Django REST framework —— 权限组件源码分析

在上一篇文章中我们已经分析了认证组件源码，我们再来看看权限组件的源码，权限组件相对容易，因为只需要返回True 和False即可

代码

class ShoppingCarView(ViewSetMixin, APIView):
     permission_classes = [MyPermission, ]
        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)

视图类

class MyPermission(BasePermission):
    message = 'VIP用户才能访问'

    def has_permission(self, request, view):
        """
        自定义权限只有VIP用户才能访问
        """
        # 因为在进行权限判断之前已经做了认证判断，所以这里可以直接拿到request.user
        if request.user and request.user.type == 2:  # 如果是VIP用户
            return True
        else:
            return False

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

跟上一篇一样，来看代码是如何走到我自定义的权限类中的。

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) 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)

　　　　（3）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)
                )

　　　　（4）self.get_permissions():

    def get_permissions(self):
        """
        Instantiates and returns the list of permissions that this view requires.
        """
        return [permission() for permission in self.permission_classes]  列表生成式，把自定义的权限类的对象，放在一个对象中

　　　　（5）self.permission_classes

　　　　

　　　　这里默认去settings全局中去找，如果局部配置了静态变量，就直接去找局部的静态变量

 　　　　（6）在看看我们继承的BasePermission

class BasePermission(object):
    """
    A base class from which all permission classes should inherit.
    """

    def has_permission(self, request, view):
        """
        Return `True` if permission is granted, `False` otherwise.
        """
        return True

    def has_object_permission(self, request, view, obj):
        """
        Return `True` if permission is granted, `False` otherwise.
        """
        return True

 默认是没有任何逻辑判断的，所以我们在自定义权限类的时候，得自己写这两个方法。

 另外说明一下下面这个犯法的作用  

def has_object_permission(self, request, view, obj):
        """
        Return `True` if permission is granted, `False` otherwise.
        """
        return True

 对当前登录用户做些判断

def has_object_permission(self, request, view, obj):
    """
    判断当前评论用户的作者是不是你当前的用户
    只有评论的作者才能删除自己的评论
    """
      print('这是在自定义权限类中的has_object_permission')
      print(obj.id)
      if request.method in ['PUT', 'DELETE']:
          if obj.user == request.user:
            # 当前要删除的评论的作者就是当前登陆的用户
              return True
          else:
              return False
      else:
          return True

总结：

（1）使用

• 自己写的权限类：1.必须继承BasePermission类；  2.必须实现：has_permission方法

（2）返回值

• True   有权访问
• False  无权访问

（3）局部

• permission_classes = [MyPremission,] 

 （4）全局

REST_FRAMEWORK = {
   #权限
    "DEFAULT_PERMISSION_CLASSES":['API.utils.permission.SVIPPremission'],
}