Implementing POJOs with EJB 3 - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 397

@PersistenceContexts( {
b ➥ @PersistenceContext(name = "EntityManager") })
public class PlaceOrderFacadeUsingIntegratedDependencyInjectImpl
implements
PlaceOrderFacadeUsingIntegratedDependencyInject {

@Resource(name = "RestaurantRepository")
private RestaurantRepository restaurantRepository;

@Resource(name = "PlaceOrderFacadeResultFactory")
private PlaceOrderFacadeResultFactory resultFactory;

@Resource(name = "PlaceOrderService")
private PlaceOrderService service;
…
}
When the EJB container instantiates the PlaceOrderFacadeUsingIntegratedDepen-
dencyInjectImpl class, it looks up the JNDI names specified by the @Resource
annotations and retrieves the POJO s. Because those JNDI names are bound to ref-
erences, the JNDI implementation will end up calling the Spring bean factory,
which will create those POJO s and their dependencies. When the Spring bean fac-
tory creates the repositories, it will do a JNDI lookup to retrieve the EntityManager
that is injected into the repositories. Let's take a look.

Injecting the EntityManager into the repositories
The Spring bean factory must inject the EntityManager into the repositories. The
@PersistenceContext annotation on the session bean class binds a JNDI name to
the EntityManager , and so we just need to use the Spring JndiObjectFactoryBean ,
which is a Spring FactoryBean that looks up a JNDI object. One complication,
however, is that the EntityManager is not bound when the Spring bean factory is
called. This means that we must configure the JndiObjectFactoryBean to delay
looking up EntityManager until the first time the application calls it. This is
accomplished by using the JndiObjectFactoryBean 's lookupOnStartup and proxy-
Interface properties. Here are the bean definitions for the JndiObjectFactory-
Bean and an example repository:

<beans>
…
<bean id="EntityManager"
class="org.springframework.jndi.JndiObjectFactoryBean">
<property name="jndiName">
<value>java:comp.ejb3/env/
bbbbbb bb ➥ EntityManager</value>
</property>
<property name="lookupOnStartup">

Specifies JNDI name to look up

Delays lookup until first access