@Override
  public Object set(final Object o, final byte val) {
    ((ByteWritable) o).set(val);
    return o;
  }
The ParquetByteInspector can inspect both ByteWritables and IntWritables into bytes.
ql/src/java/org/apache/hadoop/hive/ql/io/parquet/serde/primitive/ParquetByteInspector.java