In my regard in this case a RuntimeException would be fine. That would be propagated correctly to the script level. So whenever a model class has the model annotation and something went wrong during the injection throwing a runtime exception would be correctly propagated and no other option would be tried (even when using Sightlies Use Extension)
On 28 Jul 2014, at 18:03, Justin Edelson <jus...@justinedelson.com> wrote: > Hi Konrad, > In this case, I don't see how any of the options in this thread would > actually help because the code which calls adaptTo() is not under your > control. So there would be no way for the caller (i.e. your Sightly > script) to indicate that such an exception should be thrown. > > Regards, > Justin > > On Mon, Jul 28, 2014 at 11:44 AM, Konrad Windszus <konra...@gmx.de> wrote: >> I just came up with another example from CQ: >> >> In Sightly you can instantiate a model via the use API [1]. >> Since that logic will first try to adapt from Resource then from Request and >> as fallback tries to instantiate the class leveraging the default >> constructor, you won’t get any exceptions in case required properties cannot >> be injected (and the default constructor is available). >> >> In most of the cases instantiating the class via the default constructor is >> not the right thing to do, because if the class is annotated with @Model and >> instanciation fails that should be propagated to the user. In this case it >> defers the error message to an NPE being thrown whenever someone is trying >> to access the field (which was not instantiated because the object was not >> created with Sling Models but as a regular POJO with no injections at all). >> That takes quite some time to figure out during development, that actually >> Sling Models cannot really instantiate the class and therefore the Sightly >> Use Extension will instantiate it as simple Pojo. >> That would not have happened, if Sling Models would be allowed to throw >> exceptions in case the instanciation was not successfull! >> >> [1] - >> http://docs.adobe.com/docs/en/aem/6-0/develop/sightly/use-api-in-java.html#Alternatives%20to%20WCMUse >> >> On 07 Jul 2014, at 18:42, Carsten Ziegeler <cziege...@apache.org> wrote: >> >>> 2014-07-07 18:29 GMT+02:00 Konrad Windszus <konra...@gmx.de>: >>> >>>> Provide a meaningful error message to the author or at least to the >>>> developer (leveraging the WCMDeveloperMode). By meaningful I don’t talk >>>> about something hidden within the logs. >>>> >>> >>> This doesn't really convince me - the same argument would hold true for >>> every API where the exception (cause) is logged, but the method just gives >>> back true/false,object/null. Even for APIs throwing an exception it might >>> be hard to get a meaningful message to developer. So this isn't done for >>> other APIs, why should we do it differently for adaptTo? >>> In addition, if you have a lot of client code using the adapter pattern, >>> then you end up in converting the exception to a meaningful message in >>> various places. >>> >>> It would be so easy to let the adapter factory do a meaningful log >>> statement and there are tools/apis to pick up this log message and display >>> it to the dev without requiring the developer to go to the log >>> >>> Carsten >>> >>> >>> >>>> Konrad >>>> >>>> On 07 Jul 2014, at 18:27, Carsten Ziegeler <cziege...@apache.org> wrote: >>>> >>>>> 2014-07-07 18:14 GMT+02:00 Justin Edelson <jus...@justinedelson.com>: >>>>> >>>>>> Hi, >>>>>> >>>>>> >>>>>> 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? >>>>>> >>>>>> >>>>> But again, what different action would a client take depending on the >>>> error >>>>> condition 1, 2 or 3? >>>>> >>>>> Carsten >>>>> >>>>> >>>>>> Regards, >>>>>> Justin >>>>>> >>>>>>> >>>>>>> Cheers, >>>>>>> Alex >>>>>>> >>>>>> >>>>> >>>>> >>>>> >>>>> -- >>>>> Carsten Ziegeler >>>>> Adobe Research Switzerland >>>>> cziege...@apache.org >>>> >>>> >>> >>> >>> -- >>> Carsten Ziegeler >>> Adobe Research Switzerland >>> cziege...@apache.org >>
