如何捕捉multer中的错误

Question

我已经阅读了multer的文档。但是我在代码中的当前设置是不同的，这让我很难理解如何处理错误。现在很重要，因为它发生（仅一次）文件未存储在服务器上，但代码继续将信息保存在数据库中，就好像文件的存储已经工作一样。但它可能没有。

const multer = require('multer');

var docPath = "path_to_disk_where_to_store_files";

var storage = multer.diskStorage({
    inMemory: true,
    destination: function (request, file, callback) {
        callback(null, docPath);
    },
    filename: function (request, file, callback) {
        //Just a function that creates an unique name with timestamp
        renamedFile = helpers.createUniqueName(file.originalname);
        callback(null, renamedFile);
    }
});

var fileFilter = function (req, file, cb) {
    var path = require('path');
    var ext = path.extname(file.originalname);
    if (file.mimetype !== 'application/pdf' || ext.toLowerCase() != '.pdf') {
        req.fileValidationError = 'goes wrong on the mimetype';
        return cb(null, false, new Error('goes wrong on the mimetype'));
    }
    cb(null, true);
};

const multerUploader = multer({storage: storage, fileFilter: fileFilter, limits: { fileSize: maxSize }});

router.post('/save_document',[multerUploader.single('file'),saveDocumentInDb]);

我真的不明白检查上传是否出错的 if 语句在哪里适合。

Answer 1

使用multer时的错误处理请参考以下内容：https : //github.com/expressjs/multer#error-handling

您的实现将是这样的：

const multerUploader = multer({storage: storage, fileFilter: fileFilter, limits: { fileSize: maxSize }});
const upload = multerUploader.single('file');
router.post('/save_document', function (req, res) {
  upload(req, res, function (err) {
    if (err instanceof multer.MulterError) {
      // A Multer error occurred when uploading.
    } else if (err) {
      // An unknown error occurred when uploading.
    }

    // Everything went fine and save document in DB here.
  })
})