Usage

const http = JsonHttpServiceImpl();

final myModel = await http.get<MyModel>('example.com', MyModel.fromJson);
final myResp = await http.post<MyResp>('example.com', MyResp.fromJson, body: JsonEncode(model.toJson()));

You can use body serializers:

final http = JsonHttpServiceImpl(defaultBodySerializer: jsonBodySerializer);

final myResp = http.post<MyResp>('example.com', MyResp.fromJson, body: myModel.toJson());

also you can pass serializer as a method argument to override default serializer (or to disable it at all)

final http = JsonHttpServiceImpl(defaultBodySerializer: jsonBodySerializer);

final myResp = http.post<MyResp>('example.com', MyResp.fromJson, body: JsonEncode(myModel.toJson()), bodySerializer: noOpBodySerializer);

This package was designed to work well with injectable package:

@module  
abstract class RegisterModule {  
  @Injectable(as: HttpService<JsonSource>)
  JsonHttpServiceImpl get httpService;  
}  

also you can specify default body serializer

@module  
abstract class RegisterModule {  
  @Injectable(as: HttpService<JsonSource>)
  JsonHttpServiceImpl get httpService => JsonHttpServiceImpl(defaultBodySerializer: jsonBodySerializer);  
}  

Also you can notice that injectable gives you an opprotunity to register HttpService with source type provided, so, you can have multiple http services for different responce types.

You can even extend it:

@named 
@Injectable(as: HttpService<JsonSource>)
class OpenWeatherHttpServiceImpl extends JsonHttpServiceImpl {

  @override
  FutureOr<AppHttpRequest> beforeHook(String url, HttpVerb verb, Object? body, Map<String, String>? headers, BodySerializer bodySerializer) async {
    final req = await super.beforeHook(url, verb, body, headers, bodySerializer);
    final uri = req.uri.replace(queryParameters: {...req.uri.queryParameters}
      ..putIfAbsent('appid', () => '********'));
      
    return AppHttpRequest(
      uri: uri,
      body: req.body,
      headers: req.headers
    );
  }
}

To support any responce formats you can extend HttpServiceBase class:

class JsonHttpServiceImpl extends HttpServiceBase<JsonSource> {
  @override
  List<Map<String, dynamic>> parseListResult(Response response) {
    return jsonDecode(response.body).cast<Map<String, dynamic>>();
  }

  @override
  Map<String, dynamic> parseResult(Response response) {
    return jsonDecode(response.body);
  }
}

Real life usage:

@Injectable(as: LocationService)
class LocationServiceImpl implements LocationService {
  static const _apiBase = "https://api.openweathermap.org/";
  static const _locationEndpoint = "geo/1.0/direct";
  final HttpService<JsonSource> _httpService;

  LocationServiceImpl(
      @Named.from(OpenWeatherHttpServiceImpl) this._httpService);

  @override
  Future<LocationDto> getLocationByCityName(String cityname) async {
    final url = "$_apiBase$_locationEndpoint?q=$cityname";
    final responce = await _httpService.getList<LocationResponce>(
        url, LocationResponce.fromJson);
    final locationResponce = responce.first;

    return LocationDto(
        longtitute: locationResponce.lon, latitude: locationResponce.lat);
  }
}