Dart: convert Map to JSON with all elements quoted

I'm serializing a form in Dart into JSON then posting it to a Spring MVC backend using Jackson to deserialize the JSON.

In dart, if I print out the JSON, I'm getting:

{firstName: piet, lastName: venter}

Jackson doesn't like the data in this format, it returns a status 400 and The request sent by the client was syntactically incorrect.

If I put quotes around all the fields, Jackson accepts the data and I get a response back.

{"firstName": "piet", "lastName": "venter"}

In dart I build a Map<String, String> data = {}; then loop through all form fields and do data.putIfAbsent(input.name, () => input.value);

Now when I call data.toString(), I get the unquoted JSON which I'm guessing is invalid JSON.

If I import 'dart:convert' show JSON; and try JSON.encode(data).toString(); I get the same unquoted JSON.

Manually appending double-quotes seems to work:

data.putIfAbsent("\"" + input.name + "\"", () => "\"" + input.value + "\"");

On the Java side there's no rocket science:

@Controller
@RequestMapping("/seller")
@JsonIgnoreProperties(ignoreUnknown = true)
public class SellerController {

    @ResponseBody
    @RequestMapping(value = "/create", method = RequestMethod.POST, headers = {"Content-Type=application/json"})
    public Seller createSeller(@RequestBody Seller sellerRequest){

So my question, is there a less hacky way in Dart to build quoted JSON (other than manually escaping quotes and adding quotes manually) that Jackson expects? Can Jackson be configured to allow unquoted JSON ?

Solution 1:

import 'dart:convert';
...
json.encode(data); // JSON.encode(data) in Dart 1.x

always resulted in quoted JSON for me.
You don't need to call toString()

Solution 2:

Simple way

import 'dart:convert';
Map<String, dynamic> jsonData = {"name":"vishwajit"};
print(JsonEncoder().convert(jsonData));

Solution 3:

If the data content dynamic, below is a function to help to send JSON data with Quoted send on the server. This function can be used just like you would with a convert a String in Dart.

Import the builtin convert library, which includes the jsonDecode() and jsonEncode() methods:

import 'dart:convert';   //Don't forget to import this

dynamic convertJson(dynamic param) {
  const JsonEncoder encoder = JsonEncoder();
  final dynamic object = encoder.convert(param);
  return object;
}

You would use/call it like

Future<dynamic> postAPICallWithQuoted(String url, Map param, BuildContext context) async {
  final String encodedData = convertJson(param);
  print("Calling parameters: $encodedData");
  var jsonResponse;
  try {
    final response =  await http.post(url,
        body: encodedData).timeout(const Duration(seconds: 60),onTimeout : () => throw TimeoutException('The connection has timed out, Please try again!'));
  } on SocketException {
    throw FetchDataException(getTranslated(context, "You are not connected to internet"));
  } on TimeoutException {
    print('Time out');
    throw TimeoutException(getTranslated(context, "The connection has timed out, Please try again"));
  }
  return jsonResponse;
}