@Override
    public Object convert(Object obj) {
      Message msg = (Message)obj;
      Object[] ret = new Object[fields.length];
      for (int i = 0; i < fields.length; ++i) {
        ret[i] = convertors[i].extractAndConvert(fields[i], msg);
      }
      return ret;
    }
Convert the given writable to a message.
@param writable The writable object containing the message.
@return The converted message object.
@throws SerDeException
ql/src/java/org/apache/hadoop/hive/ql/io/protobuf/ProtobufSerDe.java