How to redirect to the login page when the session expires? - session

Question

I have three JSF 2.0 web modules and I need to redirect to the login page when the session expires.
I have tried it using a HttpSessionListener, it is calling the sessionDestroyed() event method, but I am not able to forward/redirect the request in there. I think it is becasue there are no HttpServletRequest and HttpServletResponse objects.
I also tried it using a PhaseListener, but it results in a "too many redirects" error in the webbrowser.
public class SessionListener implements PhaseListener {
public PhaseId getPhaseId() {
return PhaseId.RESTORE_VIEW;
}
public void beforePhase(PhaseEvent event) {
if (!FacesContext.getCurrentInstance().isPostback()) {
try {
System.out.println("Session Destroyed");
FacesContext.getCurrentInstance().getExternalContext().redirect("login.jsf");
}
catch (Exception e) {
System.out.println("error" + e);
}
}
}
public void afterPhase(PhaseEvent event) {
try {
System.out.println("Session Created");
}
catch (Exception e) {
System.out.println("error" + e);
}
}
}
Why do those attempts not work and how can I solve it the best?

Answer 1

It's not possible to send a redirect at exactly the moment when the session is expired. The client has namely not sent any HTTP request at that moment which you could then respond with a redirect.
You should just keep your existing authentication mechanism which redirects to the login page when the user is not logged-in anymore. You can at best improve it by adding a check if the user is been redirected to the login page because the session has been expired, or just because he has never logged in before (i.e. it's a fresh new request).
You can check for that by if HttpServletRequest#getRequestedSessionId() doesn't return null (which means that the client has sent a session cookie and thus assumes that the session is still valid) and HttpServletRequest#isRequestedSessionIdValid() returns false (which means that the session has been expired at the server side). You can do that in the very same filter where you're checking for the logged-in user (you do already have one, right? or are you using container managed authentication?).
User user = (User) session.getAttribute("user");
if (user == null) {
String loginURL = request.getContextPath() + "/login.jsf";
if (request.getRequestedSessionId() != null && !request.isRequestedSessionIdValid()) {
response.sendRedirect(loginURL + "?expired=true");
} else {
response.sendRedirect(loginURL);
}
} else {
chain.doFilter(request, response);
}
And then in the login.xhtml page check for it
<h:panelGroup rendered="#{param.expired}">
<p>You have been redirected to the login page, because your session was expired.</p>
</h:panelGroup>
Your phase listener approach makes by the way no sense. It indeed sends a redirect on every single request causing it to run in an infinite loop. The restore view phase has absolutely nothing to do with the session expiration.

Answer 2

Try to use
FacesContext.getCurrentInstance().getApplication().getNavigationHandler().
handleNavigation(context, null, "LoginForm");
But note that you should use Servlet Filter for these purposes, it's better to do not any redirection from PhaseListener because it's really error prone.