AVRO-4324: [Java] Align ReflectDatumReader.readArray with GenericDatumReader eager-allocation guards - #3920
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ReflectDatumReader.readArray allocated the backing Java array for the declared array block count (Array.newInstance) before reading any element, unlike GenericDatumReader.readArray which already validates the count against the bytes remaining and caps element types whose minimum encoded size is zero. Apply the same guards (ensureAvailableCollectionBytes plus checkMaxCollectionAllocation for zero-byte element types) before the eager allocation, so a malformed or truncated record mapped to a Java array field (e.g. long[]) fails fast with an EOFException instead of over-allocating. Valid arrays continue to read unchanged.
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What changes were proposed in this pull request?
GenericDatumReader.readArrayalready validates a 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, before eagerly allocating the backing storage.The
ReflectDatumReader.readArrayoverride did not apply these guards: it callednewArray(old, (int) l, ...)→Array.newInstance(elementClass, count)using the declared block count directly, so a malformed or truncated record mapped to a Java array field (for examplelong[]) could drive a large eager allocation before a single element was read.This aligns
ReflectDatumReader.readArraywith the generic reader by applying the sameensureAvailableCollectionBytesandcheckMaxCollectionAllocationguards before the allocation. Malformed input now fails fast (EOFException) instead of over-allocating; valid arrays read unchanged.How was this patch tested?
TestReflectDatumReader:read_PojoWithArray_rejectsOversizedArrayCount— a record declaring a ~2e9 array block count with no elements now fails fast instead of attempting a large allocation. Existing round-trip tests act as negative controls.avromodule test suite passes.JIRA