java - Hibernate Criteria API - adding a criterion: string should be in collection

Question

I have to following entity object

@Entity
public class Foobar {
    ...
    private List<String> uuids;
    ...
}

Now I'd like to make a criteria query which would fetch all Foobar pojos whose uuids list contains the string "abc123", I'm just not sure how to make the appropriate criterion.

Answer 1

I assume you are using a version of Hibernate that implements JPA 2.0. Here's a JPA 2.0 solution that should work with any compliant implementation.

Please annotate uuids with JPA's @ElementCollection annotation. Don't use Hibernate's @CollectionOfElements as mentioned in some of the other answer comments. The latter has equivalent functionality but is being deprecated.

Foobar.java will look approximately like this:

@Entity
public class Foobar implements Serializable {

    // You might have some other id
    @Id
    private Long id;

    @ElementCollection
    private List<String> uuids;

    // Getters/Setters, serialVersionUID, ...

}

Here's how you can build a CriteriaQuery to select all Foobars whose uuids contain "abc123".

public void getFoobars() {
{
    EntityManager em = ... // EM by injection, EntityManagerFactory, whatever

    CriteriaBuilder b = em.getCriteriaBuilder();
    CriteriaQuery<Foobar> cq = b.createQuery(Foobar.class);
    Root<Foobar> foobar = cq.from(Foobar.class);

    TypedQuery<Foobar> q = em.createQuery(
            cq.select(foobar)
              .where(b.isMember("abc123", foobar.<List<String>>get("uuids"))));

    for (Foobar f : q.getResultList()) {
        // Do stuff with f, which will have "abc123" in uuids
    }
}

I made a self-contained proof-of-concept program while playing with this. I can't push it out right now. Please comment if you want the POC pushed to github.