权限组件的源码分析

忘羡一曲远，曲终人不散

我在前面的博客里已经讲过了，我们一般编写API的时候用的方式

class CoursesView(ViewSetMixin,APIView):
        pass

这种方式的有点是，灵活性比较大，可以根据自己的业务逻辑来自定义各种组件逻辑。

这边文章，我将带大家对 认证组件做一个源码分析，写这边文章的原因也是因为自己虽然知道怎么写，但是不知道为什么要这么写，今天看了源码，所以想把自己的一些心得写出来和大家分享。

先看代码

视图类

class ShoppingCarView(ViewSetMixin, APIView):
    authentication_classes = [LuffyAuthtication,]
        def list(self,request, *args, **kwargs):
        """
        查看购物车信息
        :param args:
        :param kwargs:
        :return:
        """
        try:
            ret = BaseResponse()
            pay_course_list = []
            # key = 'shoppingcar_%s_%s' % (USERID, '*')
            key = settings.SHOPCAR_FORMAT.format( request.user.id, "*")
            user_key_list = COON.keys(pattern=key)  # 取到这个用户对应的所有课程字典 对应的键
            for key in user_key_list:
                # 对应的每个键值 去取每个课程对应的信息 和价格列表
                temp = {
                    'id': COON.hget(key, 'id').decode('utf8'),
                    'name': COON.hget(key, 'name').decode('utf8'),
                    'img': COON.hget(key, 'img').decode('utf8'),
                    'default': COON.hget(key, 'default').decode('utf8'),
                    'price_dict': json.loads(COON.hget(key, 'price_dict').decode('utf8')),
                }
                pay_course_list.append(temp)
            ret.data = pay_course_list
        except Exception as e:
            ret.data = '查看失败'
            ret.code = 00000
        return Response(ret.dict)

认证类

from app01 import models
from rest_framework.authentication import BaseAuthentication
from rest_framework.exceptions import AuthenticationFailed


class LuffyAuthtication(BaseAuthentication):

    def authenticate(self, request):
        """
        用于做用户认证
        :param request:
        :return:
        """
        token = request.query_params.get('token')
        token_obj = models.UserToken.objects.filter(token=token).first()
        if not  token_obj:
            raise AuthenticationFailed({'code':10000,'error':'认证失败'})
        return token_obj.user,token_obj

url.py

urlpatterns = [
    url(r'^payment/$', payment.PaymentView.as_view({'post': 'create','put': 'update','get':'list'})),
]

以上的就是逻辑代码，就是一个必须要验证为注册用户才能查看购物车的内容。

下面来进行源码分析，来看代码是如何走到我自定义的认证类中的。

1.首先从url中分析

1.先来到视图类中的as.view()方法

而我们的自定义的方法中没有as.view()方法，那就要去父类ViewSetMixin和APIView中去找，好看源码

2.分析源码

1.先看ViewSetMixin类中

class ViewSetMixin(object):
    """
    This is the magic.

    Overrides `.as_view()` so that it takes an `actions` keyword that performs
    the binding of HTTP methods to actions on the Resource.

    For example, to create a concrete view binding the 'GET' and 'POST' methods
    to the 'list' and 'create' actions...

    view = MyViewSet.as_view({'get': 'list', 'post': 'create'})
    """

    @classonlymethod
    def as_view(cls, actions=None, **initkwargs):
        """
        Because of the way class based views create a closure around the
        instantiated view, we need to totally reimplement `.as_view`,
        and slightly modify the view function that is created and returned.
        """
        # The suffix initkwarg is reserved for displaying the viewset type.
        # eg. 'List' or 'Instance'.
        cls.suffix = None

        # The detail initkwarg is reserved for introspecting the viewset type.
        cls.detail = None

        # Setting a basename allows a view to reverse its action urls. This
        # value is provided by the router through the initkwargs.
        cls.basename = None

        # actions must not be empty
        if not actions:
            raise TypeError("The `actions` argument must be provided when "
                            "calling `.as_view()` on a ViewSet. For example "
                            "`.as_view({'get': 'list'})`")

        # sanitize keyword arguments
        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" % (
                    cls.__name__, key))

        def view(request, *args, **kwargs):
            self = cls(**initkwargs)
            # We also store the mapping of request methods to actions,
            # so that we can later set the action attribute.
            # eg. `self.action = 'list'` on an incoming GET request.
            self.action_map = actions

            # Bind methods to actions
            # This is the bit that's different to a standard view
            for method, action in actions.items():
                handler = getattr(self, action)
                setattr(self, method, handler)

            if hasattr(self, 'get') and not hasattr(self, 'head'):
                self.head = self.get

            self.request = request
            self.args = args
            self.kwargs = kwargs

            # And continue as usual
　　　　　　　# 前面都是在对传参做判断和重新赋值，重要的是下面这一步，最后return 调用了dispatch方法

            return self.dispatch(request, *args, **kwargs)

2.找dispatch方法在哪里，答案肯定是在APIView中

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)
　　　　　## request = Request(.....)
        self.request = request
        self.headers = self.default_response_headers  

        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

所有的关键点都在dispatch方法里面：

(1) 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(),
            authenticators=self.get_authenticators(),    #[BasicAuthentication(),],把对象封装到request里面了
　　　　　　　negotiator=self.get_content_negotiator(), parser_context=parser_context )

(2)authenticators=self.get_authenticators()

通过列表生成式，返回对象的列表

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

(3)authentication_classes

APIView里面有个 authentication_classes 字段 ，这里如果写了静态变量就直接在类的静态变量中找，否则就到全局配置文文件中去找 可以看到默认是去全局的配置文件找（api_settings）

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

(4)开始验证

(5)self.initial(request,*args,**kwargs)

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)    认证
        self.check_permissions(request)　　　　　　权限
        self.check_throttles(request)　　　　　　　　频率

(6)self.perform_authentication(request)

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

　　#这里没有返回值，直接调用了request.user，那这个user方法是谁的呢？？？？

还记得这个Request吧，对没错就是他的，我们点进去看看

(7)request.user (8)self._authenticate()方法

def _authenticate(self):
        """
        Attempt to authenticate the request using each authentication instance
        in turn.
        """
        #循环认证类的所有对象
        for authenticator in self.authenticators:
            try:
                #执行认证类的authenticate方法
                #这里分三种情况
                #1.如果authenticate方法抛出异常，self._not_authenticated()执行
                #2.有返回值，必须是元组：（request.user,request.auth）
                #3.返回None，表示当前认证不处理，等下一个认证来处理
                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    #元祖
                return

        self._not_authenticated()

返回的元组就是上面自定义认证类代码中的

token_obj.user, 可以再后续的request.user中取到

token_obj ，可以再后续的request.auth中取到

到这里整个认证组件的源码就分析完了

自己写认证类方法梳理

1.创建认证类

继承BaseAuthentication

• 1.重写authenticate方法；
• 2.authenticate_header方法直接写pass就可以（这个方法必须写）

  2.authenticate()返回值（三种）

• None —–»>当前认证不管，等下一个认证来执行,可用于对请求的过滤上
• raise exceptions.AuthenticationFailed(‘用户认证失败’)
  from rest_framework import exceptions
• 有返回值元祖形式：（元素1，元素2） #元素1复制给request.user; 元素2复制给request.auth

  3.局部使用

• authentication_classes = [BaseAuthentication,]

  4.全局使用

  #设置全局认证 REST_FRAMEWORK = { “DEFAULT_AUTHENTICATION_CLASSES”:[‘API.utils.auth.Authentication’,] }

源码流程

• —»dispatch

  • —>封装request

    • —>获取定义的认证类（全局/局部），通过列表生成式创建对象

      • —>initial

        • —>peform_authentication

          • —>request.user （每部循环创建的对象）