[webbeans-dev] Re: @Supports

I've been thinking about the problem of implementing re-usable components like our JMS endpoints. What I'm trying to do is implement the requirements of JMS endpoints as a simple Web Bean. To do that today, I would need to create a class which implemented all the API types: @ApplicationScoped public class QueueEndpoint implements Queue, QueueSession, QueueSender, QueueConnection { ... } and I would have to go and implement every one of the operations of each of those interfaces to delegate to the correct object. (A bunch of tedious code.) However, if we assume that the client proxy is smart enough, we could let the Web Bean manager automagically do that delegation for us. We would need a new annotation that could be applied to fields or methods, for example: @ApplicationScoped public class QueueEndpoint { ... @Supports Queue getQueue() { ... } @Supports QueueSession getQueueSession() { ... } @Supports QueueSender getQueueSender() { ... } @Supports QueueConnection getQueueConnection() { ... } } We no longer need to write all those annoying delegation methods! The client proxy would just call the correct @Supports method when the QueueEndpoint type did not define the method that was invoked by the client, and delegate the method to the returned object. To make this really work, we would need to say: * the set of API types of the Web Bean includes all types of @Supports methods/fields * if a certain method name appears on more than one @Supports method/field type, it must also be implemented directly by the impl class * if a certain method name appears on more than one @Supports method/field type, or on both the impl class and a @Supports method/field type, it is always called on the impl class Therefore, close() would need to be implemented by QueueEndpoint: @ApplicationScoped public class QueueEndpoint { ... @Supports Queue getQueue() { ... } @Supports QueueSession getQueueSession() { ... } @Supports QueueSender getQueueSender() { ... } @Supports QueueConnection getQueueConnection() { ... } void close() { throw new UnsupportedOperationException(); } } You're probably thinking that we can do all this with @Producer methods, however, the semantics are not exactly the same, since the association b/w the producer object and produced object is lost as soon as the producer method returns. Furthermore, @Producer methods aren't really appropriate for 3rd-party reusable objects, since the XML configuration of a producer method is verbose. I don't believe that Web Beans 1.0 absolutely has to have this feature, but I know its useful, and I know that we will implement it in the RI, so I would prefer if it was portable. What do you guys think? Useful? Too much magic? Let me know... Seam already has an extremely primitive/braindead version of this feature, that I've found *extremely* useful when writing reusable components: http://docs.jboss.com/seam/2.1.0.SP1/reference/en-US/html/concepts.html#d... (@Factory is more or less like @Produces, whereas @Unwrap is a really crappy version of @Supports.) -- Gavin King gavin.king(a)gmail.com http://in.relation.to/Bloggers/Gavin http://hibernate.org http://seamframework.org