[jira] [Commented] (SLING-4447) Improve JavaUseProvider to not fall back to a simple Pojo instanciation in case a Java class with @Model annotation cannot be instanciated

["Konrad Windszus (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SLING-4447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14329178#comment-14329178 ] 

Konrad Windszus commented on SLING-4447:
----------------------------------------

Would it be acceptable for Sightly to have a dependency to Sling Models? Otherwise the ModelFactory cannot be used. One could make that dependency optional though (similar to what was done SLING-4161 to make Sling Validation optional for Sling Models).

> Improve JavaUseProvider to not fall back to a simple Pojo instanciation in case a Java class with @Model annotation cannot be instanciated
> ------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: SLING-4447
>                 URL: https://issues.apache.org/jira/browse/SLING-4447
>             Project: Sling
>          Issue Type: Improvement
>          Components: Scripting
>    Affects Versions: Scripting Sightly Engine 1.0.0
>            Reporter: Konrad Windszus
>
> Currently in case a Java class is a Sling Model (i.e. has the Model annotation) and cannot be instanciated (e.g. required injections not possible) Sightly falls back to instanciate those as simple Pojos.
> This is never good, since a lot of NullPointerException happen then, because all injections have not been performed then.
> Therefore in the following code should be used instead 
> {code}
> if (modelFactory.isModelClass(resource, cls)) {
>   if (modelFactory.canCreateFromAdaptable(resource, cls)) {
>     obj = modelFactory.createModel(resource, cls);
>   } else if (modelFactory.canCreateFromAdaptable(request, cls)) {
>     obj = modelFactory.createModel(request, cls);
>   } else {
>     throw new IllegalStateException("Could not adapt the given Sling Model from neither resource nor request: " + cls);
>   }
> }
> {code}
> That way, exceptions would be propagated in case a Sling model cannot be instanciated and developers more easily see why the Sling Model does not work (instead of running into NullPointerExceptions in their model because it was instanciated as simple 



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