Django--中间件

Posted 2020-06-23 大亮头

1、原理

在django中，中间件其实就是一个类，在请求到来和结束后，django会根据自己的规则在合适的时机执行中间件中相应的方法。

请求到来时，在wsgi和urls中间有一层中间件，准确的说是4层方法和Django框架的处理：

1. process_request(self,request)

2. process_view(self, request, callback, callback_args, callback_kwargs)

3. views

4. process_exception(self, request, exception)

5. process_response(self, request, response)

这些函数的名称和参数不能改变，任何一个环节具有Response，就会交给process_response（）处理，从而返回给用户。

2、自定义中间件

创建package

middle1.py

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class mmm(object):     def process_request(self,request):         print "mmm.process_request"     def process_view(self,request,callback,callback_args,callback_kwargs):         print "mmm.process_view"     def process_response(self,request,response):         print "mmm.process_response"         return  response   class xxx(object):     def process_request(self,request):         print "xxx.process_request"     def process_view(self,request,callback,callback_args,callback_kwargs):         print "xxx.process_view"     def process_response(self,request,response):         print "xxx.process_response"         return  response

settings.py

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MIDDLEWARE_CLASSES = [     ‘django.middleware.security.SecurityMiddleware‘,     ‘django.contrib.sessions.middleware.SessionMiddleware‘,     ‘django.middleware.common.CommonMiddleware‘,     # ‘django.middleware.csrf.CsrfViewMiddleware‘,     ‘django.contrib.auth.middleware.AuthenticationMiddleware‘,     ‘django.contrib.auth.middleware.SessionAuthenticationMiddleware‘,     ‘django.contrib.messages.middleware.MessageMiddleware‘,     ‘django.middleware.clickjacking.XFrameOptionsMiddleware‘,     ‘middleware.middle1.mmm‘,     ‘middleware.middle1.xxx‘, ]

views.py

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def index(request):     print "view"     return HttpResponse("index")

IDE

可以看到执行顺序，注意的是，process_response（）的执行顺序是从后往前的。

3、源码

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#Django自动去settings里找 MIDDLEWARE_CLASSES process_request_list=[] process_view_list=[] process_response_list=[] process_exception_list=[] for class in  MIDDLEWARE_CLASSES:     obj = class()     if hasattr(obj,process_request):         process_request_list.append(obj.process_request)     if hasattr(obj,process_view):         process_view_list.append(obj.process_view)     if hasattr(obj,process_response):         process_response_list.append(obj.process_response)     if hasattr(obj,process_exception):         process_exception_list.append(obj.process_exception) for i in process_request_list:     i() for i in process_view_list:     i() #Django渲染 for i in process_exception_list:     i() for i in process_response_list:     i()

4、process_exception

views.py

1 2	def index(request):     raise Exception("报错了")

middleware/middle.py

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class mmm(object):     def process_request(self,request):         print "mmm.process_request"     def process_view(self,request,callback,callback_args,callback_kwargs):         print "mmm.process_view"     def process_response(self,request,response):         print "mmm.process_response"         return  response     def process_exception(self, request, exception):         print exception         return request

browser

IDE

注意：?

• process_request和process_view方法是按自定义中间件的顺序执行
  

• process_exception和process_response是按中间件从后往前的顺序执行
  

来自为知笔记(Wiz)