Django中CBV和Restful API中的APIView源码分析

Posted 2021-11-07 5j421

Django中CBV和Restful API中的APIView源码分析

 

python的Django框架的视图处理可以用FBV, 也可以采用CBV。首先定义一个CBV视图：

from django.views import View
from django.http import JsonResponse
class Book(View):
    def get(self, request):
        ll = [{‘key‘:value}]
        return JsonResponse(ll, safe=false, json_dumps_params={‘ensure‘:false})
    def post(self, request):
        return HttpResponse(‘ok‘)
    

#前台路由的配置
 url(r‘^books/‘, views.Books.as_view()),

 

首先，一个CBV（class base views 类方式完成视图响应）视图定义时类方法的名称必须有请求名，为什么要这样定义？

首先，由路由的分发可以看出，

从继承的父类View开始：

views.Books.as_view() ，其实是调用了我们自定义视图模型类Book的as_view函数，可是明明自己未定义该函数，那么需要去父类观察。

 

源码：--------------分析以注释说明-----------------------

class View(object):
    """
    Intentionally simple parent class for all views. Only implements
    dispatch-by-method and simple sanity checking.
    """
?
    http_method_names = [‘get‘, ‘post‘, ‘put‘, ‘patch‘, ‘delete‘, ‘head‘, ‘options‘, ‘trace‘]
?
    def __init__(self, **kwargs):
        """
        Constructor. Called in the URLconf; can contain helpful extra
        keyword arguments, and other things.
        """
        # Go through keyword arguments, and either save their values to our
        # instance, or raise an error.
        for key, value in six.iteritems(kwargs):
            setattr(self, key, value)
?
    @classonlymethod
    def as_view(cls, **initkwargs):
        """
        Main entry point for a request-response process.
        """
        for key in initkwargs:
            if key in cls.http_method_names:
                raise TypeError("You tried to pass in the %s method name as a "
                                "keyword argument to %s(). Don‘t do that."
                                % (key, cls.__name__))
            if not hasattr(cls, key):
                raise TypeError("%s() received an invalid keyword %r. as_view "
                                "only accepts arguments that are already "
                                "attributes of the class." % (cls.__name__, key))
?
        def view(request, *args, **kwargs):
            self = cls(**initkwargs)
            if hasattr(self, ‘get‘) and not hasattr(self, ‘head‘):
                self.head = self.get
            self.request = request
            self.args = args
            self.kwargs = kwargs
            return self.dispatch(request, *args, **kwargs)
        view.view_class = cls
        view.view_initkwargs = initkwargs
?
        # take name and docstring from class
        update_wrapper(view, cls, updated=())
?
        # and possible attributes set by decorators
        # like csrf_exempt from dispatch
        update_wrapper(view, cls.dispatch, assigned=())
        return view
?
    def dispatch(self, request, *args, **kwargs):
        # Try to dispatch to the right method; if a method doesn‘t exist,
        # defer to the error handler. Also defer to the error handler if the
        # request method isn‘t on the approved list.
        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
        return handler(request, *args, **kwargs)
?
    def http_method_not_allowed(self, request, *args, **kwargs):
        logger.warning(
            ‘Method Not Allowed (%s): %s‘, request.method, request.path,
            extra={‘status_code‘: 405, ‘request‘: request}
        )
        return http.HttpResponseNotAllowed(self._allowed_methods())
?
    def options(self, request, *args, **kwargs):
        """
        Handles responding to requests for the OPTIONS HTTP verb.
        """
        response = http.HttpResponse()
        response[‘Allow‘] = ‘, ‘.join(self._allowed_methods())
        response[‘Content-Length‘] = ‘0‘
        return response
?
    def _allowed_methods(self):
        return [m.upper() for m in self.http_method_names if hasattr(self, m)]
?

 

 

Restful API中的APIView

在Django中的RestfulAPI 的CBV定义

from rest_framework.views import APIView
class Books(APIView):
    def get(self, request):
        # 获取所有的图书：
        books = Book.objects.all()
        # print(books)
        ll = []
        for book in books:
            # print(book.id)
            # print(book.name)
            # print(book.author)
            dic = {
                "id": book.id,
                "name": book.name,
                "author": book.author
            }
            ll.append(dic)
            return render(request, ‘show_books.html‘, locals())
        # return JsonResponse(ll, safe=False, json_dumps_params={‘ensure_ascii‘: False}
            # 增加图书
    def post(self, request):
        id = request.data[‘id‘]
        name = request.data[‘name‘]
        author = request.data[‘author‘]
        print(id, name, author)
        Book.objects.create(id=id, name=name, author=author)
        return redirect(‘/books/‘)
?
 # 路由分发
 url(r‘^books/‘, views.Books.as_view()),

定义方式和Django继承的父类不同，但是路由分发相同

那么我们需要看继承的父类APIView如何处理

源码：

?

 

Request源码

class Request(object):
    """
    Wrapper allowing to enhance a standard `HttpRequest` instance.
?
    Kwargs:
        - request(HttpRequest). The original request instance.
        - parsers_classes(list/tuple). The parsers to use for parsing the
          request content.
        - authentication_classes(list/tuple). The authentications used to try
          authenticating the request‘s user.
    """
?
    def __init__(self, request, parsers=None, authenticators=None,
                 negotiator=None, parser_context=None):
        assert isinstance(request, HttpRequest), (
            ‘The `request` argument must be an instance of ‘
            ‘`django.http.HttpRequest`, not `{}.{}`.‘
            .format(request.__class__.__module__, request.__class__.__name__)
        )
?
        self._request = request
        self.parsers = parsers or ()
        self.authenticators = authenticators or ()
        self.negotiator = negotiator or self._default_negotiator()
        self.parser_context = parser_context
        self._data = Empty
        self._files = Empty
        self._full_data = Empty
        self._content_type = Empty
        self._stream = Empty
?
        if self.parser_context is None:
            self.parser_context = {}
        self.parser_context[‘request‘] = self
        self.parser_context[‘encoding‘] = request.encoding or settings.DEFAULT_CHARSET
?
        force_user = getattr(request, ‘_force_auth_user‘, None)
        force_token = getattr(request, ‘_force_auth_token‘, None)
        if force_user is not None or force_token is not None:
            forced_auth = ForcedAuthentication(force_user, force_token)
            self.authenticators = (forced_auth,)
?
    def _default_negotiator(self):
        return api_settings.DEFAULT_CONTENT_NEGOTIATION_CLASS()
?
    @property
    def content_type(self):
        meta = self._request.META
        return meta.get(‘CONTENT_TYPE‘, meta.get(‘HTTP_CONTENT_TYPE‘, ‘‘))
?
    @property
    def stream(self):
        """
        Returns an object that may be used to stream the request content.
        """
        if not _hasattr(self, ‘_stream‘):
            self._load_stream()
        return self._stream
?
    @property
    def query_params(self):
        """
        More semantically correct name for request.GET.
        """
        return self._request.GET
?
    @property
    def data(self):
        if not _hasattr(self, ‘_full_data‘):
            self._load_data_and_files()
        return self._full_data
?
    @property
    def user(self):
        """
        Returns the user associated with the current request, as authenticated
        by the authentication classes provided to the request.
        """
        if not hasattr(self, ‘_user‘):
            with wrap_attributeerrors():
                self._authenticate()
        return self._user
?
    @user.setter
    def user(self, value):
        """
        Sets the user on the current request. This is necessary to maintain
        compatibility with django.contrib.auth where the user property is
        set in the login and logout functions.
?
        Note that we also set the user on Django‘s underlying `HttpRequest`
        instance, ensuring that it is available to any middleware in the stack.
        """
        self._user = value
        self._request.user = value
?
    @property
    def auth(self):
        """
        Returns any non-user authentication information associated with the
        request, such as an authentication token.
        """
        if not hasattr(self, ‘_auth‘):
            with wrap_attributeerrors():
                self._authenticate()
        return self._auth
?
    @auth.setter
    def auth(self, value):
        """
        Sets any non-user authentication information associated with the
        request, such as an authentication token.
        """
        self._auth = value
        self._request.auth = value
?
    @property
    def successful_authenticator(self):
        """
        Return the instance of the authentication instance class that was used
        to authenticate the request, or `None`.
        """
        if not hasattr(self, ‘_authenticator‘):
            with wrap_attributeerrors():
                self._authenticate()
        return self._authenticator
?
    def _load_data_and_files(self):
        """
        Parses the request content into `self.data`.
        """
        if not _hasattr(self, ‘_data‘):
            self._data, self._files = self._parse()
            if self._files:
                self._full_data = self._data.copy()
                self._full_data.update(self._files)
            else:
                self._full_data = self._data
?
            # if a form media type, copy data & files refs to the underlying
            # http request so that closable objects are handled appropriately.
            if is_form_media_type(self.content_type):
                self._request._post = self.POST
                self._request._files = self.FILES
?
    def _load_stream(self):
        """
        Return the content body of the request, as a stream.
        """
        meta = self._request.META
        try:
            content_length = int(
                meta.get(‘CONTENT_LENGTH‘, meta.get(‘HTTP_CONTENT_LENGTH‘, 0))
            )
        except (ValueError, TypeError):
            content_length = 0
?
        if content_length == 0:
            self._stream = None
        elif not self._request._read_started:
            self._stream = self._request
        else:
            self._stream = io.BytesIO(self.body)
?
    def _supports_form_parsing(self):
        """
        Return True if this requests supports parsing form data.
        """
        form_media = (
            ‘application/x-www-form-urlencoded‘,
            ‘multipart/form-data‘
        )
        return any([parser.media_type in form_media for parser in self.parsers])
?
    def _parse(self):
        """
        Parse the request content, returning a two-tuple of (data, files)
?
        May raise an `UnsupportedMediaType`, or `ParseError` exception.
        """
        media_type = self.content_type
        try:
            stream = self.stream
        except RawPostDataException:
            if not hasattr(self._request, ‘_post‘):
                raise
            # If request.POST has been accessed in middleware, and a method=‘POST‘
            # request was made with ‘multipart/form-data‘, then the request stream
            # will already have been exhausted.
            if self._supports_form_parsing():
                return (self._request.POST, self._request.FILES)
            stream = None
?
        if stream is None or media_type is None:
            if media_type and is_form_media_type(media_type):
                empty_data = QueryDict(‘‘, encoding=self._request._encoding)
            else:
                empty_data = {}
            empty_files = MultiValueDict()
            return (empty_data, empty_files)
?
        parser = self.negotiator.select_parser(self, self.parsers)
?
        if not parser:
            raise exceptions.UnsupportedMediaType(media_type)
?
        try:
            parsed = parser.parse(stream, media_type, self.parser_context)
        except Exception:
            # If we get an exception during parsing, fill in empty data and
            # re-raise.  Ensures we don‘t simply repeat the error when
            # attempting to render the browsable renderer response, or when
            # logging the request or similar.
            self._data = QueryDict(‘‘, encoding=self._request._encoding)
            self._files = MultiValueDict()
            self._full_data = self._data
            raise
?
        # Parser classes may return the raw data, or a
        # DataAndFiles object.  Unpack the result as required.
        try:
            return (parsed.data, parsed.files)
        except AttributeError:
            empty_files = MultiValueDict()
            return (parsed, empty_files)
?
    def _authenticate(self):
        """
        Attempt to authenticate the request using each authentication instance
        in turn.
        """
        for authenticator in self.authenticators:
            try:
                user_auth_tuple = authenticator.authenticate(self)
            except exceptions.APIException:
                self._not_authenticated()
                raise
?
            if user_auth_tuple is not None:
                self._authenticator = authenticator
                self.user, self.auth = user_auth_tuple
                return
?
        self._not_authenticated()
?
    def _not_authenticated(self):
        """
        Set authenticator, user & authtoken representing an unauthenticated request.
?
        Defaults are None, AnonymousUser & None.
        """
        self._authenticator = None
?
        if api_settings.UNAUTHENTICATED_USER:
            self.user = api_settings.UNAUTHENTICATED_USER()
        else:
            self.user = None
?
        if api_settings.UNAUTHENTICATED_TOKEN:
            self.auth = api_settings.UNAUTHENTICATED_TOKEN()
        else:
            self.auth = None
?
    def __getattr__(self, attr):
        """
        If an attribute does not exist on this instance, then we also attempt
        to proxy it to the underlying HttpRequest object.
        """
        try:
            return getattr(self._request, attr)
        except AttributeError:
            return self.__getattribute__(attr)
?
    @property
    def DATA(self):
        raise NotImplementedError(
            ‘`request.DATA` has been deprecated in favor of `request.data` ‘
            ‘since version 3.0, and has been fully removed as of version 3.2.‘
        )
?
    @property
    def POST(self):
        # Ensure that request.POST uses our request parsing.
        if not _hasattr(self, ‘_data‘):
            self._load_data_and_files()
        if is_form_media_type(self.content_type):
            return self._data
        return QueryDict(‘‘, encoding=self._request._encoding)
?
    @property
    def FILES(self):
        # Leave this one alone for backwards compat with Django‘s request.FILES
        # Different from the other two cases, which are not valid property
        # names on the WSGIRequest class.
        if not _hasattr(self, ‘_files‘):
            self._load_data_and_files()
        return self._files
?
    @property
    def QUERY_PARAMS(self):
        raise NotImplementedError(
            ‘`request.QUERY_PARAMS` has been deprecated in favor of `request.query_params` ‘
            ‘since version 3.0, and has been fully removed as of version 3.2.‘
        )
?
    def force_plaintext_errors(self, value):
        # Hack to allow our exception handler to force choice of
        # plaintext or html error responses.
        self._request.is_ajax = lambda: value
?

 

 

class Request(object):
    """
    Wrapper allowing to enhance a standard `HttpRequest` instance.

    Kwargs:
        - request(HttpRequest). The original request instance.
        - parsers_classes(list/tuple). The parsers to use for parsing the
          request content.
        - authentication_classes(list/tuple). The authentications used to try
          authenticating the request‘s user.
    """

    def __init__(self, request, parsers=None, authenticators=None,
negotiator=None, parser_context=None):
        assert isinstance(request, HttpRequest), (
            ‘The `request` argument must be an instance of ‘
            ‘`django.http.HttpRequest`, not `{}.{}`.‘
.format(request.__class__.__module__, request.__class__.__name__)
        )

        self._request = request
        self.parsers = parsers or ()
        self.authenticators = authenticators or ()
        self.negotiator = negotiator or self._default_negotiator()
        self.parser_context = parser_context
        self._data = Empty
        self._files = Empty
        self._full_data = Empty
        self._content_type = Empty
        self._stream = Empty

        if self.parser_context is None:
            self.parser_context = {}
        self.parser_context[‘request‘] = self
        self.parser_context[‘encoding‘] = request.encoding or settings.DEFAULT_CHARSET

        force_user = getattr(request, ‘_force_auth_user‘, None)
        force_token = getattr(request, ‘_force_auth_token‘, None)
        if force_user is not None or force_token is not None:
            forced_auth = ForcedAuthentication(force_user, force_token)
            self.authenticators = (forced_auth,)

    def _default_negotiator(self):
        return api_settings.DEFAULT_CONTENT_NEGOTIATION_CLASS()

    @property
def content_type(self):
        meta = self._request.META
        return meta.get(‘CONTENT_TYPE‘, meta.get(‘HTTP_CONTENT_TYPE‘, ‘‘))

    @property
def stream(self):
        """
        Returns an object that may be used to stream the request content.
        """
        if not _hasattr(self, ‘_stream‘):
            self._load_stream()
        return self._stream

    @property
def query_params(self):
        """
        More semantically correct name for request.GET.
        """
        return self._request.GET

    @property
def data(self):
        if not _hasattr(self, ‘_full_data‘):
            self._load_data_and_files()
        return self._full_data

    @property
def user(self):
        """
        Returns the user associated with the current request, as authenticated
        by the authentication classes provided to the request.
        """
        if not hasattr(self, ‘_user‘):
            with wrap_attributeerrors():
                self._authenticate()
        return self._user

    @user.setter
def user(self, value):
        """
        Sets the user on the current request. This is necessary to maintain
        compatibility with django.contrib.auth where the user property is
        set in the login and logout functions.

        Note that we also set the user on Django‘s underlying `HttpRequest`
        instance, ensuring that it is available to any middleware in the stack.
        """
        self._user = value
        self._request.user = value

    @property
def auth(self):
        """
        Returns any non-user authentication information associated with the
        request, such as an authentication token.
        """
        if not hasattr(self, ‘_auth‘):
            with wrap_attributeerrors():
                self._authenticate()
        return self._auth

    @auth.setter
def auth(self, value):
        """
        Sets any non-user authentication information associated with the
        request, such as an authentication token.
        """
        self._auth = value
        self._request.auth = value

    @property
def successful_authenticator(self):
        """
        Return the instance of the authentication instance class that was used
        to authenticate the request, or `None`.
        """
        if not hasattr(self, ‘_authenticator‘):
            with wrap_attributeerrors():
                self._authenticate()
        return self._authenticator

    def _load_data_and_files(self):
        """
        Parses the request content into `self.data`.
        """
        if not _hasattr(self, ‘_data‘):
            self._data, self._files = self._parse()
            if self._files:
                self._full_data = self._data.copy()
                self._full_data.update(self._files)
            else:
                self._full_data = self._data

            # if a form media type, copy data & files refs to the underlying
            # http request so that closable objects are handled appropriately.
if is_form_media_type(self.content_type):
                self._request._post = self.POST
                self._request._files = self.FILES

    def _load_stream(self):
        """
        Return the content body of the request, as a stream.
        """
        meta = self._request.META
        try:
            content_length = int(
                meta.get(‘CONTENT_LENGTH‘, meta.get(‘HTTP_CONTENT_LENGTH‘, 0))
            )
        except (ValueError, TypeError):
            content_length = 0

if content_length == 0:
            self._stream = None
        elif not self._request._read_started:
            self._stream = self._request
        else:
            self._stream = io.BytesIO(self.body)

    def _supports_form_parsing(self):
        """
        Return True if this requests supports parsing form data.
        """
        form_media = (
            ‘application/x-www-form-urlencoded‘,
‘multipart/form-data‘
)
        return any([parser.media_type in form_media for parser in self.parsers])

    def _parse(self):
        """
        Parse the request content, returning a two-tuple of (data, files)

        May raise an `UnsupportedMediaType`, or `ParseError` exception.
        """
        media_type = self.content_type
        try:
            stream = self.stream
        except RawPostDataException:
            if not hasattr(self._request, ‘_post‘):
                raise
# If request.POST has been accessed in middleware, and a method=‘POST‘
            # request was made with ‘multipart/form-data‘, then the request stream
            # will already have been exhausted.
if self._supports_form_parsing():
                return (self._request.POST, self._request.FILES)
            stream = None

        if stream is None or media_type is None:
            if media_type and is_form_media_type(media_type):
                empty_data = QueryDict(‘‘, encoding=self._request._encoding)
            else:
                empty_data = {}
            empty_files = MultiValueDict()
            return (empty_data, empty_files)

        parser = self.negotiator.select_parser(self, self.parsers)

        if not parser:
            raise exceptions.UnsupportedMediaType(media_type)

        try:
            parsed = parser.parse(stream, media_type, self.parser_context)
        except Exception:
            # If we get an exception during parsing, fill in empty data and
            # re-raise.  Ensures we don‘t simply repeat the error when
            # attempting to render the browsable renderer response, or when
            # logging the request or similar.
self._data = QueryDict(‘‘, encoding=self._request._encoding)
            self._files = MultiValueDict()
            self._full_data = self._data
            raise

# Parser classes may return the raw data, or a
        # DataAndFiles object.  Unpack the result as required.
try:
            return (parsed.data, parsed.files)
        except AttributeError:
            empty_files = MultiValueDict()
            return (parsed, empty_files)

    def _authenticate(self):
        """
        Attempt to authenticate the request using each authentication instance
        in turn.
        """
        for authenticator in self.authenticators:
            try:
                user_auth_tuple = authenticator.authenticate(self)
            except exceptions.APIException:
                self._not_authenticated()
                raise

            if user_auth_tuple is not None:
                self._authenticator = authenticator
                self.user, self.auth = user_auth_tuple
                return

self._not_authenticated()

    def _not_authenticated(self):
        """
        Set authenticator, user & authtoken representing an unauthenticated request.

        Defaults are None, AnonymousUser & None.
        """
        self._authenticator = None

        if api_settings.UNAUTHENTICATED_USER:
            self.user = api_settings.UNAUTHENTICATED_USER()
        else:
            self.user = None

        if api_settings.UNAUTHENTICATED_TOKEN:
            self.auth = api_settings.UNAUTHENTICATED_TOKEN()
        else:
            self.auth = None

    def __getattr__(self, attr):
        """
        If an attribute does not exist on this instance, then we also attempt
        to proxy it to the underlying HttpRequest object.
        """
        try:
            return getattr(self._request, attr)
        except AttributeError:
            return self.__getattribute__(attr)

    @property
def DATA(self):
        raise NotImplementedError(
            ‘`request.DATA` has been deprecated in favor of `request.data` ‘
            ‘since version 3.0, and has been fully removed as of version 3.2.‘
)

    @property
def POST(self):
        # Ensure that request.POST uses our request parsing.
if not _hasattr(self, ‘_data‘):
            self._load_data_and_files()
        if is_form_media_type(self.content_type):
            return self._data
        return QueryDict(‘‘, encoding=self._request._encoding)

    @property
def FILES(self):
        # Leave this one alone for backwards compat with Django‘s request.FILES
        # Different from the other two cases, which are not valid property
        # names on the WSGIRequest class.
if not _hasattr(self, ‘_files‘):
            self._load_data_and_files()
        return self._files

    @property
def QUERY_PARAMS(self):
        raise NotImplementedError(
            ‘`request.QUERY_PARAMS` has been deprecated in favor of `request.query_params` ‘
            ‘since version 3.0, and has been fully removed as of version 3.2.‘
)

    def force_plaintext_errors(self, value):
        # Hack to allow our exception handler to force choice of
        # plaintext or html error responses.
self._request.is_ajax = lambda: value