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from django.utils.deprecation import MiddlewareMixinclass Middle1(MiddlewareMixin): def process_request(self,request):  print("来了") def process_response(self, request,response):  print('走了')

2、在setings文件中注册这个 py文件

django项目的settings模块中，有一个 MIDDLEWARE_CLASSES变量，其中每一个元素就是一个中间件

MIDDLEWARE = [ 'django.middleware.security.SecurityMiddleware', 'django.contrib.sessions.middleware.SessionMiddleware', 'django.middleware.common.CommonMiddleware', 'django.middleware.csrf.CsrfViewMiddleware', 'django.contrib.auth.middleware.AuthenticationMiddleware', 'django.contrib.messages.middleware.MessageMiddleware', 'django.middleware.clickjacking.XFrameOptionsMiddleware', 'M1.Middle1',]

执行结果

为啥报错了呢?

因为自定义的中间件response方法没有return，交给下一个中间件，导致http请求中断了！！！

注意自定义的中间件request 方法不要return 因为返回值中间件不再往下执行，导致 http请求到达不了视图层，因为request在视图之前执行！

from django.utils.deprecation import MiddlewareMixinclass Middle1(MiddlewareMixin): def process_request(self,request):  print("来了") #不用return Django内部自动帮我们传递 def process_response(self, request,response):  print('走了')  return response #执行完了这个中间件一定要 传递给下一个中间件

中间件（类）中5种方法

中间件中可以定义5个方法，分别是：

process_request(self,request) process_view(self, request, callback, callback_args, callback_kwargs) process_template_response(self,request,response) process_exception(self, request, exception) process_response(self, request, response

1、 process_view（self, request, callback, callback_args, callback_kwargs）方法介绍

(1)执行完所有中间件的request方法‘

(2)url匹配成功

(3)拿到视图函数的名称、参数，（注意不执行）再执行process_view()方法

(4)最后去执行视图函数

玩法1（常规）

from django.utils.deprecation import MiddlewareMixinclass M1(MiddlewareMixin): def process_request(self, request):  print('M1.request')  def process_view(self, request,callback,callback_args,callback_kwargs ):  print("M1.process_view")   def process_response(self, request, response):  print('M1.response')  return response class M2(MiddlewareMixin): def process_request(self, request):  print('M2.request')  def process_view(self, request,callback,callback_args,callback_kwargs ):  print("M2.process_view")  def process_response(self, request, response):  print('M2.response')  return response

执行结果

玩法2

既然 process_view 拿到视图函数的名称、参数，（不执行）再执行process_view()方法，最后才去执行视图函数！

那可以在执行process_view环节直接把函数执行返回吗？

from django.utils.deprecation import MiddlewareMixinclass M1(MiddlewareMixin): def process_request(self, request):  print('M1.request')     # callback视图函数名称 callback_args,callback_kwargs 视图函数执行所需的参数 def process_view(self, request,callback,callback_args,callback_kwargs ):  print("M1.process_view")  response=callback(request,*callback_args,**callback_kwargs)  return response def process_response(self, request, response):  print('M1.response')  return responseclass M2(MiddlewareMixin): def process_request(self, request):  print('M2.request')  def process_view(self, request,callback,callback_args,callback_kwargs ):  print("M2.process_view") def process_response(self, request, response):  print('M2.response')  return response

执行结果

结论：

如果process_view函数有返回值，跳转到最后一个中间件，执行最后一个中间件的response方法，逐步返回。

和 process_request方法不一样哦！ request方法在当前中间件的response方法返回。

2、process_exception(self, request, exception)方法

from django.utils.deprecation import MiddlewareMixinclass M1(MiddlewareMixin): def process_request(self, request):  print('M1.request')   def process_view(self, request,callback,callback_args,callback_kwargs ):  print("M1.process_view") def process_response(self, request, response):  print('M1.response')  return response def process_exception(self, request,exception):  print('M1的process_exception')class M2(MiddlewareMixin): def process_request(self, request):  print('M2.request')  def process_view(self, request,callback,callback_args,callback_kwargs ):  print("M2.process_view") def process_response(self, request, response):  print('M2.response')  return response def process_exception(self, request, exception):  print('M2的process_exception')

我去加了process_exception方法咋啥也没执行呢？！！原来是process_exception默认不执行！！！

大爷的原来process_exception方法在视图函数执行出错的时候才会执行

M1.requestM2.requestM1.process_viewM2.process_view执行indexM2的process_exceptionM1的process_exceptionInternal Server Error: /index/Traceback (most recent call last): File "C:\Users\Administrator\AppData\Local\Programs\python/' target='_blank'>python\Python36\lib\site-packages\django\core\handlers\exception.py", line 41, in inner response = get_response(request) File "C:\Users\Administrator\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\handlers\base.py", line 187, in _get_response response = self.process_exception_by_middleware(e, request) File "C:\Users\Administrator\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\handlers\base.py", line 185, in _get_response response = wrapped_callback(request, *callback_args, **callback_kwargs) File "F:\untitled1\app01\views.py", line 7, in index int("ok")ValueError: invalid literal for int() with base 10: 'ok'M2.responseM1.response[03/Jul/2017 16:43:59] "GET /index/ HTTP/1.1" 500 62663

1、执行完所有 request 方法

2、执行所有 process_view方法

3、如果视图函数出错，执行process_exception（最终response，process_exception的return值）

如果process_exception 方法有了返回值就不再执行其他中间件的 process_exception，直接执行response方法响应

4.执行所有response方法

5.最后返回process_exception的返回值

M1.requestM2.requestM1.process_viewM2.process_view执行indexM2的process_exception （有了return值，直接执行response）M2.responseM1.response

process_exception的应用

在视图函数执行出错时，返回错误信息。这样页面就不会报错了！

class M1(MiddlewareMixin): def process_request(self, request):  print('M1.request') def process_view(self, request,callback,callback_args,callback_kwargs ):  print("M1.process_view") def process_response(self, request, response):  print('M1.response')  return response def process_exception(self, request,exception):  print('M1的process_exception')class M2(MiddlewareMixin): def process_request(self, request):  print('M2.request') def process_view(self, request,callback,callback_args,callback_kwargs ):  print("M2.process_view") def process_response(self, request, response):  print('M2.response')  return response def process_exception(self, request, exception):  print('M2的process_exception')  return HttpResponse('出错了兄弟！！！')

3、process_template_response()

from django.utils.deprecation import MiddlewareMixinfrom django.shortcuts import HttpResponseclass M1(MiddlewareMixin): def process_request(self, request):  print('M1.request') def process_view(self, request,callback,callback_args,callback_kwargs ):  print("M1.process_view") def process_response(self, request, response):  print('M1.response')  return response def process_exception(self, request,exception):  print('M1的process_exception')class M2(MiddlewareMixin): def process_request(self, request):  print('M2.request') def process_view(self, request,callback,callback_args,callback_kwargs ):  print("M2.process_view") def process_response(self, request, response):  print('M2.response')  return response def process_exception(self, request, exception):  print('M2的process_exception') def process_template_response(self,request,response):  print('M2process_template_response')  return response

process_template_response()默认不执行

rocess_template_response()特性

只有在视图函数的返回对象中有render方法才会执行！

并把对象的render方法的返回值返回给用户（注意不返回视图函数的return的结果了，而是返回视图函数 return值（对象）的render方法）

from django.utils.deprecation import MiddlewareMixinfrom django.shortcuts import HttpResponseclass M1(MiddlewareMixin): def process_request(self, request):  print('M1.request') def process_view(self, request,callback,callback_args,callback_kwargs ):  print("M1.process_view") def process_response(self, request, response):  print('M1.response')  return response def process_exception(self, request,exception):  print('M1的process_exception')class M2(MiddlewareMixin): def process_request(self, request):  print('M2.request') def process_view(self, request,callback,callback_args,callback_kwargs ):  print("M2.process_view") def process_response(self, request, response):  print('M2.response')  return response def process_exception(self, request, exception):  print('M2的process_exception') def process_template_response(self,request,response): #如果视图函数中的返回值 中有render方法，才会执行 process_template_response  print('M2process_template_response')  return response

视图函数

from django.shortcuts import render,HttpResponse# Create your views here.class Foo(): def __init__(self,requ):  self.req=requ def render(self):  return HttpResponse('OKKKK')def index(request): print("执行index") obj=Foo(request) return obj

执行结果

应用：

既然process_template_respnse,不返回视图函数的return的结果，而是返回视图函数 return值（对象）的render方法;(多加了一个环节)

就可以在这个视图函数返回对象的 render方法里，做返回值的二次加工了！多加工几个，视图函数就可以随便使用了！

（好比喷雾器有了多个喷头，换不同的喷头喷出不同水，返回值就可以也组件化了）

from django.shortcuts import render,HttpResponse# Create your views here.class Dict(): #对视图函数返回值做二次封装 ！！ def __init__(self,requ,msg):  self.req=requ   self.msg=msg def render(self):  a=self.msg #在render方法里面 把视图函数的 返回值 制作成字典 、列表等。。。      # 如果新增了其他 一个视图函数直接，return对象 即可！不用每个视图函数都写 制作字典 列表 拼接的逻辑了  return HttpResponse(a) #def index(request): print("执行index") obj=Dict(request,"vv") return obj