General-Purpose Serialization and Deserialization for Avro-Generated SpecificRecords

[Gary Steelman]

Hi all,

Here's my use case: I've got a bunch of different Java objects generated
from Avro schema files. So the class definition headers look something like
this: public class MyObject extends
org.apache.avro.specific.SpecificRecordBase implements
org.apache.avro.specific.SpecificRecord. I've got many other types than
MyObject too. I need to write a method which can serialize (from MyObject
or another class to byte[]) and deserialize (from byte[] to MyObject or
another class) in memory (not writing to disk).

I couldn't figure out how to write one method to handle it for
SpecificRecord, so I tired serializing/deserializing these things as
GenericRecord instead:

  public static byte[] serializeFromAvro(GenericRecord gr) {
    try {
      DatumWriter<GenericRecord> writer2 = new
GenericDatumWriter<GenericRecord>(gr.getSchema());
      ByteArrayOutputStream bao2 = new ByteArrayOutputStream();
      BinaryEncoder encoder2 =
EncoderFactory.get().directBinaryEncoder(bao2, null);
      writer2.write(gr, encoder2);
      byte[] avroBytes2 = bao2.toByteArray();
      return avroBytes2;
    } catch (IOException e) {
      LOG.debug(e);
      return null;
    }
  }

  // Here I use a DataType enum and the AvroSchemaFactory to quickly
retrieve a Schema object for a supported DataType.
  public static GenericRecord deserializeFromAvro(byte[] avroBytes,
DataType dataType) {
    try {
      Schema schema = AvroSchemaFactory.getInstance().getSchema(dataType);
      DatumReader<GenericRecord> reader2 = new
GenericDatumReader<GenericRecord>(schema);
      ByteArrayInputStream bai2 = new ByteArrayInputStream(avroBytes);
      BinaryDecoder decoder2 =
DecoderFactory.get().directBinaryDecoder(bai2, null);
      GenericRecord gr2 = reader2.read(null, decoder2);
      return gr2;
    } catch (Exception e) {
      LOG.debug(e);
      return null;
    }
  }

And use them like such:

// Remember MyObject is the SpecificRecord implementing class.
MyObject x = new MyObject();
byte[] avroBytes = serializeFromAvro(x);
MyObject x2 = (MyObject) deserializeFromAvro(avroBytes, DataType.MyObject);

Which results in this:
java.lang.ClassCastException: org.apache.avro.generic.GenericData$Record
cannot be cast to datatypes.generated.avro.MyObject

Is there an easier way to achieve my use case, or some way I can fix my
methods to allow the sort of behavior I want?

Thanks,
Gary