The basic programming model for templating looks as follows, for methods that can be part of any custom data access object or business service. There are no restrictions on the implementation of the surrounding object at all, it just needs to provide a Hibernate SessionFactory. It can get the latter from anywhere, but preferably as bean reference from a Spring IoC container - via a simple setSessionFactory(..) bean property setter. The following snippets show a DAO definition in a Spring container, referencing the above defined SessionFactory, and an example for a DAO method implementation.

<beans>

    <bean id="myProductDao" class="product.ProductDaoImpl">
        <property name="sessionFactory" ref="mySessionFactory"/>
    </bean>

</beans>

public class ProductDaoImpl implements ProductDao {

    private HibernateTemplate hibernateTemplate;

    public void setSessionFactory(SessionFactory sessionFactory) {
        this.hibernateTemplate = new HibernateTemplate(sessionFactory);
    }

    public Collection loadProductsByCategory(String category) throws DataAccessException {
        return this.hibernateTemplate.find("from test.Product product where product.category=?", category);
    }
}

The HibernateTemplate class provides many methods that mirror the methods exposed on the Hibernate Session interface, in addition to a number of convenience methods such as the one shown above. If you need access to the Session to invoke methods that are not exposed on the HibernateTemplate, you can always drop down to a callback-based approach like so.

public class ProductDaoImpl implements ProductDao {

    private HibernateTemplate hibernateTemplate;

    public void setSessionFactory(SessionFactory sessionFactory) {
        this.hibernateTemplate = new HibernateTemplate(sessionFactory);
    }

    public Collection loadProductsByCategory(final String category) throws DataAccessException {
        return this.hibernateTemplate.execute(new HibernateCallback() {
            public Object doInHibernate(Session session) {
                Criteria criteria = session.createCriteria(Product.class);
                criteria.add(Expression.eq("category", category));
                criteria.setMaxResults(6);
                return criteria.list();
            }
        };
    }

}

A callback implementation effectively can be used for any Hibernate data access. HibernateTemplate will ensure that Session instances are properly opened and closed, and automatically participate in transactions. The template instances are thread-safe and reusable, they can thus be kept as instance variables of the surrounding class. For simple single step actions like a single find, load, saveOrUpdate, or delete call, HibernateTemplate offers alternative convenience methods that can replace such one line callback implementations. Furthermore, Spring provides a convenient HibernateDaoSupport base class that provides a setSessionFactory(..) method for receiving a SessionFactory, and getSessionFactory() and getHibernateTemplate() for use by subclasses. In combination, this allows for very simple DAO implementations for typical requirements:

public class ProductDaoImpl extends HibernateDaoSupport implements ProductDao {

    public Collection loadProductsByCategory(String category) throws DataAccessException {
        return this.getHibernateTemplate().find(
            "from test.Product product where product.category=?", category);
    }

}

As alternative to using Spring’s HibernateTemplate to implement DAOs, data access code can also be written in a more traditional fashion, without wrapping the Hibernate access code in a callback, while still respecting and participating in Spring’s generic DataAccessException hierarchy. The HibernateDaoSupport base class offers methods to access the current transactional Session and to convert exceptions in such a scenario; similar methods are also available as static helpers on the SessionFactoryUtils class. Note that such code will usually pass false as the value of the getSession(..) methods allowCreate argument, to enforce running within a transaction (which avoids the need to close the returned Session, as its lifecycle is managed by the transaction).

public class HibernateProductDao extends HibernateDaoSupport implements ProductDao {

    public Collection loadProductsByCategory(String category) throws DataAccessException, MyException {
        Session session = getSession(false);
        try {
            Query query = session.createQuery("from test.Product product where product.category=?");
            query.setString(0, category);
            List result = query.list();
            if (result == null) {
                throw new MyException("No search results.");
            }
            return result;
        }
        catch (HibernateException ex) {
            throw convertHibernateAccessException(ex);
        }
    }
}

The advantage of such direct Hibernate access code is that it allows any checked application exception to be thrown within the data access code; contrast this to the HibernateTemplate class which is restricted to throwing only unchecked exceptions within the callback. Note that you can often defer the corresponding checks and the throwing of application exceptions to after the callback, which still allows working with HibernateTemplate. In general, the HibernateTemplate class' convenience methods are simpler and more convenient for many scenarios.