REST framework （組件源碼流程分析）

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閱讀目錄

1、APIView & View

2、組件源碼流程

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1、APIView & View

• View
  • 路徑：django.views.View
  • 使用：
    • urls: path('xxx/', views.xxxx.as_view(), name='xxx')
    • 視圖：class xxxx(View):
• ApiView
  • 路徑：from rest_framework.views import APIView
  • 使用：
    • urls: path('xxx/', views.xxAPI.as_view(), name='xxx')
    • 視圖：class xxAPI(APIView):
  • APIView繼承View，重寫as_view()，增長擴展配置

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2、組件源碼流程分析　

1. APIView源碼分析

    1.路由：url(r'^books/$', views.BookView.as_view(),name="books") #  View下的view

    2.請求：books/一旦被訪問 執行APIView.as_view() -> APIView: dispatch()
                 view = super(APIView, cls).as_view(**initkwargs)

    3.def dispatch():      # APIView
        # request加工
        request = self.initialize_request(request, *args, **kwargs) 
        
                  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(), # 解析器
                            authenticators=self.get_authenticators(), # 認證組件
                            negotiator=self.get_content_negotiator(),
                            parser_context=parser_context
                        )
        
        # 構建request對象
        self.request=Request(request)
                     class Request(object):
　　　　                  self._request = request  # 原request
　　　　                  def query_params(self):
　　　　　　                   return self._request.GET
　　　　                  def data(self):
　　　　　　                   return post.data # post請求數據

       self.request._request
       self.request.GET  # get
       self.request.data # POST  PUT
        
       # 初始化組件信息
       self.initial(request, *args, **kwargs)
  
       分發----if get請求：
       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) # 視圖： self.get(request, *args, **kwargs)               
       return response

    4.csrf_exempt(view)   #排除csrf

1.1 APIView().initial() 流程

def initial(self, request, *args, **kwargs):
    """
    Runs anything that needs to occur prior to calling the method handler.
    """
    # 1.肯定請求是否包含「.json」樣式格式後綴
    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)

        def perform_content_negotiation(self, request, force=False):
            """
            Determine which renderer and media type to use render the response.
            """
            # 2.渲染器
            renderers = self.get_renderers()   # [renderer() for renderer in self.renderer_classes]
            # 3.協商類
            conneg = self.get_content_negotiator()
            # if not getattr(self, '_negotiator', None):
            #      self._negotiator = self.content_negotiation_class()
            # return self._negotiator

            try:
                # 選擇渲染器
                return conneg.select_renderer(request, renderers, self.format_kwarg)
            except Exception:
                if force:
                    return (renderers[0], renderers[0].media_type)
                raise
    # 調用request對象__setattr__賦值
    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)
        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)
            # 4.version組件
            scheme = self.versioning_class() # api_settings.DEFAULT_VERSIONING_CLASS
            return (scheme.determine_version(request, *args, **kwargs), scheme
    # 調用request對象__setattr__賦值
    request.version, request.versioning_scheme = version, scheme



    # Ensure that the incoming request is permitted
    # 5.認證組件
    self.perform_authentication(request)
        # 默認執行    
        def perform_authentication(self, request):
            request.user   #執行request的user，這是的request已是加工後的request了

    　　@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  #返回user

　　　　# 執行self._authenticate() 開始用戶認證，若是驗證成功後返回元組： (用戶,用戶Token)
　　　　def _authenticate(self):

        　　"""
        　　Attempt to authenticate the request using each authentication instance
        　　in turn.
       　　 """
       　　 #循環對象列表
        　　for authenticator in self.authenticators:
            　　try:
               　　 #執行每個對象的authenticate 方法
               　　 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  #返回一個元組，user，和auth，賦給了self,
               　　 # 只要實例化Request，就會有一個request對象，就能夠request.user,request.auth了
               　　 return
        　　self._not_authenticated() 

　　　　　# 若是沒有認證成功
　　　　　def _not_authenticated(self):

        　　"""
        　　Set authenticator, user & authtoken representing an unauthenticated request.
        　　Defaults are None, AnonymousUser & None.
        　　"""
        　　#若是跳過了全部認證，默認用戶和Token和使用配置文件進行設置
        　　self._authenticator = None  #
       　　 if api_settings.UNAUTHENTICATED_USER:
       　　     self.user = api_settings.UNAUTHENTICATED_USER() # 默認值爲：匿名用戶AnonymousUser
      　　  else:
         　　   self.user = None  # None 表示跳過該認證
      　　  if api_settings.UNAUTHENTICATED_TOKEN:
       　　     self.auth = api_settings.UNAUTHENTICATED_TOKEN()  # 默認值爲：None
       　　 else:
           　　 self.auth = None
    　　　　# (user, token)
    　　　　# 表示驗證經過並設置用戶名和Token；
    　　　　# AuthenticationFailed異常

　　# 6.權限組件
　　self.check_permissions(request)
    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)
                )    
                        #if request.authenticators and not request.successful_authenticator:
                        #   raise exceptions.NotAuthenticated()
                        # raise exceptions.PermissionDenied(detail=message)
　　# 7.頻率組件
　　self.check_throttles(request)
    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())    # exceptions.Throttled(wait)

APIView().dispatch()  執行結束分發至視圖，緊接着執行視圖中的 def get(request, *args, **kwargs) ，def post(request, *args, **kwargs) 等

2. 視圖執行流程

操做數據：以Book表爲例
    class BookView(APIView):
        # 查看全部書籍
        def get(self,request):
            book_list=Book.objects.all()
            bs=BookModelSerializers(book_list,many=True,context={'request': request})
            return Response(bs.data)

        # 添加一本書籍
        def post(self,request):
            # post請求的數據
            bs=BookModelSerializers(data=request.data)
            if bs.is_valid():
                print(bs.validated_data)
                bs.save()# create方法
                return Response(bs.data)
            else:
                return Response(bs.errors)
    class BookDetailView(APIView):
        # 查看一本書籍
        def get(self,request,id):

            book=Book.objects.filter(pk=id).first()
            bs=BookModelSerializers(book,context={'request': request})
            return Response(bs.data)
        # 更新一本書籍
        def put(self,request,id):
            book=Book.objects.filter(pk=id).first()
            bs=BookModelSerializers(book,data=request.data)
            if bs.is_valid():
                bs.save()
                return Response(bs.data)
            else:
                return Response(bs.errors)
        # 刪除某一本書籍
        def delete(self,request,id):
            Book.objects.filter(pk=id).delete()

            return Response()

操做數據：以Book表爲例

分析：獲取全部書籍，執行get方法查詢數據庫，返回對象/queryset交給自定製序列化類，分頁後Response返回給前端，這個過程當中DRF組件體現：

• 序列化組件  
• 分頁組件 
• 渲染器 

3、總結

根據上面的分析，總結DRF包含的幾大組件以下：

請求進來：

1. 路由（可自定製路由）
2. 版本
3. 認證
4. 權限
5. 頻率
6. 獲取數據（解析器）請求頭解析
7. 序列化
8. 分頁
9. 渲染器
10. 視圖   # DRF視圖不僅有APIView

 本文基於APIView源碼流程分析總結DRF幾大組件，組件的使用請見 REST framework （組件使用）