Produce an Entitymanager with extended persistence context via CDI - ejb

Question

We are trying to build a system, which "produces" an entitymanager depending on the logged-in user (kind of multitenancy). Therefor we implemented a stateless ejb like this:
#Stateless
#TransactionAttribute(TransactionAttributeType.SUPPORTS)
public class CustomEntityManagerFactory {
#PersistenceContext(unitName = "EM1")
private EntityManager em1;
#PersistenceContext(unitName = "EM2")
private EntityManager em2;
#Produces
#RequestScoped
public EntityManager getEntityManager() {
// check which entitymanager to return
}
}
The entitymanager is injected like this:
#Stateless
public class EmployeeService {
#Inject
private EntityManager em;
...
}
This producer works as long as only an entitymanager without extended persistence context is needed (in stateless ejb). Unfortunately we also have some stateful ejbs, which need the extended persistence context. Is there a way to implement a CDI producer for this purpose or does this approach only work for stateless ejb with transactional entitymanager?

Answer 1

My guess is you need this:
Create two factories here:
#ApplicationScoped
public class EntityManagerFactoryProducer {
private static EntityManagerFactory factory;
private static EntityManagerFactory factory2;
#Produces
public EntityManagerFactory getEntityManagerFactory(InjectionPoint ip) {
// if the field is named exactly factory2 then factory2 is produced
if (ip.getMember().getName().equals("factory2")) {
if (factory2 == null) {
factory2 = Persistence.createEntityManagerFactory("EM2");
}
return factory2;
}
else {
if (factory == null) {
factory = Persistence.createEntityManagerFactory("EM1");
}
return factory;
}
}
Use factories to createEntityManagers
public class EntityManagerProducer {
#Inject
private EntityManagerFactory factory;
#Inject
private EntityManagerFactory factory2;
#Produces
#RequestScoped
public EntityManager getEntityManager() {
return factory.createEntityManager();
}
#Produces
#RequestScoped
#MyCustomQualifier
public EntityManager getEntityManager2() {
return factory2.createEntityManager();
}
}
The qualifier used to differ between entitymanagers
#Qualifier
#Retention(RUNTIME)
#Target({FIELD })
public #interface MyCustomQualifier {
#Nonbinding
public String value() default "";
}
end usage:
#Inject
EntityManager em;
#Inject
#MyCustomQualifier
EntityManager em2;
Of course you can use the qualifier to differ between factories instead of checking the name of the field. I just wanted to get some more depth into the answer.