上传文件保存文件到本地（本文是pdf,实际什么类型都可以）

@PostMapping("/add")
	@ApiOperationSupport(order = 11)
	@ApiOperation(value = "新增图纸", notes = "")
	public R addDrawingInfo(@RequestParam MultipartFile file, @RequestParam Long projectId,@RequestParam String remark) {
		if (file.isEmpty()) {//判断文件是否为空
			return R.fail("上传数据非法");
		}
		String fileName = file.getOriginalFilename(); //获得文件名
		if(!fileName.endsWith(".pdf")){
			log.error(fileName + "不是pdf文件");
			return R.fail(fileName + "不是pdf文件");
		}
		//验证是否已存在该图纸
		DrawingInfoTO condition = new DrawingInfoTO();
		condition.setProjectId(projectId);
		condition.setName(fileName);
		condition.setIsDeleted(0);
		List<DrawingInfo> drawings = drawingInfoService.list(Condition.getQueryWrapper(condition));
		if (drawings.size() > 0) {
			log.error(fileName + "图纸已存在");
			return R.fail(fileName + StatusEnum.DRAWING_EXIST.getCod