g dfn HttpRequest对象拥有的属性和方法：
self.GET = QueryDict(mutable=True) #GET请求的参数字典集合
self.POST = QueryDict(mutable=True) #POST请求的参数字典集合
self.COOKIES = {} #获取cookie
self.META = {} #获取META
self.FILES = MultiValueDict()
self.path = '' #获取请求路径
self.path_info = ''
self.method = None #请求方法类型
self.resolver_match = None
self._post_parse_error = False
self.content_type = None #获取content_type
self.content_params = None
get_host(self): #获取host
get_port(self)：#获取端口port
get_full_path(self, force_append_slash=False): #获取全路径
