Overview of persisting a domain model - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 129

argument. HibernateTemplate is typically instantiated by Spring's bean factory and
passed by dependency injection to the repositories that need it.
Using an ORM template class also facilitates testing. The repository methods
that call a convenience method can be tested with a mock template object. A test
case can construct a repository passing in a mock template object and verify that
the expected method is called.
Despite these advantages, you cannot always use the convenience methods
because they do not expose all of the functionality of the persistence framework's
API s.

4.4.3 Making repositories easier to test

A repository must call the persistence framework API s directly if the ORM template
does not expose the functionality that it needs. It could use the SessionFactory-
Utils and PersistenceManagerFactoryUtils classes to obtain a connection, but
code that uses those classes is more difficult to test because it can't be tested with
mock objects. A better approach is to use an ORM template class to execute what
Spring refers to as a callback.

The trouble with anonymous callback classes
A Spring callback object is an instance of a class that implements a callback inter-
face. It has a method that is passed a persistence framework connection as a
parameter, and it can manipulate persistent objects. The simplest way to execute a
callback with an ORM template class is to use an anonymous class. For example,
the RestaurantRepository 's findRestaurants() method could use the JdoTem-
plate to execute a callback that uses the Query interface directly:

public class JDORestaurantRepositoryImpl extends JdoDaoSupport
implements RestaurantRepository {

public List findRestaurants(final Address deliveryAddress,
final Date deliveryTime) {
JdoTemplate jdoTemplate = getJdoTemplate();
return (List) jdoTemplate.executeFind(new JdoCallback() {
public Object doInJdo(PersistenceManager pm) {
Map parameters = makeParameters(deliveryAddress,
deliveryTime);
Query query = pm.newQuery(Restaurant.class);
query.declareVariables("TimeRange tr");
…
return query.executeWithMap(parameters);
}
});
}