suppose i have a simple entity with an embedded one:



when i create a JPA2 criteria:



and then run it using hibernate 3.5.6-Final, i get the following exceptions depending on which "where" line i use:
first one

second one

equivalent JPQL queries run just fine both ways:



Example #3 in Section 6.7 of JSR promises us that joining on embedded entities should work just fine... is it something known not to work? is there a workaround?

I think your criteria query has been defined incorrectly. Here's my explanation:

In this createQuery call you are basically saying that you are going to select a list of TestEntity objects.


However, in this line you are selecting the id, not the object (and you are also specifying <TestEntity> with generics here which is incorrect):


The first exception is thrown because you are selecting the "id" attribute but you have specified that the results will be TestEntity objects.
The second exception is thrown because you are selecting the "id" attribute and trying to join id.embeddedAttribute which of course doesn't exist.

So, the fix should be pretty simple. Use this instead:


The second query should work fine once you fix the select clause :)
I recommend using the first where clause but both should work.

Sadly it is very easy to make such simple mistakes with JPA 2 criteria queries and the exceptions can be very hard to understand. I've spent a lot of time debugging some of my queries where I defined a field name of type incorrectly.
If you want more safety, I suggest using the canonical metamodel which solves most type safety issues. In your queries the metamodel would enable you to replace the "magical" string values "id", "embeddedAttribute" and "enumeratedAttribute" with type-safe references.

it doesn't matter what you select (and should not because what is selected has nothing to do with what is restricted). you can see it for yourself as it works both ways: with select(r) and with select(r.get("id")).

the problem i experience is that hibernate seems not to allow to join on embedded entities, while JSR clearly says that it should ;).

the fix for this problem is when you need to join on an embedded entity, you must do a "get" instead of "join", which is absolutely not convenient:




i can't use metamodel, because i need to be able to address attributes without knowing which attribute this actually is.

Yes, you're right. Sorry, I read your code too quickly and I was distracted by the mismatch between the types in q.select and builder.createQuery.



I made a quick test project using your code and tested it with EclipseLink 2.1.1. It worked fine so indeed this seems like a Hibernate bug.
Even Hibernate 3.6.0.CR1 had the same behaviour. I guess you'll have to report the bug and hope it'll be fixed at some point :(

I had the same problem, must be a bug in Hibernate.

Workaround is to use metamodel (I tried it it works).

You can always have a if-else for metamodel if you need the field to be dynamically determined.