It was one of the other ways to do it, I just wanted to avoid more
code in my architecture just to do this (MVP has the disadvantage of
added boilerplate for simple tasks like this one).
Anyway I found a workaroud, passing the URL in an invisible div in my
page and then reading and populating another field in my page using
GWT RootPanel.get(id), using different ids for various parts of the
page.