首先檔案要有存放的地方

在application.yml中配置

spring:
  servlet:
    multipart:
      location: /Users/chenweiqi/IdeaProjects/mq/temp/file

controller中接收，儲存檔案

   @RequestMapping(value = "/test/upload/file",method = RequestMethod.POST)
    public R upload(@RequestParam("file") MultipartFile multipartFile){
        if (multipartFile.isEmpty()){
            //檔案為空的時候返回錯誤
            return R.Error();
        }

        String fileName = multipartFile.getOriginalFilename();
        //int size = (int) multipartFile.getSize();
        
        File file = new File(fileName);
        if (file.getParentFile()!=null && !file.getParentFile().exists()){
            file.getParentFile().mkdirs();
        }
        try {
            //儲存檔案
            multipartFile.transferTo(file);
        } catch (IOException e) {
            e.printStackTrace();
            return R.Error();
        }

        return R.Ok();
    }
 

檔案儲存了 現在前端請求需要返回檔案了

controller 中定義變數。獲取最開始定義的檔案路徑

 @Value("${spring.servlet.multipart.location}")
 String filePath;

返回檔案有很多寫法。這裡通過 response 直接寫入。 

直接根據url請求獲取檔名。讀取後直接返回。

    @RequestMapping(value = "/test/file/{fileName:[a-zA-Z0-9\\.]+}",method = RequestMethod.GET)
    public void getFile(@PathVariable(name = "fileName") String fileName, HttpServletResponse response){
        File file = new File(filePath+File.separator+fileName);
        System.out.println(file);
        if (!file.exists()){
            throw new RuntimeException("檔案不存在");
        }

        try {
            FileInputStream fileInputStream =new FileInputStream(file);

            ServletOutputStream outputStream = response.getOutputStream();

            byte[] temp = new byte[1024];
            while(fileInputStream.read(temp) >0){
                outputStream.write(temp);
            }

            fileInputStream.close();
            outputStream.flush();
            outputStream.close();

        } catch (Exception e) {
            e.printStackTrace();
        }

    }