@Override
  protected Writable transformToUTF8(Writable blob) {
    Text text = (Text)blob;
    return SerDeUtils.transformTextToUTF8(text, this.charset);
  }
Transform Writable data from UTF-8 to charset before serialize.
@param blob
@return
hcatalog/core/src/main/java/org/apache/hive/hcatalog/data/JsonSerDe.java