[jboss-as7-dev] MSC service names in AS7

[David Bosschaert]

... replies inline ...

----- Original Message -----
> From: "David M. Lloyd" <david.lloyd at redhat.com>
> To: jboss-as7-dev at lists.jboss.org
> Sent: Wednesday, 1 June, 2011 9:51:04 PM
> Subject: Re: [jboss-as7-dev] MSC service names in AS7
> On 06/01/2011 03:08 PM, David Bosschaert wrote:
> >
> > One further question. Let's say my service performs some async
> > action in start() and when that action is finished I'm not really
> > interested in the service any more. Should I remove it somehow from
> > the system then?
> 
> In other words, a one-time task which is triggered when all its
> dependencies start? We don't have a generalized API for this. There
> are subtle conceptual issues.

Yes, correct.

> First, using a service will cause its dependencies to automatically
> start if they are, say, ON_DEMAND. However if your service then
> immediately stops or is removed, the dependency services will stop
> again, which is not a useful semantic.
>
> You can use listeners instead, however a listener can only presently
> be
> added to an installed service (i.e. you can't install a listener on a
> name in anticipation of a future service).
> 
> So the real question is, what problem are you trying to solve here?

Ok, so let's look at an example. In the AutoInstallIntegration service in the OSGi subsystem it first installs the bundles asynchronously and then, on line 140 it creates an anonymous service that runs once the install of all bundles is finished to start them. 

Is this correct service usage?

> > Additionally, let's say I have a service that can run more than
> > once, should I give it a different name every time?
> 
> Services can be stopped and started repeatedly, and in fact it is part
> of the contract of a service that it must be able to do so.

Hmmm, it looks like the services in [1] don't adhere to this contract, as the stop is a no-op...

Cheers,

David

[1] http://github.com/bosschaert/jboss-as/blob/master/osgi/service/src/main/java/org/jboss/as/osgi/service/AutoInstallIntegration.java