public void xlsx() throws JRException {
    long start = System.currentTimeMillis();
    File sourceFile = new File("build/reports/DataSourceReport.jrprint");

    JasperPrint jasperPrint = (JasperPrint) JRLoader.loadObject(sourceFile);

    File destFile = new File(sourceFile.getParent(), jasperPrint.getName() + ".xlsx");

    JRXlsxExporter exporter = new JRXlsxExporter();

    exporter.setParameter(JRExporterParameter.JASPER_PRINT, jasperPrint);
    exporter.setParameter(JRExporterParameter.OUTPUT_FILE_NAME, destFile.toString());

    exporter.exportReport();

    System.err.println("XLSX creation time : " + (System.currentTimeMillis() - start));
  }
  public void xlsx() throws JRException {
    long start = System.currentTimeMillis();
    File sourceFile = new File("build/reports/FirstJasper.jrprint");

    JasperPrint jasperPrint = (JasperPrint) JRLoader.loadObject(sourceFile);

    File destFile = new File(sourceFile.getParent(), jasperPrint.getName() + ".xlsx");

    Map dateFormats = new HashMap();
    dateFormats.put("EEE, MMM d, yyyy", "ddd, mmm d, yyyy");

    JRXlsxExporter exporter = new JRXlsxExporter();

    exporter.setParameter(JRExporterParameter.JASPER_PRINT, jasperPrint);
    exporter.setParameter(JRExporterParameter.OUTPUT_FILE_NAME, destFile.toString());
    exporter.setParameter(JRXlsExporterParameter.IS_DETECT_CELL_TYPE, Boolean.TRUE);
    exporter.setParameter(JRXlsExporterParameter.FORMAT_PATTERNS_MAP, dateFormats);

    exporter.exportReport();

    System.err.println("XLSX creation time : " + (System.currentTimeMillis() - start));
  }