This is a little demo of how you can (and can't) use polymorphic queries in Objectify for Google AppEngine. I wrote a detailed writeup on my blog.
I created this based on the help I got from Jeff Schnitzer in the objectify-appengine Google group.
appengine-api-labs.jar
appengine-api-stubs.jar
appengine-api.jar
appengine-testing.jar
junit-4.10.jar
objectify-4.0b1.jar