About Question enthuware.oce-ejbd.v6.2.507 :

[ETS User]

Possible inconsistency between answer marked as true:

"Make Y implement MessageListener instead of MessageDrivenBean."

and explanation:

"MessageDrivenBean is not required in EJB 3.x. A valid JMS MDB should use @MessageDriven on the class and the class must implement javax.jms.MessageListener interface. MessageListener interface has only one method - onMessage(Message msg)."?

[ptie1981]

Why "Provide a public no-args constructor for class Y"?

By default, class Y has a public no-args constructor.

[admin]

Hello,
The explanation looks ok. An MDB is not required to implement the MessageDrivenBean interface anymore. But it must implement MessageListener interface. Since Y extends X, it already has the method required for this interface.

No-args constructor is required for Y because it has a one-arg constructor already defined. So it will not get the default no-args constructor automatically.

HTH,
Paul.

[ptie1981]

Your right, I did not noticed it

But anyway, today I passed the exam with 93%, thanks to the mock exams. Thanks!

[Misha]

None of the options indicates adding @MessageDriven, so with all the options selected it still won't be a valid MDB. Or am I missing something?

[Guest]

None of the options indicates adding @MessageDriven, so with all the options selected it still won't be a valid MDB. Or am I missing something?

You can describe it as MDB in the deployment descriptor, so an annotation is not strictly required.

I believe the same is true about all EJB annotations.

[Misha]

You can describe it as MDB in the deployment descriptor, so an annotation is not strictly required.
I believe the same is true about all EJB annotations.

In this case option 3 is correct too:
"Make Y implement MessageListener also".
Although it says MessageDrivenBean is not required, it's not forbidden either.

[Guest]

Although it says MessageDrivenBean is not required, it's not forbidden either.

As a matter of fact - yes. My glassfish just allowed me to build an MDB with both MessageListener and MessageDrivenBean interfaces, and it works. IT even calls the MessageDrivenBean methods when expected.

Don't know wha to make out of it.

[admin]

Class Y has now been annotated with @MessageDriven to avoid this confusion.

thank you for your feedback!
Paul.

[Christian]

Proposal for improvement of explanation:

Make Y implement MessageListener instead of MessageDrivenBean.

is true and

Make Y implement MessageListener also.

is false not because of

MessageDrivenBean is not required in EJB 3.x. A valid JMS MDB should use @MessageDriven on the class and the class must implement javax.jms.MessageListener interface. MessageListener interface has only one method - onMessage(Message msg).

since - as someone has already pointed out - the bean can both be annotated with @MessageDriven and implement the interface MessageDrivenBean, but because Y does not implement the methods from the MessageDrivenBean interface (ejbRemove and setMessageDrivenContext).

[admin]

Proposal for improvement of explanation:

Make Y implement MessageListener instead of MessageDrivenBean.

is true and

Make Y implement MessageListener also.

is false not because of

MessageDrivenBean is not required in EJB 3.x. A valid JMS MDB should use @MessageDriven on the class and the class must implement javax.jms.MessageListener interface. MessageListener interface has only one method - onMessage(Message msg).

since - as someone has already pointed out - the bean can both be annotated with @MessageDriven and implement the interface MessageDrivenBean, but because Y does not implement the methods from the MessageDrivenBean interface (ejbRemove and setMessageDrivenContext).

The explanation that you have quoted is associated with the second option "Make Y implement MessageListener instead of MessageDrivenBean.".

Additional explanation has been added as per your suggestion.

thank you for your feedbac,
Paul.