java编写简单的文件上传与下载

两个接口由于时间关系，都是按照最简单的方式编写，还有很多问题，但文件的处理方式没有问题。

1.文件上传

文件上传，使用表单方式上传 MultipartFile multipartFile 参数 后端就收到文件，存储到指定的文件夹下，并进行重命名

 @RequestMapping(value = "/uploadFile",method = RequestMethod.POST)
    public void uploadFileTest(MultipartFile multipartFile) throws  Exception{
        String orgFile = multipartFile.getOriginalFilename();
        String fileName = UUID.randomUUID().toString().replace("-","")+orgFile.substring(orgFile.lastIndexOf("."));
        Path path = Paths.get("D:/resFile/".concat(fileName));
        if (Files.notExists(path)){
            path = Files.createFile(path);
        }
        Long s = Files.copy(multipartFile.getInputStream(),path, StandardCopyOption.REPLACE_EXISTING);
        System.out.println("文件大小为:"+s);
    }

2.文件下载

文件下载，浏览器传递文件名或者路径到后台接口，后台根据路径将文件下载。

    @GetMapping(value = "/downFile")
    public void downFileTest(
            @RequestParam(name = "fileName")String fileName, HttpServletResponse response) throws Exception{
        String filePath = "D:/resFile/";
        String contentType = Files.probeContentType(Paths.get(filePath));
        response.setHeader("Content-Type", contentType);
        response.setHeader("Content-Disposition", "attachment;filename="
                + new String(fileName.getBytes(StandardCharsets.UTF_8), StandardCharsets.ISO_8859_1));
        File file = new File(filePath+fileName);
        FileChannel inChannel = null;
        WritableByteChannel outChannel = null;
        outChannel = Channels.newChannel(response.getOutputStream());
        inChannel = new FileInputStream(file).getChannel();
        inChannel.transferTo(0,inChannel.size(),outChannel);
        inChannel.close();
    }