Specifications - getting @OneToMany entity

[xees]

Hi,

I have a problem with getting List<Note> from entity Person using Spring data JPA specifications (because of pagination). I need to get all notes by person but dependency between these two entities is on Person side. I don't know how to create my Predicate because Note doesn't contain any attribute related to Person.

I simply can get List<Note> with Persons getter but i can't use this way because i need returned data paginated. I am using findAll(Specifications,Pageable).

    @Entity
    public class Person implements Serializable {
    
    	@Id
    	private Long personId;
    
    	@OneToMany
    	@JoinColumn(name = "personId")
    	private List<Note> notes;
    
    }

    @Entity
    public class Note implements Serializable {
    
    	@Id
    	private Long noteId;
    }

I'm sure that Specifications are able to create query what I want, but I don't know how.Normally, I would write something like this, but i don't have an attribute person in Note and database can't be remapped at this stage.

    public static Specification<Note> notesByPerson(final Long personId) {
    		return new Specification<Note>() {
    			@Override
    			public Predicate toPredicate(final Root<Note> root, final CriteriaQuery<?> query,
    					final CriteriaBuilder builder) {
    
    				final Path<Person> per = root.<Person> get("person");
    
    				return builder.equal(per.<Long> get("personId"), personId);
    
    			}
    		};
    	}

Thank you,
Zdend

[xees]

Solved..

	public static Specification<Note> notesByPerson(final Long personId) {
		return new Specification<Note>() {

			@Override
			public Predicate toPredicate(final Root<Note> noteRoot, final CriteriaQuery<?> query,
					final CriteriaBuilder cb) {

				final Subquery<Long> personQuery = query.subquery(Long.class);
				final Root<Person> person = personQuery.from(Person.class);
				final Join<Person, Note> notes = person.join("notes");
				personQuery.select(notes.<Long> get("noteId"));
				personQuery.where(cb.equal(person.<Long> get("personId"), personId));

				return cb.in(noteRoot.get("noteId")).value(personQuery);
			}
		};
	}