Advanced Queries Using Criteria - Beginning Hibernate: From Novice to Professional - page 218

Criteria crit = session.createCriteria(Product.class);
Criterion price = Restrictions.gt("price",new Double(25.0));
crit.setMaxResults(1);
Product product = (Product) crit.uniqueResult();
Again, we stress that you need to make sure that your query only returns one or zero
results if you use the uniqueResult() method. Otherwise, Hibernate will throw a
NonUniqueResultException exception, which may not be what you would expect—Hibernate
does not just pick the first result and return it.
Sorting the Query's Results
Sorting the query's results works much the same way with criteria as it would with HQL or
SQL. The Criteria API provides the org.hibernate.criterion.Order class to sort your result
set in either ascending or descending order, according to one of your object's properties.
Create an Order object with either of the two static factory methods on the Order class:
asc() for ascending or desc() for descending. Both methods take the name of the property as
their only argument. After you create an Order , use the addOrder() method on the Criteria
object to add it to the query.
This example demonstrates how you would use the Order class:
Criteria crit = session.createCriteria(Product.class);
crit.add(Restrictions.gt("price",new Double(25.0)));
crit.addOrder(Order.desc("price"));
List results = crit.list();
You may add more than one Order object to the Criteria object. Hibernate will pass
them through to the underlying SQL query. Your results will be sorted by the first order,
then any identical matches within the first sort will be sorted by the second order, and so
on. Beneath the covers, Hibernate passes this on to an SQL ORDER BY clause after substitut-
ing the proper database column name for the property.
Associations
To add a restriction on a class that is associated with your criteria's class, you will need to
create another Criteria object. Pass the property name of the associated class to the
createCriteria() method, and you will have another Criteria object. You can get the
results from either Criteria object, although you should pick one style and be consistent
for readability's sake. We find that getting the results from the top-level Criteria object
(the one that takes a class as a parameter) makes it clear what type of object is expected in
the results.
The association works going from one-to-many as well as from many-to-one. First, we
will demonstrate how to use one-to-many associations to obtain suppliers who sell products
with a price over $25. Notice that we create a new Criteria object for the products property,
add restrictions to the products' criteria we just created, and then obtain the results from the
supplier Criteria object: