Flutter response non-json structure form server getting html code - dart

Question

when i connect to server for checking username and password like with this structure
{
"Username":"1",
"Password":"1"
}
i get 0 or 1, without any json format, first letters of username and password are Capital letters, Username,Password,
now i want to get this response with flutter and post http verb
UserInformation class
class UserInformation {
String Username;
String Password;
UserInformation(this.Username, this.Password);
Map<String, dynamic> toJson() {
final Map<String, dynamic> json = new Map<String, dynamic>();
json['Username'] = this.Username;
json['Password'] = this.Password;
return json;
}
}
LoginRepository class:
class LoginRepository {
Future<int> authenticate(
{#required String username, #required String password}) async {
UserInformation userInformation = UserInformation(username, password);
/*this line print {Username: 1, Password: 1}*/
print(userInformation.toJson().toString());
final response = await http.post(
Constants.loginApi, body: userInformation.toJson());
final responseString = jsonDecode(response.body);
if (response.statusCode == 200) {
return responseString;
} else {
throw Exception('fail to get response');
}
}
}
and then this output is response from server:
[ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: FormatException: Unexpected character (at character 1)
<?xml version="1.0" encoding="utf-8"?>

Answer 1

First: Check for statusCode before accessing response.body. If the call fails, response.body will be an empty String and jsonDecode will fail.
Second: Since you don't get a json formated answer, there is no need to call jsonDecode with the response. final int responseInt = response.body should be enough (maybe you will need int.parse(response.body); needs to be tested.