According to the documentation here: https://code.google.com/p/objectify-appengine/wiki/IntroductionToObjectify#Relationships
To perform transaciton, you need Objectify ofy = ObjectifyService.beginTransaction(); However, I just downloaded Objectify5 and ObjectifyService does not have beginTransaction.
Am I missing something or the documentation is out of date?
You're looking at the long-obsolete documentation for Objectify v3 (as mentioned at the top of the page).
The best place for documentation now is:
https://github.com/objectify/objectify/wiki