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From Felix Meschberger <fmesc...@adobe.com>
Subject Re: [osgi] Using Inventory API in Commons Log
Date Mon, 03 Feb 2014 09:24:44 GMT
Hi

Am 03.02.2014 um 10:03 schrieb Chetan Mehrotra <chetan.mehrotra@gmail.com>:

> Thanks for the clarification Felix!
> 
> Just to confirm though ... if Inventory bundle is later
> patched/refreshed it would then lead to refresh of Commons Log bundle
> also.

Yes

> Would that mean framework would be bought down to level 1 and
> restarted again

no, but … all logging would be "disabled and would have to be reconfigured" if the commons
log bundle is refreshed …

So the question really is: what happens to the logger instances held by the bundles ….

Regards
Felix

> Chetan Mehrotra
> 
> 
> On Mon, Feb 3, 2014 at 2:21 PM, Felix Meschberger <fmeschbe@adobe.com> wrote:
>> Hi
>> 
>> Am 03.02.2014 um 09:41 schrieb Chetan Mehrotra <chetan.mehrotra@gmail.com>:
>> 
>>> Hi,
>>> 
>>> For SLING-3264 I was thinking to provide Inventory integration in
>>> Commons Logs. However the Commons Log bundle starts at level 1 while
>>> the Inventory bundle starts at Level 5. The log bundle would use the
>>> ServiceFactory approach to expose the Inventory service and would not
>>> have required dependency on Inventory API.
>>> 
>>> So just wanted to confirm that would it be fine to depend on classes
>>> from a bundle which starts at later start level or not?
>> 
>> Sure. This is what we are using ServiceFactory and dynamic/delayed import all over
places. See for example the Configuration Admin binding the Apache Felix SCR bundle.
>> 
>> So, what seems to boild down to kind of a best practice is to:
>> 
>>  * use ServiceFactory for optional services
>>  * use Import-Package with resolution:=optional to have
>>      static wiring if possible
>>  * use DynamicImport-Package to have dynamic wiring
>>      on-demand
>> 
>> It is just very important to thouroughly test this to not get inadvertend ClassNotFoundExceptions,
for example if the optional classes appear in the method signature of a required class (see
the ResourceResolverActivator.getFeaures() method which returns Object to work around this
issue).
>> 
>> Regards
>> Felix


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