Java web實現賬號單一登錄,防止同一賬號重復登錄(踢人效果)

 更新時間:2019年10月23日 15:44:33   作者:老孫的博客   我要評論
這篇文章主要介紹了Java web實現賬號單一登錄,防止同一賬號重復登錄,有點類似于qq登錄踢人效果,本文給大家介紹的非常詳細,具有一定的參考借鑒價值,需要的朋友可以參考下

實現了Java web開發賬號單一登錄的功能,防止同一賬號重復登錄,后面登錄的踢掉前面登錄的,使用過濾器Filter實現的。可以先下載項目下來測試下效果。

有博客寫的是沒個一段時間(比如500ms)讀取后臺的session進行驗證,這種方法除了會占用資源,還會出現訪問session(請求1)的返回值和自己提交請求(請求2)的返回值發生沖突。比如請求1先提交,此時請求1的返回值還未返回到前端,請求2提交,實際上我們想要的是請求1的返回值先返回,然后再返回請求2的返回值,但是這不是肯定會發生的,ajax的機制所導致的,具體什么原因沒查到。總之出現了請求2先返回了返回值,這時候請求1接收到了請求2的返回值,妥妥的前端出現錯誤,但是后臺卻是成功的。

下面進入主題

工程下載鏈接:鏈接: https://pan.baidu.com/s/1Rp09wv7hTJLqx9DiQ_KSeA 提取碼: xyym

其中:jquery-1.11.3.js是網上的工具

在這里插入圖片描述

建立兩個簡單的界面

登錄界面:為了簡單沒有設置密碼,直接輸入賬號點擊登錄就行

在這里插入圖片描述

// index.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%>" rel="external nofollow" rel="external nofollow" >
 <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" rel="external nofollow" rel="external nofollow" >
 -->
 </head>
 
 <body>
 <input id="username" name="username" type="text">
 <!-- <a href="singlecount.jsp" rel="external nofollow" target="_self"> -->
 <button id="btnlogin" name="btnlogin">登錄</button><!-- </a> -->
 
 <!-- 引入jQuery -->
 <script type="text/javascript" src="js/jquery-1.11.3.js"></script>
 <script type="text/javascript" src="js/jsSubmit.js"></script>
 </body>
</html>

主頁面:簡單的一個提交按鈕

在這里插入圖片描述

<%@ 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%>" rel="external nofollow" rel="external nofollow" >
 <title>My JSP 'SingleCount.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" rel="external nofollow" rel="external nofollow" >
 -->

 </head>
 
 <body>
 已登錄. <br>
 <button id="btnsubmit" name="submit">提交</button>
 
 <!-- 引入jQuery -->
 <script type="text/javascript" src="js/jquery-1.11.3.js"></script>
 <script type="text/javascript" src="js/jsSubmit.js"></script>
 </body>
</html>

寫ajax,向后臺提交請求

// jsSubmit.js

$(document).ready(function() {
 // 登錄按鈕
 $("#btnlogin").click(function() {
 //data,dataType,type,url
 $.ajax({
 url: 'LoginServlet?method=login',
 type: 'post',
 data: {username: $("input[name='username']").val()}, // 將用戶名傳給servlet
 //dataType:'json',
 success: function(msg) { // msg為從servlet接收到的返回值
 if (msg == 1) { // 接收到后臺數據為1,正常登錄
 window.location.href = "singlecount.jsp";
 } 
 },
 error:function(){
 window.alert("錯誤!");
 }
 });
 });
 // 提交按鈕
 $("#btnsubmit").click(function() {
 //data,dataType,type,url
 $.ajax({
 url: 'SubmitServlet?method=submit',
 type: 'post',
 //dataType:'json',
 success: function(msg) { // msg為從servlet接收到的返回值
 if (msg >= 1) { // 正常
 window.alert("提交總數" + msg);
 } 
 },
 error:function(jqXHR){
 if(jqXHR.status == 900){ // 900狀態碼
 window.alert("登錄狀態失效,請重新登錄!");
 window.location.href = "/OneLogin";
 }
 }
 });
 });
});

servlet

這部分有點長,其實主要內容直接看doPost方法就可以了。

// LoginServlet
package servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.ServletConfig;
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;
@SuppressWarnings("serial")
//注解表明什么樣的情況下可以訪問該內容
@WebServlet(urlPatterns={"/LoginServlet"})
public class LoginServlet extends HttpServlet {
 private PrintWriter out; // 輸出流
 private String user;
 private String method;
 private HttpSession session;
 // 建立一個Map存儲session信息,key-用戶名,value-session
 public static Map<String, HttpSession> user_Session = new HashMap<String, HttpSession>();
 
 @Override
 public void init(ServletConfig config) throws ServletException {
 // TODO Auto-generated method stub
 super.init(config);
 }
 @Override
 protected void doDelete(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 // TODO Auto-generated method stub
 super.doDelete(req, resp);
 }
 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 // TODO Auto-generated method stub
 doPost(req, resp);
 }
 @Override
 // 在這里實現方法
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 // TODO Auto-generated method stub
 resp.setContentType("text/html");
 //語言編碼
 req.setCharacterEncoding("utf-8");
 resp.setCharacterEncoding("utf-8");
 out = resp.getWriter();
 
 user = req.getParameter("username"); // 獲取index界面username的內容
 method = req.getParameter("method"); // 獲取方法名
 session = req.getSession(); // 獲取session
 switch (method) {
 case "login":
 mLogin();
 break;
 default:
 break;
 }
 out.flush();
 out.close();
 
 }

 private void mLogin() { // 按登錄按鈕調用的方法
 // TODO Auto-generated method stub
 removeUser(user);
 session.setAttribute("name", user);
 user_Session.put(user, session); // 新增或覆蓋session
 System.out.println(user_Session);
 out.println(1); // 返回值1,隨意選個值,和前端對應就可以
 }
 
 /**
 * 判斷是否有重復用戶,
 * 若出現重復用戶,踢掉前面登錄的用戶,即刪除其session
 */
 private void removeUser(String user) {
 if(user_Session.containsKey(user))
 user_Session.get(user).invalidate();
 }
}

// SubmitServlet
package servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@SuppressWarnings("serial")
//注解表明什么樣的情況下可以訪問該內容 會在js和web.xml中使用
@WebServlet(urlPatterns={"/SubmitServlet"})
public class SubmitServlet extends HttpServlet {
 
 private PrintWriter out; // 輸出流
 private String method;
 private int number = 0; // 計數
 @Override
 public void init(ServletConfig config) throws ServletException {
 // TODO Auto-generated method stub
 super.init(config);
 }
 @Override
 protected void doDelete(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 // TODO Auto-generated method stub
 super.doDelete(req, resp);
 }
 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 // TODO Auto-generated method stub
 doPost(req, resp);
 }
 @Override
 // 在這里實現方法
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 // TODO Auto-generated method stub
 resp.setContentType("text/html");
 //語言編碼
 req.setCharacterEncoding("utf-8");
 resp.setCharacterEncoding("utf-8");
 out = resp.getWriter();
 
 method = req.getParameter("method"); // 獲取方法名
 switch (method) {
 case "submit":
 mSubmit();
 break;
 default:
 break;
 }
 out.flush();
 out.close();
 }
 
 private void mSubmit() { // 按提交按鈕調用的方法
 // TODO Auto-generated method stub
 number++;
 out.println(number);
 }
}

過濾器

過濾器的原理這里就不說了,簡單來說就是請求要先經過過濾器才能到達servlet,也就是說如果請求不滿足要求就無法通過過濾器,這里的要求是要有session。

package filter;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebFilter("/SessionFilter")
public class SessionFilter implements Filter {
 @Override
 public void destroy() {
 // TODO Auto-generated method stub
 
 }
 @Override
 public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)
 throws IOException, ServletException {
 // TODO Auto-generated method stub
 HttpServletRequest request = (HttpServletRequest) arg0;
 HttpServletResponse response = (HttpServletResponse) arg1;
 String strURL = request.getRequestURL().toString(); // 獲取請求路徑
 // System.out.println(strURL);
 // 只過濾來自SubmitServlet請求和singlecount.jsp的加載,可以設置成自己想過濾的
 // 需要在web.xml中添加<filter>
 if(strURL.indexOf("SubmitServlet") != -1 || strURL.indexOf("singlecount.jsp") != -1){ 
 if(request.getSession().getAttribute("name") == null){
 request.getSession().invalidate();
 response.sendError(900, "登錄失效,請重新登錄!"); // 自定義狀態碼,session失效
 // 900 到ajax的error中處理
 return;
 }
 else {
 arg2.doFilter(arg0, arg1);
 }
 }
 else {
 arg2.doFilter(arg0, arg1);
 }
 }
 @Override
 public void init(FilterConfig arg0) throws ServletException {
 // TODO Auto-generated method stub
 
 }
}

配置web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
 <display-name>OneLogin</display-name>
 <welcome-file-list>
 <welcome-file>index.html</welcome-file>
 <welcome-file>index.htm</welcome-file>
 <welcome-file>index.jsp</welcome-file>
 <welcome-file>default.html</welcome-file>
 <welcome-file>default.htm</welcome-file>
 <welcome-file>default.jsp</welcome-file>
 </welcome-file-list>

 <filter>
 <filter-name>filter.SessionFilter</filter-name>
 <filter-class>filter.SessionFilter</filter-class>
 </filter>
 <filter-mapping>
 <filter-name>filter.SessionFilter</filter-name> 
 <url-pattern>/singlecount.jsp</url-pattern> <!-- 給界面添加過濾器 -->
 </filter-mapping>
 <filter-mapping>
 <filter-name>filter.SessionFilter</filter-name>
 <url-pattern>/SubmitServlet</url-pattern> <!-- 給servlet添加過濾器 -->
 </filter-mapping>
</web-app>

實現效果

可以使用兩個不同的瀏覽器當兩個客戶端,或者電腦多就用多臺電腦。

相同賬號登錄時,前面賬號再點提交請求就會給出提示,跳轉到登錄界面

在這里插入圖片描述

未登錄直接進入:http://localhost:8080/OneLogin/singlecount.jsp

在這里插入圖片描述

如果也想實現跳轉效果,在jsSubmit.js的$(document).ready(function() {…}); 前面加入是否有session的判斷,沒有就給出提示,跳轉到登錄界面。

總結

以上所述是小編給大家介紹的Java web實現賬號單一登錄,防止同一賬號重復登錄,希望對大家有所幫助,如果大家有任何疑問請給我留言,小編會及時回復大家的。在此也非常感謝大家對腳本之家網站的支持!
如果你覺得本文對你有幫助,歡迎轉載,煩請注明出處,謝謝!

相關文章

最新評論

2019开奖结果