@Override
        protected HiveDecimalWritable convert(Binary binary) {
          DecimalLogicalTypeAnnotation logicalType =
              (DecimalLogicalTypeAnnotation) type.getLogicalTypeAnnotation();
          return new HiveDecimalWritable(binary.getBytes(), logicalType.getScale());
        }
ETypeConverter is an easy way to set the converter for the right type.
ql/src/java/org/apache/hadoop/hive/ql/io/parquet/convert/ETypeConverter.java