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最近遇到一个权限相关的需求，要判断用户有没有当前接口的权限，打算放到中间件中判断，权限判断方法都直接写在了中间件类中。
在自定义中间件中，调用current_url的时候遇到了线程安全问题。

class PermissionMiddleware(MiddlewareMixin):
	def __call__(self, request):
        self.request = request
        return super().__call__(request)
    
    @property
    def current_url(self):
        """
        当前url
        @return:
        """
        return str(self.request.path_info).strip()
	
	def process_request(self, request):
		pass
	
	...

看了一下MiddlewareMixin源码，他的__init__方法全局只会调用一次，所以上面的current_url可能并不是当前访问的url

class MiddlewareMixin:
    def __init__(self, get_response=None):
        self.get_response = get_response
        super().__init__()

    def __call__(self, request):
        response = None
        if hasattr(self, 'process_request'):
            response = self.process_request(request)
        response = response or self.get_response(request)
        if hasattr(self, 'process_response'):
            response = self.process_response(request, response)
        return response

解决： 单独写个类判断权限

class PermissionMiddleware(MiddlewareMixin):
	def __call__(self, request):
        self.request = request
        return super().__call__(request)
   
   def process_request(self, request):
		 check_perm = CheckPermissioin(request)
		 ...

class CheckPermissioin():
	"""
	判断有没有当前接口权限
	"""
    def __init__(self, request):
        self.request = request
  
    @property
    def current_url(self):
        """
        当前url
        @return:
        """
        return str(self.request.path_info).strip()
    ...