How do I access and print the elements in my http Response; Flutter, Dart

I am Logging in to the website using this block of code and printing the status code as well as the response body in the console.

void sendLogin() async {

    var map = <String, dynamic>{
      "UserName": _usernameController.text,
      "Password": _passwordController.text,
    };

    var res = await http.post(
      Uri.parse("http://192.168.1.8:8080/HongLeong/LOGIN_REQUEST.do"),
      body: map,
    );
    
    print(res.statusCode);
    print(res.body);
  }

and this is what is being printed in the console

I/flutter ( 9739): null
I/flutter ( 9739): 200
I/flutter ( 9739): {"RESPONSE":{"BASEL_RESPONSE":{"UserDate":"0","UserTime":"0","module_config_1":"0","module_config_2":"0","ErrEntity":{"MessageID":"1110","Message":"Field Code is mandatory","last_req_id":"50029","table_id":"0","operation_id":"0"},"is_csv":"0","VersionName":"DYMA @ 6.1.24.0, ORG @ 2017.3.22.15.0.41, GRC @ 2017.3.22.15.0.55, LDC @ 2017.3.22.15.1.8, DYMA_XML @ 2017.3.22.15.0.30, NAS @ 2017.3.22.15.1.22 - Config: 0 - Node: OPRISK_DATACOLLECTOR","ExpiryDate":"31/01/2030","count_key":"0","id_Us":"0","is_popup":"0","tot_messages":"0","my_messages":"0","product":"0"},"RESPONSE_HEADER":{"NomeRichiesta":"LOGIN_REQUEST","ltimeStart":"23531871","ltimeStop":"23531884","ldate_null":"19900101","product":"1","server_name":"OPRISK_DATACOLLECTOR","cell_context_id":"538058","operation_key":"1000000","operation_sub_num":"-1"}}}

How do I access then print the ErrEntity with its contents from the response body

"ErrEntity":{"MessageID":"1110","Message":"Field Code is mandatory","last_req_id":"50029","table_id":"0","operation_id":"0"}

heres a better view of the response body in formatted Json

{
   "RESPONSE":{
      "BASEL_RESPONSE":{
         "UserDate":"0",
         "UserTime":"0",
         "module_config_1":"0",
         "module_config_2":"0",
         "ErrEntity":{
            "MessageID":"1110",
            "Message":"Field Code is mandatory",
            "last_req_id":"50029",
            "table_id":"0",
            "operation_id":"0"
         },
         "is_csv":"0",
         "VersionName":"DYMA @ 6.1.24.0, ORG @ 2017.3.22.15.0.41, GRC @ 2017.3.22.15.0.55, LDC @ 2017.3.22.15.1.8, DYMA_XML @ 2017.3.22.15.0.30, NAS @ 2017.3.22.15.1.22 - Config: 0 - Node: OPRISK_DATACOLLECTOR",
         "ExpiryDate":"31/01/2030",
         "count_key":"0",
         "id_Us":"0",
         "is_popup":"0",
         "tot_messages":"0",
         "my_messages":"0",
         "product":"0"
      },
      "RESPONSE_HEADER":{
         "NomeRichiesta":"LOGIN_REQUEST",
         "ltimeStart":"23531871",
         "ltimeStop":"23531884",
         "ldate_null":"19900101",
         "product":"1",
         "server_name":"OPRISK_DATACOLLECTOR",
         "cell_context_id":"538058",
         "operation_key":"1000000",
         "operation_sub_num":"-1"
      }
   }
}

Thanks for the help :)

Solution

You need to use the dart:convert library to convert the JSON response into a Map. Then you can access the key/value pairs as your would with a regular Map. You'll also have to add a cast (in my example at least) for the correct type using the as keyword. For example:

import 'dart:convert';

void main() {
final s = """
  {
   "RESPONSE":{
      "BASEL_RESPONSE":{
         "UserDate":"0",
         "UserTime":"0",
         "module_config_1":"0",
         "module_config_2":"0",
         "ErrEntity":{
            "MessageID":"1110",
            "Message":"Field Code is mandatory",
            "last_req_id":"50029",
            "table_id":"0",
            "operation_id":"0"
         },
         "is_csv":"0",
         "VersionName":"DYMA @ 6.1.24.0, ORG @ 2017.3.22.15.0.41, GRC @ 2017.3.22.15.0.55, LDC @ 2017.3.22.15.1.8, DYMA_XML @ 2017.3.22.15.0.30, NAS @ 2017.3.22.15.1.22 - Config: 0 - Node: OPRISK_DATACOLLECTOR",
         "ExpiryDate":"31/01/2030",
         "count_key":"0",
         "id_Us":"0",
         "is_popup":"0",
         "tot_messages":"0",
         "my_messages":"0",
         "product":"0"
      },
      "RESPONSE_HEADER":{
         "NomeRichiesta":"LOGIN_REQUEST",
         "ltimeStart":"23531871",
         "ltimeStop":"23531884",
         "ldate_null":"19900101",
         "product":"1",
         "server_name":"OPRISK_DATACOLLECTOR",
         "cell_context_id":"538058",
         "operation_key":"1000000",
         "operation_sub_num":"-1"
      }
   }
}
  """;
final data = jsonDecode(s);
print((data as Map)['RESPONSE']['BASEL_RESPONSE']['ErrEntity']);


}

Prints:

{MessageID: 1110, Message: Field Code is mandatory, last_req_id: 50029, table_id: 0, operation_id: 0}

In your case, you'll ned to use:

final data = jsonDecode(res.body);

to convert the data.

I do though recommend that you use a Class model instead. You can use quicktype.io to generate one for you automatically.

See: