源码分析
GenericAPIView继承自APIView，也就是在APIView基础上再做了一层封装，源码如下：
class GenericAPIView(views.APIView):
queryset = None
serializer_class = None
lookup_field = 'pk'
lookup_url_kwarg = None
filter_backends = api_settings.DEFAULT_FILTER_BACKENDS
pagination_class = api_settings.DEFAULT_PAGINATION_CLASS
def get_queryset(self):
assert self.queryset is not None, (
"'%s' should either include a `queryset` attribute, "
"or override the `get_queryset()` method."
% self.__class__.__name__
)
queryset = self.queryset
if isinstance(queryset, QuerySet):
queryset = queryset.all()
return queryset
def get_object(self):
queryset = self.filter_queryset(self.get_queryset())
lookup_url_kwarg = self.lookup_url_kwarg or self.lookup_field
assert lookup_url_kwarg in self.kwargs, (
'Expected view %s to be called with a URL keyword argument '
'named "%s". Fix your URL conf, or set the `.lookup_field` '
'attribute on the view correctly.' %
(self.__class__.__name__, lookup_url_kwarg)
)
filter_kwargs = {self.lookup_field: self.kwargs[lookup_url_kwarg]}
obj = get_object_or_404(queryset, **filter_kwargs)
self.check_object_permissions(self.request, obj)
return obj
def get_serializer(self, *args, **kwargs):
serializer_class = self.get_serializer_class()
kwargs.setdefault('context', self.get_serializer_context())
return serializer_class(*args, **kwargs)
def get_serializer_class(self):
assert self.serializer_class is not None, (
"'%s' should either include a `serializer_class` attribute, "
"or override the `get_serializer_class()` method."
% self.__class__.__name__
)
return self.serializer_class
def get_serializer_context(self):
return {
'request': self.request,
'format': self.format_kwarg,
'view': self
}
def filter_queryset(self, queryset):
for backend in list(self.filter_backends):
queryset = backend().filter_queryset(self.request, queryset, self)
return queryset
@property
def paginator(self):
if not hasattr(self, '_paginator'):
if self.pagination_class is None:
self._paginator = None
else:
self._paginator = self.pagination_class()
return self._paginator
def paginate_queryset(self, queryset):
if self.paginator is None:
return None
return self.paginator.paginate_queryset(queryset, self.request, view=self)
def get_paginated_response(self, data):
assert self.paginator is not None
return self.paginator.get_paginated_response(data)
我们可以看到GenericAPIView中定义了6个类属性和8个方法，接下来一个个分析
- queryset = None
- serializer_class = None
- lookup_field = 'pk'
- lookup_url_kwarg = None
- filter_backends = api_settings.DEFAULT_FILTER_BACKENDS
- pagination_class = api_settings.DEFAULT_PAGINATION_CLASS
queryset
queryset是用来控制视图返回给前端的数据。如果没什么逻辑，可以直接写在视图的类属性中，如果逻辑比较复杂，也可以重写get_queryset方法用来返回一个queryset对象。如果重写了get_queryset，那么以后获取queryset的时候就需要通过调用get_queryset方法。因为queryset` 这个属性只会调用一次，以后所有的请求都是使用他的缓存。
serializer_class
serializer_class用来验证和序列化数据的。也是可以通过直接设置这个属性，也可以通过重写get_serializer_class来实现。
lookup_field
在检索的时候，根据什么参数进行检索。默认是pk，也就是主键。
lookup_url_kwarg
在检索的url中的参数名称。默认没有设置，跟lookup_field保持一致。
filter_backends
用于过滤查询集的过滤器后端类的列表。默认值与DEFAULT_FILTER_BACKENDS 设置的值相同。
pagination_class
当分页列出结果时应使用的分页类。默认值与 DEFAULT_PAGINATION_CLASS 设置的值相同，即 'rest_framework.pagination.PageNumberPagination'。
- get_queryset
- get_object
- get_serializer
- get_serializer_class
- get_serializer_context
- filter_queryset
get_queryset
def get_queryset(self):
# 断言queryset是否不为None
assert self.queryset is not None, (
"'%s' should either include a `queryset` attribute, "
"or override the `get_queryset()` method."
% self.__class__.__name__
)
# 定义queryset属性，获取父类的queryset，如果父类没有定义类属性`queryset`，那么默认值就是None，就会报上面断言的错误
queryset = self.queryset
# 如果queryset是QuerySet对象，那么返回全部内容
if isinstance(queryset, QuerySet):
queryset = queryset.all()
# 如果不是queryset，那么直接返回
return queryset
get_queryset默认是返回数据库全部数据，如果想返回其他数据，需要自定义
get_object
def get_object(self):
queryset = self.filter_queryset(self.get_queryset())
# 查找过滤的条件，默认是pk
lookup_url_kwarg = self.lookup_url_kwarg or self.lookup_field
assert lookup_url_kwarg in self.kwargs, (
'Expected view %s to be called with a URL keyword argument '
'named "%s". Fix your URL conf, or set the `.lookup_field` '
'attribute on the view correctly.' %
(self.__class__.__name__, lookup_url_kwarg)
)
filter_kwargs = {self.lookup_field: self.kwargs[lookup_url_kwarg]}
obj = get_object_or_404(queryset, **filter_kwargs)
# 可能会引发权限被拒绝
self.check_object_permissions(self.request, obj)
return obj
该方法是用于在数据检索(通过pk查找)的时候，返回一条数据的。
get_serializer
def get_serializer(self, *args, **kwargs):
serializer_class = self.get_serializer_class()
kwargs.setdefault('context', self.get_serializer_context())
return serializer_class(*args, **kwargs)
返回应该用于验证和反序列化输入以及序列化输出的序列化器实例
get_serializer_class
def get_serializer_class(self):
assert self.serializer_class is not None, (
"'%s' should either include a `serializer_class` attribute, "
"or override the `get_serializer_class()` method."
% self.__class__.__name__
)
return self.serializer_class
返回用于序列化的类。默认使用self.serializer_class。如果您需要根据传入请求提供不同的序列化，您可能需要重写它。
get_serializer_context
def get_serializer_context(self):
return {
'request': self.request,
'format': self.format_kwarg,
'view': self
}
提供给序列化的额外上下文。
filter_queryset
def filter_queryset(self, queryset):
for backend in list(self.filter_backends):
queryset = backend().filter_queryset(self.request, queryset, self)
return queryset
给定一个查询集，使用正在使用的过滤器对其进行过滤。您不太可能想要覆盖此方法，但如果您想将配置的过滤后端应用到默认查询集，您可能需要从列表视图或自定义get_object 方法中调用它。
class StudentsGenericView(GenericAPIView):
queryset = Student.objects.all() # 定义了类属性queryset，告诉视图要针对哪个模型做处理
serializer_class = StudentModelSerializer # 定义类属性serlializer_class，告诉视图你的序列化的类是什么
def get(self, request, *args, **kwargs):
pk = kwargs.get("pk")
if pk:
many = False
query = self.get_object() # 通过pk检索数据，返回一条数据
else:
many = True
query = self.get_queryset() # 返回动态的数据集，默认返回全部
serializer = self.get_serializer(query, many=many) # 如果数据对象是queryset对象，many需要为True
return APIResponse(results=serializer.data)
