Implementing POJOs with EJB 3 - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 392

}

public PlaceOrderServiceImpl(
PendingOrderRepository pendingOrderRepository,
RestaurantRepository restaurantRepository) {
bb this.pendingOrderRepository = pendingOrderRepository;
bb this.restaurantRepository = restaurantRepository;
}
The restaurantRepository and pendingOrderRepository fields have an @EJB anno-
tation that tells the EJB container to initialize them. Like the PlaceOrderFacade , the
PlaceOrderService has two constructors: a default constructor for the EJB con-
tainer to use and another for the mock object tests.

Annotating the repositories
The repositories are also configured as stateless session beans. They are injected
with the EntityManager . Here is the bean class for the PendingOrderRepository :

@Stateless
public class EJB3PendingOrderRepository implements
PendingOrderRepository {

@PersistenceContext
private EntityManager entityManager;

public EJB3PendingOrderRepository() {
}

public EJB3PendingOrderRepository(EntityManager entityManager) {
bb this.entityManager = entityManager;
}
The entityManager field has an @PersistenceContext annotation that tells the EJB
container to initialize the field with a reference to the EntityManager . The other
repositories are annotated in a similar fashion. Once we have made these
changes, the EJB container will wire together the PlaceOrderFacade and its com-
ponents and configure the repositories with the EntityManager .
EJB 3 dependency injection is certainly a simple yet effective mechanism for
wiring together components that are implemented as EJB s. Unfortunately, it
might not make sense or even be possible to implement all of the components as
session beans. Let's look at how to inject POJO s into session beans.

10.4.2 Integrating Spring and EJB dependency injection

The Spring framework has a very powerful dependency injection mechanism.
Spring beans are arbitrary POJO s and can be injected with other Spring beans as