Hi, On Mon, Jul 7, 2014 at 5:57 PM, Alexander Klimetschek <aklim...@adobe.com> wrote: > On 07.07.2014, at 17:08, Carsten Ziegeler <cziege...@apache.org> wrote: > >> 2014-07-07 14:55 GMT+02:00 Justin Edelson <jus...@justinedelson.com>: >> >>> Here's a sightly more real world case... let's say you have a call like >>> this: >>> >>> Comment comment = resource.adaptTo(Comment.class); >>> >>> And for a Resource to be successfully adapted to a Comment, it must >>> satisfy two criteria: >>> 1) The resource type must be myco/comment >>> 2) It must have a property called "commentType" (OK, this part isn't >>> so real world). >>> >>> Right now, the caller has no way of knowing which of these critera >>> wasn't met. That's IMHO the crux of this request - to provide a way >>> for AdapterFactories to surface the failure reason back to the caller. >>> >>> >> Hmm, this assumes the caller can do something meaningful with it. Given >> your example, what could the client do?
Konrad could probably articulate this better than I can :) > > Right. > > In this case I would assume that if 1) is present, you get a Comment back, > otherwise null. Then Comment has a getter method for the type 2), which would > also handle the case of a missing type: usually you would fall back to a > default if no type is specified, since that reduces the constraints the > content has to follow; but you could also have the application handle the > no-type case itself and fail in some way (as you were trying to with an > exception that is passed through from adapterfactory to application code). > > Next example please :D I found a more concrete example in the AEM codebase (so apologies to the non-Adobe people on this thread who will just have to take my word for it). The adapter factory which adapts Resources into Scene7 "set" objects makes a number of validations before returning a non-null result: 1) Is the Resource an Asset? 2) Does the Asset represet a Scene7 set? (which is done by looking at a property) 3) Does the requested set class correspond to the set type of the Asset? Regards, Justin > > Cheers, > Alex >
