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AVRO-4322: [Java] Use reader/writers constently with model #3924

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Merged
RyanSkraba merged 1 commit into from
Aug 6, 2026
+13 −5
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AVRO-4322: [Java] Use reader/writers constently with model #3924

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12 changes: 7 additions & 5 deletions lang/java/avro/src/test/java/org/apache/avro/io/FastReaderBuilderJavaClassTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -29,8 +29,6 @@
import org.apache.avro.Schema;
import org.apache.avro.SchemaBuilder;
import org.apache.avro.generic.GenericData;
import org.apache.avro.generic.GenericDatumReader;
import org.apache.avro.generic.GenericDatumWriter;
import org.apache.avro.generic.GenericRecord;
import org.apache.avro.generic.GenericRecordBuilder;
import org.apache.avro.specific.SpecificData;
Expand Down Expand Up @@ -70,20 +68,24 @@ public class FastReaderBuilderJavaClassTest {
.set("prices", Map.of("-0.0002", "cheap", "12345.678", "expensive")).build();

/**
* Reusable round-trip logic for a record, using the given model.
* Reusable round-trip logic for a record, using the given model. The reader is
* built via {@link GenericData#createDatumReader(Schema, Schema)} so that
* SpecificData produces a real {@code SpecificDatumReader}, rather than a
* {@code GenericDatumReader} wrapping a SpecificData instance.
*/
@SuppressWarnings("unchecked")
public static GenericRecord roundTrip(GenericRecord record, GenericData model) throws IOException {
byte[] serialized;

try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
GenericDatumWriter<GenericRecord> writer = new GenericDatumWriter<>(record.getSchema());
DatumWriter<GenericRecord> writer = model.createDatumWriter(record.getSchema());
BinaryEncoder encoder = EncoderFactory.get().binaryEncoder(baos, null);
writer.write(record, encoder);
encoder.flush();
serialized = baos.toByteArray();
}

GenericDatumReader<GenericRecord> reader = new GenericDatumReader<>(record.getSchema(), record.getSchema(), model);
DatumReader<GenericRecord> reader = model.createDatumReader(record.getSchema(), record.getSchema());
BinaryDecoder decoder = DecoderFactory.get().binaryDecoder(serialized, null);
return reader.read(null, decoder);
}
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6 changes: 6 additions & 0 deletions lang/java/avro/src/test/java/org/apache/avro/specific/TestSpecificDatumReader.java
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Expand Up @@ -68,6 +68,12 @@ public String getContent() {

public static class MyReader extends SpecificDatumReader<MyData> {

MyReader() {
// Use a new data model instead of the singleton in order to avoid modifying the
// setFastReaderEnabled state for other tests.
super(null, null, new SpecificData());

@RyanSkraba RyanSkraba Aug 6, 2026

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OK, it looks like this was a hidden bug -- if we setFastReaderEnabled(true) or setFastReaderEnabled(false) on the singleton instance of SpecificData, it overrides the system property and in other tests we end up not testing what we thought we were testing...

I checked through the code and this looks like the only spot where it gets changed in the singleton.

@iemejia iemejia Aug 6, 2026 •
edited
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Oh wow, that's a bit weird so we were not really testing everything correctly ufff. Oh wait that's Test specific, I see now.

}

@Override
protected Class findStringClass(Schema schema) {
return MyData.class;
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