code: protected DBObject createChunk(final Object id, final int currentChunkNumber, final byte[] writeBuffer) {
          return new BasicDBObject("files_id", id)
                 .append("n", currentChunkNumber)
                 .append("data", writeBuffer);
      }
docs: Creates a new chunk of this file. Can be over-ridden, if input files need to be split into chunks using a different mechanism.
  
  @param id                 the file ID
  @param currentChunkNumber the unique id for this chunk
  @param writeBuffer        the byte array containing the data for this chunk
  @return a DBObject representing this chunk.