Controller.java
L new FileOutputStream(${path})で、保存場所を指定する
@RequestMapping(value="upload", method=RequestMethod.POST)
public void handle(
HttpServletResponse response,
@RequestParam MultipartFile file
) {
if(file.isEmpty()) {
response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
return;
}
try {
BufferedInputStream in = new BufferedInputStream(file.getInputStream());
BufferedOutputStream out = new BufferedOutputStream(
new FileOutputStream("./target/" + file.getOriginalFilename()));
} catch (IOException e) {
throw new RuntimeException("Error uploading file.", e);
}
}

なるほど、resourcesのstaticの中に置くこともできますね。
new FileOutputStream(“./src/main/resources/static/file/” + file.getOriginalFilename())
### filenameをreturn
res.getWriter().write(file.getOriginalFilename());

OK、後は基本機能としてはログインのみなんだよなー