1.中间件的概念
中间件，是介于request与response处理之间的处理程序，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，所以需要谨慎使用，否则会影响性能。
如果想修改views.py中的HttpRequest对象或HttpResponse对象，可以通过中间件来实现。
Django中默认的中间件
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',
]2.自定义中间件
2.1中间件共有四个方法
process_request
process_view
process_exception
process_response2.2自带中间件的process_request与process_response
当用户发起请求的时候，首先执行所有中间件的process_request函数。
之后到达views函数。
然后执行process_response函数。
最后返回给请求者。
下面是dajngo中的自带中间件，
2.3自定义中间件的process_request与process_response
settings.py
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',
'app1.my_middleware.Md1',
'app1.my_middleware.Md2',
]views.py
from django.shortcuts import render,HttpResponse,redirect
def index(request):
print("view函数")
return HttpResponse("OK")my_middleware.py
#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author: vita
from django.utils.deprecation import MiddlewareMixin
from django.shortcuts import HttpResponse
class Md1(MiddlewareMixin):
def process_request(self,request):
print("Md1请求")
def process_response(self,request,response):
print("Md1返回")
return response
class Md2(MiddlewareMixin):
def process_request(self,request):
print("Md2请求")
#return HttpResponse("Md2中断")
def process_response(self,request,response):
print("Md2返回")
return response
结果
Md1请求
Md2请求
view函数
Md2返回
Md1返回
如果在Md2中直接返回return HttpResponse("Md2中断"),程序将跳过views中的视图函数，直接执行中间件的process_response
结果为
Md1请求
Md2请求
Md2返回
Md1返回
2.4process_view()函数
2.4.1process_view()
process_view(self, request, callback, callback_args, callback_kwargs)my_middleware.py
from django.utils.deprecation import MiddlewareMixin
from django.shortcuts import HttpResponse
class Md1(MiddlewareMixin):
def process_request(self,request):
print("Md1请求")
#return HttpResponse("Md1中断")
def process_response(self,request,response):
print("Md1返回")
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print("Md1view")
class Md2(MiddlewareMixin):
def process_request(self,request):
print("Md2请求")
#return HttpResponse("Md2中断")
def process_response(self,request,response):
print("Md2返回")
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print("Md2view")运行结果
Md1请求
Md2请求
Md1view
Md2view
view函数
Md2返回
Md1返回
2.4.2process_view()调用视图函数
my_middleware.py
from django.utils.deprecation import MiddlewareMixin
from django.shortcuts import HttpResponse
class Md1(MiddlewareMixin):
def process_request(self,request):
print("Md1请求")
#return HttpResponse("Md1中断")
def process_response(self,request,response):
print("Md1返回")
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print("Md1view")
# 调用视图函数
response = callback(request, *callback_args, **callback_kwargs)
return response
class Md2(MiddlewareMixin):
def process_request(self,request):
print("Md2请求")
#return HttpResponse("Md2中断")
def process_response(self,request,response):
print("Md2返回")
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print("Md2view")结果
Md1请求
Md2请求
Md1view
view函数
Md2返回
Md1返回
2.4.3process_view()中return HttpResponse
my_middleware.py
from django.utils.deprecation import MiddlewareMixin
from django.shortcuts import HttpResponse
class Md1(MiddlewareMixin):
def process_request(self,request):
print("Md1请求")
#return HttpResponse("Md1中断")
def process_response(self,request,response):
print("Md1返回")
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print("Md1view")
# process_view中返回HttpResponse
return HttpResponse("Md1view 中断")
class Md2(MiddlewareMixin):
def process_request(self,request):
print("Md2请求")
#return HttpResponse("Md2中断")
def process_response(self,request,response):
print("Md2返回")
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print("Md2view")结果
Md1请求
Md2请求
Md1view
Md2返回
Md1返回
2.5process_exception()函数
2.5.1process_exception()
my_middleware.py
from django.utils.deprecation import MiddlewareMixin
from django.shortcuts import HttpResponse
class Md1(MiddlewareMixin):
def process_request(self, request):
print("Md1请求")
# return HttpResponse("Md1中断")
def process_response(self, request, response):
print("Md1返回")
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
# return HttpResponse("hello")
# response=callback(request,*callback_args,**callback_kwargs)
# return response
print("md1 process_view...")
def process_exception(self, request, exception):
print("md1 process_exception...")
class Md2(MiddlewareMixin):
def process_request(self, request):
print("Md2请求")
# return HttpResponse("Md2中断")
def process_response(self, request, response):
print("Md2返回")
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print("md2 process_view...")
def process_exception(self, request, exception):
print("md2 process_exception...")views.py
from django.shortcuts import render,HttpResponse,redirect
def index(request):
print("view函数")
ui
return HttpResponse("OK")结果
Md1请求
Md2请求
md1 process_view...
md2 process_view...
view函数
md2 process_exception...
md1 process_exception...
Md2返回
Md1返回
2.5.2process_exception()中return HttpResponse
my_middleware.py
from django.utils.deprecation import MiddlewareMixin
from django.shortcuts import HttpResponse
class Md1(MiddlewareMixin):
def process_request(self, request):
print("Md1请求")
# return HttpResponse("Md1中断")
def process_response(self, request, response):
print("Md1返回")
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
# return HttpResponse("hello")
# response=callback(request,*callback_args,**callback_kwargs)
# return response
print("md1 process_view...")
def process_exception(self, request, exception):
print("md1 process_exception...")
class Md2(MiddlewareMixin):
def process_request(self, request):
print("Md2请求")
# return HttpResponse("Md2中断")
def process_response(self, request, response):
print("Md2返回")
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print("md2 process_view...")
def process_exception(self, request, exception):
print("md2 process_exception...")
# 返回HttpResponse
return HttpResponse("Md2exception中断")结果
Md1请求
Md2请求
md1 process_view...
md2 process_view...
view函数
md2 process_exception...
Md2返回
Md1返回
2.6应用案例
1.做IP访问频率限制
某些IP访问服务器的频率过高，进行拦截，比如限制每分钟不能超过20次。
2.URL访问过滤
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！
尝试阅读
'django.contrib.sessions.middleware.SessionMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',