""" Provides an APIView class that is the base of all views in REST framework. """ from __future__ import unicode_literals import inspect import warnings from django.core.exceptions import PermissionDenied from django.db import models from django.http import Http404 from django.utils import six from django.utils.encoding import smart_text from django.utils.translation import ugettext_lazy as _ from django.views.decorators.csrf import csrf_exempt from rest_framework import exceptions, status from rest_framework.compat import HttpResponseBase, View, set_rollback from rest_framework.request import Request from rest_framework.response import Response from rest_framework.settings import api_settings from rest_framework.utils import formatting def get_view_name(view_cls, suffix=None): """ Given a view class, return a textual name to represent the view. This name is used in the browsable API, and in OPTIONS responses. This function is the default for the `VIEW_NAME_FUNCTION` setting. """ name = view_cls.__name__ name = formatting.remove_trailing_string(name, 'View') name = formatting.remove_trailing_string(name, 'ViewSet') name = formatting.camelcase_to_spaces(name) if suffix: name += ' ' + suffix return name def get_view_description(view_cls, html=False): """ Given a view class, return a textual description to represent the view. This name is used in the browsable API, and in OPTIONS responses. This function is the default for the `VIEW_DESCRIPTION_FUNCTION` setting. """ description = view_cls.__doc__ or '' description = formatting.dedent(smart_text(description)) if html: return formatting.markup_description(description) return description def exception_handler(exc, context): """ Returns the response that should be used for any given exception. By default we handle the REST framework `APIException`, and also Django's built-in `Http404` and `PermissionDenied` exceptions. Any unhandled exceptions may return `None`, which will cause a 500 error to be raised. """ if isinstance(exc, exceptions.APIException): headers = {} if getattr(exc, 'auth_header', None): headers['WWW-Authenticate'] = exc.auth_header if getattr(exc, 'wait', None): headers['Retry-After'] = '%d' % exc.wait if isinstance(exc.detail, (list, dict)): data = exc.detail else: data = {'detail': exc.detail} set_rollback() return Response(data, status=exc.status_code, headers=headers) elif isinstance(exc, Http404): msg = _('Not found.') data = {'detail': six.text_type(msg)} set_rollback() return Response(data, status=status.HTTP_404_NOT_FOUND) elif isinstance(exc, PermissionDenied): msg = _('Permission denied.') data = {'detail': six.text_type(msg)} set_rollback() return Response(data, status=status.HTTP_403_FORBIDDEN) # Note: Unhandled exceptions will raise a 500 error. return None 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 @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 cls.queryset._result_iter = force_evaluation # Django <= 1.5 view = super(APIView, cls).as_view(**initkwargs) view.cls = cls # 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): """ If request is not permitted, determine what kind of exception to raise. """ if not request.successful_authenticator: raise exceptions.NotAuthenticated() raise exceptions.PermissionDenied(detail=message) 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.__class__, getattr(self, 'suffix', None)) 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.__class__, 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 # 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) ) 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) ) def check_throttles(self, request): """ Check if request should be throttled. Raises an appropriate exception if the request is throttled. """ for throttle in self.get_throttles(): if not throttle.allow_request(request, self): self.throttled(request, throttle.wait()) 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) # Ensure that the incoming request is permitted self.perform_authentication(request) self.check_permissions(request) self.check_throttles(request) # 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 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() 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.settings.EXCEPTION_HANDLER if len(inspect.getargspec(exception_handler).args) == 1: warnings.warn( 'The `exception_handler(exc)` call signature is deprecated. ' 'Use `exception_handler(exc, context) instead.', DeprecationWarning ) response = exception_handler(exc) else: context = self.get_exception_handler_context() response = exception_handler(exc, context) if response is None: raise response.exception = True return response # 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)