【Django】中间件

中间件是介于request与response处理之间的一道处理过程，在全局上改变django的输入与输出

Django默认的Middleware：

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',
]

当用户发起请求的时候会依次经过所有的的中间件，这个时候的请求为process_request,最后到达views的函数中，views函数处理后，再依次穿过中间件，这个时候是process_response,最后返回给请求者

自定义中间件：

首先需要自己创建一个py文件，包含自定义的Middleware类（继承MiddlewareMixin）

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


class CustomerMiddleware(MiddlewareMixin):

	def process_request(self, request):
		print('CustomerMiddleware process_request...')
		# return HttpResponse('<h1>forbidden</h1>')

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

	def process_view(self, request, callback, callback_args, callback_kwargs):
		print('CustomerMiddleware process_view')
		print('callback(视图函数):', callback)

	def process_exception(self, request, exception):
		print('CustomerMiddleware process_exception')


class CustomerMiddleware2(MiddlewareMixin):

	def process_request(self, request):
		print('CustomerMiddleware2 process_request...')

	def process_response(self, request, response):
		print('CustomerMiddleware2 process_response...')
		print('request:', request)
		print('response:', response)
		return response

	def process_view(self, request, callback, callback_args, callback_kwargs):
		print('CustomerMiddleware2 process_view')

	def process_exception(self, request, exception):
		print('CustomerMiddleware2 process_exception')
		return HttpResponse('<h3>Error:%s</h3>' % exception)

在settings.py配置自定义的中间件：

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.MyMiddleware.CustomerMiddleware',
    'app01.MyMiddleware.CustomerMiddleware2',
]

运行结果：

CustomerMiddleware process_request...
CustomerMiddleware2 process_request...
CustomerMiddleware process_view
callback(视图函数): <function index at 0x0471F3D8>
CustomerMiddleware2 process_view
view...
CustomerMiddleware2 process_response...
request: <WSGIRequest: GET '/index/'>
response: <HttpResponse status_code=200, "text/html; charset=utf-8">
CustomerMiddleware process_response...
request: <WSGIRequest: GET '/index/'>
response: <HttpResponse status_code=200, "text/html; charset=utf-8">

中间件包含这四种方法：

process_request  # 请求接收请求数据
process_view  # process_request执行后，依次执行process_view，最后调用视图函数，如果有返回值，会越过其他的process_view以及视图函数，但是所有的process_response都还会执行。
process_exception  #  在视图函数执行出错的时候才会执行该方法
process_response  # 用于返回数据