Hello Clement,
I changed to the following line:
PropertyDescription[] propDescs =
configHandlerDescription.getProperties();
But I still get an NPE. Have you tried to call these methods from within an
interceptor?
/Bengt
2013/11/28 Clement Escoffier <[email protected]>
>
> On 28 nov. 2013, at 12:17, Bengt Rodehav <[email protected]> wrote:
>
> > Hello again Clement!
> >
> > I was away on business yesterday which is why I'm late replying.
> >
> > I've come a bit further now but still have problems accessing my
> > component's "extenders" property. Here is what my code looks like now:
> >
> > * public List<ServiceReference> getServiceReferences(DependencyModel
> > theDependencyModel,*
> > * List<ServiceReference> theMatching) {*
> >
> > * ComponentInstance instance =
> > theDependencyModel.getComponentInstance();*
> > * InstanceDescription instanceDescription =
> > instance.getInstanceDescription();*
> > * ComponentTypeDescription componentTypeDescription =
> > instanceDescription.getComponentDescription();*
> > * String factoryName =
> > componentTypeDescription.getFactory().getFactoryName();*
> >
> > * if (FACTORY_NAME.equals(factoryName)) {*
> > * System.out.println("Found a GenericService2");*
> > * ConfigurationHandlerDescription configHandlerDescription =
> > (ConfigurationHandlerDescription) instanceDescription*
> > * .getHandlerDescription("org.apache.felix.ipojo.properties");*
> > * int state = instanceDescription.getState();*
> > * System.out.println("State: " + state);*
> > * if(ComponentInstance.VALID == instanceDescription.getState()) {*
> > * PropertyDescription propDesc =
> > configHandlerDescription.getPropertyByName("extenders"); // NPE*
> > * if(propDesc != null) {*
> > * String extenders = propDesc.getValue();*
> > * System.out.println("Extenders: " + extenders);*
> > * }*
> > * else {*
> > * System.out.println("Extenders is null");*
> > * }*
> > * }*
> > * }*
> >
> > I check the factory name to determine if this is a component that I
> should
> > intercept. Presently I wait until the component is valid but I'm not sure
> > if I can wait since my interceptor has to kick in before that. Presently
> I
> > get a null pointer exception when I try to retrieve my property. Do you
> > have any idea why? It doesn't seem possible to retrieve properties at
> this
> > pont.
>
> Did you try to inter ate over the set of properties and see what are they ?
>
> >
> > I also noticed that the method PropertyDescription.getValue() always
> > returns a String. In my case the underlying object is an array of String
> > (String[]). Is it possible to get the value in the correct type?
>
> Yes, there is a getObjectValue(BundleContext context) method, but you need
> to give a bundle context object used if it needs to load classes.
>
> Clement
>
> >
> > /Bengt
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > 2013/11/27 Clement Escoffier <[email protected]>
> >
> >> Hi,
> >>
> >> On 26 nov. 2013, at 16:00, Bengt Rodehav <[email protected]> wrote:
> >>
> >>> I'm getting a bit closer regarding the interceptors. Still two problems
> >> for
> >>> me:
> >>>
> >>> a) I still don't understand how to get hold of my intercepted instance
> >> from
> >>> within my interceptor. I get a reference to a DependencyModel from
> which
> >> I
> >>> can get a ComponentInstance. But how do I go from there to my
> ComponentA
> >>> class. I need to access the property "extenders" in order for my
> >>> interceptor to do its job.
> >>>
> >>
> >> It depends how how is managed the extender property, let’s imagine it’s
> a
> >> @Property. In this case, from the Dependency Model, you can retrieve the
> >> component instance. From the instance, you have access to the
> introspection
> >> layer (getInstanceDescription()), which let you analyze the iPOJO
> container.
> >>
> >> To be a bit more clear, let’s see some code:
> >>
> >> //First retrieve the configuration handler description from the instance
> >> container:
> >> ConfigurationHandlerDescription description =
> >> (ConfigurationHandlerDescription)
> >>
> model.getComponentInstance().getInstanceDescription().getHandlerDescription("org.apache.felix.ipojo.properties”);
> >> // Find the extenders property
> >> String extenders =
> description.getPropertyByName("extenders").getValue();
> >> // You have your value !
> >>
> >>> b) Also, when the property "extenders" is changed, I need to force the
> >>> interceptor to recalculate the dependencies. How can I accomplish that?
> >>
> >> It also depends on how this reconfiguration happen. Let’s say that the
> >> instance is reconfigured from the configuration admin or iPOJO
> >> reconfiguration abilities. In these case being notified is quite
> simple, as
> >> you can register a ConfigurationListener on the
> >> ConfigurationHandlerDescription object:
> >>
> >> description.addListener(new ConfigurationListener() {
> >> public void configurationChanged(ComponentInstance instance,
> >> Map<String, Object> configuration) {
> >> // The extender property may have been modified
> >> }
> >> });
> >>
> >> Don’t forget to unregister the listener when the interceptor is
> unplugged
> >> from the instance.
> >>
> >>>
> >>> Getting deeper into iPojo than I've been before…
> >>
> >> It’s just the beginning…. (contributions are welcome if you see some
> >> dark(er) area)
> >>
> >>>
> >>> /Bengt
> >>>
> >>>
> >>> 2013/11/26 Bengt Rodehav <[email protected]>
> >>>
> >>>> Thanks Clement!
> >>>>
> >>>>
> >>>> 2013/11/26 Clement Escoffier <[email protected]>
> >>>>
> >>>>> Hi,
> >>>>>
> >>>>> On 25 nov. 2013, at 20:19, Bengt Rodehav <[email protected]> wrote:
> >>>>>
> >>>>>> Hello Clement and as always thanks for your detailed answer!
> >>>>>>
> >>>>>
> >>>>> You’re welcome.
> >>>>>
> >>>>>> It does seem a bit complicated to "require" an interceptor. Perhaps
> an
> >>>>>> easier way of doing this might be possible in the future.
> >>>>>
> >>>>> I think it would be a good addition. Thinking about it.
> >>>>>
> >>>>>> Anyway, I'm not
> >>>>>> exactly sure that I understood what you meant. Just to clarify:
> >>>>>>
> >>>>>> My Component A (the component to be intercepted) has the following
> >> code:
> >>>>>>
> >>>>>> @Property(name = "extenders", mandatory = false)
> >>>>>> private String[] mExtenderIds;
> >>>>>>
> >>>>>> @Requires(optional = true, id = "extenders")
> >>>>>> private IExtender[] mExtenders;
> >>>>>>
> >>>>>> Do you mean that I should put a filter on the @Requires with
> >>>>> id="extenders"
> >>>>>> (the intercepted = true) so that it can only be satisfied if my
> >>>>> interceptor
> >>>>>> has added that property?
> >>>>>
> >>>>> Exactly.
> >>>>>
> >>>>>>
> >>>>>> But how do I then handle the situation where my Component A does not
> >>>>>> require any extenders? In that case I was planning on setting the
> >>>>>> dependency to optional to make my instance valid without any
> >> extenders.
> >>>>>>
> >>>>>> Or, perhaps I could first set the @Requires to mandatory (with the
> >>>>> filter):
> >>>>>>
> >>>>>> @Requires(optional = false, id = "extenders",
> >>>>> filter="(intercepted=true)")
> >>>>>> private IExtender[] mExtenders;
> >>>>>>
> >>>>>> Then, if my interceptor sees that the instance does not require any
> >>>>>> extenders it can set the dependency to become optional. This way I
> >> both
> >>>>>> require the interceptor (via the filter) and I ensure that the only
> >> way
> >>>>> to
> >>>>>> allow the instance to be valid without the dependency is if the
> >>>>> interceptor
> >>>>>> has explicitly set the dependency to optional.
> >>>>>
> >>>>> That would work. You can change the optionality status of the
> >> dependency
> >>>>> from the dependency model you get in the interceptor.
> >>>>>
> >>>>> Regards,
> >>>>>
> >>>>> Clement
> >>>>>
> >>>>>>
> >>>>>> /Bengt
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> 2013/11/25 Clement Escoffier <[email protected]>
> >>>>>>
> >>>>>>> Hi,
> >>>>>>>
> >>>>>>>
> >>>>>>> On 25 nov. 2013, at 11:04, Bengt Rodehav <[email protected]>
> wrote:
> >>>>>>>
> >>>>>>>> I've started to investigate using iPojo interceptors. I'm using
> >> iPojo
> >>>>>>>> version 1.11.0. I want to accomplish the following:
> >>>>>>>>
> >>>>>>>> Component A can be "extended" by specifying a list of (required)
> >>>>>>>> "extenders" (actually their id's), like this:
> >>>>>>>>
> >>>>>>>> @Property(name = "extenders", mandatory = false)
> >>>>>>>> private String[] mExtenderIds;
> >>>>>>>>
> >>>>>>>> @Requires(optional = true, id = "extenders")
> >>>>>>>> private IExtender[] mExtenders;
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> The property is optional but if any extenderId's are listed then
> the
> >>>>>>>> @Requires should require that IExtender's with the corresponding
> >>>>>>> extenderId
> >>>>>>>> is started.
> >>>>>>>>
> >>>>>>>> The IExtender interface contains the following method:
> >>>>>>>>
> >>>>>>>> public String getExtenderId();
> >>>>>>>>
> >>>>>>>> Thus, every extender has an extenderId and if that id is listed
> in a
> >>>>>>>> components "extender" property then the corresponding service
> should
> >>>>> be
> >>>>>>>> required, otherwise not.
> >>>>>>>>
> >>>>>>>> My idea (actually Clement's idea from a previous conversation on
> >> this
> >>>>>>>> list). is to use a RankingInterceptor that returns an empty array
> >>>>> until
> >>>>>>> all
> >>>>>>>> required services are present.
> >>>>>>>>
> >>>>>>>> I think this is doable but in order for my RankingInterceptor to
> >>>>> work, it
> >>>>>>>> must have access to the component's "extenders" property. It would
> >>>>> then
> >>>>>>> go
> >>>>>>>> through all the services implementing the IExtender interface and
> if
> >>>>>>> there
> >>>>>>>> are extenders corresponding to the required extenderId's it would
> >>>>> return
> >>>>>>>> all of those, otherwise it would return an empty list. Also, if a
> >>>>> list of
> >>>>>>>> extenderId's was specified, then the service dependency is set to
> >>>>>>>> mandatory, otherwise to optional.
> >>>>>>>>
> >>>>>>>> My problem is how to gain access to the configuration property
> (the
> >>>>>>>> "extenders" property) of my component from the interceptor. How
> can
> >> I
> >>>>> do
> >>>>>>>> this?
> >>>>>>>
> >>>>>>> When the interceptor is hooked to a dependency, it receives the
> >>>>> dependency
> >>>>>>> model object. From this object you can retrieve the component
> >> instance
> >>>>> and
> >>>>>>> get the introspection metadata.
> >>>>>>>
> >>>>>>>>
> >>>>>>>> Another question I have is how to make sure that the interceptor
> is
> >>>>>>> active.
> >>>>>>>> If the interceptor is not active then my component could become
> >>>>>>> erroneously
> >>>>>>>> valid. Would it be feasible to have a mandatory dependency on the
> >>>>>>>> interceptor?
> >>>>>>>
> >>>>>>> Unfortunately not, at least not easily. What you can do is a
> >>>>> combination
> >>>>>>> between a filter and two interceptors: the ranking interceptors as
> >> you
> >>>>> did,
> >>>>>>> and a tracking interceptor. Let me explain:
> >>>>>>>
> >>>>>>> Let’s imagine your consumer with your service dependency. Add a
> >> filter
> >>>>>>> that will be resolved only if your interceptor is there, something
> >>>>> like:
> >>>>>>> (intercepted=true).
> >>>>>>> Your interceptor implement both tracking and ranking interceptors.
> >> When
> >>>>>>> the accept method is called on your interceptor, it can
> ‘transform’
> >>>>> the
> >>>>>>> original service reference to add the ‘intercepted’ property
> >>>>>>> (ref.addProperty(“intercepted”, true);) This modified service
> >> reference
> >>>>>>> matches your filter. Then, do your ranking policy are we discussed.
> >>>>>>>
> >>>>>>> This solution ensure that your dependency can only be resolved if
> >> your
> >>>>>>> interceptor is there. Indeed without the interceptor, the filter
> does
> >>>>> not
> >>>>>>> match.
> >>>>>>>
> >>>>>>> Regards,
> >>>>>>>
> >>>>>>> Clement
> >>>>>>>
> >>>>>>>>
> >>>>>>>> /Bengt
> >>>>>>>
> >>>>>>>
> >>>>>>>
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> >>>>>>> For additional commands, e-mail: [email protected]
> >>>>>>>
> >>>>>>>
> >>>>>
> >>>>>
> >>>>> ---------------------------------------------------------------------
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> >>>>> For additional commands, e-mail: [email protected]
> >>>>>
> >>>>>
> >>>>
> >>
> >>
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> >> For additional commands, e-mail: [email protected]
> >>
> >>
>
>
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