Hibernate performs unwanted queries (@ManyToOne)

I have an entity A linked to B with a ManyToOne relation, of type Lazy

public class A extends BaseEntity {

@Enumerated(EnumType.STRING)
private TipoTurnoEnum tipo;

private String number;
private String state;
private Date date;

@JoinColumn(name = "id_b", referencedColumnName = "ID")
@ManyToOne(fetch = FetchType.LAZY)
private B b; 
/* Se excluye el resto de la entidad */

When I make a query about entity A, and in the result attribute B is not null, Hibernate makes a second query, this time on B.

i.e.:

2018-10-09 14:51:32.176 DEBUG 15484 --- [nio-8080-exec-2] org.hibernate.SQL                        : 
select
    A.numero as numero1_1_,
    A.estado as estado2_1_,
    A.fecha as fecha3_1_,
    A.b as b7_1_ 
from
    A
where
    A.numero=?

If A.b is not null, then Hibernate executes:

select
    B.id as id1_15_0_,
    B.descripcion as descripcion_15_0_
from
    B
where
    B.id=?

Being? in B.id, replaced by the value of A.b obtained in the first query. The request object that passed as a filter of the frontend (typescript) was defined as:

let request = {
    A: {number: 1}
};

How do I prevent Hibernate from doing this? Why does this happen even when the relationship is explicitly defined as Lazy? I'm only interested in the values of A, except when I send an attribute to filter B, that is:

A: {
    number: 1, 
    b: {
        id: 2
    }
}

I am using the findOne function of crudRepository (invoking from the genericRepository interface)

    @PostMapping(value = "/findOne", produces = MediaType.APPLICATION_JSON_VALUE, consumes = MediaType.APPLICATION_JSON_VALUE)
public BaseEntity findone(@RequestBody FiltroRequest request) throws GenericException {

    return genericService.findOne(request);
}

Thank you very much, in advance.