Enthuware

In the explanation, acknowledgeMode is set to be either Auto_acknowledge or DUPS_OK_ACKNOLWEDGE for BMT.

According to session 5.4.15, message receipt acknowledgment is handled by the container in both CMT and BMT.
(The only difference is message receipt is part of the transaction in CMT, but it is not in BMT).

Why the MDB bean developer can specify acknowledgeMode as DUPS_OK_ACKNOWLEDGE when the acknowledgement is handled by the container, not the JMS API ?

This is just a customization option for the BMT. The container will handle the acknowledgement based on the type of acknowledgement selected by the bean.

HTH,
Paul.