I'm a Java developer who is using JPA all the time. However, the exam is a little bit tricky and in details. Without good preparation and mock exam it's very difficult to pass.
For my preparation:
I used Pro JPA 2 and JPA Spec 2.1 as main study material.
+ JPA Source code (there are good amount of document in the code itself, especially good for study exceptions and annotations)
+ Mock exams from Ethuware.