Flutter Dart HTTP POST request body is empty on server side

Question

I am working on a Flutter tablet app. Once one input field is inputted, I am trying to send a post request to the server. Following is the method I am invoking for this:

    Future < http.Response > _postRequest() async {
    print(globals.novaCoord.toString() + ' XYZXYZXYZXYZXYZ');

    var url = globals.URL + 'api/nova_position';

    Map data = {
      'id_nova': '1',
      'position.x': '1',
      'position.y': '1',
      'position.z': '1',
      'position.pitch': '1',
      'position.yaw': '1',
      'position.roll': '1',
    };
    //encode Map to JSON
    var body = json.encode(data);

    http.Response response = await http.post(url,
      headers: {
        "Content-Type": "application/json"
      },
      body: body
    );
    print("${response.statusCode}");
    print("${response.body}");
    return response;
  }

And on the NodeJs server side I have this:

app.post('/api/nova_position/', async (req,res) => {
    console.log("NOVA POSITION");
    console.log(req.body.id_nova);
    const id_nova = req.body.id_nova;
    const x = req.body.position.x;
    const y = req.body.position.y;
    const z = req.body.position.z;
    const pitch = req.body.position.pitch;
    const yaw = req.body.position.yaw;
    const roll = req.body.position.roll;

    const position = await db.db.create_position(id_nova,x,y,z,pitch,yaw,roll);
});

However, on the server-side, I am receiving an empty "body" for the request I sent and I receive the following error:

(node:23939) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'x' of undefined

I need help at this point. I appreciate any help and guidance.

Are you calling http.createServer somewhere? Where's that code? Are you able to exercise your server with Postman? — Richard Heap
– Richard Heap, Commented Sep 6, 2019 at 16:04
Hi @RichardHeap I have a nodeJs server and even when I try with PostMan, I see that the server somehow, has an empty "body". I simply have to make sure of the server side. — dramaticlook
– dramaticlook, Commented Sep 9, 2019 at 18:34
Does this answer your question? Flutter POST json request body is empty/null on server side — Karolina Hagegård
– Karolina Hagegård, Commented Sep 13, 2022 at 14:14

Kreem Allam · Accepted Answer · 2020-06-19 08:07:45Z

12

Sending Map<String,dynamic> with http.post won't send your data properly.

To solve this, change the content-type of the header to:

Map<String, String> customHeaders = {
...
"content-type": "application/json"
...
};

Then, you can use http.post as follows:

http.post(url, headers: customHeaders, body);

answered Jun 19, 2020 at 8:07

Kreem Allam

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Comments

Hardik Kumbhani · Accepted Answer · 2019-09-07 03:09:02Z

4

You have to jsonEncode before pushing into Post request Like

String bodyF = jsonEncode(body);

And i hope you will get your solution.

answered Sep 7, 2019 at 3:09

Hardik Kumbhani

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2 Comments

dramaticlook Over a year ago

Yes you are correct. After I do the suggested fix, I have an updated code. I now am sure that I have an issue about the server. Received body from PostMan is empty too.

Karolina Hagegård Over a year ago

Empty body on server side may be caused by a mis-match of type between sending and receiving, which may be caused by headers. Plz see this answer for clarification!: stackoverflow.com/a/73599552/14335655

sɐunıɔןɐqɐp · Accepted Answer · 2020-08-14 09:25:12Z

2

The solution I have found was simply to add Content-Length : x to your header, with x being the size of your json body.

edited Aug 14, 2020 at 9:25

sɐunıɔןɐqɐp

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answered Aug 14, 2020 at 8:35

Marvin

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