@Override
  public Object deserialize(Writable blob) throws SerDeException {
    if (blob == null) {
      return null;
    }
    Message message = toMessage(blob);
    if (message == null) {
      return null;
    }
    return convertor.convert(message);
  }
SerDe to convert ProtoWritable messages to Hive formats.
The serde supports the following properties:
<ul>
  <li>proto.class: This is required and specifies the class to be used to read the messages.</li>
  <li>proto.maptypes: This is optional it declares set of protobuf types that have to be
      converted to map objects instead of struct type. It is applied only on a repeated struct
      field. The message should have 2 fields, first is used as key and second is used as value.
  </li>
</ul>
ql/src/java/org/apache/hadoop/hive/ql/io/protobuf/ProtobufSerDe.java