How to learn about Message Driven Beans... without too many pre-requisites.

[HG]

It seems that most j2ee tutorials get overly caught up in server
configuration, deployment descriptors, etc, and then details about
entity beans, bmp/cmp, etc.

I want to learn about Message Driven Beans, with some simple examples
(that don't requre me to jump through the above topics first).

Anyone got any recommendations? JBoss would be the ideal server, but
possibly the Sun reference implementation.

Thanks
hoss