Hibernate - Return collection of entities by ID knowing only the class

Question

How do I load a collection of entities of a given class, with only a single trip to the database, e.g.:

 public Collection<Object> getEntities(Class<?> entityClass,Collection<Serializable> listOfIDs);

I know that if I were only wanting to fetch a single entity, I could use:

sessionFactory.getCurrentSession().get(Class,Serializable);

but there doesn't seem to be a matching option for a collection of Serializables.

Note that as I only know the class, I don't know the name of the Identity Column, so simple HQL / Criteria API is not an option, without first discovering the ID column.

Answer 1

Can't you just execute an HQL query - "from MyEntity where ...", which will return a list of the entities? Just build the where clause manually. Another option is to use Criteria API.

Edit: Use "where id = ...". Hibernate will automatically find the id column for you, no matter how it is named.

Answer 2

Hibernate does not provide support for that out of the box. But you can achieve this in HQL with the help of the special id property:

14.5. Referring to identifier property

There are 2 ways to refer to an entity's identifier property:

• The special property (lowercase) id may be used to reference the identifier property of an entity provided that the entity does not define a non-identifier property named id.
• If the entity defines a named identifier property, you can use that property name.

So you could do something like this:

Query q = session.createQuery("from " + clazz.getName() + " where id IN :idList")