Messenger: Subscribe.xml

[Christian, William]

Is the subscribe.xml specific to servlet-based implementations? I would like
to configure a listener class to a specific topic, but I am unclear if I
need to instantiate the class before it can listen or how to configure
messenger to use the subscribe.xml to determine applicable listeners. A
short example of its usage would be great! I've reviewed the code, but got
lost in the details.
 
Thanks for the help
billc