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From "Richard S. Hall" <he...@ungoverned.org>
Subject Re: Dynamically change the bound service
Date Sun, 18 Dec 2011 22:48:56 GMT
That doesn't sound right. I'd say there is something else simple going 
wrong. If you are using field injection in the consumer, you could look 
to add method injection too to see if you are getting proper callbacks 
when services come and go. Regardless, this sounds like pretty basic 
behavior, so I have to assume there is a simple mistake.

-> richard

On 12/18/11 5:38 PM, Fabio Fonseca wrote:
> Hello all,
>
> I'm starting to develop my master thesis and this is my first post to this
> forum. My research concerns the challenges of developing Self-Adaptable
> software (software that can change its behavior in response to a change in
> its operation context). Right now I'm doing an assessment aiming to find
> which technologies are available today that could help achieving a
> self-adaptable software.
>
> I'm using Apache Felix + iPOJO to develop a simple test. I have a consumer
> which wants to consume providers that implement a interface named
> InterfaceOne. I have two providers that fits this requirement (named
> ProviderA and ProviderB). They all do nothing useful, I am just trying to
> produce a self-adaptable behavior.
>
> I am using the launcher.jar which is provided with the code that comes with
> the great book "OSGi in Action". This launcher creates an instance of the
> Felix Framework and loads the bundles found in the bundles/ directory passed
> as a parameter when running the launcher.jar.
>
> So I have 4 bundles. Each one of them has an iPOJO component inside it,
> except the first one that just has the InterfaceOne interface:
> . services-1.0.jar
> . consumer-1.0.jar
> . providerA-1.0.jar
> . providerB-1.0.jar
>
> The consumer is a simple http listener that uses localhost port 8080 to
> listen to anything that may appear. When something access the port 8080, it
> calls the available provider.
>
> When I start the launcher, all bundles are active and OSGi chooses one of
> the providers and binds it to the consumer. Using the shell commands I'm
> able to stop the providers' bundles and when I do it, the consumer is
> invalidated (as per the iPOJO lifecycle).
>
> I concluded that when I start the consumer bundle the available provider is
> bound to the consumer and it remains bound even when I stop its bundle (in
> the OSGi lifecycle). The cenario is:
>
> - start ProviderA
> - start Consumer (consumer starts since its dependency is satisfied)
> - start ProviderB
> - stop ProviderA (consumer is still valid in the OSGI's lifecycle, since
> there is a provider (ProviderB) that satisfy its dependency)
>
> At this moment, if I call localhost:8080, the consumer uses ProviderA, even
> when ProviderA is not available anymore. I conclude that the binding between
> Consumer and its provider (which is in this case still the ProviderA)
> continues to exist even when I stop ProviderA. I read somewhere that iPOJO
> lifecycle takes over OSGi's lifecycle, but when I stop ProviderA, the
> component becames Invalidated (I know because I placed a method that is
> called when the provider is invalidated). So, even with the provider
> Invalidated, it is still called. I  also read somewhere that each component
> is implemented as a Singleton by default, and I have not changed its
> behavior. So, I'm lost here. I expected that, in the above cenario,
> ProviderB would be called instead of ProviderA.
>
> Anyone has a clue that could help me understand how this mechanism works?
> Attached you can find a file with all my source code and ant tasks I'm using
> to play with iPOJO and OSGi.
>
> http://old.nabble.com/file/p32999833/OIA%2BCode.zip OIA+Code.zip
>
> Thanks a lot in advance!
> Fabio Fonseca

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