JPA TABLE_PER_CLASS inheritance: How to only SELECT superclass entries?

Question

I'm using EclipseLink as the JPA provider. Further I'm using the following TABLE_PER_CLASS inheritance structure

@javax.persistence.Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
@NamedQueries({
    @NamedQuery(name=Parent.QUERY_FIND_ALL, query="SELECT p FROM Parent p")
})
public class Parent {
        // the class code follows here
}

@javax.persistence.Entity 
@NamedQueries({
    @NamedQuery(name=Child.QUERY_FIND_ALL, query="SELECT c FROM Child c")
})

public class Child extends Parent {
        // the class code follows here
}

The problem now is that I only want to receive entries of the parent class. But with the named query "SELECT p FROM Parent p" also all entries from the child table are returned.

The select or find code is as follows:

public List findWithNamedQuery(String query) {
        return em.createNamedQuery(query).getResultList();
}

Thereby query is i.e. the "SELECT p FROM Parent p".

How can I only receive really the parent entries and not all entries of this inheritacne hierarchy?

In short: How can I leave all child entries untouched, and return only the parent entries?

EDIT 1:
I'm using EclipseLink 2.0.1, but every time I try axtavt's solution via the type expression, I get the following error:

"Invalid Type Expression on [my.domain.Parent].  The class does not have a descriptor, or a descriptor that does not use inheritance or uses a ClassExctractor for inheritance".

I've updated also to the latest stable version 2.1.1 of EclipseLink, but it doesn't resolve the issue.

Jellyfish

Did you ever figure this out? I'm trying to do the same thing. For my query I only want the parent rows returned but the child rows are returned as well. – Vardar

any update on this question ?I mean have you ever found the answer for this @Jellyfish – Paramecium

Answer 1

The Type expression in combination with TABLE_PER_CLASS inheritance doesn' t work under EclipseLink 2.1.1, this seems to be a bug.

See also the answer to JPA 2.0: TYPE expression exception

Jellyfish

Answer 2

If your version of EclipseLink supports JPA 2.0, you can write

SELECT p FROM Parent p WHERE TYPE(p) = Parent

Scission