Django的請求的生命周期：

中間件

process_request(self,request)

參數：

request 請求的對象，和視圖中的request是同一個

執行時間：視圖函數之前

執行順序：

按照注冊的順序 順序執行

傳回值

None ： 正常流程

HttpReponse: 目前中間件之後的中間件的process_request方法、路由比對、視圖也不執行，直接執行目前中間件的process_response方法

settings：

"""
Django settings for about_middleware project.

Generated by 'django-admin startproject' using Django 1.11.26.

For more information on this file, see
https://docs.djangoproject.com/en/1.11/topics/settings/

For the full list of settings and their values, see
https://docs.djangoproject.com/en/1.11/ref/settings/
"""

import os

# Build paths inside the project like this: os.path.join(BASE_DIR, ...)
BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))


# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/1.11/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = '^t344mb401h!=^hd&igb4_-39*z$ldlb(0$4a==4r7lu+6)yb8'

# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = True

ALLOWED_HOSTS = []


# Application definition

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'app01.apps.App01Config',
]

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.middlewares.my_middleware.MD1',  #注冊中間件1
    'app01.middlewares.my_middleware.MD2',  #注冊中間件2
]

ROOT_URLCONF = 'about_middleware.urls'

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [os.path.join ( BASE_DIR, 'templates' )]
        ,
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

WSGI_APPLICATION = 'about_middleware.wsgi.application'


# Database
# https://docs.djangoproject.com/en/1.11/ref/settings/#databases

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
    }
}


# Password validation
# https://docs.djangoproject.com/en/1.11/ref/settings/#auth-password-validators

AUTH_PASSWORD_VALIDATORS = [
    {
        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
    },
]


# Internationalization
# https://docs.djangoproject.com/en/1.11/topics/i18n/

LANGUAGE_CODE = 'en-us'

TIME_ZONE = 'UTC'

USE_I18N = True

USE_L10N = True

USE_TZ = True


# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/1.11/howto/static-files/

STATIC_URL = '/static/'
定義中間件my_middleware：
      

from django.utils.deprecation import MiddlewareMixin
from django.shortcuts import HttpResponse

class MD1(MiddlewareMixin):
    def process_request(self,request):
        # print(id(request))
        # request.name = "alexdsb"
        print(" MD1 process_request ")
        return HttpResponse("md1 response")

class MD2(MiddlewareMixin):
    def process_request(self,request):
        print("MD2 process_request")      

process_response(self, request, response)

response 傳回的響應對象

執行時間：視圖函數之後

按照注冊的順序 倒叙執行

HttpReponse: 必須傳回響應對象

process_view(self, request, view_func, view_args, view_kwargs)

view_func 視圖函數

view_args 視圖函數的位置參數

view_kwargs 視圖函數的關鍵字參數

執行時間：路由比對之後，視圖函數之前

None 正常流程

HttpReponse: 目前中間件之後的process_view、視圖不執行，執行最後一個中間的process_response

process_exception(self, request, exception)

exception 錯誤對象

執行時間（觸發條件）：視圖層面有錯誤才執行

None 目前中間沒有處理異常，交由下一個中間件處理異常，所有的中間件都沒有處理，Django處理錯誤

HttpReponse: 目前中間處理好異常，之後執行最後一個中間件的process_response方法

pocess_template_response(self,request,response)

執行時間：視圖必須傳回一個template_response對象

 response.template_name = 'index1.html'  # 改模闆
 response.context_data # 改變量