src/main/java/js/http/encoder/MultipartFormArgumentsReader.java
private static UploadStream getUploadStream(HttpServletRequest httpRequest, Type[] formalParameters) throws IOException {
		FormIterator form = new FormIteratorImpl(httpRequest);
		if (!form.hasNext()) {
			throw new IllegalArgumentException("Empty form.");
		}
		Part part = form.next();
		if (!(part instanceof UploadStream)) {
			throw new IllegalArgumentException("Illegal form. Expected uploaded stream but got field |%s|.", part.getName());
		}
		return (UploadStream) part;
	}
private static UploadStream getUploadStream(HttpServletRequest httpRequest, Type[] formalParameters) throws IOException {
		FormIterator form = new FormIteratorImpl(httpRequest);
		if (!form.hasNext()) {
			throw new IllegalArgumentException("Empty form.");
		}
		Part part = form.next();
		if (!(part instanceof UploadStream)) {
			throw new IllegalArgumentException("Illegal form. Expected uploaded stream but got field |%s|.", part.getName());
		}
		return (UploadStream) part;
	}
Get upload stream from given HTTP request. This method expects on HTTP request a multipart form with a single part of
byte stream type. Returns an upload stream instance wrapping the form stream part.

@param httpRequest HTTP request,
@param formalParameters used only for exception message.
@return upload stream.
@throws IOException if reading form HTTP request fails.
@throws IllegalArgumentException if there is no valid multipart form on HTTP request.