主流的网站都是限制用户单点登录的,为什么要实现单点登录?
1、避免单账号多用户操作占用大量数据库连接,减轻webserver的压力;
2、安全防范,强制下线非法用户;
传统的web服务器(如tomcat)对session有专门的管理,我们通过session来控制用户的登录生存周期。单点登录原理如下:
1、将当前的session以Collections的形式缓存在application当中,用户产生新的session,即清除用户之前的session,保证collection里面的usersession都是唯一的;
2、实现效果每次用户登录都会挤掉之前用户的登录,每个用户只能唯一在线;
1 ServletContext application =request.getSession().getServletContext();2 Collection sessions = null;3 if (application.getAttribute("usercount") == null) {4 sessions = new ArrayList();5 application.setAttribute("usercount", sessions);6 } else{7 sessions = (Collection) application8 .getAttribute("usercount");9 }10 newLoginManager().login(sessions, session);11 SessionHandler.handleSession(session);
1 public static booleanisLogin(HttpServletRequest request) {2 TuserEntity tuser =getUser(request);3
4 if(tuser!=null){5 Map map = (Map) request.getSession()6 .getServletContext().getAttribute("sessionMap");7 if(map.get(tuser.getLogname())==null){8 request.getSession().invalidate();9 return false;10 }11 }12 return getUser(request) != null;13 }
LoginManager.java
1 public classLoginManager {2
3 public HttpSession login(Collectionsessions,4 HttpSession session) {5 ArrayList sessionde = new ArrayList();6
7 for(HttpSession s : sessions) {8 try{9 int historyuser = ((TuserEntity) s.getAttribute("user_session")).getId();10 int nowuser = ((TuserEntity) session.getAttribute("user_session"))11 .getId();12 if (historyuser ==nowuser) {13
14 sessions.remove(s); //移除集合中的重复session元素
15
16 if(!s.equals(session)){17 s.invalidate();//废弃之前登陆的session
18 }19 break;20 }21
22 } catch(Exception e) {23 //e.printStackTrace();
24 sessionde.add(s);25 }26
27 }28 for (int i = 0; i < sessionde.size(); i++) {29 sessions.remove((HttpSession) sessionde.get(i));30 }31 sessions.add(session);32 return null;33 }34 }
新增和废弃ServletContext里面的sessionMap的用户session
1 public static voidhandleSession(HttpSession session) {2 try{3 Map sessionMap = (Map) session.getServletContext().getAttribute("sessionMap");4 TuserEntity tuser =(TuserEntity) session.getAttribute(Keys.USER_SESSION_KEY);5 if(sessionMap.get(tuser.getLogname())!=null){6 sessionMap.remove(tuser.getLogname());7 }8 sessionMap.put(tuser.getLogname(), session);9 } catch(Exception e) {10 System.out.println("session error!");11 }12 }
1 public voidsessionDestroyed(HttpSessionEvent se) {2 Map sessionMap = (Map) se.getSession().getServletContext().getAttribute("sessionMap");3 TuserEntity tuser =(TuserEntity) se.getSession().getAttribute(Keys.USER_SESSION_KEY);4 if(tuser!=null){5 sessionMap.remove(tuser.getLogname());6 }7 }
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