@Override
            protected HiveDecimalWritable convert(Binary binary) {
              DecimalLogicalTypeAnnotation logicalType = (DecimalLogicalTypeAnnotation) type.getLogicalTypeAnnotation();
              return HiveDecimalUtils.enforcePrecisionScale(
                  new HiveDecimalWritable(binary.getBytes(), logicalType.getScale()),
                  (DecimalTypeInfo) hiveTypeInfo);
            }
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