Some comments inline... On 15 Mar 2011, at 22:42 , Pierre De Rop wrote:
> Hi Vladimir, > > I'm not sure to understand: when you are talking about "AspectService", are > you talking about DependencyManager "AspectService" ? > if true, then I don't think it works in your case, because DM AspectService > only work if you track "MetadataProvider" with DependencyManager > "ServiceDependency". > in other words, I don't think it's possible to mix DM AspectService with > DeclarativeService, but may be Marcel have to confirm this ? You're right. Aspects that "intercept" services are implemented as services with a higher ranking as the original. If you have only one original, then a plain service tracker works just fine, as it will always return the highest ranked service if you are only looking for one service. If you have multiple originals, you need to somehow distinguish between the N originals and N aspects on top of them. Like Pierre says, if you use the service dependencies that are available in the dependency manager, this is handled transparantly for you. If you track services yourself, you need to do some manual work: Whenever a new service is added to the tracker, you need to check if it is an aspect on top of an original service or not. Each aspect has an extra service property to recognize it and to link it to the original service. So if an aspect comes in, you need to add it to your tracker AND hide the original service from the consumer of that tracker. Same thing (the other way round) if a service is removed. The dependency manager actually has a modified ServiceTracker that you can use if you want to do that (but not want to use its ServiceDependency). > So, coming back to your use case, if you don't want to use DM > ServiceDependency for tracking the MetadataProvider, but DeclarativeService > (as it seems to be the case), then may be you could take a look at service > hooks ? My personal opinion: service hooks are pretty much useless for *dynamically* adding an aspect on top of an existing service because the hooks *must* be in place before the rest of the framework starts. The hooks are not capable of "removing" any services that were already out there when an aspect is added. But if you know upfront you want to intercept something and you can install the hooks when the framework starts, they work just fine. > > The following tutorial explains how to intercept all service method > invocation using Event/Find Hooks: > > http://java.dzone.com/articles/osgi-service-hook-log-all > > and you can checkout the sample code from: > > svn checkout http://osgiservicelogger.googlecode.com/svn/trunk/ > > If, however, you would like to consider using DependencyManager > ServiceDependency for tracking the MetadataProvider services, then you could > implement the following thing: > > import org.apache.felix.dm.annotation.api.Component; > > @Component > public class MetadataProviderTracker { > @ServiceDependency(required=false, removed="unbindMetadataProvider") > protected void bindMetadataProvider(MetadataProvider mp) { > providerMap.put(mp.getType(), mp); > } > > protected void unbindMetadataProvider(MetadataProvider mp) { > providerMap.remove(mp.getType()); > } > > // ... > } > > > and simply define your MetadataProvider interceptor, like this: > > @AspectService(ranking = 10 /* the ranking of this Aspect service used to > chain aspects in the proper order */ ) > public class MetadataProviderInterceptor implements MetadataProvider > { > /** > * This is the MetadataProvider this interceptor is applying to > (injected by reflection). > */ > private volatile MetadataProvider originalMetadataProvider; > > public void callMethod() { > // Intercept method call, and eventually invoke > this.originalMetadataProvider.callMehod() , if required > } > } > > > Alternatively, you can also use AspectService with a real DynamicProxy: > > @AspectService(ranking = 10, service=MetadataProvider.class, > factoryMethod="create") > public class MetadataProviderInterceptor implements InvocationHandler { > static Object create() { > return > Proxy.newProxyInstance(MetadataProviderInterceptor.class.getClassLoader(), > new Class[] { > MetadataProviderInterceptor.class }, > new MetadataProviderInterceptor()); > } > > // Injected by reflection > private volatile MetadataProvider originalMetadataProvider; > > public Object invoke(Object proxy, Method method, Object[] args) > throws Throwable { > if (method.getName().equals("callMethod")) { > // Intercept "callMethod" > } else { > return method.invoke(this.originalMetadataProvider, args); > } > } > } > > > > Dos this correspond to your actual needs ? > > Kind Regards; > /pierre > > > > > > On Mon, Mar 14, 2011 at 4:51 PM, TVladimir > <[email protected]>wrote: > >> >> Hello, >> Could you please suggest solution for the following issue: >> >> Description: >> There are number of implementations of MetadataProvider interface, these >> implementations are collected into map as described below, and then used by >> application logic >> >> @Reference(name = "metadataProvider", strategy = ReferenceStrategy.EVENT, >> policy = ReferencePolicy.DYNAMIC, referenceInterface = >> MetadataProvider.class, cardinality = >> ReferenceCardinality.OPTIONAL_MULTIPLE) >> >> >> protected void bindMetadataProvider(MetadataProvider mp) { >> providerMap.put(mp.getType(), mp); >> } >> >> protected void unbindMetadataProvider(MetadataProvider mp) { >> providerMap.remove(mp.getType()); >> } >> >> >> Task: >> I would like to decorate/intercept one of the implementation's method. >> If you do: providerMap.get(“type”).callMethod(), callMethod() should be >> intercepted. >> >> Issue: >> AspectService approach doesn’t work here. When I created AspectService >> for >> MetadataProvider interface, “bind” registered all implementations + aspect >> services for all implementations. >> >> Any ideas how to make it? >> >> Thanks, >> Vladimir >> >> -- >> View this message in context: >> http://old.nabble.com/AspectService-for-dynamic-reference-tp31145479p31145479.html >> Sent from the Apache Felix - Users mailing list archive at Nabble.com. >> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: [email protected] >> For additional commands, e-mail: [email protected] >> >> --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
