code: @Override
  public RecordWriter<NullWritable,SpreadSheetCellDAO> getRecordWriter(TaskAttemptContext context) throws IOException {
  	// check if mimeType is set. If not assume new Excel format (.xlsx)
  	Configuration conf=context.getConfiguration();
  	String defaultConf=conf.get(HadoopOfficeWriteConfiguration.CONF_MIMETYPE,ExcelFileOutputFormat.DEFAULT_MIMETYPE);
  	conf.set(HadoopOfficeWriteConfiguration.CONF_MIMETYPE,defaultConf);
  	// add suffix	
  	Path file = getDefaultWorkFile(context,ExcelFileOutputFormat.getSuffix(conf.get(HadoopOfficeWriteConfiguration.CONF_MIMETYPE)));
  
  
  	 	try {
  			return new ExcelRecordWriter<>(HadoopUtil.getDataOutputStream(conf,file,context,getCompressOutput(context),getOutputCompressorClass(context, ExcelFileOutputFormat.defaultCompressorClass)),file.getName(),conf);
  		} catch (InvalidWriterConfigurationException | InvalidCellSpecificationException | FormatNotUnderstoodException
  				| GeneralSecurityException | OfficeWriterException e) {
  			LOG.error(e);
  		}
  
  	return null;
  }
docs: /*
  Returns a new record writer, if mimetype is not specified it is assumed that the new Excel format (.xlsx) should be used
  
  @param context MR context
  
  @return Excel Record Writer