中间件
中间件是介于request与response处理之间的一道处理过程，相对比较轻量级，并且在全局上改变django的输入与输出。因为改变的是全局，所以需要谨慎实用，用不好会影响到性能。
Django的中间件的定义：
Middleware is a framework of hooks into Django’s request/response processing. <br>It’s a light, low-level “plugin” system for globally altering Django’s input or output.
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', ]
每一个中间件都有具体的功能。
django默认7个中间件，其实就是一个类。
django请求周期
自定义中间件
中间件一共有四个方法：
process_request
process_view
process_exception
process_response
当用户发起请求的时候会依次经过所有的的中间件，这个时候的请求时process_request,最后到达views的函数中，views函数处理后，在依次穿过中间件，这个时候是process_response,最后返回给请求者。
上述截图中的中间件都是django中的，我们也可以自己定义一个中间件，我们可以自己写一个类，但是必须继承MiddlewareMixin
需要导入：
from django.utils.deprecation import MiddlewareMixin
process_response是在中间件里边一层层的传，先到第一个个中间件，再到第二个，是依次执行的
视图函数在校验时候，可以把校验写在某个中间件里边去，在这里边写一次，进来的所有请求都可以校验下，不用一个个加装饰器了。
from django.utils.deprecation import MiddlewareMixin class CustomerMiddleware(MiddlewareMixin): def process_request(self, request): print('CustomerMiddleware1 process_request') class CustomerMiddleware2(MiddlewareMixin): def process_request(self, request): print('CustomerMiddleware2 process_request')
'app01.my_middlewares.CustomerMiddleware', 'app01.my_middlewares.CustomerMiddleware2', #这两个中间件里边的process_request依次执行； 它是全局的逻辑处理
CustomerMiddleware1 process_request CustomerMiddleware2 process_request index #先走中间件，再进视图函数打印它 [15/Jun/2018 10:01:38] "GET /index/ HTTP/1.1" 200 5
from django.shortcuts import render, HttpResponse # Create your views here. def index(request): print('index') return HttpResponse("INDEX") #相应体就是INDEX这个字符串，先执行后边的中间件，先交给CustomerMiddleware2的process_response，执行完自己的逻辑，又把response交给了它上一个中间件的process_response，然后执行它的逻辑打印，就这样子传接力棒 def index_new(request): return HttpResponse('index_new')
from django.utils.deprecation import MiddlewareMixin class CustomerMiddleware(MiddlewareMixin): def process_request(self, request): print('CustomerMiddleware1 process_request') def process_response(self, request,response): #response就是HttpResponse（INDEX）相应体对象 print('CustomeerMiddleware1 process_request') return response #它必须要有返回值，就像接力棒一层层传给别人；在process_request里边必须要写返回值。 class CustomerMiddleware2(MiddlewareMixin): def process_request(self, request): print('CustomerMiddleware2 process_request') def process_response(self, request,response): print('CustomeerMiddleware2 process_request') return response
CustomerMiddleware1 process_request CustomerMiddleware2 process_request index CustomeerMiddleware2 process_request CustomeerMiddleware1 process_request [15/Jun/2018 10:11:12] "GET /index/ HTTP/1.1" 200 5
#相应体就是INDEX这个字符串，先执行后边的中间件，先交给CustomerMiddleware2的process_response，执行完自己的逻辑，
又把response交给了它上一个中间件的process_response，然后执行它的逻辑打印，就这样子传接力棒
如果非要在process_request加个返回值，
from django.utils.deprecation import MiddlewareMixin from django.shortcuts import HttpResponse class CustomerMiddleware(MiddlewareMixin): def process_request(self, request): print('CustomerMiddleware1 process_request') return HttpResponse('forbidden..') def process_response(self, request,response): #response就是HttpResponse（INDEX）相应体对象 print('CustomeerMiddleware1 process_request') return response #它必须要有返回值，就像接力棒一层层传给别人 class CustomerMiddleware2(MiddlewareMixin): def process_request(self, request): print('CustomerMiddleware2 process_request') def process_response(self, request,response): print('CustomeerMiddleware2 process_request') return response
CustomerMiddleware1 process_request CustomeerMiddleware1 process_request [15/Jun/2018 10:29:42] "GET /index/ HTTP/1.1" 200 11 #访问http://127.0.0.1:8000/index/打印的是forbidden..
没有执行中间件2的内容，也没有执行视图。
url请求中间件1的process_request的时候，一旦加了返回值，直接把相应体交给自己的process_response，交给浏览器。一下子给拦截了。应用场景：拦截，你的ip频率太高；session进行校验的时候没有登录也给你拦截下来。
process_view
[15/Jun/2018 10:40:45] "GET /index/ HTTP/1.1" 200 5 CustomerMiddleware1 process_request CustomerMiddleware2 process_request CustomerMiddleware1:process_view CustomerMiddleware2:process_view index CustomeerMiddleware2 process_request CustomeerMiddleware1 process_request
#Author:Kris from django.utils.deprecation import MiddlewareMixin from django.shortcuts import HttpResponse class CustomerMiddleware(MiddlewareMixin): def process_request(self, request): print('CustomerMiddleware1 process_request') #return HttpResponse('forbidden..') def process_view(self, request, callback, callback_args, callback_kwargs): print("CustomerMiddleware1:process_view") def process_response(self, request,response): #response就是HttpResponse（INDEX）相应体对象 print('CustomeerMiddleware1 process_request') return response #它必须要有返回值，就像接力棒一层层传给别人 class CustomerMiddleware2(MiddlewareMixin): def process_request(self, request): print('CustomerMiddleware2 process_request') def process_response(self, request,response): print('CustomeerMiddleware2 process_request') return response def process_view(self, request, callback, callback_args, callback_kwargs): #print("===>",callback) #===> <function index at 0x0000000003DE11E0> 视图函数 #在进入到2的视图函数的时候，把相应体返回了 123，那么视图函数就不执行了，接着往下执行process_response print("===>",callback(callback_args)) print("CustomerMiddleware2:process_view") ret = callback(callback_args) ###可以进行拦截。 return ret #把它的结果返回了就可以拿到index了 #return HttpResponse('123')
process_exception
CustomerMiddleware1 process_request CustomerMiddleware2 process_request CustomerMiddleware1:process_view CustomerMiddleware2:process_view index #打印完视图就报错了，报错没有拿到相应体HttpResponse(index),直接走下面的process_exception CustomeerMiddleware2 process_exception CustomeerMiddleware1 process_exception Internal Server Error: /index/ 出错
CustomeerMiddleware2 process_request
CustomeerMiddleware1 process_request
#Author:Kris from django.utils.deprecation import MiddlewareMixin from django.shortcuts import HttpResponse class CustomerMiddleware(MiddlewareMixin): def process_request(self, request): print('CustomerMiddleware1 process_request') #return HttpResponse('forbidden..') def process_view(self, request, callback, callback_args, callback_kwargs): print("CustomerMiddleware1:process_view") def process_response(self, request,response): #response就是HttpResponse（INDEX）相应体对象 print('CustomeerMiddleware1 process_request') return response #它必须要有返回值，就像接力棒一层层传给别人 def process_exception(self, request, exception): print('CustomeerMiddleware1 process_exception') class CustomerMiddleware2(MiddlewareMixin): def process_request(self, request): print('CustomerMiddleware2 process_request') def process_response(self, request,response): print('CustomeerMiddleware2 process_request') return response def process_view(self, request, callback, callback_args, callback_kwargs): #print("===>",callback) #===> <function index at 0x0000000003DE11E0> 视图函数 #在进入到2的视图函数的时候，把相应体返回了 123，那么视图函数就不执行了，接着往下执行process_response #print("===>",callback(callback_args)) print("CustomerMiddleware2:process_view") # ret = callback(callback_args) # return ret #把它的结果返回了就可以拿到index了 #return HttpResponse('123') def process_exception(self, request, exception): print('CustomeerMiddleware2 process_exception') return HttpResponse(exception) #一旦有一个return了，后边1的process_exception就不执行了
CustomerMiddleware1 process_request CustomerMiddleware2 process_request CustomerMiddleware1:process_view CustomerMiddleware2:process_view index CustomeerMiddleware2 process_exception CustomeerMiddleware2 process_request CustomeerMiddleware1 process_request [15/Jun/2018 11:34:36] "GET /index/ HTTP/1.1" 200 26
如果把写到1里边，2不要，return HttpResponse(exception)
CustomerMiddleware1 process_request CustomerMiddleware2 process_request CustomerMiddleware1:process_view CustomerMiddleware2:process_view index CustomeerMiddleware2 process_exception CustomeerMiddleware1 process_exception CustomeerMiddleware2 process_request CustomeerMiddleware1 process_request [15/Jun/2018 11:37:28] "GET /index/ HTTP/1.1" 200 26
应用URL访问过滤 在auth_Demo
如果用户访问的是login视图（放过）
如果访问其他视图，需要检测是不是有session认证，已经有了放行，没有返回login，这样就省得在多个视图函数上写装饰器了！
from django.utils.deprecation import MiddlewareMixin from django.shortcuts import HttpResponse,redirect from authDemo import settings class AuthMiddleware(MiddlewareMixin): def process_request(self, request): white_list = settings.WHITE_LIST if request.path in white_list: return None if not request.user.is_authenticated: return redirect("/login/")