if (islogin === "null" || islogin === "notlogin"||islogin.length===0) { 19 $("#ts").html("你还没有登录，请先登录"); 20 return; 21 }else { 22 //$("#ts").html(islogin+"已经登录"); 23 $.ajax({ 24 type:"post", 25 url:"login", 26 data:{user:islogin}, 27 success:function (res) { //回调函数 28 $("#ts").html(res); //显示登录的返回信息 29 } 30 }) 31 } 32 } 33 setInterval("heart()", 3000); 34 </script> 35 </html>
