REST framework （组件源码流程分析）

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阅读目录

一、APIView & View

二、组件源码流程

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一、APIView & View

• View
  • 路径：django.views.View
  • 使用：
    • urls: path('xxx/', views.xxxx.as_view(), name='xxx')
    • 视图：class xxxx(View):
• ApiView
  • 路径：from rest_framework.views import APIView
  • 使用：
    • urls: path('xxx/', views.xxAPI.as_view(), name='xxx')
    • 视图：class xxAPI(APIView):
  • APIView继承View，重写as_view()，增加扩展配置

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二、组件源码流程分析　

1. APIView源码分析

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

    2.请求：books/一旦被访问 执行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(), # 认证组件
                            negotiator=self.get_content_negotiator(),
                            parser_context=parser_context
                        )
        
        # 构建request对象
        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请求数据

       self.request._request
       self.request.GET  # get
       self.request.data # POST  PUT
        
       # 初始化组件信息
       self.initial(request, *args, **kwargs)
  
       分发----if get请求：
       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) # 视图： 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.确定请求是否包含“.json”样式格式后缀
    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.协商类
            conneg = self.get_content_negotiator()
            # if not getattr(self, '_negotiator', None):
            #      self._negotiator = self.content_negotiation_class()
            # return self._negotiator

            try:
                # 选择渲染器
                return conneg.select_renderer(request, renderers, self.format_kwarg)
            except Exception:
                if force:
                    return (renderers[0], renderers[0].media_type)
                raise
    # 调用request对象__setattr__赋值
    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组件
            scheme = self.versioning_class() # api_settings.DEFAULT_VERSIONING_CLASS
            return (scheme.determine_version(request, *args, **kwargs), scheme
    # 调用request对象__setattr__赋值
    request.version, request.versioning_scheme = version, scheme



    # Ensure that the incoming request is permitted
    # 5.认证组件
    self.perform_authentication(request)
        # 默认执行    
        def perform_authentication(self, request):
            request.user   #执行request的user，这是的request已经是加工后的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

　　　　# 执行self._authenticate() 开始用户认证，如果验证成功后返回元组： (用户,用户Token)
　　　　def _authenticate(self):

        　　"""
        　　Attempt to authenticate the request using each authentication instance
        　　in turn.
       　　 """
       　　 #循环对象列表
        　　for authenticator in self.authenticators:
            　　try:
               　　 #执行每一个对象的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  #返回一个元组，user，和auth，赋给了self,
               　　 # 只要实例化Request，就会有一个request对象，就可以request.user,request.auth了
               　　 return
        　　self._not_authenticated() 

　　　　　# 如果没有认证成功
　　　　　def _not_authenticated(self):

        　　"""
        　　Set authenticator, user & authtoken representing an unauthenticated request.
        　　Defaults are None, AnonymousUser & None.
        　　"""
        　　#如果跳过了所有认证，默认用户和Token和使用配置文件进行设置
        　　self._authenticator = None  #
       　　 if api_settings.UNAUTHENTICATED_USER:
       　　     self.user = api_settings.UNAUTHENTICATED_USER() # 默认值为：匿名用户AnonymousUser
      　　  else:
         　　   self.user = None  # None 表示跳过该认证
      　　  if api_settings.UNAUTHENTICATED_TOKEN:
       　　     self.auth = api_settings.UNAUTHENTICATED_TOKEN()  # 默认值为：None
       　　 else:
           　　 self.auth = None
    　　　　# (user, token)
    　　　　# 表示验证通过并设置用户名和Token；
    　　　　# AuthenticationFailed异常

　　# 6.权限组件
　　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.频率组件
　　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()  执行结束分发至视图，紧接着执行视图中的 def get(request, *args, **kwargs) ，def post(request, *args, **kwargs) 等

2. 视图执行流程

操作数据：以Book表为例
    class BookView(APIView):
        # 查看所有书籍
        def get(self,request):
            book_list=Book.objects.all()
            bs=BookModelSerializers(book_list,many=True,context={'request': request})
            return Response(bs.data)

        # 添加一本书籍
        def post(self,request):
            # post请求的数据
            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):
        # 查看一本书籍
        def get(self,request,id):

            book=Book.objects.filter(pk=id).first()
            bs=BookModelSerializers(book,context={'request': request})
            return Response(bs.data)
        # 更新一本书籍
        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)
        # 删除某一本书籍
        def delete(self,request,id):
            Book.objects.filter(pk=id).delete()

            return Response()

分析：获取所有书籍，执行get方法查询数据库，返回对象/queryset交给自定制序列化类，分页后Response返回给前端，这个过程中DRF组件体现：

• 序列化组件  
• 分页组件 
• 渲染器 

三、总结

根据上面的分析，总结DRF包含的几大组件如下：

请求进来：

1. 路由（可自定制路由）
2. 版本
3. 认证
4. 权限
5. 频率
6. 获取数据（解析器）请求头解析
7. 序列化
8. 分页
9. 渲染器
10. 视图   # DRF视图不只有APIView

 本文基于APIView源码流程分析总结DRF几大组件，组件的使用请见 REST framework （组件使用）