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Posted to users@felix.apache.org by Bulu <bu...@romandie.com> on 2014/10/08 10:00:38 UTC
Dependency Manager: registering FrameworkListener
Hello all
I'm declaring a component using DM which gets created when all
dependencies are met. This component should also get notified of
framework events and thus implements FrameworkListener.
Does the OSGi framework also use a whiteboard pattern for delivering
these events, meaning I only need to publish my component as a
FrameworkListener.class service and it will get called by the framework
when needed?
If not, is there an elegant way of registering it using DM?
Thanks & regards
Philipp
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Re: Dependency Manager: registering FrameworkListener
Posted by Bulu <bu...@romandie.com>.
There were two things I had in mind.
1. Has OSGi been expanded to handle it's own listeners with the
whiteboard pattern? The original paper "Listeners considered harmful..."
is from 2001, so maybe in these 13 years they have adopted it themselves...
My main problem here was: how should I google that (if I don't find
anything, is it because I don't know how to google or because it's not
there?). You clarified that point.
2. Using DM, I was wondering if there is an elegant way to add the
listener, in particular at the place where you define the component, but
I only came up with the following (see below) which I thought, was a bit
of a hack. As I'm pretty new in DM, I was wondering if I had overlooked
a clean way of doing the registration. You clarified that point as well.
mgr.add(createComponent()
.setImplementation(MyFrameworkListener.class)
.setCallbacks(new Object(){ // create callback object
public void start(Component c){
BundleContext bc =
c.getDependencyManager().getBundleContext();
bc.addFrameworkListener((FrameworkListener)
c.getService());
}
public void stop(Component c){
BundleContext bc =
c.getDependencyManager().getBundleContext();
bc.removeFrameworkListener((FrameworkListener) c.getService());
}
}, "notUsed", "start", "stop", "notUsed"));
Thanks & regards Philipp
PS: I understand that writing a whiteboard handler is not the issue -
the issue is probably that in the JavaDoc of FrameworkListener it says
"The Framework deliversFrameworkEvent objects to a FrameworkListener in
order (...)". Although its not specified in "what" order (order of
registration?), using a whiteboard approach cannot guarantee this
(AFAIU). Maybe some client code depends on the call order being the
registration order...
On 09.10.2014 12:17, Marcel Offermans wrote:
> Let me reverse the question: what would be a newer/better way and how should that be implemented. I mean I can see somebody writing a whiteboard style handler and donating it to (for example) Felix. Is that what you would like, or??
>
> On 09 Oct 2014, at 9:02 am, Bulu <bu...@romandie.com> wrote:
>
>> Hello Marcel
>> Yes I already knew the standard way you describe. I just wanted to clarify whether a newer/better method existed.
>>
>> Thanks again for your answer.
>> Philipp
>>
>> On 08.10.2014 11:24, Marcel Offermans wrote:
>>> From the spec: "A FrameworkListener object is registered with the Framework using the BundleContext.addFrameworkListener method.”
>>>
>>> So it is not whiteboard-style (it pre-dates the whiteboard pattern afaik).
>>>
>>> In DM I would do:
>>>
>>> in the init:
>>> dm.add(createComponent().setImplementation(Comp.class));
>>>
>>> and then the component:
>>> public class Comp implements FrameworkListener {
>>> private volatile BundleContext m_context;
>>> public void start() {
>>> m_context.addFrameworkListener(this);
>>> }
>>> public void stop() {
>>> m_context.removeFrameworkListener(this);
>>> }
>>> // implement the FrameworkListener methods here
>>> }
>>>
>>> of course it would also be possible to create a whiteboard style handler for this (just like one exists to handle Servlets for HttpService)…
>>>
>>> Greetings, Marcel
>>>
>>> On 8 Oct 2014 at 10:06:01 , Bulu (bulu@romandie.com) wrote:
>>>
>>> Hello all
>>>
>>> I'm declaring a component using DM which gets created when all
>>> dependencies are met. This component should also get notified of
>>> framework events and thus implements FrameworkListener.
>>>
>>> Does the OSGi framework also use a whiteboard pattern for delivering
>>> these events, meaning I only need to publish my component as a
>>> FrameworkListener.class service and it will get called by the framework
>>> when needed?
>>>
>>> If not, is there an elegant way of registering it using DM?
>>>
>>> Thanks & regards
>>> Philipp
>>>
>>>
>>> ---------------------------------------------------------------------
>>> To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
>>> For additional commands, e-mail: users-help@felix.apache.org
>>>
>>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
>> For additional commands, e-mail: users-help@felix.apache.org
>>
>
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> To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
> For additional commands, e-mail: users-help@felix.apache.org
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Re: Dependency Manager: registering FrameworkListener
Posted by Marcel Offermans <ma...@luminis.eu>.
Let me reverse the question: what would be a newer/better way and how should that be implemented. I mean I can see somebody writing a whiteboard style handler and donating it to (for example) Felix. Is that what you would like, or??
On 09 Oct 2014, at 9:02 am, Bulu <bu...@romandie.com> wrote:
> Hello Marcel
> Yes I already knew the standard way you describe. I just wanted to clarify whether a newer/better method existed.
>
> Thanks again for your answer.
> Philipp
>
> On 08.10.2014 11:24, Marcel Offermans wrote:
>> From the spec: "A FrameworkListener object is registered with the Framework using the BundleContext.addFrameworkListener method.”
>>
>> So it is not whiteboard-style (it pre-dates the whiteboard pattern afaik).
>>
>> In DM I would do:
>>
>> in the init:
>> dm.add(createComponent().setImplementation(Comp.class));
>>
>> and then the component:
>> public class Comp implements FrameworkListener {
>> private volatile BundleContext m_context;
>> public void start() {
>> m_context.addFrameworkListener(this);
>> }
>> public void stop() {
>> m_context.removeFrameworkListener(this);
>> }
>> // implement the FrameworkListener methods here
>> }
>>
>> of course it would also be possible to create a whiteboard style handler for this (just like one exists to handle Servlets for HttpService)…
>>
>> Greetings, Marcel
>>
>> On 8 Oct 2014 at 10:06:01 , Bulu (bulu@romandie.com) wrote:
>>
>> Hello all
>>
>> I'm declaring a component using DM which gets created when all
>> dependencies are met. This component should also get notified of
>> framework events and thus implements FrameworkListener.
>>
>> Does the OSGi framework also use a whiteboard pattern for delivering
>> these events, meaning I only need to publish my component as a
>> FrameworkListener.class service and it will get called by the framework
>> when needed?
>>
>> If not, is there an elegant way of registering it using DM?
>>
>> Thanks & regards
>> Philipp
>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
>> For additional commands, e-mail: users-help@felix.apache.org
>>
>>
>
>
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Re: Dependency Manager: registering FrameworkListener
Posted by Bulu <bu...@romandie.com>.
Hello Marcel
Yes I already knew the standard way you describe. I just wanted to
clarify whether a newer/better method existed.
Thanks again for your answer.
Philipp
On 08.10.2014 11:24, Marcel Offermans wrote:
> From the spec: "A FrameworkListener object is registered with the Framework using the BundleContext.addFrameworkListener method.”
>
> So it is not whiteboard-style (it pre-dates the whiteboard pattern afaik).
>
> In DM I would do:
>
> in the init:
> dm.add(createComponent().setImplementation(Comp.class));
>
> and then the component:
> public class Comp implements FrameworkListener {
> private volatile BundleContext m_context;
> public void start() {
> m_context.addFrameworkListener(this);
> }
> public void stop() {
> m_context.removeFrameworkListener(this);
> }
> // implement the FrameworkListener methods here
> }
>
> of course it would also be possible to create a whiteboard style handler for this (just like one exists to handle Servlets for HttpService)…
>
> Greetings, Marcel
>
> On 8 Oct 2014 at 10:06:01 , Bulu (bulu@romandie.com) wrote:
>
> Hello all
>
> I'm declaring a component using DM which gets created when all
> dependencies are met. This component should also get notified of
> framework events and thus implements FrameworkListener.
>
> Does the OSGi framework also use a whiteboard pattern for delivering
> these events, meaning I only need to publish my component as a
> FrameworkListener.class service and it will get called by the framework
> when needed?
>
> If not, is there an elegant way of registering it using DM?
>
> Thanks & regards
> Philipp
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
> For additional commands, e-mail: users-help@felix.apache.org
>
>
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Re: Dependency Manager: registering FrameworkListener
Posted by Marcel Offermans <ma...@luminis.nl>.
From the spec: "A FrameworkListener object is registered with the Framework using the BundleContext.addFrameworkListener method.”
So it is not whiteboard-style (it pre-dates the whiteboard pattern afaik).
In DM I would do:
in the init:
dm.add(createComponent().setImplementation(Comp.class));
and then the component:
public class Comp implements FrameworkListener {
private volatile BundleContext m_context;
public void start() {
m_context.addFrameworkListener(this);
}
public void stop() {
m_context.removeFrameworkListener(this);
}
// implement the FrameworkListener methods here
}
of course it would also be possible to create a whiteboard style handler for this (just like one exists to handle Servlets for HttpService)…
Greetings, Marcel
On 8 Oct 2014 at 10:06:01 , Bulu (bulu@romandie.com) wrote:
Hello all
I'm declaring a component using DM which gets created when all
dependencies are met. This component should also get notified of
framework events and thus implements FrameworkListener.
Does the OSGi framework also use a whiteboard pattern for delivering
these events, meaning I only need to publish my component as a
FrameworkListener.class service and it will get called by the framework
when needed?
If not, is there an elegant way of registering it using DM?
Thanks & regards
Philipp
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