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2. PersistentFacesState.getInstance().redirectTo

After some user interaction I launch a thread to do some background processing and return the user to a waiting screen. Once the thread is finished doing its processing it calls PersistentFacesState.getInstance().redirectTo to redirect the user to a new page. Sometimes the call will hang for upwards of 15 minutes before it actually does the redirect. It always eventually does the ...

3. Why PersistentFacesState.getInstance(); return null???

You'll need to call it from a bean in the page and then pass the instance to the servlet somehow, perhaps in the session. This is necessary because the Servlet really has no way of knowing which page the user is viewing, unlike the bean which is invoked when the page is rendered.