package auction.dao.hibernate;import auction.dao.CategoryDAO;import auction.model.Category;import org.hibernate.criterion.Expression;import java.util.Collection;/** * Hibernate-specific implementation of the <tt>CategoryDAO</tt> * non-CRUD data access object. * * @author Christian Bauer */public class CategoryDAOHibernate        extends     GenericHibernateDAO<Category, Long>        implements  CategoryDAO {    public Collection<Category> findAll(boolean onlyRootCategories) {        if (onlyRootCategories)            return findByCriteria( Expression.isNull("parent") );        else            return findAll();    }}