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Separate client from server errors as much as possible in this order: - raise MultipartException when resolving a multipart arg and the request is not a multipart request (400) - raise IllegalArgumentException when the arg type is MultipartFile but the request is not of type MultipartHttpServletRequest (500) - raise MissingServletRequestPartException when a MultipartResolver is in use but the part is not found (400) - detect presence of Servlet 3.0 before using standard multipart parsing to find a request part or raise IllegalArgumentException (500) Unfortunately it is not always possible to separate client from server errors mainly because the Servlet 3.0 API does not distinguish between the case of 0 request parts vs multipart processing not being configured.