How can I get the fieldnames of the PK (@Id) of a JPA @Entity

Question

I'm using JPA2 (Hibernate 4) and have a bunch of @Entity classes with my PKs defined using @Id. How can I programatically retrieve the fieldnames of the PKs of each entity class?

The business case for this is that I want to use Spring's BeanUtils.copyProperties method to copy over entity objects, but want to make sure that I ignore the id fields of my entities while copying.

Is there a way to find this information? Does JPA provide this information? I realize that I can use reflection to go through every class, but hoped there would be an easier solution. I looked into scanning the PropertyDescriptors of the class, but cannot seem to find any method on the PropertyDescriptor that would give me the annotations of a property.

Answer 1

Try this:

@PersistenceUnit
private EntityManagerFactory emf;

Metamodel metamodel = emf.getMetamodel();
metamodel.entity(MyEntity.class).getId();