public String save (@ RequestBody @ Valid Stad stad)
there is no problem when there is only an object. Now, when saving the object, there is still a file to upload at the same time.
because the object encapsulates json in the data, can I convert the json to an object and verify it again?

public String save(
            @RequestParam("file")MultipartFile file,
            @Valid Stad stad,
            @Valid @NotNull String name
    )