在 Node.js 中使用 multer 中间件验证文件大小的问题

Question

我在 Node.js 应用程序中使用 multer 中间件验证文件大小时遇到问题。我已经实现了一个自定义中间件

setFileLimit

来根据文件类型设置文件大小限制，但执行中间件时似乎

req.file

和

req.files

未定义。

在将所选媒体上传到 multer 之前无法验证文件大小

前端代码：

// 1. Frontend code that sends the media
if (file) {
  const formData = new FormData()
  formData.append('medias', file)
  console.log('send rrrr--');
  console.log('type of formdata--', typeof formData);
  const mediatoCloudinary = await uploadMedia(formData)
  if (mediatoCloudinary?.status === 400) {
    console.log('media upload error', mediatoCloudinary);
    setMediaError('No media file found.')
  }
}

export const uploadMedia = async(formData) => {
  try {
    console.log('rrr--', formData);
    const result = await axiosApi.post(messagesRoute.sendMedia, formData)
    console.log('media link', result);
    return result.data
  } catch (error) {
    console.log('media error', error.message);
    return error.response
  }
}

//2.Backend Route:

router.post('/sendMedia', setFileLimit, multerMid.single('medias'), catchAsyncErrors((req: Req, res: Res, next: Next) => {
  console.log('in send media route');
  messageController.saveMediaToCloudinary(req, res, next)
}))


//3.Multer Middleware and setFileLimit function in backend:

// Custom middleware to set limits based on file type using startsWith
const setFileLimit = (req: Req, res: Res, next: Next) => {
  // Access the file using the correct key ('medias')
  console.log('Accessing file:', req.file, 'req.files--', req.files);
  const file = req.file
  if (!file) {
    return res.status(400).send('No media file found.');
  }

  let maxSize;
  if (file.mimetype.startsWith('image/')) {
    maxSize = 5 * 1024 * 1024; // 5 MB for images
  } else if (file.mimetype.startsWith('video/')) {
    maxSize = 10 * 1024 * 1024; // 10 MB for videos
  } else {
    maxSize = 5 * 1024 * 1024; // Default to 5 MB for other documents
  }

  if (file.size > maxSize) {
    return res.status(400).json({ error: 'File size exceeds the limit.' });
  }

  next()
}

const storage = multer.diskStorage({
  destination: (req, file, cb) => {
    const uploadDirectory = path.join(__dirname, '../public/media')
    if (!fs.existsSync(uploadDirectory)) {
      fs.mkdirSync(uploadDirectory, { recursive: true });
    }
    cb(null, uploadDirectory);
  },
  filename: (req, file, cb) => {
    console.log('file in multer--', file);
    const uniqueSuffix = uuidv4() + '-' + file.originalname
    cb(null, uniqueSuffix);
  },
});

const multerMid = multer({
  storage: storage,
  limits: {
    fieldNameSize: 100,
    fieldSize: 5 * 1024 * 1024
  }
});

export { multerMid, setFileLimit }

Answer 1

尝试重新安排中间件，以便在 setFileLimit 之前执行 multerMid.single('medias')

router.post('/sendMedia', multerMid.single('medias'), setFileLimit,catchAsyncErrors((req: Req, res: Res, next: Next) => {  console.log('in send media route');  messageController.saveMediaToCloudinary(req, res, next)}))