JPA2 - Repositório (CRUD).

EntityManagerFactory factory = Persistence . createEntityManagerFactory ("nsa");
EntityManager manager = factory . createEntityManager ();
EditoraRepository editoraRepository = new EditoraRepository ( manager );
List < Editora > editoras = editoraRepository.buscaTodas ();

class EditoraRepository {
private EntityManager manager ;

public EditoraRepository ( EntityManager manager ) {
this . manager = manager ;
}

public void adiciona ( Editora e) {
this . manager . persist (e);
}

public Editora busca ( Long id) {
return this . manager . find ( Editora .class , id);
}
public List < Editora > buscaTodas () {
Query query = this . manager . createQuery (" SELECT e FROM Editora e");
return query . getResultList ();
}
}