Django中间件的详细介绍

写了几周的脚本，今天终于开始接触web框架了~学习Python的web框架，那么Django就几乎是必修课了，这次的工作是先打打下手，主要的任务是在setting中添加版本号,在渲染静态css,js的路径时附带版本号,例如“example.v1124.css”，然后再在request请求中祛除掉版本号。为什么要这么做呢？因为这样做的话在前端输出静态文件的路径就会加上就会加上版本号，这样当开发出新的静态文件的时候，客户端就会强制刷新本地的缓存，为了达到这个目的就要首先要在settings文件中配置，这样就可以每次修改的时候直接从settings读取版本号了

一、Django中间件的请求周期

我们从浏览器发出一个请求 Request，得到一个响应后的内容 HttpResponse ，这个请求传递到 Django的过程如下：

也就是说，每一个请求都是先通过中间件中的 process_request 函数，这个函数返回 None 或者 HttpResponse 对象，如果返回前者，继续处理其它中间件，如果返回一个 HttpResponse，就处理中止，返回到网页上。

二、自定义及注册中间件

1. 创建中间件

在project根目录下创建中间件py文件：

 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. 注册中间件

在settings.py文件中，按照欲执行的顺序注册：

ps. 在1.9及之前的版本中，中间件的关键字为：MIDDLEWARE_CLASSES

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

三、中间件中方法的执行顺序

1. 正常状况

 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和process_view返回None

执行顺序：

1. m1.request

2. m2.request

3. m1.view

4. m2.view

5. m2.response

6. m1.response

2. 在版本1.10及之后

若process_request返回HttpResponse 对象，则从当前中间件的process_response向前返回

 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的process_request返回HttpResponse

执行顺序：

1. m1.request

2. m1.response

process_view与process_request类似：

 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的process_view返回HttpResponse

执行顺序：

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

3. 在版本1.10之前

若process_request返回HttpResponse 对象，则当前中间件之后的process_request都不会执行，而从最后一个中间件的process_response向前返回

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