Bad state: Cannot set the body fields of a Request with content-type "application/json"

Question

Map<String,String> headers = {'Content-Type':'application/json','authorization':'Basic c3R1ZHlkb3RlOnN0dWR5ZG90ZTEyMw=='};

var response = await post(Urls.getToken,
        headers: headers,
        body: {"grant_type":"password","username":"******","password":"*****","scope":"offline_access"},
      );

When I execute this I am unable to recieve data and the error thrown is

try - `body: json.encode({"grant_type":"password","username":"******","password":"*****","scope":"offline_access"}),` — anmol.majhail, Feb 24 '19 at 07:35
Watch out that you have post also your `username/password` even if they could be of a test user, this is not a good practice... — shadowsheep, Mar 28 '19 at 16:33

score 218 · Accepted Answer · edited Sep 21 '20 at 08:49

218

You need to wrap the body in jsonEncode.

import 'package:http/http.dart' as http;
import 'dart:convert';

Map<String,String> headers = {'Content-Type':'application/json','authorization':'Basic c3R1ZHlkb3RlOnN0dWR5ZG90ZTEyMw=='};
final msg = jsonEncode({"grant_type":"password","username":"******","password":"*****","scope":"offline_access"});

var response = await post(Urls.getToken,
               headers: headers,
               body: msg,
            );

edited Sep 21 '20 at 08:49

Mubashar Abbas

5,536
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answered Mar 20 '19 at 19:29

Monza

2,304
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3

Thanks! At first I didn't see the difference between your answer and the question, but now I see that the key is to wrap the map literal in a jsonEncode – Philip Jan 03 '20 at 03:57

Rohit Nishad · Answer 2 · 2022-01-19T14:43:51.190

Use jsonEncode to wrap your body object.

import 'package:http/http.dart' as http;
import 'dart:convert';

var headers = {
    'Content-Type':'application/json',
    'authorization':'Basic c3R1ZHlkb3RlOnN0dWR5ZG90ZTEyMw=='
};

final body = {
    'username':'foo',
    'password':'pass123'
}

var response = await post(
    Urls.getToken,
    headers: headers,
    body: jsonEncode(body), // use jsonEncode()
);

Why jsonEncode?

body: It can be a HTML, JSON or XML, etc. This mean is we need to send/recive data in that perticular format. You can set this in content-type header its default value is text/plain.

As you set the content-type header to JSON you must have to pass a "valid" JSON as the body. But you are passing Map<String, String> as the body, which obviously throws an error.

So to solve this issue you need to change (or encode) your Map<String, String> data to JSON data.

Best way to do this is to use jsonEncode function.

score 3 · Answer 3 · edited Aug 14 '20 at 10:48

had similar issue with http library...changed for dio 2.1.0 and the problem with headers is gone.

jsonEncode(body) didn't do the trick, because the docs say:

Sends an HTTP POST request with the given headers and body to the given URL, which can be a [Uri] or a [String].

[body] sets the body of the request. It can be a [String], a [List] or a [Map<String, String>]. If it's a String, it's encoded using [encoding] and used as the body of the request. The content-type of the request will default to "text/plain".

If [body] is a List, it's used as a list of bytes for the body of the request.

If [body] is a Map, it's encoded as form fields using [encoding]. The content-type of the request will be set to "application/x-www-form-urlencoded"; this cannot be overridden. [encoding] defaults to [utf8].

For more fine-grained control over the request, use [send] instead.

Future<Response> post(url, {Map<String, String> headers, body, Encoding encoding});

score 3 · Answer 4 · answered Nov 26 '20 at 11:20

Map<String,String> header = {'Content-Type':'application/json-patch+json','accept':'application/json'};
    final msg = jsonEncode({"username":"$emailorPhoneN","password":"$passwrod"});

    try {
      var response = await http.post(UrlConstants.loginUrl, headers: header, body: msg,
      ).timeout(Duration(seconds: httpDuration));
      var convert = json.decode(response.body);
      print('**********Data from server $convert');

      if (convert == null) {
        return null;
      } else {
        String token = convert['token'];

        if (token != null) {
          SignUpModel signUpModel = SignUpModel.fromJson(convert);
          return signUpModel;
        } else {
          //*** GET Error message from the API provider.....
          SignUpModel signUpModel = SignUpModel.fromJson(convert);
          return signUpModel;
        }
      }

score 1 · Answer 5 · edited Sep 30 '21 at 15:00

1

For me, jsonencode(body) did not work. This is worked for me instead:

body = json.encode(body);
http.post(Uri.parse(uri), headers: header, body: body);

edited Sep 30 '21 at 15:00

ouflak

2,458
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answered Sep 30 '21 at 14:27

seyhmus gumus

76
4

Bad state: Cannot set the body fields of a Request with content-type "application/json"

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