Django中的MiddleWare中間件

1. middleware簡介

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Django的middleware的概念相當於SSH框架里面的filter的概念。中間鍵的作用就是對所有的request，在request前，和在response后做一定的處理。

Django的中間鍵類型分為五種:

　　 請求(Request)中間件->對應函數process_request
　　視圖(View)中間件->對應函數process_view
　　模板(Template)中間件->對應函數process_template_response（不常用）
　　響應(Response)中間件->對應函數process_response
　　異常(Exception)中間件->對應函數process_exception（不常用）

2. middleware中間鍵函數的執行順序和過程

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 （1）請求（Request）中間件和響應（Response）中間件的正常執行順序

接下來就用程序演示：

m1.py

from django.utils.deprecation import MiddlewareMixin

class ROW1(MiddlewareMixin):
    def process_request(self,request):
        print("朱三")

    def process_response(self,request,response):
        print('趙六')
        return response

class ROW2(MiddlewareMixin):
    def process_request(self,request):
        print("李四")

    def process_response(self,request,response):
        print('薛七')
        return response

class ROW3(MiddlewareMixin):
    def process_request(self,request):
        print("王五")

    def process_response(self,request,response):
        print('宋八')
        return response
 

views.py

def test(request):
    # int("asdsadsad")
    print('小豬->沒帶錢')
    return HttpResponse("OK")

所以順序為：朱三-->李四-->王五-->小豬-->沒帶錢-->宋八-->薛七-->趙六

如果在中間件中發生錯誤，那么其執行順序為

 m1.py

from django.utils.deprecation import MiddlewareMixin

class ROW1(MiddlewareMixin):
    def process_request(self,request):
        print("朱三")
    def process_response(self,request,response):
        print('趙六')
        return response
    

from django.shortcuts import HttpResponse
class ROW2(MiddlewareMixin):
    def process_request(self,request):
        print("李四")
        return HttpResponse('離開')

    def process_response(self,request,response):
        print('薛七')
        return response


class ROW3(MiddlewareMixin):
    def process_request(self,request):
        print("王五")

    def process_response(self,request,response):
        print('宋八')
        return response
    

views與上面一樣，執行順序為：朱三-->李四-->薛七-->趙六

 （2）視圖中間件執行順序

from django.utils.deprecation import MiddlewareMixin

class ROW1(MiddlewareMixin):
    def process_request(self,request):
        print("朱三")

    def process_response(self,request,response):
        print('趙六')
        return response

     def process_view(self, request, veiw_func, veiw_func_args, veiw_func_kwargs):
         print('張欣彤')


from django.shortcuts import HttpResponse
class ROW2(MiddlewareMixin):
    def process_request(self,request):
        print("李四")
       

    def process_response(self,request,response):
        print('薛七')
        return response

     def process_view(self, request, veiw_func, veiw_func_args, veiw_func_kwargs):
         print('張需要')


class ROW3(MiddlewareMixin):
    def process_request(self,request):
        print("王五")

    def process_response(self,request,response):
        print('宋八')

        return response
     def process_view(self, request, veiw_func, veiw_func_args, veiw_func_kwargs):
         print('邵林')

    

views.py代碼與其最上的views.py代碼相同

則執行順序為：朱三-->李四-->王五-->張欣彤-->張需要-->邵林-->小豬-->沒帶錢-->宋八-->薛七-->趙六

而模板中間件（函數中出現render才生效）和異常中間價（函數出現錯誤才生效）因為不常用，默認不生效，所以就不詳細介紹了。

3.自定義中間件

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（1）創建中間件

class RequestExeute(object):
      
    def process_request(self,request):
        pass
    def process_view(self, request, callback, callback_args, callback_kwargs):
        i =1
        pass
    def process_exception(self, request, exception):
        pass
      
    def process_response(self, request, response):
        return response

（2）注冊中間件

MIDDLEWARE_CLASSES = (
    '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',
    'wupeiqi.middleware.auth.RequestExeute',
)