@Override
    public boolean isValid(String s, ConstraintValidatorContext constraintValidatorContext) {
        if(s == null || s.equals("")){
            return true;
        }
        else {
            if(s.contains(" ")){
                return false;
            }
            for(String reservedElement : RESERVED_BLOCK_ID){
                if(reservedElement.equals(s)){
                    return false;
                }
            }
            List<HomePageItem> allHomePageItems = homePageItemService.getItems();
            for (HomePageItem el : allHomePageItems){
                if(el.getItemBlockId().equals(s)){
                    return false;
                }
            }
            return true;
        }
    }