Criteria query containing a collection valued property - jpa

Question

Is it possible (and if so how) to create a criteria query that results in a tuple or array of which some elements are collections from a collection valued property?
Given an entity Dummy which has a List<SubEntities> with name subs
class Dummy {
String name;
List<SubEntity> subs;
}
class SubEntity {
// some attributes
}
I want a criteria API query which results in something with the structure
Tuple>
An Array instead of a Tuple would be fine, same for an Array or similar for List.
I tried the following:
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Object[]> q = cb.createQuery(Object[].class);
Root<DummyEntityWithCollection> root = q.from(DummyEntityWithCollection.class);
Join<Object, Object> subs = root.join("subs");
q.select(cb.array(root.get("name"), subs));
List<Object[]> list = em.createQuery(q).getResultList();
But the Object[]s contained in list have as the second element SubEntitys instead of List<SubEntity>.
This one fails in the same way:
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Tuple> q = cb.createTupleQuery();
Root<DummyEntityWithCollection> root = q.from(DummyEntityWithCollection.class);
Join<Object, Object> subs = root.join("subs");
q.multiselect(root.get("name"), subs);
List<Tuple> list = em.createQuery(q).getResultList();
This variant
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Object[]> q = cb.createQuery(Object[].class);
Root<DummyEntityWithCollection> root = q.from(DummyEntityWithCollection.class);
q.select(cb.array(root.get("name"), root.get("subs")));
List<Object[]> list = em.createQuery(q).getResultList();
Doesn't work at all and results in an invalid SQL statement with a single . as one select column (at least for Hibernate and HSQLDB).
The question How can I retrieve a collection property using criteria Api seems to indicate that it is not possible but it is based on Hibernate and I would like to get a JPA based answer. Especially an answer pointing out the section of the JPA spec that makes it clear that this is not possible would be appreciated.

Answer 1

JPQL defines the select clause in section 4.8 as
select_clause ::= SELECT [DISTINCT] select_item {, select_item}*
select_item ::= select_expression [[AS] result_variable]
select_expression ::= single_valued_path_expression | scalar_expression | aggregate_expression | identification_variable | OBJECT(identification_variable) | constructor_expression
so you can see that multi-valued expressions are not selectable in JPQL.
Criteria is simply a way to create a query using an API and objects. See JPA spec chapter 6.1:
The semantics of criteria queries are designed to reflect those of Java Persistence query
language queries.
So it's reasonable to assume the same constraint applies to the Criteria API.