Sleeping Criteria: Joining a Table Without Associated Association

Question

I would like to use the hibernate api criteria to formulate a specific request that combines two objects. Let me say that I have two entities: Pet and Owner with an owner having many pets, but to a decisive extent this association does not appear in the Java or xml annotation.

With hql, I can select owners who have a pet named "fido" by specifying the connection in the request (instead of adding a set of pets to the owner class).

Can this be done using sleep criteria? If so, how?

Thanks J

Answer 1

I understand that if you do this using HQL, you are creating a Cartesian connection to the filter, not an internal connection. Criteria requests do not support this.

Answer 2

This is really possible with the 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)); 

Refresh . This actually performs a subquery instead of a join, but it allows you to use criteria for two objects that are not related to hibernation.

Answer 3

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

 DetachedCriteria pets = DetachedCriteria.For<Pet>("pet") .SetProjection(Projections.Property("pet.ownername")) .Add(/* some filters */ ); session.CreateCriteria(typeof(Owner)) .Add(Subqueries.PropertyIn("name", pets); 

It is assumed that it is connected to the name of the owner.

Answer 4

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

Answer 5

There is a SQLCriterion that 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 object."