How to use hibernate criteria to return only one element of an object instead the entire object?

Question

I think you could do that with Projections, something like

Criteria.forClass(bob.class.getName())
        .add(Restrictions.gt("id", 10))
        .setProjection(Projections.property("id"))
        );

Similarly you can also:

Criteria criteria = session.createCriteria(bob.class);

criteria.add(Expression.gt("id", 10));

criteria.setProjection(Projections.property("id"));

criteria.addOrder(Order.asc("id"));

return criteria.list();

or setProjection(Projections.id())

http://www.devarticles.com/c/a/Java/Hibernate-Criteria-Queries-in-Depth/2/