Re: Deserialize Avro Object Without Schema

[Simone Leo]

Hello,

here is a full working example of deserialization without schema (same 
as the one at http://avro.apache.org/docs/1.7.7/gettingstartedjava.html, 
but using the 0-arg constructor for GenericDatumReader, i.e., no schema):

import java.io.File;

import org.apache.avro.generic.GenericRecord;
import org.apache.avro.generic.GenericDatumReader;
import org.apache.avro.io.DatumReader;
import org.apache.avro.file.DataFileReader;


public class TryRead {

  public static void main(String[] args) throws Exception {
    String fName = null;
    try {
      fName = args[0];
    } catch (ArrayIndexOutOfBoundsException e) {
      System.err.println("Usage: TryRead AVRO_FILE");
      System.exit(1);
    }
    File file = new File(fName);
    DatumReader<GenericRecord> datumReader =
        new GenericDatumReader<GenericRecord>();
    DataFileReader<GenericRecord> dataFileReader =
        new DataFileReader<GenericRecord>(file, datumReader);
    GenericRecord user = null;
    while (dataFileReader.hasNext()) {
      user = dataFileReader.next(user);
      System.out.println(user);
    }
  }
}

On 03/25/2015 10:08 AM, Rendy Bambang Junior wrote:
Hi,

I'm new in Avro. One of Avro's benefit is dynamic typing which code need
not to be generated to deserialize Avro schema.

I'm trying to find an example to deserialize Avro without specify the
schema but all of them require me to pass schema to GenericDatumReader
constructor or set the schema after construct the reader.

So, I'm wondering, *is it possible to deserialize Avro without defining
it's schema?*

I mean, it's like getting value from Map<String, Object> and cast to
desired data type without knowing the schema.

It should be possible right? Since the schema itself is embedded in the
data.

Attached my sample code, it get null pointer exception because I don't
specify the schema.

Thanks!

Rendy

--
Simone Leo
Data Fusion - Distributed Computing
CRS4
POLARIS - Building #1
Piscina Manna
I-09010 Pula (CA) - Italy
e-mail: simone....@crs4.it
http://www.crs4.it

--
Simone Leo
Data Fusion - Distributed Computing
CRS4
POLARIS - Building #1
Piscina Manna
I-09010 Pula (CA) - Italy
e-mail: simone....@crs4.it
http://www.crs4.it