i want to show my error message from controller to html thymleaf spring boots

            if(checkcode.isPresent()){ 
            
            redirectAttributes.addFlashAttribute("errorMessage", "This products have already !");
            return "redirect:/save-product";
            
        } else if (checkname.isPresent()) {
            
            redirectAttributes.addFlashAttribute("errorMessage", "This product have already !");
        开发者_Python百科    return "redirect:/save-product";
             
        }

<div th:if="${errorMessage}">
    <div th:text="${errorMessage}"></div>
</div>

This is my Controller and my div show error message to thymleaf but this one can't show on my thymleaf page

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addFlashAttribute() Modify to addAttribute()