How to create Predicate BooleanExpression for many to many relations in QueryDSL - spring

Question

How can inner join be done on Many to Many relations using Predicate BooleanExpression?
I have 2 entities
public class A {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
#ManyToMany(fetch = FetchType.LAZY,
cascade = { CascadeType.DETACH, CascadeType.MERGE,
CascadeType.REFRESH, CascadeType.PERSIST})
#JoinTable(name = "a_b_maps",
joinColumns = #JoinColumn(name = "a_id", nullable =
false,referencedColumnName = "id"),
inverseJoinColumns = #JoinColumn(name = "b_id", nullable = false,
referencedColumnName = "id")
)
private Set<B> listOfB = new HashSet<B>();
}
public class B {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
#ManyToMany(fetch = FetchType.LAZY,
cascade = { CascadeType.DETACH, CascadeType.MERGE,
CascadeType.REFRESH, CascadeType.PERSIST})
#JoinTable(name = "a_b_maps",
joinColumns = #JoinColumn(name = "b_id", nullable =
false,referencedColumnName = "id"),
inverseJoinColumns = #JoinColumn(name = "a_id", nullable = false,
referencedColumnName = "id")
)
private Set<A> listOfA = new HashSet<A>();
}
A Base repo
#NoRepositoryBean
public interface BaseRepository<E, I extends Serializable>
extends JpaRepository<E, I> {
}
And a repository class for A
public interface Arepo extends BaseRepository<A, Integer>,
QueryDslPredicateExecutor<A> {
Page<A> findAll(Predicate predicate, Pageable pageRequest);
}
Now I want to use A Repo with Predicate query. I need to form a predicate where I can load A based on some given Bs
I tried
QA a = QA.a;
QB b = QB.b;
BooleanExpression boolQuery = null;
JPQLQuery<A> query = new JPAQuery<A>();
query.from(a).innerJoin(a.listOfB, b)
.where(b.id.in(someList));
Now I am able to form a JPQLQuery, but the repository expects a Predicate. How can I get Predicate from the JPQLQuery??
Or, how can the inner join be achieved using Predicate?

Answer 1

I am able to create a Predicate with the help of answer given here
https://stackoverflow.com/a/23092294/1969412.
SO, instead of using JPQLQuery, I am directly using
a.listOfB.any()
.id.in(list);
This is working like a charm.