The easiest way to enable Google authentication for the GWT app? (No gae organized)

Question

What is the easiest way to enable an existing GWT application to authenticate users with a Google account? I tried googling (lol), but did not find solutions that could work out of the box. Is there a library to solve this problem in 10 lines of code?

PS The application I mentioned is not hosted on Google Apps, if that matters.

Answer 1

I recently reviewed gwt-oauth2 for this purpose. It looks pretty decent and the documents are simple. Perhaps this may be interesting.