flask0.1版本源码浅析——Request
4 请求(request)
from flask import request
request接收了WSGI server 传递过来的 environ
字典变量,并提供了很多常用的属性和方法可以使用,比如请求的 method、path、args 等。
同时request还有一个特性——它不能被应用修改,应用只能读取请求的数据。
---> 4.1 Request(RequestBase)
其中 from werkzeug.wrappers import Request as RequestBase
该类继承 werkzeug的 request后,定义了一些 @property属性
---> werkzeug.wrappers:Request
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class Request(BaseRequest, AcceptMixin, ETagRequestMixin, UserAgentMixin, AuthorizationMixin, CommonRequestDescriptorsMixin): """Full featured request object implementing the following mixins: - :class:`AcceptMixin` for accept header parsing - :class:`ETagRequestMixin` for etag and cache control handling - :class:`UserAgentMixin` for user agent introspection - :class:`AuthorizationMixin` for http auth handling - :class:`CommonRequestDescriptorsMixin` for common headers """
---> BaseRequest
class BaseRequest(object): def __init__(self, environ, populate_request=True, shallow=False): self.environ = environ if populate_request and not shallow: self.environ['werkzeug.request'] = self self.shallow = shallow
主要就是传入了 self.environ 作为字段。
然后用 @cached_property 定义了一些属性, 像 args, form, cookies等等
---> cached_property
接下来我们看看 增强版的 property
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class cached_property(property): """A decorator that converts a function into a lazy property. The function wrapped is called the first time to retrieve the result and then that calculated result is used the next time you access the value. The class has to have a `__dict__` in order for this property to work. """ # implementation detail: A subclass of python's builtin property # decorator, we override __get__ to check for a cached value. If one # choses to invoke __get__ by hand the property will still work as # expected because the lookup logic is replicated in __get__ for # manual invocation. def __init__(self, func, name=None, doc=None): self.__name__ = name or func.__name__ self.__module__ = func.__module__ self.__doc__ = doc or func.__doc__ self.func = func def __set__(self, obj, value): obj.__dict__[self.__name__] = value def __get__(self, obj, type=None): if obj is None: return self value = obj.__dict__.get(self.__name__, _missing) if value is _missing: value = self.func(obj) obj.__dict__[self.__name__] = value return value
这个装饰器同时也是实现了 __set__
和 __get__
方法的描述器。 访问它装饰的属性,就会调用 __get__
方法,这个方法先在 obj.__dict__
中寻找是否已经存在对应的值。如果存在,就直接返回;如果不存在,调用底层的函数 self.func
,并把得到的值保存起来,再返回。这也是它能实现缓存的原因:因为它会把函数的值作为属性保存到对象中。 ---cizixs