MDB's superclass as MDB - allowed or not?

[Piotr Nowicki]

Howdy Ranchers!

Quick question - can a MDB have a superclass which is another MDB? I'm a bit confused after reading this:

EJB 3.1 spec, p. 151, 5.6.2 wrote:A message-driven bean class must not have a superclass that is itself a message-driven bean class.

EJB 3.1 spec, p. 151, 5.6.3 wrote:A message-driven bean class is permitted to have superclasses that are themselves message-driven bean classes.

So... can or can not? :-)

Thanks in advance!

Cheers.

[Lucas Smith]

Can anyone clear this out? This is a kind of inconsistency.

[Dieter Quickfend]

Just wanted to bring this back from the dead as I've just come across this inconsistency in the spec, and would like to have it cleared out.

So, can an MDB have a superclass that is also an MDB... or not?

[Frits Walraven]

Hi Dieter,

I have concluded that it is possible (with the same explanation as is used the Session Beans): "the use of message-driven bean classes as superclasses merely represents a convenient use of implementation inheritance, but does not have component inheritance semantics."

in other words:
"A listener interface exposed by a particular message driven bean is not inherited by a subclass"

@MessageDriven
public class A implements Echo { ... }
@MessageDriven
public class B extends A implements Talk

Message Driven Bean A exposes the message listener interface Echo and Message Driven Bean B exposes the message listener interface Talk, but not Echo (unless explicitly put as an implementer).

I guess this is a theoretical discussion as I can not think of any practical solution where you would need something like this.

Regards,
Frits

[Dieter Quickfend]

So it's permitted - thanks Frits!