Redirect user to same page and keep form data

Question

I'm trying to do some custom validation using this code:

Spring endpoint:

@PostMapping(value = "/validate_pairs")
public String validatePair(Model model, RedirectAttributes attributes) {

    // Do here some SQL queries and checks
    attributes.addFlashAttribute("validation_message", "Successful validation!");

    return "redirect:/pairs";
}

    <div class="row g-3 align-items-center mb-1 mt-1">
        <div class="col-auto">
            <input id="pair" class="form-control" name="pair" type="text"
                   placeholder="Pair to be added."
                   th:field="*{pair}"
                   required
                   autofocus>
        </div>
        <div class="col-auto">
            <input id="passthrough_active" type="checkbox"
                   name="active"
                   th:field="*{active}">
        </div>
    </div>

    <br>
    <div class="form-group mb-1 mt-1">
        <button type="submit" name="action" value="validatePair" th:formaction="@{/validate_pairs}" class="btn btn-primary">Validate</button>
    </div>

</form>

As you can see I send the form data to Spring Endpoint and I redirect again the user to the same page. The problem is that the form is empty. I need some way to preserve the data again when the user is redirected. Is there some solution?