In TopLink Essentials you can use a DescriptorCustomizer to add a QueryKey to your TopLink descriptor for the type field. You will then be able to query on this query key in JPQL.

i.e.
public class MyDescriptorCustomizer implements DescriptorCustomizer { public void customize(ClassDescriptor descriptor) { descriptor.addQueryKey("type", "ABSTRACT_ENTITY.ABSTRACT_ENTITY_TYPE"); } }

You can add the customizer in your persistence.xml.