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From Jonathan Natkins <na...@cloudera.com>
Subject Re: Looking for some guidance in building a basic Avro pipeline
Date Fri, 07 Dec 2012 01:56:42 GMT
Ok, I'm still a little confused. Let's say I use Avros.generics(), and then
I modify my code to use GenericData.Records. Those Records still don't
implement the Writable interface, so I'm still getting a class cast
exception. Did I do something totally wrong?


On Thu, Dec 6, 2012 at 5:19 PM, Jonathan Natkins <natty@cloudera.com> wrote:

> Well, the problem with that is that I really want to work with my objects,
> rather than use Avros.generics, because then I'm forced to treat everything
> as a GenericData.Record. It's just a pain in the butt.
>
>
> On Thu, Dec 6, 2012 at 5:17 PM, Josh Wills <josh.wills@gmail.com> wrote:
>
>> You don't want to create an AvroType yourself, you want to call
>> o.a.c.types.avro.Avros.records or one of its friends and pass it a Class
>> object.
>>
>> Interesting though, I would still want that case to work correctly.
>>
>> Josh
>> On Dec 6, 2012 5:14 PM, "Jonathan Natkins" <natty@cloudera.com> wrote:
>>
>>> So I've been futzing with Crunch a bit, and trying to understand how to
>>> build a pipeline that outputs Avro data files. Roughly, I'm doing something
>>> along these lines:
>>>
>>>     Schema.Parser schemaParser = new Schema.Parser();
>>>     final Schema avroObjSchema = schemaParser.parse(
>>> schemaJsonString);
>>>
>>>     AvroType avroType = new AvroType<MyAvroObject>(MyAvroObject.class,
>>>         avroObjSchema, new
>>> AvroDeepCopier.AvroReflectDeepCopier<MyAvroObject>(
>>>         MyAvroObject.class, avroObjSchema));
>>>
>>>     PCollection<MyAvroObject> words = logs.parallelDo(new DoFn<String,
>>> MyAvroObject>() {
>>>       public void process(String line, Emitter<MyAvroObject> emitter) {
>>>         emitter.emit(convertStringToAvroObj(line));
>>>       }
>>>     }, avroType);
>>>
>>> However, this results in a class cast exception:
>>>
>>> Exception in thread "main" java.lang.ClassCastException: class
>>> com.company.MyAvroObject
>>>     at java.lang.Class.asSubclass(Class.java:3039)
>>>     at
>>> org.apache.crunch.types.writable.Writables.records(Writables.java:250)
>>>     at
>>> org.apache.crunch.types.writable.WritableTypeFamily.records(WritableTypeFamily.java:86)
>>>     at org.apache.crunch.types.PTypeUtils.convert(PTypeUtils.java:61)
>>>     at org.apache.crunch.types.writable.WritableTypeFamily.as
>>> (WritableTypeFamily.java:135)
>>>     at
>>> org.apache.crunch.impl.mr.MRPipeline.writeTextFile(MRPipeline.java:319)
>>>
>>> Anybody have any thoughts? There's got to be a magical incantation that
>>> I have slightly off.
>>>
>>
>

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