Fw: [sca-j] ISSUE 25 - Callback Simplification

I'm forwarding this to the list on behalf
of Michael R.  He's unable to post directly at the moment.

    Simon

Simon C. Nash, IBM Distinguished Engineer

Member of the IBM Academy of Technology

Tel. +44-1962-815156  Fax +44-1962-818999

----- Forwarded by Simon
Nash/UK/IBM on 03/04/2008 16:43 -----

"Michael Rowley"
<> 

03/04/2008 15:40

Please respond to



To

Simon Nash/UK/IBM@IBMGB, 

cc

Subject

RE: [sca-j] ISSUE 25 - Callback Simplification

I like the fact that, in Simon's
model, callbacks always go back to the instance that made the outbound
call.  However, it looks like he does not take advantage of that fact
in the interfaces of the examples that he created.  For example, he
has the following:

 

@Callback(OrderCallback.class)

public interface Order {

            void placeOrder(String
orderID, String orderData);

}

public interface OrderCallback {

            void confirm(String
orderID);

            void update(String
orderID, String status);

}

 

However, since you know that
the order callback goes back to the right instance, you should be able
to define the callback interface as follows:

 

public interface OrderCallback {

            void confirm();

            void update(String
status);

}

 

In Simon's model this should
be possible, but there is a catch.  If the callback interface is defined
this way, the client has to use a conversational scope.  If the client
is stateless or composite scoped, then the routing of the callback to the
right instance doesn't say anything useful about what is being confirmed.

I would like to enable this
style of callback interface irrespective of the scope of the client.  As
with Simon's approach, if the client is conversational scoped, then the
client is especially simple and does not have to do any correlation at
all.  However, if the client needs to use some other scope, for whatever
reason, then the service with the callback can still be used.  However,
it just needs to get the callback ID (or conversation ID) that is associated
with the callback in order to determine what the callback is talking about.

 

Michael

 

From: Simon Nash [mailto:]

Sent: Thursday, March 27, 2008 11:47 AM

To: 

Subject: Re: [sca-j] ISSUE 25 - Callback Simplification

 

There's an update to this proposal at 

http://www.oasis-open.org/apps/org/workgroup/sca-j/download.php/27733/JAVA-25-Proposal-2.doc

This version removes conversational callbacks as all my attempts to define
these involve more complexity than is justified by the functional value
of this capability. 

    Simon 

Simon C. Nash, IBM Distinguished Engineer

Member of the IBM Academy of Technology

Tel. +44-1962-815156  Fax +44-1962-818999 

Simon Nash/UK/IBM@IBMGB 

20/03/2008 11:01 

To



cc

 

Subject

[sca-j] ISSUE 25 - Callback Simplification

 

 
 

Last week I took an action to produce a written up proposal for callback
simplification by today.  I have uploaded this to the document repository
as 

 http://www.oasis-open.org/apps/org/workgroup/sca-j/download.php/27649/JAVA-25-Proposal.doc.

The content of this proposal corresponds to the "Callback Simplification"
section of the proposal sent out by Michael R, and does not address the
changes proposed in the "API Simplification" section.  I
think it is best to have these discussions separately.

This proposal corresponds to what I was describing at the sca-j F2F with
two changes / additions: 

1. Outstanding callbacks don't pin conversational objects after the conversation's
creator has ended the conversation. 

2. In all cases, the caller of a bidirectional interface creates the callback
EPR that will be used (including any reference parameters needed).  
  

I believe the issues that still need to be discussed and resolved are as
follows: 

a) Should all 4 combinations of conversational and non-conversational forward
and callback interfaces be allowed, or only 2 of these?

b) Should the callback interface used to make callbacks to a conversation-scoped
component be marked as conversational? 

c) Should each forward request within a conversation generate a unique
ID that is not part of business data and is returned with the callback?

   Simon 

Simon C. Nash, IBM Distinguished Engineer

Member of the IBM Academy of Technology

Tel. +44-1962-815156  Fax +44-1962-818999

 

Unless stated otherwise above:

IBM United Kingdom Limited - Registered in England and Wales with number
741598. 

Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
3AU 

 

Unless stated otherwise above:

IBM United Kingdom Limited - Registered in England and Wales with number
741598. 

Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
3AU 

Unless stated otherwise above:

IBM United Kingdom Limited - Registered in England and Wales with number
741598. 

Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
3AU