Django(中间件)

1.新建mid模块，模块下新建middle.py
------------middle.py
from django.utils.deprecation import MiddlewareMixin
from django.shortcuts import HttpResponse

class MYMiddlewareMixin(MiddlewareMixin):                        #自定义类，用时拷贝即可
    def __init__(self, get_response=None):
        self.get_response = get_response
        super().__init__()

    def __call__(self, request):
        response = None
        if hasattr(self, ‘process_request‘):                     #判断类中是否有process_request()，名字可以更改
            response = self.process_request(request)
        if not response:
            response = self.get_response(request)
        if hasattr(self, ‘process_response‘):
            response = self.process_response(request, response)
        return response


class GYK(MYMiddlewareMixin):
    def process_request(self,request):        #1请求
        print("11")
        # return HttpResponse("你大爷")         #如果有return，不会执行下一个中间件
    def process_response(self,request,response):   #4返回
        print("22")
        return response
class BYK(MYMiddlewareMixin):
    def process_request(self,request):        #2
        print("33")
    def process_response(self,request,response):   #3
        print("44")
        return response



-------------settings.py(csrf也是中间件)
ps:以下中间件按照顺序执行

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‘,
    "app01.mid.middle.GYK",                   
    "app01.mid.middle.BYK",
]


-------------urls.py

urlpatterns = [
    path(‘admin/‘, admin.site.urls),
    path("middle/",views.middle),
]

---------------views.py

def middle(req):
    return HttpResponse("Test")


ps：因为中间件按照顺序执行,所以打印结果为：
1.11
2.33
3.44
4.22

一般的执行顺序：1.先执行请求函数process_request  2.执行views函数  3.再执行回应函数process_response。views.py函数中返回“Test”，传给BYK中的response，再传给GYK中的response，再返回给客户。
二般的执行顺序：如果A中间件的process_request()有return HttpResponse("xxx"),不会执行下一个中间件，也不会执行到views.py函数，只执行A中间件，返回给用户xxx
只有将自定义的中间件添加进settings.py中才能执行