@Override
              protected LongWritable convert(Binary binary) {
                Preconditions.checkArgument(binary.length() == 12, "Must be 12 bytes");
                ByteBuffer buf = binary.toByteBuffer();
                buf.order(ByteOrder.LITTLE_ENDIAN);
                long longVal = buf.getLong();
                return new LongWritable(longVal);
              }
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