I have doubts about Async WebService (Java) that supports the Callback mechanism.
I read a few links, and this appears promising: http://axis.apache.org/axis2/java/core/docs/jaxws-guide.html#Async
Will both Java and .NET clients be able to make use of WebService Callback mechanism?
How does a Callback Handler "really" gets called back.
How does the Service know the location (or address) of the Client... ? I guess there is some ws-addressing magic involved.. but its that isn't ws-addressing Java specification?
WS-addressing has a set of implementation independent parameters. You can use WS-addressing/ async web services with .NET, Java EE and other languages/platforms. Read more on http://www.w3.org/Submission/ws-addressing