The error suggests that you are attempt to parse a message encoded with
TestRecordV1 and you use TestRecordV2 as writer schema instead of TestRecordV1.
make sure when you de-serialize an TestRecordV1 array into a TestRecordV2
array, you initialize your Json decoder with the writer schema not the reader
one:
> Decoder decoder = DECODER_FACTORY.jsonDecoder(readArrSchema writeArrSchema,
> jsonArrayString);
hope it helps.
—Z
> On Dec 1, 2019, at 8:16 PM, Austin Cawley-Edwards <austin.caw...@gmail.com>
> wrote:
>
> Hi,
>
> We are trying to encode a list of records into JSON with one schema and then
> decode the list into Avro objects with a compatible schema. The schema
> resolution between the two schemas works for single records, but the
> deserialization fails when the read schema differs from the write.
> Deserialization works, however, when the same schema is used for both.
>
> When decoding, an exception is thrown:
>
> org.apache.avro.AvroTypeException: Attempt to process a item-end when a int
> was expected.
> org.apache.avro.io.parsing.Parser.advance(Parser.java:93)
> org.apache.avro.io.JsonDecoder.advance(JsonDecoder.java:139)
> org.apache.avro.io.JsonDecoder.arrayNext(JsonDecoder.java:360)
>
> It seems like the decoder is not moving the proper number of bytes down to
> read the next element.
>
> We encode like so:
>
> public static <T extends GenericRecord> String toJSONArrayString(List<T>
> avroRecords, Schema schema) throws IOException {
>
> if (avroRecords == null || avroRecords.isEmpty()) {
> return "[]";
> }
>
> ByteArrayOutputStream baos = new ByteArrayOutputStream();
> Encoder encoder = ENCODER_FACTORY.jsonEncoder(Schema.createArray(schema),
> baos);
> DatumWriter<T> datumWriter = avroRecords.get(0) instanceof SpecificRecord
> ? new SpecificDatumWriter<>(schema)
> : new GenericDatumWriter<>(schema);
>
> encoder.writeArrayStart();
> encoder.setItemCount(avroRecords.size());
> for (T record : avroRecords) {
> encoder.startItem();
> datumWriter.write(record, encoder);
> }
> encoder.writeArrayEnd();
> encoder.flush();
>
> return baos.toString();
> }
>
> And decode similarly:
> public static <T extends GenericRecord> List<T> fromJSONArrayString(String
> jsonArrayString, Schema writeSchema, Schema readSchema) throws IOException {
> Schema readArrSchema = Schema.createArray(readSchema);
> Decoder decoder = DECODER_FACTORY.jsonDecoder(readArrSchema,
> jsonArrayString);
> DatumReader<T> datumReader;
> if (writeSchema.equals(readSchema)) {
> datumReader = new SpecificDatumReader<>(readSchema);
> } else {
> datumReader = new SpecificDatumReader<>(writeSchema, readSchema);
> }
>
> List<T> avroRecords = new ArrayList<>();
> for (long i = decoder.readArrayStart(); i != 0; i = decoder.arrayNext()) {
> for (long j = 0; j < i; j++) {
> avroRecords.add(datumReader.read(null, decoder));
> }
> }
>
> return avroRecords;
> }
>
>
> Our two schemas look like:
> {
> "type": "record",
> "name": "TestRecordV1",
> "fields": [
> {
> "name": "text",
> "type": "string"
> }
> ]
> }
> {
> "type": "record",
> "name": "TestRecordV2",
> "fields": [
> {
> "name": "text",
> "type": "string"
> },
> {
> "name": "number",
> "type": "int",
> "default": 0
> }
> ]
> }
>
>
> Is there something simple we are missing or is it not possible to do schema
> resolution dynamically on an entire array?
>
> Thank you!
> Austin
>
>
