实现单一登录（后者挤掉前者）

Myth丶恋晨 2021-09-19 04:04 412阅读 0赞

【一】单一登录/单点登录

单一登录：

单点登录：

【二】实现思路、实现代码

实现代码：

import java.io.IOException;
    import java.util.Map;
    import java.util.concurrent.ConcurrentHashMap;
    
    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 gentai.webapp.domain.User;
    import gentai.webapp.service.UserService;
    import gentai.webapp.util.MD5Util;
    
    @WebServlet("/Loginservlet")
    public class Loginservlet extends HttpServlet {
    	private static final long serialVersionUID = 1L;
    	public static Map<String,HttpSession> USERID_SESSION = new ConcurrentHashMap<String,HttpSession>();//uid--session
    	public Loginservlet() {
    		super();
    	}
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response)
    			throws ServletException, IOException {
    		doPost(request, response);
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response)
    			throws ServletException, IOException {
    		//
    		request.setCharacterEncoding("UTF-8");
    		response.setContentType("text/html;charset=utf-8");
    		MD5Util md=new MD5Util();
    		String uid = request.getParameter("username");//当前登录的用户(new_session)
    		String upassword = request.getParameter("password");
    		UserService userService = new UserService();
    		User user = userService.findUserByUId(uid);
    		HttpSession new_session = request.getSession();
    		//判断部分
    			try {
    				System.out.println(System.currentTimeMillis()+"现登录的"+new_session);
    				if(user!=null&&user.getUpasswd().equals(md.md5Encode(upassword)))	{
    					// 1.实现单一登录 踢人效果
    					if(USERID_SESSION.get(user.getUid()) == null) {
    						//第一次登录
    						USERID_SESSION.put(user.getUid(), new_session);
    						new_session.setAttribute("otherLogin", false);
    						
    					}else {
    					//第二次登录
    						HttpSession old_session=USERID_SESSION.get(user.getUid());
    						/*old_session.removeAttribute("user");*/
    						old_session.setAttribute("otherLogin", true);
    						USERID_SESSION.remove(uid);
    						
    						new_session.setAttribute("otherLogin", false);
    						USERID_SESSION.put(user.getUid(), new_session);
    					}
    					String sign = user.getUsign();
    					new_session.setAttribute("usign", sign);
    					new_session.setAttribute("uid",uid);
    					response.sendRedirect(request.getContextPath()+"/authority.jsp");
    				}else {
    					//用户为空或者密码有问题
    					request.setAttribute("loginsign", "fail");
    					request.getRequestDispatcher("/login.jsp").forward(request, response);
    				}
    			} catch (Exception e) {
    				e.printStackTrace();
    			}
    	}
    }

校验：

import java.io.IOException;
    import java.io.PrintWriter;
    import java.util.HashMap;
    import java.util.Map;
    
    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 org.json.JSONObject;
    @WebServlet("/checkOtherLogin.do")
    public class CheckOtherLogin extends HttpServlet{
    
    	/**
    	 * 
    	 */
    	private static final long serialVersionUID = 1L;
    	@Override
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		doPost(req, resp);
    	}
    	@Override
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		Map<String,Object> map = new HashMap<>();
    		if (!(boolean) req.getSession().getAttribute("otherLogin")) {
    			map.put("single", true);
    		}else {
    			map.put("single", false);
    		}
    		req.setAttribute("map", map);
    		resp.setContentType("application/json");
    		resp.setCharacterEncoding("UTF-8");
    		PrintWriter out =  resp.getWriter();
    		out.write(new JSONObject(map).toString());
    	}
    
    }

退出：

import java.io.IOException;
    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;
    
    @WebServlet("/ExitServlet")
    public class ExitServlet extends HttpServlet {
    	private static final long serialVersionUID = 1L;
    
    	public ExitServlet() {
    		super();
    	}
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response)
    			throws ServletException, IOException {
    		doPost(request, response);
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response)
    			throws ServletException, IOException {
    		HttpSession session = request.getSession(false);
    		// 把session内的所有属性都清除
    		session.invalidate();
    		// 跳转到登陆页面
    		response.sendRedirect(request.getContextPath()+"/login.jsp");
    	}
    
    }

前台登录界面省略：

登录成功后的界面(需添加的必要代码)：

<%@page import="java.util.*" %>
    
    
    
    <%
    	Map<String, Object> map = (Map<String, Object>) request.getSession().getAttribute("map");
    %>
    <script>
    var getting = {
    		
    	    url:'${pageContext.request.contextPath }/checkOtherLogin.do',
    	    dataType:'json',
    	  success:function(data){
    		   if(data.single == false) {
    			   alert("您的帐号在异地登录!");
    			   window.location = "${pageContext.request.contextPath }/login.jsp";
    		   }
    		   else {
    				$.ajax(getting);
    		   }
    		}
    	}
    	$.ajax(getting);
    	window.onbeforeunload = function(){	//关闭浏览器的时候退出
    		$.post('${pageContext.request.contextPath }/ExitServlet.do')
    	}
    </script>

【三】遗留问题、解决方法

遗留问题：

项目部署后，隔天打开，成功登录后停留在空白界面。控制台没有任何错误信息，以及network处没有加载一些东西。但已加载的loginservlet处于200状态。

有的时候过几个小时，会出现同一网址，不同用户登录，有的可以成功登录，有的不能登录成功。

解决方法：还没有找到问题出在哪里。。。

不知道出现上述问题，是逻辑的问题，还是session的问题，还是servlet的问题，还是checkotherlogin轮询的问题。