xlsx

public void createExcel(OutputStream os) {

        try (InputStream is = new ClassPathResource("templates/" + template).getInputStream()) {

            XSSFWorkbook wb = new XSSFWorkbook(is);
            // PoiTransformer transformer =
            // PoiTransformer.createSxssfTransformer(wb);

            XSSFSheet sheet = wb.getSheet("Sheet1");
            int lastRow = wb.getSpreadsheetVersion().getLastRowIndex();
            int sheetIdx = 1;
            for (ValidationRule rule : rules) {
                if (rule.validationDatas.length == 0)
                    continue;
                XSSFSheet hidden = wb.createSheet("hidden" + sheetIdx);
                for (int i = 0, length = rule.validationDatas.length; i < length; i++) {
                    String name = rule.validationDatas[i];
                    Row row = hidden.createRow(i);
                    Cell cell = row.createCell(0);
                    cell.setCellValue(name);
                }
                XSSFName namedCell = wb.createName();
                namedCell.setNameName("hidden" + sheetIdx);
                namedCell.setRefersToFormula("hidden" + sheetIdx + "!$A$1:$A$" + rule.validationDatas.length);
                XSSFDataValidationHelper dvHelper = new XSSFDataValidationHelper(sheet);
                XSSFDataValidationConstraint constraint = (XSSFDataValidationConstraint) dvHelper
                        .createFormulaListConstraint("hidden" + sheetIdx);

                wb.setSheetHidden(sheetIdx++, true);
                createListBox(dvHelper, sheet, rule.start_validation_row, rule.start_validation_col, lastRow,
                        rule.validationDatas, constraint);
            }
            wb.write(os);

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }