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Posted to dev@sling.apache.org by "Radu Cotescu (Jira)" <ji...@apache.org> on 2020/10/19 10:31:00 UTC

[jira] [Closed] (SLING-8858) Model Cache causes NPE in sling.models.impl 1.4.10+

     [ https://issues.apache.org/jira/browse/SLING-8858?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Radu Cotescu closed SLING-8858.
-------------------------------

> Model Cache causes NPE in sling.models.impl 1.4.10+
> ---------------------------------------------------
>
>                 Key: SLING-8858
>                 URL: https://issues.apache.org/jira/browse/SLING-8858
>             Project: Sling
>          Issue Type: Bug
>          Components: Sling Models
>    Affects Versions: Sling Models Impl 1.4.10
>         Environment: Java SE 1.8.0_231
>            Reporter: Frank Pauleickhoff
>            Assignee: Dan Klco
>            Priority: Major
>             Fix For: Sling Models Impl 1.4.14
>
>          Time Spent: 40m
>  Remaining Estimate: 0h
>
> In AEM 6.4 ServicePack 6 we face NullPointerExceptions when using the Sling model cache that used to work before (in SP 3).
> *Exception Stacktrace is:*
> {code:java}
> 22.11.2019 15:29:22.525 *ERROR* [127.0.0.1 [1574432957337] GET /content/mypage.html HTTP/1.1] org.apache.sling.engine.impl.SlingRequestProcessorImpl service: Uncaught SlingException
> org.apache.sling.scripting.sightly.SightlyException: org.apache.sling.api.SlingException: Cannot get DefaultSlingScript: org.apache.sling.api.SlingException: Cannot get DefaultSlingScript: org.apache.sling.api.SlingException: Cannot get DefaultSlingScript: org.apache.sling.api.SlingException: Cannot get DefaultSlingScript: org.apache.sling.api.SlingException: Cannot get DefaultSlingScript: org.apache.sling.api.SlingException: Cannot get DefaultSlingScript: Identifier xx.xxx.MyModel cannot be correctly instantiated by the Use API
> [...]
> Caused by: java.lang.NullPointerException: null
>  at org.apache.sling.models.impl.ModelAdapterFactory.internalCreateModel(ModelAdapterFactory.java:407)
>  at org.apache.sling.models.impl.ModelAdapterFactory.createModel(ModelAdapterFactory.java:314)
> {code}
> Problem seems to be related to introduction of WeakReferences in SLING-7586. Without knowing any details and being deeply into the Sling Model Caching implementation, I think a null-check is missing for "SoftReference" in Line 407:
> {code:java}
> SoftReference<Object> SoftReference = adaptableCache.get(requestedType);
> ModelType cachedObject = (ModelType) SoftReference.get();
> {code}
> That seems to cause caching to throw NPE for any not yet cached model.



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