上传文件时获取 API 和 multer 错误

Question

我正在尝试使用 fetch API 将文件上传到 node.js 服务器（如果与它有关，我正在使用 github 的 pollyfill：https://github.com/github/fetch）。

请求是这样完成的：

const data = new FormData();
data.append('file', file);
return fetch(this.concatToUrl(url), {
  method: 'post',
  headers: Object.assign({}, this.getHeaders(), {'Content-Type': 'multipart/form-data'}),
  body: data,
});

在我的服务器端，这个路由声明：

app.post('/media', upload.single('file'), mediaRoutes.postMedia);

并尝试像这样获取文件：

exports.postMedia = function(req, res) {
  console.log('req.file', req.file, req.files, req.body);
  return res.sendStatus(200);
}

但是req.file 没有被填充。

我也从快递方面收到此错误：

Error: Multipart: Boundary not found
[2]     at new Multipart (/Users/jmanzano/Development/web/test/node_modules/busboy/lib/types/multipart.js:58:11)
[2]     at Multipart (/Users/jmanzano/Development/web/test/node_modules/busboy/lib/types/multipart.js:26:12)
[2]     at Busboy.parseHeaders (/Users/jmanzano/Development/web/test/node_modules/busboy/lib/main.js:64:22)
[2]     at new Busboy (/Users/jmanzano/Development/web/test/node_modules/busboy/lib/main.js:21:10)
[2]     at multerMiddleware (/Users/jmanzano/Development/web/test/node_modules/multer/lib/make-middleware.js:32:16)
[2]     at Layer.handle [as handle_request] (/Users/jmanzano/Development/web/test/node_modules/express/lib/router/layer.js:95:5)
[2]     at next (/Users/jmanzano/Development/web/test/node_modules/express/lib/router/route.js:131:13)
[2]     at Route.dispatch (/Users/jmanzano/Development/web/test/node_modules/express/lib/router/route.js:112:3)
[2]     at Layer.handle [as handle_request] (/Users/jmanzano/Development/web/test/node_modules/express/lib/router/layer.js:95:5)
[2]     at /Users/jmanzano/Development/web/test/node_modules/express/lib/router/index.js:277:22
[2]     at Function.process_params (/Users/jmanzano/Development/web/test/node_modules/express/lib/router/index.js:330:12)
[2]     at next (/Users/jmanzano/Development/web/test/node_modules/express/lib/router/index.js:271:10)
[2]     at cors (/Users/jmanzano/Development/web/test/node_modules/cors/lib/index.js:178:7)
[2]     at /Users/jmanzano/Development/web/test/node_modules/cors/lib/index.js:228:17
[2]     at originCallback (/Users/jmanzano/Development/web/test/node_modules/cors/lib/index.js:217:15)
[2]     at /Users/jmanzano/Development/web/test/node_modules/cors/lib/index.js:222:13
[2]     at optionsCallback (/Users/jmanzano/Development/web/test/node_modules/cors/lib/index.js:203:9)
[2]     at /Users/jmanzano/Development/web/test/node_modules/cors/lib/index.js:208:7
[2]     at Layer.handle [as handle_request] (/Users/jmanzano/Development/web/test/node_modules/express/lib/router/layer.js:95:5)
[2]     at trim_prefix (/Users/jmanzano/Development/web/test/node_modules/express/lib/router/index.js:312:13)
[2]     at /Users/jmanzano/Development/web/test/node_modules/express/lib/router/index.js:280:7
[2]     at Function.process_params (/Users/jmanzano/Development/web/test/node_modules/express/lib/router/index.js:330:12)

这是通过中间件进行的配置：

app.use(bodyParser.urlencoded({extended: true}));
app.use(bodyParser.json());
app.use(expressValidator());
app.use(logger('dev'));
app.use(cookieParser());
app.use(methodOverride());
app.use(passport.initialize());
app.use(passport.session());
app.set('JWTSuperSecret', jwtConfig.secret);

if (process.env.NODE_ENV !== 'production') {
  app.use(cors());
}

此外，这可以与 POSTMAN 一起正常工作。所以，我认为我的请求有问题。

谢谢！

Answer 1

无需指定标题{Content-Type': 'multipart/form-data'}：浏览器会替换它自己的标题。

但是如果你暴露它，那么它在Request Headers 之前的content-type:multipart/form-data; boundary=... 之后没有指定boundary Request Payload 并且这会导致服务器端的错误。

如果您打开浏览器控制台并看到标题，就会看到。

所以，只是：

fetch(this.concatToUrl(url), {
  method: 'post',
  body: data,
});

或者，如果您需要自定义标题，您可以像这样添加它们：

var headers = Object.assign({},
                            {'content-type': 'application/json'},
                            this.getHeaders(), 
                            {'Content-Type': 'multipart/form-data'}
);

   // Removal should be case insensitive, or in any case, the header will be included:


Object.keys(headers)
      .forEach( function(k) { 
         if (k.toLowerCase()==='content-type') delete headers[k] 
      })

const data = new FormData();
data.append('file', file);
return fetch(this.concatToUrl(url), {
  method: 'post',
  headers: headers,
  body: data,
});

Answer 2

对于那些在使用邮递员时遇到错误的人，请确保不要在标题中指定内容类型。