Re: [sca-j] ISSUE 4 - Dependency reinjection

[Mike Edwards <mike_edwards@uk.ibm.com>]

Reza,

This is a good contribution to settling
this item of work.

I suggest one addition to the table
- "Target Service Undeployed" is OK for services within the SCA
Domain - to deal with services elsewhere,
"Target Service becomes Unavailable"
is a better description (we don't know anything about HOW it became unavailable),
but the effects are the same.

		Effect on
Change Event	Reference	Existing ServiceReference Object	Subsequent Invocations of ComponentContext. getServiceReference() or cast()
Change to the Target of a Reference	MAY be reinjected (if other conditions apply). If not reinjected, then it MUST continue to work as if the reference target was not changed.	MUST continue to work as if the reference target was not changed.	Result corresponds to the injected  reference (i.e. changed only if reinjection occurred).
Targeted Service Undeployed Target Service becomes Unavailable	Business methods SHOULD throw InvalidServiceException.	Business methods SHOULD throw InvalidServiceException.	Result SHOULD be a reference to the undeployed service. Business methods SHOULD throw InvalidServiceException.
Targeted Service Changed	MAY continue to work, depending on the runtime and the type of change that was made. If it doesn't work, the exception thrown will depend on the runtime and the cause of the failure.	MAY continue to work, depending on the runtime and the type of change that was made. If it doesn't work, the exception thrown will depend on the runtime and the cause of the failure.	Result SHOULD be a reference to the changed service.

Now, I'd like to propose the following,
which I realize changes some of the decisions we made previously, but I
am getting concerned about complexity:

1. No reinjection of references occurs
by default for any component of any scope

2. Any component of any scope can declare
that it requires reinjection.  My suggestion is to provide a parameter
to the @Reference
annotation reinject="true",
which only has meaning for References which are a) Fields b) accessible
via a setter method (ie it cannot apply to a
reference injected via the constructor).

This I believe is much simpler and it
gives the component writer a chance to decide for themselves whether they
want to be concerned about
wiring changes occurring dynamically
during the lifetime of a component.  It will also make it simpler
for us to give a good description of the
kinds of circumstance in which it might
be good to react to wiring changes.


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:  mike_edwards@uk.ibm.com

"Reza Shafii" <rshafii@bea.com>

04/01/2008 22:19

To	<sca-j@lists.oasis-open.org>
cc
Subject	[sca-j] ISSUE 4 - Dependency reinjection

Hi All,
 
In an effort to try to put more structure around a potential solution to
issue 4, Michael and I put together the attached table. Most of the content
is derived from conlusions reached by the TC's past discussions. A matrix
such as this might help us better focus future discussions.
 
Looking forward to your feedback,
 
Reza

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