| Re: [e4-dev] e4, conventions, OSGi, ... - We need to set up rules |
> From:
>
> Tom Schindl <tom.schindl@xxxxxxxxxxxxxxx>
> 3. Declarative Services vs Extension Points
> -------------------------------------------
> I think we should use DS instead of extension points because using
> extension points forces our bundles to be a singleton - which is not
> needed OSGi experts please correct me - with Declarative Services
>
Both tools have their purposes. I don't think we should move 100% towards one or the other. If singletons are a big deal then lets work on removing that restriction from the eclipse extension registry. Even when using OSGi services with the white board pattern you have to use singletons implementations in many cases. For example, the event admin specification uses the white board pattern to allow multiple bundles register as many EventHanders as they want. But you still would only want one singleton implementation of the event admin service to actually use and fire events to all the EventHandlers.
I think the eclipse extension registry is very similar to this. You only want one version of a bundle to process the extension point but you could imagine multiple versions of a bundle contributing an extension to an extension point implementation.
Tom.