[Django] DRF 구조 이해 #1 (APIView)

APIView는 DRF에서 사용하는 GenericAPIView, Viewset과 같이 편리하게 사용할 수 있는 api 라이브러리들의 기반이 되는 클래스이다.

 

 

참고:)

APIView 클래스 전체

class APIView(View):

    # The following policies may be set at either globally, or per-view.
    renderer_classes = api_settings.DEFAULT_RENDERER_CLASSES
    parser_classes = api_settings.DEFAULT_PARSER_CLASSES
    authentication_classes = api_settings.DEFAULT_AUTHENTICATION_CLASSES
    throttle_classes = api_settings.DEFAULT_THROTTLE_CLASSES
    permission_classes = api_settings.DEFAULT_PERMISSION_CLASSES
    content_negotiation_class = api_settings.DEFAULT_CONTENT_NEGOTIATION_CLASS
    metadata_class = api_settings.DEFAULT_METADATA_CLASS
    versioning_class = api_settings.DEFAULT_VERSIONING_CLASS

    # Allow dependency injection of other settings to make testing easier.
    settings = api_settings

    schema = DefaultSchema()

    @classmethod
    def as_view(cls, **initkwargs):
        """
        Store the original class on the view function.

        This allows us to discover information about the view when we do URL
        reverse lookups.  Used for breadcrumb generation.
        """
        if isinstance(getattr(cls, 'queryset', None), models.query.QuerySet):
            def force_evaluation():
                raise RuntimeError(
                    'Do not evaluate the `.queryset` attribute directly, '
                    'as the result will be cached and reused between requests. '
                    'Use `.all()` or call `.get_queryset()` instead.'
                )
            cls.queryset._fetch_all = force_evaluation

        view = super().as_view(**initkwargs)
        view.cls = cls
        view.initkwargs = initkwargs

        # Note: session based authentication is explicitly CSRF validated,
        # all other authentication is CSRF exempt.
        return csrf_exempt(view)

    @property
    def allowed_methods(self):
        """
        Wrap Django's private `_allowed_methods` interface in a public property.
        """
        return self._allowed_methods()

    @property
    def default_response_headers(self):
        headers = {
            'Allow': ', '.join(self.allowed_methods),
        }
        if len(self.renderer_classes) > 1:
            headers['Vary'] = 'Accept'
        return headers

    def http_method_not_allowed(self, request, *args, **kwargs):
        """
        If `request.method` does not correspond to a handler method,
        determine what kind of exception to raise.
        """
        raise exceptions.MethodNotAllowed(request.method)

    def permission_denied(self, request, message=None, code=None):
        """
        If request is not permitted, determine what kind of exception to raise.
        """
        if request.authenticators and not request.successful_authenticator:
            raise exceptions.NotAuthenticated()
        raise exceptions.PermissionDenied(detail=message, code=code)

    def throttled(self, request, wait):
        """
        If request is throttled, determine what kind of exception to raise.
        """
        raise exceptions.Throttled(wait)

    def get_authenticate_header(self, request):
        """
        If a request is unauthenticated, determine the WWW-Authenticate
        header to use for 401 responses, if any.
        """
        authenticators = self.get_authenticators()
        if authenticators:
            return authenticators[0].authenticate_header(request)

    def get_parser_context(self, http_request):
        """
        Returns a dict that is passed through to Parser.parse(),
        as the `parser_context` keyword argument.
        """
        # Note: Additionally `request` and `encoding` will also be added
        #       to the context by the Request object.
        return {
            'view': self,
            'args': getattr(self, 'args', ()),
            'kwargs': getattr(self, 'kwargs', {})
        }

    def get_renderer_context(self):
        """
        Returns a dict that is passed through to Renderer.render(),
        as the `renderer_context` keyword argument.
        """
        # Note: Additionally 'response' will also be added to the context,
        #       by the Response object.
        return {
            'view': self,
            'args': getattr(self, 'args', ()),
            'kwargs': getattr(self, 'kwargs', {}),
            'request': getattr(self, 'request', None)
        }

    def get_exception_handler_context(self):
        """
        Returns a dict that is passed through to EXCEPTION_HANDLER,
        as the `context` argument.
        """
        return {
            'view': self,
            'args': getattr(self, 'args', ()),
            'kwargs': getattr(self, 'kwargs', {}),
            'request': getattr(self, 'request', None)
        }

    def get_view_name(self):
        """
        Return the view name, as used in OPTIONS responses and in the
        browsable API.
        """
        func = self.settings.VIEW_NAME_FUNCTION
        return func(self)

    def get_view_description(self, html=False):
        """
        Return some descriptive text for the view, as used in OPTIONS responses
        and in the browsable API.
        """
        func = self.settings.VIEW_DESCRIPTION_FUNCTION
        return func(self, html)

    # API policy instantiation methods

    def get_format_suffix(self, **kwargs):
        """
        Determine if the request includes a '.json' style format suffix
        """
        if self.settings.FORMAT_SUFFIX_KWARG:
            return kwargs.get(self.settings.FORMAT_SUFFIX_KWARG)

    def get_renderers(self):
        """
        Instantiates and returns the list of renderers that this view can use.
        """
        return [renderer() for renderer in self.renderer_classes]

    def get_parsers(self):
        """
        Instantiates and returns the list of parsers that this view can use.
        """
        return [parser() for parser in self.parser_classes]

    def get_authenticators(self):
        """
        Instantiates and returns the list of authenticators that this view can use.
        """
        return [auth() for auth in self.authentication_classes]

    def get_permissions(self):
        """
        Instantiates and returns the list of permissions that this view requires.
        """
        return [permission() for permission in self.permission_classes]

    def get_throttles(self):
        """
        Instantiates and returns the list of throttles that this view uses.
        """
        return [throttle() for throttle in self.throttle_classes]

    def get_content_negotiator(self):
        """
        Instantiate and return the content negotiation class to use.
        """
        if not getattr(self, '_negotiator', None):
            self._negotiator = self.content_negotiation_class()
        return self._negotiator

    def get_exception_handler(self):
        """
        Returns the exception handler that this view uses.
        """
        return self.settings.EXCEPTION_HANDLER

    # API policy implementation methods

    def perform_content_negotiation(self, request, force=False):
        """
        Determine which renderer and media type to use render the response.
        """
        renderers = self.get_renderers()
        conneg = self.get_content_negotiator()

        try:
            return conneg.select_renderer(request, renderers, self.format_kwarg)
        except Exception:
            if force:
                return (renderers[0], renderers[0].media_type)
            raise

    def perform_authentication(self, request):
        """
        Perform authentication on the incoming request.

        Note that if you override this and simply 'pass', then authentication
        will instead be performed lazily, the first time either
        `request.user` or `request.auth` is accessed.
        """
        request.user

    def check_permissions(self, request):
        """
        Check if the request should be permitted.
        Raises an appropriate exception if the request is not permitted.
        """
        for permission in self.get_permissions():
            if not permission.has_permission(request, self):
                self.permission_denied(
                    request,
                    message=getattr(permission, 'message', None),
                    code=getattr(permission, 'code', None)
                )

    def check_object_permissions(self, request, obj):
        """
        Check if the request should be permitted for a given object.
        Raises an appropriate exception if the request is not permitted.
        """
        for permission in self.get_permissions():
            if not permission.has_object_permission(request, self, obj):
                self.permission_denied(
                    request,
                    message=getattr(permission, 'message', None),
                    code=getattr(permission, 'code', None)
                )

    def check_throttles(self, request):
        """
        Check if request should be throttled.
        Raises an appropriate exception if the request is throttled.
        """
        throttle_durations = []
        for throttle in self.get_throttles():
            if not throttle.allow_request(request, self):
                throttle_durations.append(throttle.wait())

        if throttle_durations:
            # Filter out `None` values which may happen in case of config / rate
            # changes, see #1438
            durations = [
                duration for duration in throttle_durations
                if duration is not None
            ]

            duration = max(durations, default=None)
            self.throttled(request, duration)

    def determine_version(self, request, *args, **kwargs):
        """
        If versioning is being used, then determine any API version for the
        incoming request. Returns a two-tuple of (version, versioning_scheme)
        """
        if self.versioning_class is None:
            return (None, None)
        scheme = self.versioning_class()
        return (scheme.determine_version(request, *args, **kwargs), scheme)

    # Dispatch methods

    def initialize_request(self, request, *args, **kwargs):
        """
        Returns the initial request object.
        """
        parser_context = self.get_parser_context(request)

        return Request(
            request,
            parsers=self.get_parsers(),
            authenticators=self.get_authenticators(),
            negotiator=self.get_content_negotiator(),
            parser_context=parser_context
        )

    def initial(self, request, *args, **kwargs):
        """
        Runs anything that needs to occur prior to calling the method handler.
        """
        self.format_kwarg = self.get_format_suffix(**kwargs)

        # Perform content negotiation and store the accepted info on the request
        neg = self.perform_content_negotiation(request)
        request.accepted_renderer, request.accepted_media_type = neg

        # Determine the API version, if versioning is in use.
        version, scheme = self.determine_version(request, *args, **kwargs)
        request.version, request.versioning_scheme = version, scheme

        # Ensure that the incoming request is permitted
        self.perform_authentication(request)
        self.check_permissions(request)
        self.check_throttles(request)

    def finalize_response(self, request, response, *args, **kwargs):
        """
        Returns the final response object.
        """
        # Make the error obvious if a proper response is not returned
        assert isinstance(response, HttpResponseBase), (
            'Expected a `Response`, `HttpResponse` or `HttpStreamingResponse` '
            'to be returned from the view, but received a `%s`'
            % type(response)
        )

        if isinstance(response, Response):
            if not getattr(request, 'accepted_renderer', None):
                neg = self.perform_content_negotiation(request, force=True)
                request.accepted_renderer, request.accepted_media_type = neg

            response.accepted_renderer = request.accepted_renderer
            response.accepted_media_type = request.accepted_media_type
            response.renderer_context = self.get_renderer_context()

        # Add new vary headers to the response instead of overwriting.
        vary_headers = self.headers.pop('Vary', None)
        if vary_headers is not None:
            patch_vary_headers(response, cc_delim_re.split(vary_headers))

        for key, value in self.headers.items():
            response[key] = value

        return response

    def handle_exception(self, exc):
        """
        Handle any exception that occurs, by returning an appropriate response,
        or re-raising the error.
        """
        if isinstance(exc, (exceptions.NotAuthenticated,
                            exceptions.AuthenticationFailed)):
            # WWW-Authenticate header for 401 responses, else coerce to 403
            auth_header = self.get_authenticate_header(self.request)

            if auth_header:
                exc.auth_header = auth_header
            else:
                exc.status_code = status.HTTP_403_FORBIDDEN

        exception_handler = self.get_exception_handler()

        context = self.get_exception_handler_context()
        response = exception_handler(exc, context)

        if response is None:
            self.raise_uncaught_exception(exc)

        response.exception = True
        return response

    def raise_uncaught_exception(self, exc):
        if settings.DEBUG:
            request = self.request
            renderer_format = getattr(request.accepted_renderer, 'format')
            use_plaintext_traceback = renderer_format not in ('html', 'api', 'admin')
            request.force_plaintext_errors(use_plaintext_traceback)
        raise exc

    # Note: Views are made CSRF exempt from within `as_view` as to prevent
    # accidental removal of this exemption in cases where `dispatch` needs to
    # be overridden.
    def dispatch(self, request, *args, **kwargs):
        """
        `.dispatch()` is pretty much the same as Django's regular dispatch,
        but with extra hooks for startup, finalize, and exception handling.
        """
        self.args = args
        self.kwargs = kwargs
        request = self.initialize_request(request, *args, **kwargs)
        self.request = request
        self.headers = self.default_response_headers  # deprecate?

        try:
            self.initial(request, *args, **kwargs)

            # Get the appropriate handler method
            if request.method.lower() in self.http_method_names:
                handler = getattr(self, request.method.lower(),
                                  self.http_method_not_allowed)
            else:
                handler = self.http_method_not_allowed

            response = handler(request, *args, **kwargs)

        except Exception as exc:
            response = self.handle_exception(exc)

        self.response = self.finalize_response(request, response, *args, **kwargs)
        return self.response

    def options(self, request, *args, **kwargs):
        """
        Handler method for HTTP 'OPTIONS' request.
        """
        if self.metadata_class is None:
            return self.http_method_not_allowed(request, *args, **kwargs)
        data = self.metadata_class().determine_metadata(request, self)
        return Response(data, status=status.HTTP_200_OK)

 

---

APIView에서 사용자 정의 오버라이딩이 필요한 필드 및 메서드를 알아보자

 

authentication_classes

기본 인증 클래스는 django에서 전역으로 설정할 수 있다.

REST_FRAMEWORK = {
    'DEFAULT_AUTHENTICATION_CLASSES': (
        'auth.authenticate.SafeJWTAuthentication',
    ),
}

 

API 마다 서로 다른 인증 클래스를 사용하기 위해서는 authentication_classes 필드의 오버라이딩이 필요하다.

# ex.
## 커스텀 인증 클래스 import
from auth.authenticate import SafeJWTAuthentication

class ApiAuthMixin:
    authentication_classes = SafeJWTAuthentication

 

---

permission_classes

기본 인가 클래스도 django에서 전역으로 설정할 수 있다.

REST_FRAMEWORK = {
    'DEFAULT_PERMISSION_CLASSES': (
        'rest_framework.permissions.IsAuthenticated',
    ),
    'DEFAULT_AUTHENTICATION_CLASSES': (
        'auth.authenticate.SafeJWTAuthentication',
    ),
}

 

API 마다 서로 다른 인증 클래스를 사용하기 위해서는 permission_classes 필드의 오버라이딩이 필요하다.

# ex.
## rest_framework 기본 내장 permission_class import
from rest_framework.permissions import IsAuthenticatedOrReadOnly

class ApiAuthMixin:
    permission_classes = IsAuthenticatedOrReadOnly

 

 

IsAuthenticatedOrReadOnly 클래스 구조

SAFE_METHODS = ('GET', 'HEAD', 'OPTIONS')

class IsAuthenticatedOrReadOnly(BasePermission):
    """
    The request is authenticated as a user, or is a read-only request.
    """

    def has_permission(self, request, view):
        return bool(
            request.method in SAFE_METHODS or
            request.user and
            request.user.is_authenticated
        )

GET, HEAD, OPTIONS 메소드 외의 PUT, POST, DELETE 등의 메서드는

user가 인증되어야 사용할 수 있다.

 

---

throttle_classes

기본 throttling 정책은 

DEFAULT_THROTTLE_CLASSES와 DEFAULT_THROTTLE_RATES 설정을 사용하여 django 전역으로 설정할 수 있다.

throttle 기간으로 second, minute, hour, day가 포함 될 수 있다.

REST_FRAMEWORK = {
    'DEFAULT_THROTTLE_CLASSES': (
        'rest_framework.throttling.AnonRateThrottle',
    ),
    'DEFAULT_THROTTLE_RATES': {
        'anon': '100/day',
    }
}

 

AnonRateThrottle

익명 사용자(외부인)의 api를 호출횟수를 조절하는 클래스이다. 
위 코드에서는 하루에 100번으로 설정했다.

 

from rest_framework.views import APIView
from rest_framework.throttling import AnonRateThrottle
from rest_framework.response import Response

class ListView(APIView):
    throttle_classes = AnonRateThrottle

    def get(self, request, format=None):
        content = {'message': 'GET request'}
        return Response(content)

ListView API의 스로틀링 설정을 해주었다.

이제 익명 사용자들은 해당 API를 하루에 100번밖에 호출하지 못한다.

 

 

def handle_exception(self, exc)

코드 보기

def handle_exception(self, exc):
        """
        Handle any exception that occurs, by returning an appropriate response,
        or re-raising the error.
        """
        if isinstance(exc, (exceptions.NotAuthenticated,
                            exceptions.AuthenticationFailed)):
            # WWW-Authenticate header for 401 responses, else coerce to 403
            auth_header = self.get_authenticate_header(self.request)

            if auth_header:
                exc.auth_header = auth_header
            else:
                exc.status_code = status.HTTP_403_FORBIDDEN

        exception_handler = self.get_exception_handler()

        context = self.get_exception_handler_context()
        response = exception_handler(exc, context)

        if response is None:
            self.raise_uncaught_exception(exc)

        response.exception = True
        return response

핸들러 메서드에서 throw된 모든 예외는 이 메서드로 전달되어 Response인스턴스를 반환하거나 예외를 다시 발생시킨다.

API가 반환하는 오류 응답을 커스텀 해야 하는 경우 이 메서드를 오버라이딩 할 수 있다.

 

 

나머지 모든 필드 및 메서드는 일반적으로 오버라이딩 할 필요가 없다.

---

Class상속을 사용한 APIView

예제

from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework import authentication, permissions
from django.contrib.auth.models import User

class ListUsers(APIView):
    authentication_classes = [authentication.TokenAuthentication]
    permission_classes = [permissions.IsAdminUser]

    def get(self, request, format=None):
        usernames = [user.username for user in User.objects.all()]
        return Response(usernames)

from django.urls import path, include
from .views import ListUsers

urlpatterns = [
    path('users', ListUsers.as_view(), name="user-list"),
]

 

위 코드에서 get 메서드가 실행되는 순서

1. 클라이언트에서 /users 엔드포인트로 GET 요청을 보낸다.
2. ListUsers클래스의 as_view() 메서드가 호출되고, 클래스의 인스턴스가 생성된다.
3. 생성된 객체의 dispatch() 메서드를 호출한다.
   
   • dispatch()에서는 HTTP 메서드가 어느것인지 판단한다.
   • GET 요청이라면 get으로 연결된 메서드가 호출된다.
   • 만약 메서드가 없다면 exceptions.MethodNotAllowed 에러가 호출된다.

 

 

아래는 dispatch 메서드이다.

    # Note: Views are made CSRF exempt from within `as_view` as to prevent
    # accidental removal of this exemption in cases where `dispatch` needs to
    # be overridden.
    def dispatch(self, request, *args, **kwargs):
        """
        `.dispatch()` is pretty much the same as Django's regular dispatch,
        but with extra hooks for startup, finalize, and exception handling.
        """
        self.args = args
        self.kwargs = kwargs
        request = self.initialize_request(request, *args, **kwargs)
        self.request = request
        self.headers = self.default_response_headers  # deprecate?

        try:
            self.initial(request, *args, **kwargs)

            # Get the appropriate handler method
            if request.method.lower() in self.http_method_names:
                handler = getattr(self, request.method.lower(),
                                  self.http_method_not_allowed)
            else:
                handler = self.http_method_not_allowed

            response = handler(request, *args, **kwargs)

        except Exception as exc:
            response = self.handle_exception(exc)

        self.response = self.finalize_response(request, response, *args, **kwargs)
        return self.response

handler는 GET을 가질 것이다.

따라서 response = get(request, *args, **kwargs)가 될 것이고 self.response가 반환되면 우리가 원하는 get 메서드가 실행되게 된다.