Retrieve number of open sessions from ServletContainer or ApplicationServer

Question

I need to know the number of active sessions of a logged in user. Via the HttpServletRequest I can retrieve the current logged in principal -> getUserPrincipal(). Is there a way to query for the number of active sessions of that principal?

Answer 1

I don't think servlet Api provide this. but you can do it by functionly.

Create map of user and session object.

Map<User, HttpSession> logggedUserMap = new HashMap<User, HttpSession>();

Add entry inside while user logged in and remove it when logout.

so logggedUserMap.size() value is total opened user session.

Use HttpSessionBindingListener, which will track of anywhere in code session attribute bound or unbound from a session.

Create class

class SessionObject implements HttpSessionBindingListener {
        String message = "";
        User loggedInUser;
        Logger log = Logger.getLogger(SessionObject.class);
        public SessionObject(User loggedInUser) {
            this.loggedInUser=loggedInUser;
        }

        public void valueBound(HttpSessionBindingEvent event) {
            log.info("=========in valueBound method==============");
            HttpSession session =LoggedInUserSessionUtil.getLogggedUserMap().get(loggedInUser);
            try{
                if (session != null && session.getLastAccessedTime() != 0) {
                    message = "ALL_READY_LOGGEDIN";
                    return;
                }
            }catch(IllegalStateException e){
                e.printStackTrace();
                session = LoggedInUserSessionUtil.removeLoggedUser(loggedInUser);
            }
            System.out.println("*************************************"+event.getSession().getId() +"------"+loggedInUser+"*********************************************");
            log.info("=========valueBound putting in user map==============");
            LoggedInUserSessionUtil.getLogggedUserMap().put(loggedInUser, event.getSession());
            return;
        }

        public void valueUnbound(HttpSessionBindingEvent event) { 
             // This work already doing in Force logout servlet
             }

        public String getMessage() {
            return message;
        }

        public void setMessage(String message) {
            this.message = message;


        }
    }

And bind this object instance while user logged in.

SessionObject sessionObj = new SessionObject(loggedInUser);
req.getSession().setAttribute("Binder.object",sessionObj);