File destFile = new File(sourceFile.getParent(), jasperPrint.getName() + ".jxl.xls");
Map dateFormats = new HashMap();
dateFormats.put("EEE, MMM d, yyyy", "ddd, mmm d, yyyy");
JExcelApiExporter exporter = new JExcelApiExporter();
exporter.setParameter(JRExporterParameter.JASPER_PRINT, jasperPrint);
exporter.setParameter(JRExporterParameter.OUTPUT_FILE_NAME, destFile.toString());
exporter.setParameter(JRXlsExporterParameter.IS_ONE_PAGE_PER_SHEET, Boolean.TRUE);
exporter.setParameter(JRXlsExporterParameter.IS_DETECT_CELL_TYPE, Boolean.TRUE);
exporter.setParameter(JRXlsExporterParameter.FORMAT_PATTERNS_MAP, dateFormats);
exporter.exportReport();
System.err.println("XLS creation time : " + (System.currentTimeMillis() - start));
}