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https://issues.apache.org/jira/browse/SLING-3709?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14113527#comment-14113527
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Konrad Windszus commented on SLING-3709:
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I updated the PR. Now exceptions are only thrown in the adaptTo codepath if 
they are caused by invalid models (and therefore must be fixed by developers). 
The overhead for throwing and catching is negligible because those errors need 
to be fixed within the code (and therefore should never happen on production 
instances). I also enriched the  exception which is being thrown in case of no 
injector can inject a reasonable value with additional information. Can you 
review again?

> Sling Models: Allow caller to deal with exceptions
> --------------------------------------------------
>
>                 Key: SLING-3709
>                 URL: https://issues.apache.org/jira/browse/SLING-3709
>             Project: Sling
>          Issue Type: Improvement
>          Components: Extensions
>    Affects Versions: Sling Models Implementation 1.0.4, Sling Models 
> Implementation 1.0.6
>            Reporter: Konrad Windszus
>              Labels: models
>
> Currently due to the specification of the adaptTo-method to return null if 
> adaptation is not possible, the caller is not notified about any exceptions 
> (because they are caught within the ModelAdapterFactory).
> This is e.g. necessary to deal with validation exceptions properly (i.e. 
> required field injection not possible).  The problem was also discussed 
> briefly in 
> http://apache-sling.73963.n3.nabble.com/Silng-Models-Validation-Framework-td4033411.html.
> All exceptions either being thrown by the 
> @PostConstruct method or caused by the field/method injection are not 
> propagated but basically swallowed by Sling Models.
> It would be great to be able to catch those exceptions either in the view or 
> in a servlet filter. I think it should be possible to throw unchecked 
> exceptions in the ModelAdapterFactory.getFactory() method if it is requested 
> (i.e. through a global OSGi configuration flag for Sling Models).
> WDYT?
> Would you accept such a patch or do you think this breaks the API (also 
> compare with 
> https://issues.apache.org/jira/browse/SLING-2712?focusedCommentId=13561516&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13561516).
> If it does not work through the adaptTo, SlingModels should provide an 
> alternative way of instanciating models (and propagating exceptions), 
> although this is kind of tricky, because it internally relies on adaptTo as 
> well (e.g. in 
> https://github.com/apache/sling/blob/trunk/bundles/extensions/models/impl/src/main/java/org/apache/sling/models/impl/ModelAdapterFactory.java#L647)



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