base.py 文件源码

def load_middleware(self):
        """
        Populate middleware lists from settings.MIDDLEWARE_CLASSES.

        Must be called after the environment is fixed (see __call__ in subclasses).
        """
        self._view_middleware = []
        self._template_response_middleware = []
        self._response_middleware = []
        self._exception_middleware = []

        request_middleware = []
        for middleware_path in settings.MIDDLEWARE_CLASSES:
            mw_class = import_by_path(middleware_path)
            try:
                mw_instance = mw_class()
            except MiddlewareNotUsed:
                continue

            if hasattr(mw_instance, 'process_request'):
                request_middleware.append(mw_instance.process_request)
            if hasattr(mw_instance, 'process_view'):
                self._view_middleware.append(mw_instance.process_view)
            if hasattr(mw_instance, 'process_template_response'):
                self._template_response_middleware.insert(0, mw_instance.process_template_response)
            if hasattr(mw_instance, 'process_response'):
                self._response_middleware.insert(0, mw_instance.process_response)
            if hasattr(mw_instance, 'process_exception'):
                self._exception_middleware.insert(0, mw_instance.process_exception)

        # We only assign to this when initialization is complete as it is used
        # as a flag for initialization being complete.
        self._request_middleware = request_middleware