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

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

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

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,
            );

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.

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]. 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});

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;
        }
      }

the exception is caused by incorrectly setting bodyFields. See: bodyFields

bodyFields is for form-encoded data, not JSON. For an example of how to POST JSON see: Write HTTP servers

So you're trying to pass a Map as the body. In this case it would assume that you are actually doing a application/x-www-form-urlencoded. What you need to do is encode the Map as a string and then do what you're doing.

Example

  Future<http.Response> patchAPICall(
      String url, Map param, String token) async {
    var responseJson;
    try {
      final response = await http.patch(Uri.parse(url),
          body: jsonEncode(param),
          headers: {
            "Authorization": token,
            "Content-Type": "application/json"
          }).timeout(const Duration(seconds: 60),
          onTimeout: () => throw TimeoutException(
              'The connection has timed out, Please try again!'));
      responseJson = response;
    } on SocketException {
      throw FetchDataException("You are not connected to internet");
    } on TimeoutException {
      print('Time out');
      throw TimeoutException("The connection has timed out, Please try again");
    }
    return responseJson;
  }

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);