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Criteria API: filter by class type

user1557 Published in May 23, 2018, 8:42 pm

I'm relativley new to relational databases and I have some problems concerning the creation of queries. First I want to explain the situation shortly. I have several entity classes. All of them extend AbstractEntity or EntityProperty. So entities can have properties and properties have owning entities, so there is a bidirectional relation.
Now let's say ConcreteEntity extends AbstractEntity and I want to create queries like this: Get all entities of type ConcreteEntity which has at least on property with a name contained in the given list propertyNames. Until now I have the following working criteria query:

CriteriaQuery<AbstractEntity> cq = cb.createQuery(AbstractEntity.class);
Root<EntityProperty> property = cq.from(EntityProperty.class);
Join<EntityProperty, AbstractEntity> entity = property.join(EntityProperty_.owningEntities);
cq.where(property.get(EntityProperty_.name).in((Object[]) propertyNames));

But now I want only those entities of type ConcreteEntity. How could I achieve this? In JPQL I wrote "SELECT entity FROM EntityProperty property JOIN property.owningEntities entity" and here I also have no idea how to write it in the way that only a specific type is returned...

Thanks for answers in advance!

EDIT: moved the second question to criteria query: indistinct result lists and removed distinct in the code (that didn't work)

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