Detailed introduction to Django middleware

I have been writing scripts for a few weeks, and today I finally started to get in touch with web frameworks~ To learn Python’s web framework, Django is almost a required course. This time, I will start with it first. The main task is to Add the version number in the setting, attach the version number when rendering the path of static css and js, such as "example.v1124.css", and then remove the version number in the request request. Why do you do that? Because if you do this, the path to the static file output on the front end will be added with the version number. In this way, when a new static file is developed, the client will forcefully refresh the local cache. In order to achieve this purpose, you must first It must be configured in the settings file, so that the version number can be read directly from the settings every time it is modified.

1. Request cycle of Django middleware

We Send a request Request from the browser and get a response content HttpResponse. The process of passing this request to Django is as follows:

In other words, every request is first Through the process_request function in the middleware, this function returns None or HttpResponse object. If it returns the former, continue processing other middleware. If it returns an HttpResponse, the processing is aborted and returned to the web page.

2. Customize and register middleware

1. Create middleware

Create the middleware py file in the project root directory:

 1 class RequestExeute(object): 2     def process_request(self, request): 3         print('process_request') 4  5     def process_view(self, request, callback, callback_args, callback_kwargs): 6         print('process_view') 7  8     def process_exception(self, request, exception): 9         """10         当views函数出错时执行11         :param request: 
12         :param exception: 
13         :return: 
14         """15         print('process_exception')16         17     def process_response(self, request, response):18         """19         必须return HttpResponse20         :param request: 
21         :param response: 
22         :return: 
23         """24         print('process_response')25         return response26 27     def process_template_response(self, request, response):28         """29         视图函数的返回值中，如果有render方法，才被调用30         :param request:31         :param response:32         :return:33         """34         print('process_template_response')35         return response

md.py

2. Register middleware

In the settings.py file, register in the order you want to execute ：

ps. In versions 1.9 and earlier, the keyword of middleware is: MIDDLEWARE_CLASSES

MIDDLEWARE_CLASSES = ('zqxt.middleware.BlockedIpMiddleware',
    ...其它的中间件
)

3. Middle Execution sequence of methods in the file

1. Normal situation

 1 from django.shortcuts import HttpResponse 2 from django.utils.deprecation import MiddlewareMixin 3 class M1(MiddlewareMixin): 4     def process_request(self, request): 5         print('m1.request') 6         # return HttpResponse('request_m1') 7  8     def process_view(self, request, callback, callback_args, callback_kwargs): 9         print('m1.view')10         # response = callback(request, *callback_args, **callback_kwargs)11         # return response12 13     def process_response(self, request, response):14         print('m1.response')15         return response16 17     def process_exception(self, request, exception):18         print('m1.process_exception')19         return HttpResponse('m1.process_exception')20 21     def process_template_response(self, request, response):22         """23         视图函数的返回值中，如果有render方法，才被调用24         :param request:25         :param response:26         :return:27         """28         print('m1.process_template_response')29         return response30 31 32 class M2(MiddlewareMixin):33     def process_request(self, request):34         print('m2.request')35 36     def process_view(self, request, callback, callback_args, callback_kwargs):37         print('m2.view')38         # response = callback(request, *callback_args, **callback_kwargs)39         # return response40 41     def process_response(self, request, response):42         print('m2.response')43         return response44 45     def process_exception(self, request, exception):46         print('m2.process_exception')47         return HttpResponse('m2.process_exception')48 49     def process_template_response(self, request, response):50         """51         视图函数的返回值中，如果有render方法，才被调用52         :param request:53         :param response:54         :return:55         """56         print('m2.process_template_response')57         return response

process_request and process_view return None

Execution order:

1. m1.request

2. m2.request

3. m1.view

4. m2.view

5. m2.response

6. m1.response

2. In version 1.10 and later

If process_request returns an HttpResponse object, return forward from the process_response of the current middleware

 1 from django.shortcuts import HttpResponse 2 from django.utils.deprecation import MiddlewareMixin 3 class M1(MiddlewareMixin): 4     def process_request(self, request): 5         print('m1.request') 6         return HttpResponse('request_m1') 7  8     def process_view(self, request, callback, callback_args, callback_kwargs): 9         print('m1.view')10         # response = callback(request, *callback_args, **callback_kwargs)11         # return response12 13     def process_response(self, request, response):14         print('m1.response')15         return response16 17     def process_exception(self, request, exception):18         print('m1.process_exception')19         return HttpResponse('m1.process_exception')20 21     def process_template_response(self, request, response):22         """23         视图函数的返回值中，如果有render方法，才被调用24         :param request:25         :param response:26         :return:27         """28         print('m1.process_template_response')29         return response30 31 32 class M2(MiddlewareMixin):33     def process_request(self, request):34         print('m2.request')35 36     def process_view(self, request, callback, callback_args, callback_kwargs):37         print('m2.view')38         # response = callback(request, *callback_args, **callback_kwargs)39         # return response40 41     def process_response(self, request, response):42         print('m2.response')43         return response44 45     def process_exception(self, request, exception):46         print('m2.process_exception')47         return HttpResponse('m2.process_exception')48 49     def process_template_response(self, request, response):50         """51         视图函数的返回值中，如果有render方法，才被调用52         :param request:53         :param response:54         :return:55         """56         print('m2.process_template_response')57         return response58 59 60 # class RequestExeute(object):61 #     def process_request(self, request):62 #         print('process_request')63 #64 #     def process_view(self, request, callback, callback_args, callback_kwargs):65 #         print('process_view')66 #67 #     def process_exception(self, request, exception):68 #         """69 #         当views函数出错时执行70 #         :param request:71 #         :param exception:72 #         :return:73 #         """74 #         print('process_exception')75 #76 #     def process_response(self, request, response):77 #         """78 #         必须return HttpResponse79 #         :param request:80 #         :param response:81 #         :return:82 #         """83 #         print('process_response')84 #         return response85 #86 #     def process_template_response(self, request, response):87 #         """88 #         视图函数的返回值中，如果有render方法，才被调用89 #         :param request:90 #         :param response:91 #         :return:92 #         """93 #         print('process_template_response')94 #         return response

M1’s process_request returns HttpResponse

Execution order:

1. m1.request

2. m1.response

process_view is similar to process_request:

 1 from django.shortcuts import HttpResponse 2 
 from django.utils.deprecation import MiddlewareMixin 3 class M1(MiddlewareMixin): 4     
 def process_request(self, request): 5         
 print('m1.request') 6         
 # return HttpResponse('request_m1') 7  8     
 def process_view(self, request, callback, callback_args, callback_kwargs): 9         
 print('m1.view')10         response = callback(request, *callback_args, **callback_kwargs)11         
 return response12 13     def process_response(self, request, response):14         print('m1.response')15         
 return response16 17     def process_exception(self, request, exception):18         
 print('m1.process_exception')19         
 return HttpResponse('m1.process_exception')20 21     def process_template_response(self, request, response):22         """23         视图函数的返回值中，如果有render方法，才被调用24         :param request:25         :param response:26         :return:27         """28         print('m1.process_template_response')29         return response30 31 32 class M2(MiddlewareMixin):33     def process_request(self, request):34         print('m2.request')35 36     def process_view(self, request, callback, callback_args, callback_kwargs):37         print('m2.view')38         # response = callback(request, *callback_args, **callback_kwargs)39         # return response40 41     def process_response(self, request, response):42         print('m2.response')43         return response44 45     def process_exception(self, request, exception):46         print('m2.process_exception')47         return HttpResponse('m2.process_exception')48 49     def process_template_response(self, request, response):50         """51         视图函数的返回值中，如果有render方法，才被调用52         :param request:53         :param response:54         :return:55         """56         print('m2.process_template_response')57         return response

m1’s process_view returns HttpResponse

Execution order:

1. m1.request
   m2.request
   m1.view
   m2.response
   m1.respons

3. Before version 1.10

If process_request returns an HttpResponse object , then the process_request after the current middleware will not be executed, and the process_response of the last middleware will be returned forward

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