java - What does the @EJBs annotation do?

Question

I know roughly what this construction does: it creates a SomeType EJB and injects the object into another EJB.

 @EJB(name="name1")
 SomeType someVariable

Now I have a class which starts like this: (I give all class-level annotations, even though I think only the @EJBs is relevant)

@Remote(SomeClass.class)
@Stateless(name="someName")
@EJBs({@EJB(name="name1",beanInterface=Type1.class),
       @EJB(name="name2",beanInterface=Type2.class)})
@TransactionAttribute(TransactionAttributeType.REQUIRED)
@TransactionManagement(TransactionManagementType.CONTAINER)
public class X extends Y{ 
  //code

What do the @EJB s do here? They probably get or create the "name1" ... objects from JNDI, but where do they put the result? I don't see a .lookup call anywhere near, but the codebase is huge so I'm not very sure about this.

Bonus question: I presume the two @Transaction annotations simply repeat defaults?

UPDATE: Multiple persons claimed at this point that @EJBs is a proprietary extension. It is not. It is a core part of java EE5. See the JavaDoc for details.. It is simply a container for the individual @EJB annotations.

I believe everyone who claims these EJB annotations do a lookup. I just want to know what happens with the result of this lookup.

question from:https://stackoverflow.com/questions/12348542/what-does-the-ejbs-annotation-do

Answer 1

The @EJB annotation (and @Resource, @WebServiceRef, etc.) serves two purposes:

1. It declares a reference in the component namespace. For example, @EJB(name="myEJB") creates a reference java:comp/env/myEJB. If you annotate a field and do not specify a name, then it creates a reference java:comp/env/com.example.MyClass/myField.
2. If the annotation is declared on a field or setter method, then the container performs injection when the component is created.

How the reference is resolved varies, independent of whether the reference is being resolved for a lookup("java:comp/env/myEJB") or due to injection:

1. If EE 6+ is used, the lookup attribute requires a JNDI lookup to resolve the target.
2. Some application servers support mappedName, which is specified to be vendor specific. This is usually implemented by performing a lookup.
3. Application servers support bindings at deployment time. This is usually implemented by performing a lookup.
4. If no other binding information is provided and the bean interface (beanInterface or the field type) is only implemented by a single EJB in the application, then the EJB specification requires that it fall back to that.
5. If no other binding information is provided and #4 cannot work, some application servers will attempt to perform a lookup in the server namespace based on the ref name (for example, java:comp/env/myEJB might cause a lookup of myEJB in the server namespace).