#wsgi.py文件
class WSGIHandler(base.BaseHandler):
 request_class = WSGIRequest
 def __init__(self, *args, **kwargs):
 super().__init__(*args, **kwargs)
 self.load_middleware()
 def __call__(self, environ, start_response):
 set_script_prefix(get_script_name(environ))
 signals.request_started.send(sender=self.__class__, environ=environ)
 request = self.request_class(environ)
 response = self.get_response(request)
 response._handler_class = self.__class__
 status = '%d %s' % (response.status_code, response.reason_phrase)
 response_headers = list(response.items())
 for c in response.cookies.values():
 response_headers.append(('Set-Cookie', c.output(header='')))
 start_response(status, response_headers)
 if getattr(response, 'file_to_stream', None) is not None and environ.get('wsgi.file_wrapper'):
 response = environ['wsgi.file_wrapper'](response.file_to_stream)
 return response

# wsgi.py文件

# wsgi.py文件
def load_middleware(self):
　　...


 self._view_middleware = []
 self._template_response_middleware = []
 self._exception_middleware = []

 handler = convert_exception_to_response(self._get_response)
 for middleware_path in reversed(settings.MIDDLEWARE):
 middleware = import_string(middleware_path)
 try:
 mw_instance = middleware(handler)
 except MiddlewareNotUsed as exc:
　　　　　　　...

 

 handler = convert_exception_to_response(mw_instance)

 self._middleware_chain = handler

def _get_response(self, request):
 response = None

 if hasattr(request, 'urlconf'):
 urlconf = request.urlconf
 set_urlconf(urlconf)
 resolver = get_resolver(urlconf)
 else:
 resolver = get_resolver()

 resolver_match = resolver.resolve(request.path_info)
 callback, callback_args, callback_kwargs = resolver_match
 request.resolver_match = resolver_match

 ...

 if response is None:
 wrapped_callback = self.make_view_atomic(callback)
 try:
 response = wrapped_callback(request, *callback_args, **callback_kwargs)
 except Exception as e:
 response = self.process_exception_by_middleware(e, request)

 ...

 return response