@Override
  public Object evaluate(DeferredObject[] arguments) throws HiveException {
    assert (arguments.length == 3);
    if (arguments[0].get() == null || arguments[1].get() == null || arguments[2].get() == null) {
      return null;
    }

    Text input = (Text) converters[0].convert(arguments[0].get());
    Text from = (Text) converters[1].convert(arguments[1].get());
    Text to = (Text) converters[2].convert(arguments[2].get());

    populateMappingsIfNecessary(from, to);
    String resultString = processInput(input);
    result.set(resultString);
    return result;
  }
Converters for retrieving the arguments to the UDF.
ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDFTranslate.java