Root state preservation

I just started using Vaadin, and I use Vaadin 7.0.0.alpha1.

I'm trying to preserve the Root state for browser refresh & browser tabs.

I refered Migration Guide and tried Application.setRootPreserved(true), but it is not working!

Also, the WindowRefactoring mentions that 'Developer can enable Root state preservation by overriding Application.getRoot and keeping track of window.name', I tried doing this but got NPE on browser refresh -

java.lang.NullPointerException
at com.vaadin.Application.getRootId(Application.java:2322)

I also noticed that on every refresh the http session id keeps changing.

Is there any solution for this issue? appreciate if there is any sample/demo web application with this implementation.

Thanks.

jasphior g:
I refered Migration Guide and tried Application.setRootPreserved(true), but it is not working!

Got this working!! Found what I was doing wrong earlier.. (not sure whether this is the correct way, but here is how it worked)

1. Create a window in the Application's init method (this will be our main window) and add our root as its content

Window window = new Window();
home = new SimpleRoot();
//home.getApplication().setRootPreserved(true); [this won't work, so have to do this as in root's init]
//setRootPreserved(true);[this won't work either]
window.setContent(home);

2. In the root's init method set

getApplication().setRootPreserved(true);

Hope this helps people like me who doesn't read full document! :)

For now, this is working fine for me. So marking it as an answer.