[hibernate-dev] Concept of "service availability"

[Brett Meyer]

I've used similar setups frequently.  As another example, the Eclipse RCP framework provides "ExtensionPoints."  They're essentially an interface and a bit of metadata used by the bundles.  The core system provides the interfaces.  Additional plugins/bundles provide their own implementations of the extension point interface.  Then, the core system uses an ExtensionUtility to find all instances of the interface and acts upon them.  I'm not sure what the utility does under the hood, as far as a registry pattern, etc. is concerned.  I can look into it a bit.

Steve, I'll take a look at StrategySelector in the morning.  Martin, if you're interested, I'm willing to help prototype it with you.

-Brett-

----- Original Message -----
From: "Steve Ebersole" <steve at hibernate.org>
To: mailing at bibbernet.org
Cc: "Hibernate hibernate-dev" <hibernate-dev at lists.jboss.org>, jpederse at redhat.com
Sent: Tuesday, August 28, 2012 5:14:12 PM
Subject: Re: [hibernate-dev] Concept of "service availability"

I am not familiar enough to know how this hooks in with OSGi. 
StrategySelector is already pushed to master, if you want to incorporate 
what this might look like using that I will certainly take a look.


On 08/28/2012 03:33 PM, mailing at bibbernet.org wrote:
> I had a similar problem before:
>
> In an osgi project we needed the ability to extend a main system with
> functionality provided in addon bundles
> We developed a main system which could be extended and complemented with
> extenders of several kinds.
>
> The main system provided (exported) a tree of marker interfaces like
>
> public interface ExtenderMarker {};
> public interface TypeAExtender extends ExtenderMarker
> public interface TypeBExtender extends ExtenderMarker
> ....
>
> and had a "helper" which scans services, tracks services and initially
> scans the framework for interesting services (started from the bundle
> activator of the main system).
>
> The extender bundles only implemented the extenders and registered OSGI
> services with the ExtenderMarker interface and maybe also the concrete
> interface. They had no more tasks to do.
>
> Now the main system could "use" the extenders which got registered by
> the "helper" and the "helper" was handling the live cycle events, etc.
>
> Simple approach based on the whiteboard pattern.
>
> - Martin

-- 
steve at hibernate.org
http://hibernate.org
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