class BaseHandler(object)方法get_response，控制着处理请求的流程，调用中间件，返回请求。
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#获取根urlconf
urlresolvers.set_urlconf(urlconf)
resolver = urlresolvers.get_resolver(urlconf)#生成url解决子
# 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:调用中间件
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)#由路径找到url匹配的view函数
callback, callback_args, callback_kwargs = resolver_match
request.resolver_match = resolver_match#给请求添加匹配子属性 # Apply view middleware
for middleware_method in self._view_middleware:#调用view中间件
response = middleware_method(request, callback, callback_args, callback_kwargs)
if response:
break if response is None:
wrapped_callback = self.make_view_atomic(callback)#真正调用view函数
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:#调用模板中间件
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:#调用响应中间件
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按中间件的从上到下的顺序执行，process_template_response process_response、process_exception按从下到上的顺序执行。最终response都要经过process_response中间件。所以django-debug-toolbar是通过中间件在响应阶段记录数据。