Programmatically loading Entity classes with JPA 2.0?

Question

With Hibernate you can load your Entity classes as:

sessionFactory = new AnnotationConfiguration()
                    .addPackage("test.animals")
                    .addAnnotatedClass(Flight.class)
                    .addAnnotatedClass(Sky.class)
                    .addAnnotatedClass(Person.class)
                    .addAnnotatedClass(Dog.class);

Is there a way to do the same thing - programmatically loading your Entity classes - in a JPA 2.0 compliant way?

The reason for this question is because I'd like to dynamically load my Entity classes, thus not nessecarily programmatically...

Answer 1

I don't think there is such option - JPA supports scanning the classpath for entities or explicitly listing the entity classes in the persistence.xml. Since you're using hibernate as the persistence provider however you can always resort to hibernate code. Have a look at the HibernateEntityManager and HibernateEntityManagerFactory classes. You can cast entity manager factories and entity managers to them and do the usual hibernate stuff.

Answer 2

Is there a way to do the same thing - programmatically loading your Entity classes - in a JPA 2.0 compliant way?

No, this is not supported by JPA so you'll have to do this in a provider specific way. James Sutherland described the process for EclipseLink in this thread like this:

You can access the EclipseLink ServerSession from the EntityManagerFactoryImpl (getServerSession()), and use its' addDescriptor(ClassDescriptor) or addDescriptors() API to add EclipseLink ClassDescriptor. You will need to build the ClassDescriptor meta-data objects directly yourself (or use the Mapping Workbench to create them), as loading from JPA annotations or orm.xml would be more difficult.

Also have a look at this more recent thread for more code sample (the API looks like a bit verbose).

References

• Re: [eclipselink-users] Close to get it. Just a little help
• Re: JPA: adding entities to EntityManagerFactory programmatically