ISSUE 22 - When is a RequestContext available?

http://www.osoa.org/jira/browse/JAVA-22

Von: Mike Edwards 
[mailto:] 
Gesendet: Donnerstag, 31. Januar 
2008 09:16
An: OASIS Java
Betreff: RE: [sca-j] NEW ISSUE: 
When is a RequestContext available?

Folks, 

This conversation indicates a problem with our 
terminology, which we need to sort out. 

An SCA Component is indeed a configured instance of an Implementation - 
and a single 
implementation may be used 
by multiple Components. 

However, in 
Simon's original wording, "instance" was not being used in that sense at 
all. 
In Simon's wording, "instance" 
referred to a runtime instance - a particular instantiation of 
a particular component.  In Java, this would mean a 
particular Java object.  Simon's wording 
was correct in that sense, but it clearly caused confusion for some 
folks. 

Can I suggest that we use a 
term such as "runtime instance" for this case? 

Yours,  Mike.

Strategist - Emerging 
Technologies, SCA & SDO.
Co Chair OASIS SCA Assembly TC.
IBM Hursley 
Park, Mail Point 146, Winchester, SO21 2JN, Great Britain.
Phone & FAX: 
+44-1962-818014    Mobile: +44-7802-467431  
Email: 
  

  
  

    Simon 
      Nash/UK/IBM@IBMGB 
      
30/01/2008 21:32 

    
      
        
        

          
            
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Subject

          RE: [sca-j] NEW ISSUE: When is a 
            RequestContext available?

      
        
        

          
          

Sanjay,
Thanks for the pointer and for putting me straight on the 
terminology.  If 
a component is an instance (Appendix C) then just 
calling it a component 
should be enough, but perhaps "component instance" is 
clearer.  I agree 
that the term "instance of a component" that I was 
using is incorrect.

   Simon

Simon C. Nash, IBM 
Distinguished Engineer
Member of the IBM Academy of Technology
Tel. 
+44-1962-815156  Fax +44-1962-818999

"Patil, Sanjay" 
<> 
30/01/2008 20:21

To
Simon 
Nash/UK/IBM@IBMGB, 
<>
cc

Subject
RE: [sca-j] NEW 
ISSUE: When is a RequestContext available?

The 
Appendix C of the Assembly specification is the closest I can think
of for a 
glossary of the terms.

The Assembly specification in several places makes 
statements on the
lines of - A component is a configured instance of an 
implementation. So
I guess a component itself is an instance. So calling a 
component
instance as just that (that is - 'the component instance') may be 
better
than calling it 'an instance of the component' (which I 
believe
incorrectly hints at the possibility of multiple instance of the 
same
component). Now there is a possibility of multiple instances of the 
same
component in the implementation hierarchy (via 
implementation.composite)
of the SCA domain, but I guess you were not 
referring to that case. 

BTW, I searched the Assembly spec for all 
occurrences of the term
'instance' and couldn't find the term used for 
indicating 'instance of a
component' anywhere.

I get a feeling that we 
are now on the path of splitting hairs :-)

-- Sanjay

> 
-----Original Message-----
> From: Simon Nash [mailto:] 

> Sent: Wednesday, Jan 30, 2008 11:55 AM
> To: 

> Subject: RE: [sca-j] NEW ISSUE: When is a 
RequestContext available?
> 
> Sanjay,
> Here's my terminology 
model:
> A component is a configuration of an implementation.
> 
There can (in general) be many instances of an 
> implementation. 
 Each of 
> these instances is configured by the component.
> 
Invocations to a component (via a service) are dispatched to 
> an 
instance 
> of the component
> In the above, I said "...instance of 
the component" rather than 
> "...instance of the implementation" because 
the instance has had the 
> component's configuration applied to 
it
> 
> Is there an SCA glossary somewhere that provides approved 

> definitions of 
> the above terms?
> 
>     
Simon
> 
> Simon C. Nash, IBM Distinguished Engineer
> Member 
of the IBM Academy of Technology
> Tel. +44-1962-815156  Fax 
+44-1962-818999
> 
> 
> 
> "Patil, Sanjay" 
<> 
> 30/01/2008 18:12
> 
> 
To
> Simon Nash/UK/IBM@IBMGB, <>
> 
cc
> 
> Subject
> RE: [sca-j] NEW ISSUE: When is a 
RequestContext available?
> 
> 
> 
> 
> 
> 

> 
> Just a nitpick -  You have used the term 'an instance of 
the 
> component'
> a few times below. I would have thought that a 
component itself is an
> instance (of an implementation). Perhaps 
replacing 'an instance of the
> component' with 'the component instance' 
would be more appropriate!
> 
> Regarding the issue and the proposal 
- both make sense to me.
> 
> -- Sanjay
> 
> > 
-----Original Message-----
> > From: Simon Nash 
[mailto:] 
> > Sent: Wednesday, Jan 30, 2008 6:11 
AM
> > To: 
> > Subject: [sca-j] NEW 
ISSUE: When is a RequestContext available?
> > 
> > RAISER: 
Simon Nash
> > 
> > TARGET: SCA Java Annotations and APIs 
Section 7.1: ComponentContext
> > 
> > DESCRIPTION:
> 
> 
> > The decription of ComponentContext.getRequestContext() says 

> in lines 
> > 647-648 that it returns null if "... there is no 
current 
> > request or if the 
> > context is unavailable". 
 The situations where this applies 
> > need to be 
> > 
defined more precisely.  Here are some cases where a request 
> > 
context may 
> > or not be available:
> > 1. Within a business 
method for a service of the component.
> > 2. Within a property or 
reference injection setter method for 
> > an instance 
> > of 
the component.
> > 3. Within a constructor for an instance of the 
component.
> > 4. Within an Init or Destroy method for an instance of 
the 
> component. 
> > 
> > In case 1, it seems clear 
that getRequestContext() will 
> always return 
> > non-null. 
 In the other cases, it is not clear what should be 
> > 
returned.
> > 
> > PROPOSAL:
> > 
> > 
getRequestContext() MUST return non-null for case 1 and 
> > SHOULD 
return null 
> > for cases 2 through 4.
> > 
> > 

> > 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
> > 
> > 
> 
> 
> > 
> > 
> > 
> > 
> > 

> 
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> Unless stated otherwise above:
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