CODEWITHSUNDEEP
javaosgiapache-felixdeclarative-services
user5182503
user5182503

Reputation:

OSGI: do declarative services become available after bundle start

The question is simple, but I can't find answer - Can I state that all declarative services in bundle A become available after bundle A start? For example,

bundle=context.installBundle("file:bundleA-1.0.0.jar");
bundle.start();
//In this point are declarative services of bundle A 100% available?

P.S. I use apache felix, but I think it must be defined in Specs but not in implementation.

EDIT:
I assume that DS runtime is running, config is present and all mandatory references are present.

Upvotes: 0

Views: 720

Answers (2)

Peter Kriens
Peter Kriens

Reputation: 15372

The answer to your question is a very simple: NO. There are NO guarantees about availability in OSGi ever based on neither timing nor ordering. The only guarantees are specified in the service events.

It is one of the greatest causes of complexity to make timing/ordering assumptions in your code because they are always violated in the most obscure way.

DS makes it trivial to write code that correctly reacts to the service dependencies as they come and go. Making sure that you get those guarantees associated with services is incredibly complex and you destroy all that value if you start to make assumptions that something should be available after you call a method.

In your example, just rely on a service that you need. If that service is available, then you are sure all initialization is done.

If you stick to service dependencies life in OSGi is fairly easy and very robust.

UPDATED with example after questions

One the non-OSGi side:

 systemBundleContext = ... create framework
 systemBundleContext.registerService( 
    BundleActivator.class, 
    new BundleActivator() {
        public void start(BundleContext c) {
           // start non-OSGi code
        }
        public void stop(BundleContext c) {
           // stop non-OSGi code
        }
     },
     null );

DS Component:

 @Component
 public class Initiator {
    @Reference
    BundleActivator ba;

    @Referenc
    MyService myService;

    @Activate void activate(BundleContext context) throws Exception {
      ba.start(context);
    }

    @Deactivate void deactivate(BundleContext context) throws Exception {
      ba.stop(context);
    }
 }

Upvotes: 1

Christian Schneider
Christian Schneider

Reputation: 19606

You can not assume that all DS Components are available as services after bundle start. The first thing is that the DS runtime must also be running. Then DS components by default are lazily activated. This means they are active only when some other bundle requires such a service and last but not least components only are activated once all their mandatory references are present. Well ... and before I forget it it you can also define that a component is only activated if a config is present for it.

Upvotes: 0

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