[jira] [Created] (AVRO-4324) [Java] Align ReflectDatumReader.readArray with GenericDatumReader eager-allocation guards for malformed input

["Ismaël Mejía (Jira)" <ji...@apache.org>]

Ismaël Mejía created AVRO-4324:
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             Summary: [Java] Align ReflectDatumReader.readArray with GenericDatumReader eager-allocation guards for malformed input
                 Key: AVRO-4324
                 URL: https://issues.apache.org/jira/browse/AVRO-4324
             Project: Apache Avro
          Issue Type: Improvement
          Components: java
            Reporter: Ismaël Mejía


{{GenericDatumReader.readArray}} was already made robust against malformed or truncated input: it clamps the initial backing allocation ({{initialCollectionCapacity}}), validates the declared array block count against the bytes actually remaining ({{ensureAvailableCollectionBytes}}), and applies a heap-aware bound for element types whose minimum encoded size is zero.

The {{ReflectDatumReader.readArray}} override does not apply these guards. It calls {{newArray(old, (int) l, ...)}} -> {{Array.newInstance(elementClass, count)}} using the declared array block count directly, so a malformed record mapped to a Java array field (for example a {{long[]}}) can drive a large eager allocation before a single element is read.

We should bring {{ReflectDatumReader.readArray}} in line with the generic reader by applying the same {{ensureAvailableCollectionBytes}} / collection-allocation checks and clamping the initial allocation, so malformed input fails fast (e.g. {{EOFException}}) instead of over-allocating. A valid array continues to read normally.

Relevant code:
* {{lang/java/avro/src/main/java/org/apache/avro/reflect/ReflectDatumReader.java}} — {{readArray(...)}} and {{newArray(...)}} ({{Array.newInstance}}).
* {{lang/java/avro/src/main/java/org/apache/avro/generic/GenericDatumReader.java}} — {{readArray(...)}}, {{ensureAvailableCollectionBytes(...)}}, {{initialCollectionCapacity(...)}} as the reference implementation.



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