public void validate(Object obj, Errors e) {
ValidationUtils.rejectIfEmpty(e, "title", "title.empty");
PhotoUpload pu = (PhotoUpload) obj;
if (pu.getFile() == null || pu.getFile().isEmpty()) {
if (!pu.validSignature()) {
e.rejectValue("signature", "signature.mismatch");
}
}
}