JPA2 Criteria-API: select… in (select from where)

Question

I have the following database model:

A
aId

AB
aId
bId

B
bId
status

In a Spring data Specification, I want to return the instances of A wh

Answer 1

Select In - is an option but you could achieve same result with double join. And its easier to make such a jpa specification:
SELECT A.ID FROM A LEFT JOIN AB ON A.ID = AB.A_ID LEFT JOIN B ON AB.B_ID = B.ID WHERE B.STATUS = 'STATUS'
Method would look like this:

public static Specification findB(String input) {
    return new Specification() {
        @Override
        public Predicate toPredicate(Root root, CriteriaQuery cq, CriteriaBuilder cb) {
            Join AjoinAB = root.joinList(A_.AB_LIST,JoinType.LEFT);
            Join ABjoinB = AjoinAB.join(AB_.B,JoinType.LEFT);
            return cb.equal(ABjoinB.get(B_.NAME),input);
        }
    };
}

Or shorter

public static Specification findB(String input) {
    return (Specification) (root, cq, cb) -> {
        Join AjoinAB = root.joinList(A_.AB_LIST,JoinType.LEFT);
        Join ABjoinB = AjoinAB.join(AB_.B,JoinType.LEFT);
        return cb.equal(ABjoinB.get(B_.NAME),input);
    };
}

I know it's been a long time since this question arose, but I came across it when I tried to do the same. This is my solution that works and I hope it helps someone.

Entities below

@Entity
public class A {
    @Id
    private Long id;
    private String name;
    @OneToMany(mappedBy = "a")
    private List abList;
}
@Entity
public class B {
    @Id
    private Long id;
    private String status;
    @OneToMany(mappedBy = "b")
    private List abList;
}
@Entity
public class AB {
    @Id
    private Long id;
    private String name;
    @ManyToOne
    @JoinColumn(name = "a_id")
    private A a;
    @ManyToOne
    @JoinColumn(name = "b_id")
    private B b;
}