Django的中间件

django 中的中间件（middleware），在django中，中间件其实就是一个类，在请求到来和结束后，django会根据自己的规则在合适的时机执行中间件中相应的方法。

在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，如下图。

应用：对所有请求或一部分请求做批量处理

与mange.py在同一目录下，

中间件中可以定义四个方法，分别是：

• process_request(self,request)
• process_view(self, request, callback, callback_args, callback_kwargs) 如有有returnresponse则跳到最后
• process_template_response(self,request,response)  视图函数的返回值中，如果有render方法，才被调用
• process_exception(self, request, exception) 异常则跳到最后
• process_response(self, request, response) 

以上方法的返回值可以是None和HttpResonse对象，如果是None，则继续按照django定义的规则向下执行，如果是HttpResonse对象，则直接将该对象返回给用户。

　　　　　　　　　　　　　　　　　

案例：

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

"""
Django settings for 中间件 project.

Generated by 'django-admin startproject' using Django 1.11.2.

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 = '_u3mq4drv23_yumdj3_7ip62#n!vjbp74se*-qr%$35m@+-id&'

# 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',
]

from django.middleware.common import CommonMiddleware
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',
    'md.M1',
    'md.M2',
]

ROOT_URLCONF = '中间件.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 = '中间件.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/'
STATICFILES_DIRS = (
    os.path.join(BASE_DIR,'static'),
)

from django.shortcuts import render,HttpResponse,redirect

# class JSONResponse:
#     def __init__(self,req,status,msg):
#         self.req = req
#         self.status = status
#         self.msg = msg
#     def render(self):
#         import json
#         ret = {
#             'status':self.status,
#             'msg':self.msg
#         }
#         return HttpResponse(json.dumps(ret))
#
# def test(request):
#     # print('test')
#     # return HttpResponse("...")
#     # ret = {}
#     return JSONResponse(request,True,"错误信息")


def test(request):
    print('test')
    return HttpResponse("...")

from django.utils.deprecation import MiddlewareMixin
from django.shortcuts import HttpResponse
class M1(MiddlewareMixin):
    def process_request(self,request):
        print('m1.process_request')

    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.process_response')
        return response

    def process_exception(self, request, exception):
        print('m1.process_exception')

    def process_template_response(self,request,response):
        """
        视图函数的返回值中，如果有render方法，才被调用
        :param request:
        :param response:
        :return:
        """
        print('m1.process_template_response')
        return response

class M2(MiddlewareMixin):
    def process_request(self,request):
        print('m2.process_request')
    def process_view(self, request, callback, callback_args, callback_kwargs):
        print('m2.process_view')
    def process_response(self,request,response):
        print('m2.process_response')
        return response
    def process_exception(self, request, exception):
        print('m2.process_exception')
        return HttpResponse('错误了...')

process_template_response(self,request,response) 

from django.shortcuts import render,HttpResponse,redirect

class JSONResponse:
    def __init__(self,req,status,msg):
        self.req = req
        self.status = status
        self.msg = msg
    def render(self):
        import json
        ret = {
            'status':self.status,
            'msg':self.msg
        }
        return HttpResponse(json.dumps(ret))

md.py和settings.py上面一样。