Db db = new Db();
                    Connection con = db.getConnection(config);
                    String pathTMP = System.getProperty("java.io.tmpdir");
                    JRFileVirtualizer virtualizer = new JRFileVirtualizer(100, pathTMP);
                    parameters.put(JRParameter.REPORT_VIRTUALIZER, virtualizer);
                    jasperPrint = JasperFillManager.fillReport(jasperReport, parameters, con);
                    con.close();

    public void exportXlsx() throws JRException {
        Map<String, String> dateFormats = new HashMap<String, String>();
        dateFormats.put("EEE, MMM d, yyyy", "ddd, mmm d, yyyy");

        JRXlsxExporter exporter = new JRXlsxExporter();
        SimpleXlsxReportConfiguration repConfig = new SimpleXlsxReportConfiguration();
        exporter.setExporterInput(new SimpleExporterInput(jasperPrint));
		exporter.setExporterOutput(new SimpleOutputStreamExporterOutput(getOutputStream(".xlsx")));
        repConfig.setDetectCellType(Boolean.TRUE);
        repConfig.setFormatPatternsMap(dateFormats);
        exporter.setConfiguration(repConfig);
        exporter.exportReport();
    }