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OSGi service bundle start options - noobie [message #498687]

Tue, 17 November 2009 23:30

Craig Foote
Messages: 184
Registered: July 2009

Senior Member

We're using Eclipse to create 3 bundles, one defining a service
interface, another with a service implementation, and another consuming
the implementation using a ServiceTracker. We're using SpringDM so the
implementation bundle has a /META-INF/spring/bundle-context.xml declaring
a bean of type [ServiceImpl] and registers it under interface [Service].
The service consuming plugin's ServiceTracker is returning a null service
and debugging in the OSGi console indicates the ServiceImpl bundle is in
Lazy state. I understand the DM extender will register the service once
this bundle starts but I'm unsure how to start it. I know of 4 options
but would appreciate others and advice on best practice:

1. instantiate a class in the ServiceImpl bundle from another bundle -
unwanted coupling
2. add the ServiceImpl bundle to the .product's config.ini - unwieldy
and unmanageable in distributed system, i.e. many groups writing service
bundles
3. use a bundles.info file with SimpleConfigurator - I'm not real
familiar with this but it seems the same as option 2 in that it seems to
require a central list of bundles to start
4. create a plugin with a startup extension which uses its
bundlecontext to start appropriate bundles - this seems like a workaround
or hack to me

To clarify requirement, we need a process by which relatively independent
groups write plugins and service bundles for inclusion in a common
eclipse product. Each group needs to manage the starting of its own
service bundles. We want to suggest they use bundle-context.xml's to
declare services and letting the DM extender register them... once we
figure out how to start them :)

Thanks in advance,
Craig Foote

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Re: OSGi service bundle start options - noobie [message #498778 is a reply to message #498687]

Wed, 18 November 2009 10:34

Paul Webster
Messages: 6813
Registered: July 2009
Location: Ottawa

Senior Member

If I read Spring DM right (that the extender can only see bundles after they've been activated) then you're going to have to do the leg work yourself.

3 options that come to mind:

1) require everybody that provides a bundle-context.xml to use org.eclipse.ui.startup ... their IStartup implementation will be called after the workbench/workbench windows have been created (now the bundles are activated)

2) create your own extension point that bundle-context.xml providers use ... then your engine that reads the extension point can start up the bundles you want whenever necessary.

3) use eclipse DS (the first call to get a service activates the providing bundle) either by itself or in conjunction with your Spring DM ... the caveat being that someone still has to ask for the DS service in order to activate all the bundles.

But I'm not 100% sure how Spring DM work on its side, I'm just guessing.

PW

Paul Webster
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Re: OSGi service bundle start options - noobie [message #498903 is a reply to message #498778]

Thu, 19 November 2009 00:49

Craig Foote
Messages: 184
Registered: July 2009

Senior Member

Hi Paul, thanks for replying.

I like the Declarative Services idea because it minimizes dependencies. I
did a quick test and I was able to consume a declared service without
explicitly starting the bundle. Nice.

Thanks again,
Craig

On Wed, 18 Nov 2009 10:34:04 -0500, Paul Webster wrote:

> If I read Spring DM right (that the extender can only see bundles after
> they've been activated) then you're going to have to do the leg work
> yourself.
>
> 3 options that come to mind:
>
> 1) require everybody that provides a bundle-context.xml to use
> org.eclipse.ui.startup ... their IStartup implementation will be called
> after the workbench/workbench windows have been created (now the bundles
> are activated)
>
> 2) create your own extension point that bundle-context.xml providers use
> ... then your engine that reads the extension point can start up the
> bundles you want whenever necessary.
>
> 3) use eclipse DS (the first call to get a service activates the
> providing bundle) either by itself or in conjunction with your Spring DM
> ... the caveat being that someone still has to ask for the DS service in
> order to activate all the bundles.
>
> But I'm not 100% sure how Spring DM work on its side, I'm just guessing.
>
> PW

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