Hello, I need some help.
I have classes A, B, C, D.
B, C and D extend A.
And I want to create a Criteria that would get me all the instances of B and C, but not D. How can I do that?
Thanks in advance!

Maybe you can define B and C to implement a common interface, while D would not implement this interface. Then you could build the criteria object for this new interface and get what you want. If you cannot modify B and/or C then you could build a criteria for A and add Restrictions.or(Restrictions.eq("class", "DISCRIMINATOR_VALUE_FOR_B"), Restrictions.eq("class", "DISCRIMINATOR_VALUE_FOR_C")) - this will work if both B and C are mapped to the same table and use a discriminator column. If you use any other inheritance mapping then you should run two different criteria queries and merge the resulting collections on your own. This will be as efficient as anything Hibernate could do for you, since these mapping strategies will require at least one query per inherance branch anyway.