You rock ;) Really good stuffs ! It's setup on the new search service.
Thanks !
J.
Bogdan Stefanescu wrote:
> I've added today the possibility to define services inside XML
> components using the
> tags defined by OSGi.
> So you can define a service like this:
>
> <service>
> <provide
> interface="org.nuxeo.runtime.services.deployment.DeploymentService" />
> </service>
>
> You can specify one or more interfaces (through the tag provide)
> OSGi defines several type of components - immediate, delayed and factory
> components.
> Currently, NXRuntime components behaves like OSGi immediate components -
> they are activated when
> all prerequisites are met (when dependencies are resolved)
> How services declared by a NXRuntime component are handled?
> First lets talk a little about the role of NXRuntime components in the
> system and what exactly are them.
> Although they are very closed to OSGi components NXRuntime components
> have their own features and behaviors that may not be OSGi compliant.
>
> So what is a NXRuntime component?
> From wikipedia: /A component is a system element offering a predefined
> service and able to communicate with other components.
> /NXRuntime components are conform to that definition.
> So a NXRuntime component is a piece of software that may expose one or
> several services and may communicate with other components
> at deployment (setup) time through extension points and at runtime using
> NXRuntime event service or any custom event service.
>
> Until now a component exposed a single service - the component itself
> could be considered a service.
> Now, because declaring service interfaces is possible inside the XML
> descriptor of the component a component may expose several
> functionalities as services (as declared by the <service> tag)
>
> So a component may be itself a service or it may manage and expose one
> or several services.
> Also, in NXRuntime a component may even not exists as a java class. This
> means the <implementation>
> declaration is not required by NXRuntime.
> Why? because you may want to create components only for configuring
> other components through extension points.
> So you can have a component with no implementation that is only
> declaring extensions to other components.
>
> Another addition of NXRuntime components are the extension points and
> the capability to contribute extensions to other components
> in the system.
>
> I think now it is clear what is a NXRuntime component.
> So how services are handled by NXRuntime components? (services declared
> through the OSGi <service> element)
>
> The runtime service (the SCR equivalent) is managing a service registry
> The service registry is mapping service class names to RegistrationInfo
> objects which describes the component that declared the service
> (RegistrationInfo objects are component description and they are created
> directly from the XML component file)
> So when someone wants to get the service that implements
> EventService.class (full name is
> org.nuxeo.runtime.services.event.EventService)
> NXRuntime will look into the registry and will find the component that
> declared this service and then it will ask that component to return
> the service instance object.
> The service instance may be the component itself so the component will
> return a reference to itself in this case.
> If the service is a member of the component the component will return
> that member or it may also make its own lookup to get the service
> instance .. How the service is retrieved is up to the component
> implementation.
> When a component declares multiple services it should pick the right one
> that match the service class passed by the caller.
>
> Here is an example of how the service instance is retrieved by NXRuntime:
>
> -> RuntimeService.getService(EventService.class) is called
> -> ComponentManager.getService(EventService.class) - the call is
> delegated to the component manager that keeps the service registry
> The manager is getting the RegistrationInfo object of the component
> declaring the service: EventService.class
> and delegates to it the service lookup
> -> RegistrationInfo.getComponent().getAdapter(EventService.class) is called
> The ComponentInstance object is a proxy to the real component instance
> as declared by the <implementation> element in the XML component file.
> The ComponenInstance is querying now the real component object about the
> service. The following method is used:
> - if the real component is implementing the Adaptable interface then the
> service is looked up using:
> component.getAdapter(EventService.class)
> - othewrise if the component object type is compatible with given one
> (i.e. EventService.class) a dynamic cast is made and the component
> object itself is returned
> - otherwise null is returned.
>
>
> So, the recommended way for a component to expose services is to
> implement the interface Adaptable and define the method
> public <T> T getAdapter(Class<T> serviceClass);
>
> When extending DefaultComponent this interface is automatically
> implemented.
> Let's look at the EventService component. The component is exposing
> EventService.class itself as a service. So its getAdapter() method looks
> like this
>
> @SuppressWarnings("unchecked")
> public <T> T getAdapter(Class<T> adapter) {
> return adapter == this.getClass() ? (T)this : null;
> }
>
>
> Lets say you have now a component MyComponent that expose 2 services
> TypeManager.class and ActionManager.class
> You can write the getAdapter() method like this:
>
>
> @SuppressWarnings("unchecked")
> public <T> T getAdapter(Class<T> adapter) {
> if (adapter.isAssignableFrom(TypeManager.class)) {
> return typeManager;
> } else if (adapter.isAssignableFrom(ActionManager.class)) {
> return actionManager;
> } else {
> return null;
> }
> }
>
>
> And so the client to get the instance of the TypeManager service will
> make the following lookup:
>
> TypeManager typeManager =
> NXRuntime.getRuntime().getService(TypeManager.class);
>
> and that's all.
>
> Bogdan
>
> P.S.
>
> So please update your NXRuntime components and declare any service you
> want to be available locally through NXRuntime
>
>
> _______________________________________________
> ECM mailing list
> [email protected]
> http://lists.nuxeo.com/mailman/listinfo/ecm
>
--
Julien Anguenot | Nuxeo R&D (Paris, France)
Open Source ECM - http://www.nuxeo.com
Nuxeo 5 : http://www.nuxeo.org
Mobile: +33 (0) 6 72 57 57 66
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