django之def get_response(self, request):

class BaseHandler(object)方法get_response，控制着處理請求的流程，調用中間件，返回請求。

def get_response(self, request): "Returns an HttpResponse object for the given HttpRequest"

        # Setup default url resolver for this thread, this code is outside
        # the try/except so we don't get a spurious "unbound local
        # variable" exception in the event an exception is raised before
        # resolver is set
        urlconf = settings.ROOT_URLCONF#獲取根urlconf urlresolvers.set_urlconf(urlconf) resolver = urlresolvers.get_resolver(urlconf)#生成url解決子 # Use a flag to check if the response was rendered to prevent
        # multiple renderings or to force rendering if necessary.
        response_is_rendered = False try: response = None # Apply request middleware
            for middleware_method in self._request_middleware:調用中間件 response = middleware_method(request) if response: break

            if response is None: if hasattr(request, 'urlconf'): # Reset url resolver with a custom URLconf.
                    urlconf = request.urlconf urlresolvers.set_urlconf(urlconf) resolver = urlresolvers.get_resolver(urlconf) resolver_match = resolver.resolve(request.path_info)#由路徑找到url匹配的view函數 callback, callback_args, callback_kwargs = resolver_match request.resolver_match = resolver_match#給請求添加匹配子屬性 # Apply view middleware
                for middleware_method in self._view_middleware:#調用view中間件 response = middleware_method(request, callback, callback_args, callback_kwargs) if response: break

            if response is None: wrapped_callback = self.make_view_atomic(callback)#真正調用view函數 try: response = wrapped_callback(request, *callback_args, **callback_kwargs) except Exception as e: response = self.process_exception_by_middleware(e, request) # Complain if the view returned None (a common error).
            if response is None: if isinstance(callback, types.FunctionType):    # FBV
                    view_name = callback.__name__
                else:                                           # CBV
                    view_name = callback.__class__.__name__ + '.__call__'
                raise ValueError("The view %s.%s didn't return an HttpResponse object. It returned None instead."
                                 % (callback.__module__, view_name)) # If the response supports deferred rendering, apply template
            # response middleware and then render the response
            if hasattr(response, 'render') and callable(response.render): for middleware_method in self._template_response_middleware:#調用模板中間件 response = middleware_method(request, response) # Complain if the template response middleware returned None (a common error).
                    if response is None: raise ValueError( "%s.process_template_response didn't return an "
                            "HttpResponse object. It returned None instead."
                            % (middleware_method.__self__.__class__.__name__)) try: response = response.render() except Exception as e: response = self.process_exception_by_middleware(e, request) response_is_rendered = True except http.Http404 as exc: logger.warning('Not Found: %s', request.path, extra={ 'status_code': 404, 'request': request }) if settings.DEBUG: response = debug.technical_404_response(request, exc) else: response = self.get_exception_response(request, resolver, 404, exc) except PermissionDenied as exc: logger.warning( 'Forbidden (Permission denied): %s', request.path, extra={ 'status_code': 403, 'request': request }) response = self.get_exception_response(request, resolver, 403, exc) except MultiPartParserError as exc: logger.warning( 'Bad request (Unable to parse request body): %s', request.path, extra={ 'status_code': 400, 'request': request }) response = self.get_exception_response(request, resolver, 400, exc) except SuspiciousOperation as exc: # The request logger receives events for any problematic request
            # The security logger receives events for all SuspiciousOperations
            security_logger = logging.getLogger('django.security.%s' % exc.__class__.__name__) security_logger.error( force_text(exc), extra={ 'status_code': 400, 'request': request }) if settings.DEBUG: return debug.technical_500_response(request, *sys.exc_info(), status_code=400) response = self.get_exception_response(request, resolver, 400, exc) except SystemExit: # Allow sys.exit() to actually exit. See tickets #1023 and #4701
            raise

        except:  # Handle everything else.
            # Get the exception info now, in case another exception is thrown later.
            signals.got_request_exception.send(sender=self.__class__, request=request) response = self.handle_uncaught_exception(request, resolver, sys.exc_info()) try: # Apply response middleware, regardless of the response
            for middleware_method in self._response_middleware:#調用響應中間件 response = middleware_method(request, response) # Complain if the response middleware returned None (a common error).
                if response is None: raise ValueError( "%s.process_response didn't return an "
                        "HttpResponse object. It returned None instead."
                        % (middleware_method.__self__.__class__.__name__)) response = self.apply_response_fixes(request, response) except:  # Any exception should be gathered and handled
            signals.got_request_exception.send(sender=self.__class__, request=request) response = self.handle_uncaught_exception(request, resolver, sys.exc_info()) response._closable_objects.append(request) # If the exception handler returns a TemplateResponse that has not
        # been rendered, force it to be rendered.
        if not response_is_rendered and callable(getattr(response, 'render', None)): response = response.render() return response

process_request、process_view按中間件的從上到下的順序執行，process_template_response  process_response、process_exception按從下到上的順序執行。最終response都要通過process_response中間件。因此django-debug-toolbar是經過中間件在響應階段記錄數據。