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

["Frank Pauleickhoff (Jira)" <ji...@apache.org>]

Frank Pauleickhoff created SLING-8858:
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             Summary: 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


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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