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這篇文章主要介紹Java web如何實現賬號單一登錄以及防止同一賬號重復登錄的效果，文中介紹的非常詳細，具有一定的參考價值，感興趣的小伙伴們一定要看完！
下面進入主題
其中：jquery-1.11.3.js是網上的工具
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
// 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
<%@ 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
未登錄直接進入：http://localhost:8080/OneLogin/singlecount.jsp
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。
以上是“Java web如何實現賬號單一登錄以及防止同一賬號重復登錄的效果”這篇文章的所有內容，感謝各位的閱讀！希望分享的內容對大家有幫助，更多相關知識，歡迎關注億速云行業資訊頻道！
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