Examples of JPA joins on Google App Engine

Are there any good examples for using JPA joins using Google App engine? I saw an example on this site, but it seems old - are there any improvements on it? The GAE doc pages only detail join开发者_开发技巧s using the low-level API.

Why not look at the tests for GAE/J JPA plugin ? http://code.google.com/p/datanucleus-appengine/source/browse/#svn%2Ftrunk%2Ftests%2Fcom%2Fgoogle%2Fappengine%2Fdatanucleus

There is a link on this page that might help you. http://turbomanage.wordpress.com/2010/01/25/how-to-do-joins-in-appengine/