结束日期永远不会比开始日期早，并且只会显示日期格式，否则会显示服务器错误页面。

private Timestamp start_date;
private Timestamp end_date;

    @GetMapping("/bulk/add")
    public String bulkCoupon(ModelMap modelMap) {
        try {

            Map<Integer,String> redeemTypes = buildCouponRedeemTypeMap();
            Map<Integer,String> couponTypes = buildCouponTypeMap();
            modelMap.addAttribute("couponTypes",couponTypes);
            BulkCouponRequest couponCode = new BulkCouponRequest();
            couponCode.setLength(6);
            modelMap.addAttribute("redeemTypes",redeemTypes);
            modelMap.addAttribute("request",couponCode);
            modelMap.addAttribute("categories",commonService.findAll(Category.class).stream()
                    .collect(Collectors.toMap(Category::getId,Category::getcategory)));
            modelMap.addAttribute("title","Bulk Coupon Code");
            return "bulk-coupon-add";
        } catch (Exception exception) {
            LOGGER.error("context",exception);
            return "exception";
}
}