inject stateless bean into a singleton bean

Question

I have this requirement: I have a singleton bean and I have a method annotated with @PostConstruct where I perform some initialization. One of the initialization is to read some values from a DB, so I want to inject in this method a Stateless bean which is a service bean that access the DB. I don't want to inject the stateless bean as a field in the singleton bean because it is needed only in this method (nowhere else in the singleton bean). To do so I did wrote this in singleton bean:

@Singleton
public class MySingletonBean {

    @PostConstruct
    @EJB
    public void init(SLSBService service) { /* use service to read from DB */ };
    ...
}

The problem is that the Singleton bean can not be instantiated. Any idea? Thank you in advance.

Roland Tiefenbrunner · Accepted Answer · 2012-01-27T19:38:54.387

As the @PostConstruct annotated (callback) method is actually called after all references are resolved (all beans injected) I do not think this construct works.

What you could do or try out is to remove the @PostConstruct and using normal setter injection. However, be aware that other injected resources have not necessarily been resolved at this time.

@EJB
public void setService(SLSBService service){
     service.doSmg();
}

@Stateless    
public class SLSBService{
    @PersistenceContext
    private EntityManager em;

    @TransactionAttribute(TransactionAttributeType.MANDATORY)
    public void doSmg() {
        Member member = new Member();
        member.setEmail("bla@bla.de");
        member.setName("fubu");
        member.setPhoneNumber("453454534535");
        em.persist(member);
    }
}

/* edit */

Just had some time for trying it out. The construct should be usable for DAOs, as the method is executed within a transaction and also the EntityManager (within the SLBService) is injected properly. And as expected references to other EJBs have not be resolved yet, so be aware of that.

inject stateless bean into a singleton bean

1 Answers1