Hibernate criteria: Joining table without a mapped association

I'd like to use Hibernate's criteria api to formulate a particular query that joins two entities. Let's say I have two entities, Pet and Owner with a owner having many pets, but crucially that association is not mapped in the Java annotations or xml.

With hql, I could select owners that have a pet called 'fido' by specifying the join in the query (rather than adding a set of pets to the owner class).

Can the same be done using hibernate criteria? If so how?

Thanks, J

This is indeed possible with criteria:

DetachedCriteria ownerCriteria = DetachedCriteria.forClass(Owner.class);
ownerCriteria.setProjection(Property.forName("id"));
ownerCriteria.add(Restrictions.eq("ownername", "bob"));

Criteria criteria = getSession().createCriteria(Pet.class);
criteria.add(Property.forName("ownerId").in(ownerCriteria));

Update: This actually performs a sub-query instead of a join but it allows you to use Criteria on two entities that do not have a hibernate relationship defined.

My understanding is that if you do this using HQL, you are creating a Cartesian join with a filter, rather than an inner join. Criteria queries do not support doing this.

In NHibernate you can use subqueries which are defined as DetachedCriteria. Not sure if it works the same in Java, most probably it is the same:

DetachedCriteria pets = DetachedCriteria.For<Pet>("pet")
  .SetProjection(Projections.Property("pet.ownername"))
  .Add(/* some filters */ );

session.CreateCriteria(typeof(Owner))
  .Add(Subqueries.PropertyIn("name", pets);

Assumed that it is joined using the name of the owner.

Criterion ownerCriterion = Restrictions.sqlRestriction(SELECT ownerId FROM   Owner WHERE ownerName ='bob');
Criteria criteria = getSession().createCriteria(Pet.class);
criteria.createCriteria("ownerId").add(ownerCriterion);

There's a SQLCriterion, which you can give arbitrary SQL, and add to your Criteria. In the SQL string, the token {alias} "will be replaced by the alias of the root entity."