ISSUE-131: @Callback injection could be NULL

[David Booz <booz@us.ibm.com>]

http://www.osoa.org/jira/browse/JAVA-131

Dave Booz
STSM, BPM and SCA Architecture
Co-Chair OASIS SCA-Policy TC and SCA-J TC
"Distributed objects first, then world hunger"
Poughkeepsie, NY (845)-435-6093 or 8-295-6093
e-mail:booz@us.ibm.com

David Booz---02/10/2009 10:09:27 AM---TARGET: Java CAA, section 6.2.4 "Accessing Callbacks" [1] DESCRIPTION: There are situations where th

From:	David Booz/Poughkeepsie/IBM
To:	sca-j@lists.oasis-open.org
Date:	02/10/2009 10:09 AM
Subject:	NEW ISSUE: @Callback injection could be NULL

---

TARGET: Java CAA, section 6.2.4 "Accessing Callbacks" [1]

DESCRIPTION: There are situations where the field or setter with an @callback annotation (when used to obtain a reference to a callaback instance) can be injected with NULL.  As noted in section 8.2 RequestContext, the getCallback() method might return NULL in certain situations, and those situations might also occur in combination with the use of @callback.  For example, suppose a component implements two services, one has a bidirectional interface and the other does not.  The component impl could use @callback to get a callback instance.  When invoked over the bidirectional service, the @callback will non-null, but will be null when the non-bidirectional service is invoked.  AFAIK, the specs don't prohibit the example (nor do I think they should).

PROPOSAL: 
There is no pdf for [1] so bear with me:
In section 6.2.4, at the end of the first paragraph (line 395) add the following:

A field or setter method annotated with @callback might be injected or set to NULL if the implementation is invoked through a non-bidirectional service or when invoked as a callback. The component implementation should always check for null before using a callback reference (See also the getCallbackReference() method in section 8.2 "RequestContext").

In section 6.2.4, the first example (line 400) replace the example with the following:

@Callback
protected ServiceReference<MyCallback> callback;

public void someMethod() {

if (callback) {
MyCallback myCallback = callback.getCallback(); …

myCallback.receiveResult(theResult);
}
}

[1] http://www.oasis-open.org/committees/download.php/31121/sca-javacaa-1.1-spec-cd02-rev2.doc

Dave Booz
STSM, BPM and SCA Architecture
Co-Chair OASIS SCA-Policy TC and SCA-J TC
"Distributed objects first, then world hunger"
Poughkeepsie, NY (845)-435-6093  or  8-295-6093
e-mail:booz@us.ibm.com