I think its a interesting idea. Perhaps it is true that the current SCA mechanisms are sufficient but this does have some appeal (to me anyway) even if thats from a fun coding challenge perspective.
>From the list below of issues: 1. - Tuscany knows all the artifacts in a contribution so we can easily get all the classes in a package and introspect those for SCA annotations 2. - Tuscany is also in control of all the class loading so we can manipulate the byte code with asm or cglib (these are already used by the Tuscany core runtime) to add constructor interceptors to do the things like the reference proxy injection, or perhaps use AOP with aspectj. 3. - I'm not sure i follow this point, what is it about? And is the main class really needed or could it be optional and when its not used have all the classes found with @Service annotations used to make up an implementation with multiple services? ...ant On Tue, Sep 21, 2010 at 10:52 PM, Simon Nash <[email protected]> wrote: > Millies, Sebastian wrote: >> >> Hello there, >> >> I have an idea for a Tuscany extension. Would it not be possible to >> introduce an additional attribute "package" on the implementation.java >> element, the purpose of which would be to specify all classes in >> one (or more) Java package(s) as collectively making up the component >> implementation. Tuscany could then inject proxies for the referenced >> services at any point where the @Reference annotation is used in any >> class of the packages. Similarly for @Context etc. (The value of the >> "class" attribute would still denote the main class, which provides >> the component's external interface.) >> >> Would this make sense in your opinion? Would it be hard to implement? >> > I think it would be hard to implement because: > 1. Tuscany would need a way to enumerate all the classes in the > package so that it could find all the @Reference annotations. > 2. Tuscany would need to discover the runtime instance relationships > between all these application classes so that it could find the > right instance objects on which to perform the injections. > This is just about impossible because the "non-main" objects are > instantiated by the application and not by Tuscany. > 3. When Tuscany creates the instance of the "main" class, the other > application instance objects that need to be injected might not > exist at that time. > > I think the current SCA mechanisms are sufficient to allow application > classes to propagate these references to wherever they are needed, and > I think that handling such propagation is best left to application code. > > Simon > >> -- Sebastian >> >> >>> -----Original Message----- >>> From: Simon Nash [mailto:[email protected]] >>> Sent: Tuesday, September 21, 2010 8:26 PM >>> To: [email protected] >>> Subject: Re: Q: Best practice for making service references available >>> in a component? >>> >>> Millies, Sebastian wrote: >>>> >>>> Hello there, >>>> >>>> this is a question about coding style. SCA components are coarse >>> >>> grained, >>>> >>>> i. e. the actual component implementation can consist of many >>> >>> classes, only >>>> >>>> one of which is defined as _the_ component implementation class in >>> >>> the composite >>>> >>>> XML. It is only on this class that annotations like @Reference can be >>> >>> used to >>>> >>>> inject dependencies to other services. It is likely, however, that >>> >>> the referenced >>>> >>>> services really need to be called from one of the other classes in >>> >>> the component >>>> >>>> implementation. >>>> >>>> How do you pass the values of these reference variables to those >>> >>> ordinary Java >>>> >>>> classes? Is there a special "SCA way" of doing this, perhaps making >>> >>> these References >>>> >>>> globally available in a component, or do you just use normal Java >>> >>> programming idioms >>>> >>>> like property setters, or constructor/method parameters? >>>> >>>> -- Sebastian >>>> >>> There isn't any specific SCA way of doing this. You can treat >>> the injected proxy as a regular Java object and pass it around >>> however you wish. However it's useful to bear in mind that SCA >>> offers 3 different ways to obtain the reference proxy: >>> as a constructor parameter >>> as a setter parameter >>> as an injected field >>> >>> Depending on how you want to pass the value around, one or other >>> of these might be more appropriate. >>> >>> Simon >> > >
