req.file undefined when express.json() is used in gateway service

Question

I have 3 services:

A React app
A Node express gateway
A Node express backend

I send files from the React app to the backend using a proxy in the gateway. The thing is if express.json() or express.urlencoded() middlewares are set before the proxy the req.file is empty after multer encoded it.

Relevant code:

react app:

const formData = new FormData();

formData.append("file", file);
formData.append("type", "pdf");
formData.append("contentId", "srfewrgferg");

console.log(formData.get("file"));

axios.post( config.BASE_URL + "/activities/create", formData)

gateway:

const router = express();

router.use(express.json());
router.use(express.urlencoded({ extended: true }));

router.post("/activities/*", proxy( `${config.urlPresupuestos}/`, { 
  proxyReqPathResolver: ( req: Request ) => {
    return req.originalUrl;
  }
}));

backend:

const router = express();

router.use(multerMiddleware.single("file"));

router.post("/activities/create", (req, res) => {
  console.log(req.file)
});

If I remove the express middlewares in the gateway all works fine, but I need those middlewares for other routes. Any suggestion why this could be happening?

Myk Willis · Accepted Answer · 2021-04-19 03:54:26Z

1

I assume you are using express-http-proxy for your proxy.

Whether it's a bug or an intentional design, it seems that including body parsing middleware before the proxy will break POST requests.

I don't claim to know why this breaks the proxy, but you can generally work around these kinds of problems by simply re-ordering your routes such that the proxy routes are defined before your middleware:

const router = express();

// Proxy routes go here
router.post("/activities/*", proxy( `${config.urlPresupuestos}/`, { 
  proxyReqPathResolver: ( req: Request ) => {
    return req.originalUrl;
  }
}));

// Now install the middleware required by other routes
router.use(express.json());
router.use(express.urlencoded({ extended: true }));

// Other routes...
router.use(/*...*/);

Express middleware is run in the order it is installed, so even though you've installed these middleware functions at the root of your router, they won't be invoked in the event the proxy route matches and is invoked.

answered Apr 19, 2021 at 3:54

Myk Willis

12.9k5 gold badges50 silver badges65 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Knemay Over a year ago

Thanks for the quick reply. I´m using express-http-proxy indeed. I knwo I can re-order routes and middlewares and even call express middlewares just in the routes that are needed, but I would like to knwo why express middlewares are changin the req object even when the body and the content type indicates that the urlencoded payload is not json-like or urlencoded-like.

Collectives™ on Stack Overflow

req.file undefined when express.json() is used in gateway service

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related