中间件中一共有四个方法:
1. process_request
2. process_view
3. process_exception
4. process_response
中间键流程:

中间件的创建:
from django.utils.deprecation import MiddlewareMixin
class MyCustomMiddleware1(MiddlewareMixin):
def process_request(self, request):
print('MyCustomMiddleware1')
def process_response(self, request, response):
print('返回 MyCustomMiddleware2')
return response