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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