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。
应用场景,对所有请求统一进行处理,例如做身份验证、黑名单检测等
在django项目的settings模块中,有一个 MIDDLEWARE变量,其中每一个元素就是一个中间件,如下图。
一个请求的往返都会经过中间件过滤。路径图如下;
与mange.py在同一目录下的文件夹 Middle下的mi.py文件中的Row1类
中间件中可以定义四个方法,分别是:
- process_request(self,request) --->请求来的时候处理方式
- process_view(self, request, callback, callback_args, callback_kwargs) --->获取请求url参数,修改views函数逻辑
- process_template_response(self,request,response)
- process_exception(self, request, exception) --->异常处理专用,当自己写的views函数报错的时候,就执行,exception就是报错内容
- process_response(self, request, response) --->到请求处理函数后请求处理
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。
自定义中间件
1、创建中间件类m1.py
m1.py
from django.utils.deprecation import MiddlewareMixin
class Row1(MiddlewareMixin):
def process_request(self, request):
print('request Row1 ')
def process_response(self,request,response):
print('Row1-Response')
return response
class Row2(MiddlewareMixin):
def process_request(self, request):
print('request Row2 ')
def process_response(self,request,response):
print('Row2-Response')
return response
class Row3(MiddlewareMixin):
def process_request(self, request):
print('request Row3 ')
def process_response(self,request,response):
print('Row3-Response')
return response
2、注册中间件
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',
'Middle.m1.Row1',
'Middle.m1.Row2',
'Middle.m1.Row3',
]
访问:
测试中间process_response(self, request, response)返回HttpResonse对象,则直接将该对象返回给用户。
class Row2(MiddlewareMixin):
def process_request(self, request):
print('request Row2 ')
def process_response(self,request,response):
print('Row2-Response')
# return response
return HttpResponse('OK')
结果,任何请求到中间逻辑被返回
process_view(self, request, callback, callback_args, callback_kwargs)
process_view 函数执行流程在 process_request(self,request) 和 process_response(self, request, response) 之间
形参说明:
callback:处理请求的最终自定义view函数
callback_args:请求过来的url中具体的未命名正则分组变量 如
callback_kwargs: 求过来的url中具体的已命名正则分组变量字典
process_view 示例代码
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
# @Time: 2020/7/21 22:58
# @Author:zhangmingda
# @File: m1.py
# @Software: PyCharm
# Description:
from django.utils.deprecation import MiddlewareMixin
from django.shortcuts import HttpResponse
class Row1(MiddlewareMixin):
def process_request(self, request):
print('request Row1 ')
def process_response(self,request,response):
print('Row1-Response')
return response
def process_view(self,request, view_func, view_func_args, view_func_kwargs):
print('Row1_process_view')
class Row2(MiddlewareMixin):
def process_request(self, request):
print('request Row2 ')
def process_response(self,request,response):
print('Row2-Response')
# return response
return HttpResponse('OK')
def process_view(self,request, view_func, view_func_args, view_func_kwargs):
print('Row2_process_view')
class Row3(MiddlewareMixin):
def process_request(self, request):
print('request Row3 ')
def process_response(self,request,response):
print('Row3-Response')
return response
def process_view(self,request, view_func, view_func_args, view_func_kwargs):
print('Row2_process_view')
测试url请求后端输出
request Row1
request Row2
request Row3
Row1_process_view
Row2_process_view
Row2_process_view
[22/Jul/2020 12:56:53] "GET /session_login/ HTTP/1.1" 200 2
Row3-Response
Row2-Response
Row1-Response
process_exception(self, request, exception)
自定义中间件 m1.py中 某函数
def process_exception(self, request, exception):
print(exception)
if isinstance(exception,ValueError):
return HttpResponse('出现异常:%s'% exception)
views.py中故意报错测试int('a')
class SessionIndex(View):
def get(self,request):
int('a')
current_user = request.session.get('current_user')
print(current_user)
if current_user:
return render(request, 'session_index.html')
else:
return redirect('/session_login/')
请求访问,返回自定义错误提示
process_template_response(self, request, response)
当views.py 中 返回为一个对象,对象中有render()方法,此函数才被执行。下面举例ShaBi这个类实现对象。被返回
views.py
class ShaBi(object):
def render(self):
return HttpResponse('傻逼')
class SessionIndex(View):
def get(self,request):
current_user = request.session.get('current_user')
print(current_user)
if current_user:
return render(request, 'session_index.html')
else:
# return redirect('/session_login/')
return ShaBi()
m1.py
class Row3(MiddlewareMixin):
def process_template_response(self,request, response):
print('傻逼无用逻辑')
return response # 将函数return的对象中render()函数返回值返回,浏览器访问就出现傻逼了
后端输出
request Row1
request Row2
request Row3
Row1_process_view
Row2_process_view
Row2_process_view
None
傻逼无用逻辑
Row3-Response
Row2-Response
Row1-Response
[22/Jul/2020 13:59:35] "GET /session_index/ HTTP/1.1" 200 6
浏览器获取到返回值
<html><head></head><body>傻逼</body></html>