Hey,
I try your approach with cookies and seems to works fine!

Thanks :)

On Tue, Jun 22, 2010 at 3:07 PM, Rodrigo <[email protected]> wrote:

> Not sure if I understood your question.. But yes, the cookie is
> accessed both at the client and at the server. So the server would set
> it to 'loggedIn=true' upon a successful login, and clear it whenever
> the user logs out OR if the server gets a request for private
> information but the Session indicates that the user is not logged in..
> In that case, it clears the cookie and fails with an
> AuthenticationException. The client redirects the user to login
> whenever an AuthenticationException is received.
>
> Thus, the usage of the cookie allows the client to save some RPC calls
> to the server. If a page doesn't contain private user-specific
> content, but should still look different based on whether the user is
> logged in or not, then the client can go off the cookie's information
> and decide whether to display a 'Login' or 'Logout' button, for
> example.
>
> On Jun 22, 9:54 am, Bruno Lopes <[email protected]>
> wrote:
> > FYI,
> >
> >
> >
> > On Tue, Jun 22, 2010 at 2:16 PM, Rodrigo <[email protected]> wrote:
> > > Thanks for the response... A few questions come up:
> >
> > > 1. I'm using an HttpServlet for authentication, along with
> > > RemoteServiceServlets for GWT-RPCs. But if I create an HttpSession in
> > > my authentication servlet, I cannot seem to access it on the
> > > RemoteServiceServlet... How am I supposed to access it? Example:
> >
> > > // In authentication HttpServlet
> > > protected void doGet(HttpServletRequest req, HttpServletResponse resp)
> > > throws ServletException, IOException {
> > >      // ...
> > >      req.getSession().setAttribute("user", new User("testUser")); //
> > > creates a session if it didn't exist beforehand
> > >      // ...
> > > }
> >
> > > // In GWT RPC servlet
> > > public List<Offer> getOffers(int productId) {
> > >      // ...
> > >      User user  = (User)
> > > getThreadLocalRequest().getSession().getAttribute("user"); // returns
> > > null
> > >      // ...
> > > }
> >
> > > 2. Why are you using a MainSession singleton object? I don't see it...
> > > Wouldn't it also fail once you have multiple users logged in at the
> > > same time?
> >
> > > It works fine for multiple users  because for each new request a new
> >
> > different session ID will be
> > generated, and so a new session.
> >
> > 3. In your Main page, you're doing 2 sequential RPC calls before you>
> render anything: one to check logged in status, and one to load page
> > > contents. Is this advisable or could it be avoided somehow? For
> > > example, the server could set up a cookie with 'loggedIn=true' so that
> > > you can skip the first RPC at least. And whenever you actually have to
> > > fetch private content, the server can fail with a
> > > AuthenticationException if the user is in fact not logged in. So if a
> > > malicious user fakes the cookie to say he's logged in, the most he'll
> > > ever see is a 'Logout' button when there shouldn't be one. Any other
> > > place that needs to show user-specific information would still be
> > > protected at the server. Does this make sense? What are the drawbacks
> > > of this?
> >
> > > I need those 2 because I can olny load the content if the
> authentication
> >
> > was successful,
> > and when that happens on the server side, the http session is created and
> > also the user
> > information is loaded.
> > An only after this is possible to load the content.
> >
> > With a cookie, then on the client side I need to access to that cookie...
> > actually I didn't check that,
> > but the access to the cookie is not done on the server side, also ?
> >
> > > 4. I assume the SessionTimeoutControl() object just sends an RPC to
> > > the server every x seconds to check if the session is still alive or
> > > not, correct? How do HttpSessions work across tabs and browsers? If my
> > > user has 2 tabs open at my site, does he have 1 or 2 sessions? If it's
> > > 2 browsers?
> >
> > > The session time out control actual do more than that it uses the gwt
> Timer
> >
> > to  initialize an schedule in a new thread
> > for a defined period of time, and the alert the user when the session is
> > about to expire,
> > if there the user do any event it will send a keep alive and
>  re-initialize
> > the schedule, otherwise invalidate session
> > e redirects to Login page.
> >
> > Across tabs will keep the same session until the user logout or the
> session
> > time out happens.
> > Across browsers a new session is nedded.
> >
> > Hope it helps :)
> >
> > Bruno
> >
> > > Thanks!
> >
> > > On Jun 21, 6:58 pm, Bruno Lopes <[email protected]>
> > > wrote:
> > > > HI, maybe this peace of code can Help  :) :
> >
> > > > You can use two modules/entries, one for the login other after login
> >
> > > > on login
> >
> > > > Client side:
> >
> > > > public void onModuleLoad() {
> > > >         this.setLoginPanel();
> > > >         LogUtils.info("Showing Login page");
> > > >     loginButton = new Button("Login");
> > > >         loginButton.addListener(new ButtonListenerAdapter() {
> > > >             public void onClick(Button button, EventObject e) {
> > > >                 userAuthentication();
> > > >             }
> > > >         });
> >
> > > >       .....
> >
> > > > private void userAuthentication() {
> > > >         if (this.userNameField.getValueAsString().equals(""))
> > > >             Window.alert("username must not be empty.");
> > > >         else {
> > > >             loginService = GWT.create(LoginService.class);
> > > >             String username = this.userNameField.getValueAsString();
> > > >             String password = this.passwordField.getValueAsString();
> > > >             this.loginService.login(username, password,
> > > >                     new AsyncCallback<LoginResponse>() {
> > > >                 public void onFailure(Throwable caught) {
> > > >                     Window.alert("server side failure: " + caught);
> > > >                 }
> > > >                 public void onSuccess(LoginResponse result) {
> > > >                     if (result.isLoginSuccess()){
> >
> > > Window.Location.replace("./../Main.html?gwt.codesvr=
> > > > 127.0.0.1:9997");
> > > >                     }
> > > >                     else Window.alert("username or password
> invalid.");
> > > >                 }
> > > >             });
> > > >         }
> > > >     }
> >
> > > > ON SERVER SIDE (the login method):
> >
> > > > public LoginResponse login(String username, String password) {
> > > >         LoginPService loginService =
> ServiceLocator.getLoginService();
> > > >         Person person = null;
> >
> > > >         try {
> > > >             ManageLogs.info("Try to login for user: "+username);
> > > >             person = loginService.getUserByUsername(username);
> >
> > > >         if (person == null){
> > > >             return new LoginResponse(false, false);
> > > >         } else if (!loginService.checkPassword(password)){
> > > >             return new LoginResponse(false, false);
> > > >         }
> >
> > > >         } catch (Throwable e) {
> >
> > > >             return new LoginResponse(false, false);
> > > >         }
> >
> > > >         ManageLogs.info("Login sucessful for user: "+username);
> >
> > > >         LoginResponse response = new LoginResponse();
> > > >         response.setLoginSuccess(true);
> >
> > > >         /*Creates de session*/
> > > >         MainSession padroesSession = mainSession.getInstance();
> > > >         mainSession.setRequest(getThreadLocalRequest());
> >
> > > >        mainSession.setUser(person);
> > > >         return response;
> > > >     }
> >
> > > > THE MainSession
> >
> > > > private static MainSession  mainSession=null;
> >
> > > >     public static MainSession getInstance(){
> > > >         if(mainSession == null){
> > > >             mainSession = new MainSession();
> > > >             return mainSession;
> > > >         } else {
> > > >             return mainSession;
> > > >         }
> > > >     }
> >
> > > >     private MainSession(){
> >
> > > >     }
> >
> > > >     private static final String USER_SESSION = "userSession";
> > > >     private HttpServletRequest request = null;
> > > >     private HttpSession session = null;
> > > >     private String sessionId = "";
> >
> > > >     public Person getUser(){
> >
> > > >         if(null == session) return null;
> >
> > > >         return session.getAttribute(USER_SESSION) != null ?
> > > >                 (Person)session.getAttribute(USER_SESSION) : null;
> >
> > > >     }
> >
> > > >     public HttpSession getSession(){
> > > >         return session;
> > > >     }
> >
> > > >     public void invalidate(){
> > > >         if(request!=null)
> > > >             if(request.getSession(false)!= null)
> > > >                  request.getSession(false).invalidate();
> > > >         if(null != session){
> > > >             session.invalidate();
> > > >             session = null;
> > > >         }
> > > >         setSessionId(null);
> >
> > > >     }
> >
> > > >     public void setUser(Person user){
> > > >         if(null == user){
> > > >             if(session!=null) session.removeAttribute(USER_SESSION);
> > > >             return;
> > > >         }
> >
> > > >         if(null != request)
> > > >             this.session = request.getSession(true);
> >
> > > >         if(session!=null){
> > > >             session.setAttribute(USER_SESSION, user);
> > > >             setSessionId(session.getId());
> > > >         }
> >
> > > >     }
> >
> > > >     public String getId(){
> > > >         return request.getSession(false).getId();
> > > >     }
> >
> > > >     public HttpServletRequest getRequest() {
> > > >         return request;
> > > >     }
> >
> > > >     public void setRequest(HttpServletRequest request) {
> > > >         this.request = request;
> > > >     }
> >
> > > >     public String getSessionId() {
> > > >         return sessionId;
> > > >     }
> >
> > > >     public void setSessionId(String sessionId) {
> > > >         this.sessionId = sessionId;
> > > >     }
> >
> > > > ....
> >
> > > > ON THE SECOND ENTRY
> >
> > > > public void onModuleLoad() {
> > > >         LogUtils.info("Loading Padroes Module");
> > > >         MainSessionServiceAsync mainSessionService =
> > > > GWT.create(MainSessionService.class);
> >
> > > >         AsyncCallback<Boolean> callback = new
> AsyncCallback<Boolean>(){
> > > >             @Override
> > > >             public void onFailure(Throwable caught) {
> > > >                 LogUtils.debug("no session available");
> > > >                 Window.Location.replace("./../Login.html");
> > > >             }
> >
> > > >             @Override
> > > >             public void onSuccess(Boolean result) {
> > > >                 if(!result){
> > > >                     LogUtils.debug("no session available");
> > > >                     Window.Location.replace("./../Login.html");
> > > >                     return;
> > > >                 }
> >
> > > >                 LogUtils.info("creating new Session Time Out for this
> > > > session");
> > > >             /* initialize timers for session time out control */
> > > >              new SessionTimeOutControl();
> >
> > > >              /* Creates de layout +/
> > > >                 doLayout();
> >
> > > >             }
> > > >         };
> >
> > > >         try{
> >
> > > >             mainSessionService.isValidSession(callback);
> >
> > > >         }catch(Exception e){
> > > >             e.printStackTrace();
> >
> > > >         }
> >
> > > > public void doLayout(){
> > > >         AsyncCallback<PageConfiguration[]> callback = new
> > > > AsyncCallback<PageConfiguration[]>(){
> > > >             @Override
> > > >             public void onFailure(Throwable caught) {
> > > >                 LogUtils.debug("server side error on getting
> > > > PageConfiguration");
> > > >                 Window.Location.replace("./../Login.html");
> > > >             }
> >
> > ...
> >
> > read more »
>
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