CollectionAttribute testing in JPA CriteriaBuilder - jpa

Question

I have a CriteriaBuilder and am trying to create a predicate to restrict results in a CollectionAttribute. I would like to say something like get all entities in this collection where the entity's attribute A equals x. For example, I have lots of People entities. They have a collection of job titles (previous and current) and I'd like to know about all people who have had a title of "banker". Here is an example:
CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaQuery<Object> query = builder.createQuery();
Root<MheAreaLocation> root = query.from(MheAreaLocation.class);
Predicate p2 = builder.equal(root.get(Jobs_.jobs).get(Jobs_.titles), "banker");
TypedQuery<Object> q = em.createQuery(query);
List<Object> resultList = q.getResultList();
...
Any help would be great. I'm struggling to find much about CollectionAttribute and using them in predicates...and I keep getting nulls when I use the join below in the predicate :-( Thanks
This is my actual code:
CriteriaBuilder builder = em.getCriteriaBuilder();
// CriteriaQuery<Tuple> query = builder.createQuery();
CriteriaQuery<Object> query = builder.createQuery();
Root<MheAreaLocation> mheAreaLocationRoot = query.from(MheAreaLocation.class);
CollectionJoin<MheLocation, AtlasLocationGroupMap> join = mheAreaLocationRoot.join(MheAreaLocation_.childLocation).join(MheLocation_.atlasLocationGroupMapCollection);
// .join(AtlasLocationGroupMap_.atlasLocationGroup, JoinType.INNER);
Predicate p1 = builder.equal(mheAreaLocationRoot.get(MheAreaLocation_.parentLocation).get(MheLocation_.mheLocId), "AZP1B");
// Predicate p2 = builder.equal(mheAreaLocationRoot.get(MheAreaLocation_.childLocation).get(MheLocation_.atlasLocationGroupMapCollection).);
Predicate p2 = builder.equal(join.get(AtlasLocationGroupMap_.atlasLocationGroup).get(AtlasLocationGroup_.locationGroupType), "NEXT_STATION");
// query.where(builder.and(e1, e2));
// mheAreaLocationRoot.fetch(MheAreaLocation_.childLocation);
// join.fetch(MheLocation_.atlasLocationGroupMapCollection);
// query.multiselect(mheAreaLocationRoot.get(MheAreaLocation_.parentLocation),
// mheAreaLocationRoot.get(MheAreaLocation_.childLocation));
// query.select(builder.tuple(join.get(AtlasLocationGroupMap_.mheLocation)));
TypedQuery<Object> q = em.createQuery(query);
List<Object> resultList = q.getResultList();
...
Other classes (I can add more if needed):
#StaticMetamodel(MheLocation.class)
public class MheLocation_ {
public static volatile CollectionAttribute<MheLocation, AtlasLocationGroupMap> atlasLocationGroupMapCollection;
public static volatile SingularAttribute<MheLocation, String> mheLocId;
}

Answer 1

Take this example which has classes of Farm and Animal (Farm has a collection<Animal>) and we want to impose a criteria on the name of the Animal. Not exactly the same as yours I think, but may point you in the right direction
CriteriaBuilder qb = emf.getCriteriaBuilder();
CriteriaQuery<Farm> crit = qb.createQuery(Farm.class);
Root<Farm> candidate = crit.from(Farm.class);
candidate.alias("f");
crit.select(candidate);
Metamodel model = emf.getMetamodel();
ManagedType farmType = model.managedType(Farm.class);
Attribute animalAttr = farmType.getAttribute("animals");
Join animalJoin = candidate.join((ListAttribute)animalAttr);
animalJoin.alias("a");
Path nameField = animalJoin.get("name");
Predicate nameEquals = qb.equal(nameField, "Woolly Sheep");
crit.where(nameEquals);
Equates to
SELECT f FROM org.jpox.samples.annotations.one_many.bidir.Farm f JOIN f.animals a WHERE (a.name = 'Woolly Sheep')
HTH