JpaRepositoryThe Spring Data JpaRepository defines the following two methods:
getOne, which returns an entity proxy that is suitable for setting a @ManyToOne or @OneToOne parent association when persisting a child entity.findById, which returns the entity POJO after running the SELECT statement that loads the entity from the associated tableHowever, in your case, you didn't call either getOne or findById:
Person person = personRepository.findOne(1L);
So, I assume the findOne method is a method you defined in the PersonRepository. However, the findOne method is not very useful in your case. Since you need to fetch the Person along with is roles collection, it's better to use a findOneWithRoles method instead.
You can define a PersonRepositoryCustom interface, as follows:
public interface PersonRepository
extends JpaRepository<Person, Long>, PersonRepositoryCustom {
}
public interface PersonRepositoryCustom {
Person findOneWithRoles(Long id);
}
And define its implementation like this:
public class PersonRepositoryImpl implements PersonRepositoryCustom {
@PersistenceContext
private EntityManager entityManager;
@Override
public Person findOneWithRoles(Long id)() {
return entityManager.createQuery("""
select p
from Person p
left join fetch p.roles
where p.id = :id
""", Person.class)
.setParameter("id", id)
.getSingleResult();
}
}
That's it!