上传文件

    @PostMapping("/upload")
    public void uploadFile(
            @RequestParam("file") MultipartFile file) {
        //TODO
    }

下载文件

@GetMapping("/files/{filename:.+}")
@ResponseBody
public ResponseEntity<Resource> serveFile(@PathVariable String filename) {
    Resource file = storageService.loadAsResource(filename);
    return ResponseEntity.ok().header(HttpHeaders.CONTENT_DISPOSITION,
    "attachment; filename=\"" + file.getFilename() + "\"").body(file);
}