Java web实现账号单一登录,防止同一账号重复登录(踢人效果)

 // index.jsp <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>   登录

 <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>   已登录. 
提交

 $(document).ready(function() { // 登录按钮 $("#btnlogin").click(function() { //data,dataType,type,url $.ajax({ url: 'LoginServlet?method=login', type: 'post', data: {username: $("input[name='username']").val()}, // 将用户名传给servlet //dataType:'json', success: function(msg) { // msg为从servlet接收到的返回值 if (msg == 1) { // 接收到后台数据为1，正常登录 window.location.href = "singlecount.jsp"; } }, error:function(){ window.alert("错误！"); } }); }); // 提交按钮 $("#btnsubmit").click(function() { //data,dataType,type,url $.ajax({ url: 'SubmitServlet?method=submit', type: 'post', //dataType:'json', success: function(msg) { // msg为从servlet接收到的返回值 if (msg >= 1) { // 正常 window.alert("提交总数" + msg); } }, error:function(jqXHR){ if(jqXHR.status == 900){ // 900状态码 window.alert("登录状态失效，请重新登录！"); window.location.href = "/OneLogin"; } } }); }); });

 // 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") //注解表明什么样的情况下可以访问该内容 @WebServlet(urlPatterns={"/LoginServlet"}) public class LoginServlet extends HttpServlet { private PrintWriter out; // 输出流 private String user; private String method; private HttpSession session; // 建立一个Map存储session信息，key-用户名，value-session public static Map user_Session = new HashMap(); @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 // 在这里实现方法 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // TODO Auto-generated method stub resp.setContentType("text/html"); //语言编码 req.setCharacterEncoding("utf-8"); resp.setCharacterEncoding("utf-8"); out = resp.getWriter(); user = req.getParameter("username"); // 获取index界面username的内容 method = req.getParameter("method"); // 获取方法名 session = req.getSession(); // 获取session switch (method) { case "login": mLogin(); break; default: break; } out.flush(); out.close(); } private void mLogin() { // 按登录按钮调用的方法 // TODO Auto-generated method stub removeUser(user); session.setAttribute("name", user); user_Session.put(user, session); // 新增或覆盖session System.out.println(user_Session); out.println(1); // 返回值1,随意选个值，和前端对应就可以 } /** * 判断是否有重复用户， * 若出现重复用户，踢掉前面登录的用户，即删除其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") //注解表明什么样的情况下可以访问该内容 会在js和web.xml中使用 @WebServlet(urlPatterns={"/SubmitServlet"}) public class SubmitServlet extends HttpServlet { private PrintWriter out; // 输出流 private String method; private int number = 0; // 计数 @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 // 在这里实现方法 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // TODO Auto-generated method stub resp.setContentType("text/html"); //语言编码 req.setCharacterEncoding("utf-8"); resp.setCharacterEncoding("utf-8"); out = resp.getWriter(); method = req.getParameter("method"); // 获取方法名 switch (method) { case "submit": mSubmit(); break; default: break; } out.flush(); out.close(); } private void mSubmit() { // 按提交按钮调用的方法 // TODO Auto-generated method stub number++; out.println(number); } }

 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(); // 获取请求路径 // System.out.println(strURL); // 只过滤来自SubmitServlet请求和singlecount.jsp的加载，可以设置成自己想过滤的 // 需要在web.xml中添加 if(strURL.indexOf("SubmitServlet") != -1 || strURL.indexOf("singlecount.jsp") != -1){ if(request.getSession().getAttribute("name") == null){ request.getSession().invalidate(); response.sendError(900, "登录失效，请重新登录！"); // 自定义状态码，session失效 // 900 到ajax的error中处理 return; } else { arg2.doFilter(arg0, arg1); } } else { arg2.doFilter(arg0, arg1); } } @Override public void init(FilterConfig arg0) throws ServletException { // TODO Auto-generated method stub } }

   OneLogin index.htmlindex.htmindex.jspdefault.htmldefault.htmdefault.jsp filter.SessionFilterfilter.SessionFilter filter.SessionFilter/singlecount.jsp filter.SessionFilter/SubmitServlet