[java] Should I use @EJB or @Inject

I have found this question: What is the difference between @Inject and @EJB but I did not get any wiser. I have not done Java EE before nor do I have experience with dependency injection so I do not understand what I should use?

Is @EJB an old way of injecting? Is the injection done by the EJB container when using this annotation while using @Inject use the new CDI framework? Is that the difference and should I be using @Inject instead of @EJB if this is the case?

Here is a good discussion on the topic. Gavin King recommends @Inject over @EJB for non remote EJBs.

http://www.seamframework.org/107780.lace

or

https://web.archive.org/web/20140812065624/http://www.seamframework.org/107780.lace

Re: Injecting with @EJB or @Inject?

26. Nov 2009, 20:48 America/New_York | Link Gavin King

That error is very strange, since EJB local references should always be serializable. Bug in glassfish, perhaps?

Basically, @Inject is always better, since:

it is more typesafe,
it supports @Alternatives, and
it is aware of the scope of the injected object.

I recommend against the use of @EJB except for declaring references to remote EJBs.

and

Re: Injecting with @EJB or @Inject?

29. Nov 2009, 17:42 America/New_York | Link Gavin King

    Does it mean @EJB better with remote EJBs?

For a remote EJB, we can't declare metadata like qualifiers, @Alternative, etc, on the bean class, since the client simply isn't going to have access to that metadata. Furthermore, some additional metadata must be specified that we don't need for the local case (global JNDI name of whatever). So all that stuff needs to go somewhere else: namely the @Produces declaration.

Update: This answer may be incorrect or out of date. Please see comments for details.

I switched from @Inject to @EJB because @EJB allows circular injection whereas @Inject pukes on it.

Details: I needed @PostConstruct to call an @Asynchronous method but it would do so synchronously. The only way to make the asynchronous call was to have the original call a method of another bean and have it call back the method of the original bean. To do this each bean needed a reference to the other -- thus circular. @Inject failed for this task whereas @EJB worked.

@Inject can inject any bean, while @EJB can only inject EJBs. You can use either to inject EJBs, but I'd prefer @Inject everywhere.

It may also be usefull to understand the difference in term of Session Bean Identity when using @EJB and @Inject. According to the specifications the following code will always be true:

@EJB Cart cart1;
@EJB Cart cart2;
… if (cart1.equals(cart2)) { // this test must return true ...}

Using @Inject instead of @EJB there is not the same.

see also stateless session beans identity for further info

Injection already existed in Java EE 5 with the @Resource, @PersistentUnit or @EJB annotations, for example. But it was limited to certain resources (datasource, EJB . . .) and into certain components (Servlets, EJBs, JSF backing bean . . .). With CDI you can inject nearly anything anywhere thanks to the @Inject annotation.