Re: [equinox-dev] Providing a callback to an OSGi bundle

["Saminda Abeyruwan" <samindaa@xxxxxxxxx>]

Dear Tom,

Thank you for the swift reply. 

What you have suggested solved the entire problem.  I used 
Eclipse-BuddyPolicy, and Eclipse-RegisterBuddy
bundle manifest headers to get more control over wiring buddies. 

I was wondering is there a provision to standardize these bundle manifest headers in future OSGi specification. IMO this would be a very important extension to have in OSGi spec. 

Thank you!

Saminda

On Thu, Apr 17, 2008 at 7:02 PM, Thomas Watson <tjwatson@xxxxxxxxxx> wrote:

How do you know the Bundle where the configuration file is and how do you read it from Bundle B? I assume you must be getting the Bundle object for B somehow and using Bundle.getEntry to find the configuration file. If that is the case you can just call Bundle.loadClass(String name) on the bundle that has the configuration file.

But we must be missing something from your scenario because you say you are working with existing code that I assume knows nothing about OSGi, otherwise you would use services like you said. For legacy code that needs access to implementation class from other bundles that depend on it you can use the eclipse buddy class loading mechanism. Adding the following header to Bundle A's manifest will allow Bundle B (and any other bundle that depends on A) to become a buddy to Bundle A.

Eclipse-BuddyPolicy: dependent

Tom



"Saminda Abeyruwan" ---04/17/2008 04:27:46 AM---Hi Devs,

From:	"Saminda Abeyruwan" <samindaa@xxxxxxxxx>
To:	equinox-dev@xxxxxxxxxxx
Date:	04/17/2008 04:27 AM
Subject:	[equinox-dev] Providing a callback to an OSGi bundle

---

Hi Devs,

I have faced with a use-case where a callback need to be passed to an OSGi bundle.

Scenario:

Bundle A exports package "x.y" and "a.b". These are the only packages it exports. The logic of this bundle is such that it can populate a callback, when some function is finished. Say this callback should implement interface "x.y.Foo". Required callbacks are written in a configuration file, and which will be located using OSGi infrastructure.

There exist another bundle B, which has classes that implemented the interface "x.y.Foo" say "x.y.K.FooImpl1" and that bundle also contains the configuration file listing the QName of the impl classes. This bundle imports package "x.y".


When bundle A reads the configuration files from bundle B and tries to initiate the impl classes, bundle A would failed with class definition not found exception stating that it can't locate the implementation "x.y.k.FooImpl1". This is obvious because bundle A does not import package "x.y.k".

Implementation to a callback can contain any package. Thus, bundle A needs to export this some way. Java itself provides callback mechanisms and implementations are done by the users.

Is there any way to solve prior problem. Is it possible me to say in bundle A's MANIFEST.MF Export-Packaget : x.y, a.b, *; resolution:=optional. Is there a way to solve this callback issue using package admin.

My problem with callback would have been solved using OSGi services. Since I've to work with an existing code, OSGi service wouldn't be suffix.


Thank you!

Saminda


--
Saminda Abeyruwan

Senior Software Engineer

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-- 
Saminda Abeyruwan

Senior Software Engineer
WSO2 Inc. - www.wso2.org