Because sometimes I will have no influence on what build tools are used by
the developers, e.g., when using UI components developed by a third party.
However, I already discussed this issue with Jürgen and additionally I
think in my case your suggestion might be another sensible way, to what
I've discussed with Jürgen.
It took me quite some time to understand your arguments. Sometimes it's
hard to grasp the concepts after having already a specific (wrong) picture
of how things work in mind ;)
Thanks for all the input you gave on this topic.
Kind regards,
Thomas
Am Di., 26. Feb. 2019 um 15:59 Uhr schrieb BJ Hargrave <hargr...@us.ibm.com
>:
> Why not just do this at tool time? You could author a Bnd plugin which
> scans for the Vaadin annotations in the class files and generate DS xml.
> This is what we do for the DS annotations.
> --
>
> BJ Hargrave
> Senior Technical Staff Member, IBM // office: +1 386 848 1781
> OSGi Fellow and CTO of the OSGi Alliance // mobile: +1 386 848 3788
> hargr...@us.ibm.com
>
>
>
> ----- Original message -----
> From: Thomas Driessen via osgi-dev <osgi-dev@mail.osgi.org>
> Sent by: osgi-dev-boun...@mail.osgi.org
> To: "Jürgen Albert" <j.alb...@data-in-motion.biz>, OSGi Developer Mail
> List <osgi-dev@mail.osgi.org>
> Cc:
> Subject: Re: [osgi-dev] SCR API
> Date: Tue, Feb 26, 2019 3:31 AM
>
> Hi Jürgen,
>
> Thanks for the additional clarification.
>
> Regarding creating DS component descriptions programmatically:
> This could be useful for aliasing DS component annotations at runtime,
> e.g., you have third party code (non-osgi) whose structure (e.g., methods
> of superclasses or their own annotations or anything else) could be mapped
> to (a subset of) the semantic meaning of DS annotations, then you could
> write an extender which scans classes for those
> annotations/methods/whatever and declares them to be components at runtime.
> In my current usecase this would be @Route annotation of Vaadin Flow.
> Those classes I always want to be @Component(scope=ServiceScope.PROTOTYPE,
> service=HasElement.class) annotated. This could be done programmatically
> via such an API.
> If such an API would exist I could make existing (non-osgi) classes become
> components transparently. In my opinion this would make integration of some
> third-party libs easier, but I'm not that experienced, so maybe I'm
> completely wrong about this ;)
>
> Regarding the use of View:
> In Vaadin Flow there is a (non-osgi) class Instantiator which is called
> (method looks roughly like this: public HasElement
> getOrCreate(Class<HasElement> view)) whenever a View has to be created. The
> Instantiator then creates an instance of the according View and returns
> this instance to the Flow framework. In this usecase I need a reference to
> the instance, so Flow can use it for whatever it does.
> So basically it's the case where I need a reference to an osgi service
> from within a non-osgi class in a synchronous way.
>
> Kind regards,
> Thomas
>
>
>
>
>
>
>
>
> Am Mo., 25. Feb. 2019 um 17:00 Uhr schrieb Jürgen Albert via osgi-dev <
> osgi-dev@mail.osgi.org>:
>
> See my comments inline.
> Am 25/02/2019 um 16:24 schrieb Thomas Driessen:
>
> Hi Tim, hi Jürgen,
>
> thanks for your detailed answers.
>
> Just to wrap it up so I didn't get something wrong:
>
> A service is an object with an interface and properties registered in the
> OSGi service registry and can be seen as an OSGi primitive for bundle
> interoperation.
> SCR is just a DI Framework that takes OSGi's dynamism into account and
> additionally registers all its components (declarative services) as
> services in the OSGi service registry.
>
> Yes and no. The Second half of the first sentence is correct, the first
> only partial:
>
> DS creates Components, that follow a lifecycle (activate, update,
> deactivate) dependent on the availability of configurations and/or
> dependencies. If a Component declares a service class (Which can be a
> normal class, abstract class or Interface), then it is registered in the
> service un-/registry according to its life cycle.
>
>
> @Tim: I might have expressed myself ambiguously. I didn't want to propose
> to change the DS specification which standardizes how services can be
> defined declaratively and also describes the behavior of a SCR
> implementation.
> What I instead intended to do was to ask if it would be possible/sensible
> for a SCR implementation (e.g., Apache Felix SCR) to also offer an API as
> mentioned before, so that I can write an Extender that takes non-annotated
> classes at runtime and tell an SCR implementation which fields/methods have
> to be treated as if they were annotated with DS annotations.
>
> However, if that is what you understood from my last mail anyway then I
> still seem to be too dumb to get why such an API would be a request for a
> radically different component model, e.g., why it makes such a difference
> if the SCR instantiates a component because of an XML it reads or because
> another entity commands it to do so. The information that is given for the
> instantiation would be the same on the imperative as on the declarative way
> I think.
>
>
> I can see that creating new DS component descriptions programmatically
> might be useful, but I'm not quite sure, when this should be necessary.
>
> @Jürgen: I don't think this would work in my case, as I need a reference
> to the instance created. So when I create an instance via ConfigAdmin then
> I usually don't get back a reference to the instance that is created by the
> ConfigAdmin, but only have a reference on the configuration I used to
> create a new instance. Or am I wrong?
>
> What do you need to do with the View of your example? If this needs to be
> used elsewhere, then this component should await the emergence on the
> Service you have just configured via a reference with a target.
>
>
> Kind regards,
> Thomas
>
>
>
>
> ------ Originalnachricht ------
> Von: "Jürgen Albert via osgi-dev" <osgi-dev@mail.osgi.org>
> An: osgi-dev@mail.osgi.org
> Gesendet: 22.02.2019 15:34:16
> Betreff: Re: [osgi-dev] SCR API
>
>
> As an Addition to the things already suggested:
>
> Taking your example I would create the MainView as follows:
>
> @Route("")
> @Component(name="MainView ", service=HasElement.class,
> configurationPolicy=Required, scope=PROTOTYPE)
> public class MainView extends VerticalLayout{
> @Reference //what ever is required here
> SomeService someService;
> }
>
> You can then use the Configurator or Config Admin to create you component
> and even your someService target binding. Here is an example for the
> Configurator would need to be translated to the ConfigAdmin if you want to
> do this programmatically.
>
> {
> ":configurator:resource-version": 1,
> "MainView~instance1":
> {
> "someService.target": "(fancy.service.id.prop=fizzbuzz)"
> }
> }
>
> Regards,
>
> Jürgen.
>
>
> Am 22/02/2019 um 10:29 schrieb Tim Ward via osgi-dev:
>
> Hi Thomas,
>
> I’m not sure that there is a naming issue here, but possibly a different
> misunderstanding.
>
>
> From my understanding there are two kinds of "services”:
>
>
> This is not really accurate. There is only one kind of service in OSGi,
> and it’s an object which has been registered with the service registry. It
> is always registered by a call to context.registerService(...). It doesn’t
> matter whether this action is taken directly by your bundle, or on your
> bundle’s behalf by an extender bundle. The fact that all services are the
> same is important because this is how bundles interoperate. Your bundles
> can use any mechanisms that they like internally and they can still
> interact with other bundles that may be using the same, or different,
> internal details.
>
>
> 2) "Fancy services" aka DS managed by a SCR. I specify those declaratively
> via annotations, they have a lifecycle and can have references to other
> services/components via annotations like @Activate/@Deactivate (Lifecycle)
> and @Reference. Those I will call components for the rest of this mail.
>
>
> There are a large number of different component models around in Java.
> These provide lifecycle management and injection for your objects. In the
> case of OSGi aware component models they also provide support for
> registering the object instance as a service (using
> context.registerService()).
>
> For Declarative Services the programming and configuration model is
> declarative - you describe how you want your component’s lifecycle to look
> using XML (or annotations to generate the XML). This XML is packaged into
> your bundle and used by a Service Component Runtime (an implementation of
> the DS specification) at runtime to find and manage your component.
>
>
> Components on the other side have references and lifecycle methods, but in
> order to instantiate them programmatically I have to force a developer to
> annotate the class with @Component(scope=ServiceScope.PROTOTYPE) and then
> use ServiceObjects<type>#getService() to instantiate/register it.
>
> This procedure can be error-prone, e.g., when I assume that scope is
> always PROTOTYPE but the developer forgot to set it to this value. This
> problem came up during my discussion with Vaadin for a Flow-OSGi
> integration.
>
>
> This is really a decision that needs to be made by the component
> developer. It doesn’t always make sense for a component to be PROTOTYPE
> scoped, and they need to be aware that there may be multiple instances
> created
>
>
> In this context it would be great if there were a possibility to
> programmatically create components (not services) where I can tell SCR what
> fields/methods have to be treated as @Reference or lifecycle methods and
> let SCR do the heavy lifting.
>
> This is not what SCR does. SCR is a declarative component model, not a
> programmatic one. There is no “DS builder API” for creating components. If
> you want a builder API for creating a component then you need to use a
> component framework that works in this way. As Ray pointed out in a
> previous mail chain there is the Apache Aries Component DSL. You could also
> use Apache Felix Dependency Manager.
>
>
>
> Would such an API make sense? Or would it even be possible?
>
> I think in general this would be very useful in order to create OSGi
> integrations for third-party libs that need to interact with DS in OSGi.
>
> This isn’t really a question of third party libraries interacting with DS,
> it’s a request for a radically different component model with some DS-like
> capabilities. There are already framework implementations in the world that
> provide what you’re looking for, just not using DS.
>
> Best Regards,
>
> Tim
>
>
>
> On 21 Feb 2019, at 18:07, Thomas Driessen via osgi-dev <
> osgi-dev@mail.osgi.org> wrote:
>
> Hi BJ,
>
> sorry for being imprecise. I sometimes get confused regarding the proper
> naming in OSGi. I will try to clear things up by defining what my
> understanding is about services:
>
> From my understanding there are two kinds of "services":
> 1) "Old school Services": I usually register those programmatically via
> context.registerService(...). Those services are just POJOs with a little
> bit metadata, i.e., properties, and a well-defined interface. Those I will
> call services for the rest of this mail.
> 2) "Fancy services" aka DS managed by a SCR. I specify those declaratively
> via annotations, they have a lifecycle and can have references to other
> services/components via annotations like @Activate/@Deactivate (Lifecycle)
> and @Reference. Those I will call components for the rest of this mail.
>
> The difference between both (as far as I understand it) is that services
> can be instantiated and registered programmatically, but are not managed by
> SCR and therefore have no references and lifecycle methods.
>
> Components on the other side have references and lifecycle methods, but in
> order to instantiate them programmatically I have to force a developer to
> annotate the class with @Component(scope=ServiceScope.PROTOTYPE) and then
> use ServiceObjects<type>#getService() to instantiate/register it.
>
> This procedure can be error-prone, e.g., when I assume that scope is
> always PROTOTYPE but the developer forgot to set it to this value. This
> problem came up during my discussion with Vaadin for a Flow-OSGi
> integration.
>
> In this context it would be great if there were a possibility to
> programmatically create components (not services) where I can tell SCR what
> fields/methods have to be treated as @Reference or lifecycle methods and
> let SCR do the heavy lifting.
> In Flow this would enable me to easily instantiate all classes that are
> annotated with Vaadin's @Route annotation and register them as components
> with scope PROTOTYPE and also to encorporate stuff like references and
> lifecycle methods with my own annotations.
>
> So for a class that looks like this:
>
> @Route("")
> public class MainView extends VerticalLayout{
> @OSGiRef
> SomeService someService;
> }
>
> I could call some imaginary API like this:
>
> scr.createCmp(MainView.class)
> .setScope(PROTOTYPE)
> .setService(HasElement.class)
> .addReference(someService);
>
> and SCR would create this comopnent at runtime, inject the service
> someService and then return this instance so that a third-party lib can
> interact with it, while SCR still controls the lifecycle and coming/going
> of referenced services/components.
>
> Would such an API make sense? Or would it even be possible?
>
> I think in general this would be very useful in order to create OSGi
> integrations for third-party libs that need to interact with DS in OSGi.
>
>
> I hope this clarified my former email.
>
> Kind regards,
> Thomas
>
>
>
> ------ Originalnachricht ------
> Von: "BJ Hargrave" <hargr...@us.ibm.com>
> An: thomas.driessen...@gmail.com
> Gesendet: 21.02.2019 14:48:18
> Betreff: Re: Re[2]: [osgi-dev] SCR API
>
>
> I am not what you mean by a "possiblity to register services in a way to
> get references injected at runtime". Those are the different sides of a
> service: The provider of the service and the consumers of a service. Each
> side can use different models to interact. One can register with the
> service API and the other can consume with DS, CDI, etc. So service
> consumers do not need to care how the service provider is implemented. So
> you can used DS to @Reference services which have been registered by any
> method.
>
> Because everything is a service in the framework's service registry, each
> side of the service interaction can be written using different models.
>
> --
>
> BJ Hargrave
> Senior Technical Staff Member, IBM // office: +1 386 848 1781
> OSGi Fellow and CTO of the OSGi Alliance // mobile: +1 386 848 3788
> hargr...@us.ibm.com
>
>
>
> ----- Original message -----
> From: "Thomas Driessen" <thomas.driessen...@gmail.com>
> To: "BJ Hargrave" <hargr...@us.ibm.com>
> Cc:
> Subject: Re[2]: [osgi-dev] SCR API
> Date: Thu, Feb 21, 2019 7:37 AM
>
> Hi BJ,
>
> is there a possiblity to register services in a way to get references
> injected at runtime, i.e., something like the @Reference funtionality but
> for services registered programmatically?
>
> I think this would be a great enhancement for third-partyy libraries who
> want to plug in into OSGi's DI framework.
>
> Kind regards,
> Thomas
>
> ------ Originalnachricht ------
> Von: "BJ Hargrave" <hargr...@us.ibm.com>
> An: thomas.driessen...@gmail.com; osgi-dev@mail.osgi.org
> Cc: osgi-dev@mail.osgi.org
> Gesendet: 21.02.2019 13:21:06
> Betreff: Re: [osgi-dev] SCR API
>
>
> There is not plan for Declarative Services to have an API for imperatively
> creating components/services. The whole point of Declarative Services is
> the declarative nature of it. You can always use the service APIs of the
> framework to create services. Or something like felix dependency manager.
> --
>
> BJ Hargrave
> Senior Technical Staff Member, IBM // office: +1 386 848 1781
> OSGi Fellow and CTO of the OSGi Alliance // mobile: +1 386 848 3788
> hargr...@us.ibm.com
>
>
>
> ----- Original message -----
> From: Thomas Driessen via osgi-dev <osgi-dev@mail.osgi.org>
> Sent by: osgi-dev-boun...@mail.osgi.org
> To: "OSGi Developer Mail List" <osgi-dev@mail.osgi.org>
> Cc:
> Subject: [osgi-dev] SCR API
> Date: Thu, Feb 21, 2019 7:16 AM
>
> Hi,
>
> currently I'm debating on a Vaadin FLow issue how to best create
> components in OSGi programmatically. The answer of my last question on this
> mailing list regarding this topic was to use scope=PROTOTYPE and then
> ServiceObjects<Type>#getService(). This is a solution far better than the
> approach I used before but still has some flaws, resulting in the following
> question:
>
> Is there (or is it planned to create) an API for SCR to programmatically
> create components at runtime?
>
> I think of something like the Apache Felix DependencyManager where I can
> register services but not components (with refrences and stuff).
>
> What I think of would be something like this:
>
> scr.createCmp(Class class)
> .setActivateMethod(...)
> .setReferenceField(...)
> .etc...
>
> Kind regards,
> Thomas
> _______________________________________________
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>
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>
> --
> Jürgen Albert
> Geschäftsführer
>
> Data In Motion Consulting GmbH
>
> Kahlaische Str. 4
> 07745 Jena
>
> Mobil: 0157-72521634
> E-Mail: j.alb...@datainmotion.de
> Web: www.datainmotion.de
>
> XING: https://www.xing.com/profile/Juergen_Albert5
>
> Rechtliches
>
> Jena HBR 513025
>
>
> --
> Jürgen Albert
> Geschäftsführer
>
> Data In Motion Consulting GmbH
>
> Kahlaische Str. 4
> 07745 Jena
>
> Mobil: 0157-72521634
> E-Mail: j.alb...@datainmotion.de
> Web: www.datainmotion.de
>
> XING: https://www.xing.com/profile/Juergen_Albert5
>
> Rechtliches
>
> Jena HBR 513025
> _______________________________________________
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