Use GenericArray. The schema given to the generic array is not the schema of
the member elements, but the actual array schema (yes it is confusing).
new GenericData.Array<Utf8>(size,
Schema.createArray(Schema.create(Type.STRING));
It would be useful to be able to simply use Utf8[] or List<Utf8> for the
Specific API, but at this time it leverages GenericData.
On Jun 15, 2010, at 6:25 PM, Bradford Stephens wrote:
> That makes sense -- I'm getting errors during serialization, though.
>
> I convert my List<String> to Utf8[].
>
> I then do a QueueItem.put() and get "Exception in thread "main"
> java.lang.ClassCastException: [Lorg.apache.avro.util.Utf8; cannot be
> cast to org.apache.avro.generic.GenericArray"
>
> How do I handle this Java->Avro interop? It seems to me that it should
> be a lot simpler...
>
> If I try to create a GenericArray<Utf8> and add items to that, it
> complains that my schema doesn't look right...so that doesn't feel
> like the right path.
>
> My generated class looks like this:
>
> @SuppressWarnings("all")
> public class QueueItem extends
> org.apache.avro.specific.SpecificRecordBase implements
> org.apache.avro.specific.SpecificRecord {
> public static final org.apache.avro.Schema SCHEMA$ =
> org.apache.avro.Schema.parse("{\"type\":\"record\",\"name\":\"QueueItem\",\"namespace\":\"com.dts\",\"fields\":[{\"name\":\"Columns\",\"type\":[\"null\",{\"type\":\"array\",\"items\":\"string\"}]}]}");
>
> public org.apache.avro.generic.GenericArray<org.apache.avro.util.Utf8>
> Columns;
> public org.apache.avro.Schema getSchema() { return SCHEMA$; }
> public java.lang.Object get(int field$) {
>
>
> switch (field$) {
> case 0: return Columns;
> default: throw new org.apache.avro.AvroRuntimeException("Bad index");
> }
> }
> @SuppressWarnings(value="unchecked")
> public void put(int field$, java.lang.Object value$) {
> switch (field$) {
> case 0: Columns =
> (org.apache.avro.generic.GenericArray<org.apache.avro.util.Utf8>)value$;
> break;
> default: throw new org.apache.avro.AvroRuntimeException("Bad index");
> }
> }
> }
>
>
>
>
> On Tue, Jun 15, 2010 at 8:57 AM, Philip Zeyliger <[email protected]> wrote:
>> Hi Bradford,
>> I believe you use a SpecificDatumReader. Something like:
>>
>> final static SpecicificDatumReader<QueueItem> QUEUE_ITEM_READER = new
>> SpecificDatumReader<QueueItem>(QueueItem.class);
>> QueueItem q = QUEUE_ITEM_READER.read(null, decoder);
>> There doesn't seem to be a test that exercises this code path in an
>> explanatory way, but java/src/java/org/apache/avro/ipc/Requestor.java uses
>> something quite similar.
>> -- Philip
>>
>> On Mon, Jun 14, 2010 at 9:20 PM, Bradford Stephens
>> <[email protected]> wrote:
>>>
>>> Greetings,
>>>
>>> I've poked around for examples of this, but I can't find any. I
>>> imagine it's a fairly common use case.
>>>
>>> I'm serializing some simple objects into bytes for placement onto
>>> RabbitMQ. My java class is pretty simple (but it'll grow in complexity
>>> in time).:
>>>
>>> {
>>> String[] Columns;
>>> }
>>>
>>>
>>> So, I made a .json schema containing this:
>>> {
>>> "namespace": "com.dts",
>>> "name": "QueueItem",
>>> "type": "record",
>>> "fields": [
>>> {"name": "Columns", "type": ["null", {"type": "array",
>>> "items":"string"}]}
>>> ]
>>> }
>>>
>>>
>>> And generated a java class ...
>>>
>>> Now, I'm writing a test to serialize and deserialize some items. I can
>>> figure out the serialization, but not deserialization back to objects.
>>>
>>> Schema s = Schema.parse(new File("queuetype.json"));
>>>
>>> ByteArrayOutputStream bao = new ByteArrayOutputStream();
>>> GenericDatumWriter w = new GenericDatumWriter(s);
>>> Encoder e = new BinaryEncoder(bao);
>>> e.init (bao);
>>>
>>>
>>> QueueItem r = new QueueItem();
>>> r.put(0, items);
>>> w.write(r, e);
>>> e.flush();
>>>
>>> ByteArrayInputStream is = new
>>> ByteArrayInputStream(bao.toByteArray());
>>> DecoderFactory df = new DecoderFactory();
>>> Decoder d = df.createBinaryDecoder(is, null);
>>>
>>> QueueItem itemout = (QueueItem) .....
>>>
>>>
>>> And that's what I can't figure out -- how do I use a decoder method to
>>> create QueueItems?
>>>
>>> Cheers,
>>> B
>>>
>>> radford Stephens,
>>> Founder, Drawn to Scale
>>> drawntoscalehq.com
>>> 727.697.7528
>>>
>>> http://www.drawntoscalehq.com -- The intuitive, cloud-scale data
>>> solution. Process, store, query, search, and serve all your data.
>>>
>>> http://www.roadtofailure.com -- The Fringes of Scalability, Social
>>> Media, and Computer Science
>>
>>
>
>
>
> --
> Bradford Stephens,
> Founder, Drawn to Scale
> drawntoscalehq.com
> 727.697.7528
>
> http://www.drawntoscalehq.com -- The intuitive, cloud-scale data
> solution. Process, store, query, search, and serve all your data.
>
> http://www.roadtofailure.com -- The Fringes of Scalability, Social
> Media, and Computer Science
