What is the JPA CriteriaBuilder way for filtering on Sub Classes?

Question

JPA 2.0 provided a means to filter by subclass using the JPQL expressions TYPE, for example :

SELECT e
FROM entity e
WHERE TYPE(e) = :entityType

where parameter entityType would be the value of the discriminator column.

What is the recommended way for achieving the same thing with the JPA criteria builder, considering the discriminator column appears to be off limits?

I'm using JPA 2.1 and so far the only solution that seems adequate is mapping the discriminator column as a read only field within the Java entity, but I'm not sure if this is a supported feature.

Answer 1

Examples of common queries are here

Example:

CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery cq = cb.createQuery();
Root e = cq.from(Entity.class);
cq.where(cb.equal(e.type(), entityType));
Query query = em.createQuery(cq);
List<Entity> result = query.getResultList();

Answer 2

You can use Path type method as documented here:

Predicate p = cb.equal(e.type(), cb.literal(Entity.class));