Java – Avro serialization exception – java.time.Instant cannot be converted to java.lang.Long

I want to send a Kafka message with a payload that extends the SpecificRecordBase class; It is a class generated with the help of the Maven plugin.

One field of my schema has a timestamp type that corresponds to java.time.Instant in the generated class.

The fields are defined as follows:

{"name": "processingTime", "type": {
   "type": "long",
   "logicalType": "timestamp-millis"
   }
},

When I create an instance of this class and set the processing time

setProcessingTime(RandomDate.randomInstant())

Everything works fine, but when I run the program and try to send it to Kafka, I get the following error:

org.apache.kafka.common.errors.SerializationException: Can't convert value of class poc.avroGenerated.AvroMeasurement to class poc.avroSerde.AvroSerializer specified in value.serializer
Caused by: java.lang.ClassCastException: class java.time.Instant cannot be cast to class java.lang.Long (java.time.Instant and java.lang.Long are in module java.base of loader ' bootstrap')

Here is my custom serializer class:

@Override
public byte[] serialize(String topic, T data) {

byte[] result = null;
    try {
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        BinaryEncoder binaryEncoder = EncoderFactory.get().binaryEncoder(byteArrayOutputStream, null);
        DatumWriter<GenericRecord> datumWriter = new GenericDatumWriter<>(data.getSchema());
        datumWriter.write(data, binaryEncoder);
        binaryEncoder.flush();
        byteArrayOutputStream.close();
        result = byteArrayOutputStream.toByteArray();
    } catch (IOException e) {
        LOGGER.error(e);
    }
    return result;
}

Use SpecificDatumWriter instead of GenericDatumWriter.

Add that change and your custom serializer looks good!

This is often a point of confusion. In the Java implementation, “generic” data does not account for any customizations built into a particular record, including logical type conversions.