Simon Nash wrote:
I am implementing approach 1). The code is turning out to be
straightforward and this approach fully supports the SCA callback
spec AIUI.
The Axis2 callback MEP isn't the same as an SCA callback, and it's
confusing that these have the same name. With the Axis2 callback
MEP, the forward call is sent asynchronously, and the callback
message carries the result from the forward call. In SCA, the
callback is a normal call made in the reverse direction, and the
signature of the callback is unrelated to the signature of the
forward call.
Simon
Folks,
This is the correct interpretation.
SCA callback is very general and make no assumption about the nature of
the transport used between the reference and the service.
The call interface has each method able to be a full request/response,
if that is what is required. They can of course have a void return or
be a OneWay invocation.
The callback interface equally allows each method to be a full
request/response or a OneWay.
There is no assumption made about the number or the timing of the
invocations on the callback interface related to a given invocation on
the call interface. Indeed, SCA today has no metadata that captures
these relationships (it has been suggested quite seriously that it might
be possible to capture this metadata as an abstract BPEL process, but
this has not been progressed as a formal addition to the Assembly
specification).
So, the correct behaviour is for the call to be treated as a regular
SOAP/HTTP interaction, completely independent from any callback interaction.
A given call may result in 0, 1 or many callback invocations. A simple
example might be a service for placing an order. The "place order"
operation may be request/response with the response acting as a "ack"
that the order was received. However, the "place order" may then be
followed by callbacks like the following:
- "order accepted" - once credit checking and item availability checks
are done
- "order dispatched" - once the order items have been packaged and
dispatched to the shipper
Yours, Mike.
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