django中间件介绍

在学习django中间件之前,先来认识一下django的生命周期,如下图所示:

django生命周期浏览器发送的请求会先经过wsgiref模块处理解析出request(请求数据)给到中间件,然后通过路由控制执行对应的视图函数,从而和模板,db进行交互,交互完的数据再通过视图函数返回给中间件,最后wsgiref模块将返回的数据封装成http形式的数据给到浏览器并进行展示。

了解了django的生命周期后,我们就可以开始着手写一个自己的中间件了,接下来认识几个常用的中间件方法

1.process_request

单个中间件

首先在app下创建一个py文件,定义你的中间件类名

from django.utils.deprecation import MiddlewareMixin
from django.http import HttpResponse
class MiddlewareShow(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow1')

然后将你的py文件路径写入django主项目的settings的MIDDLEWARE中

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',
'proxy_pro.middleware.MiddlewareShow'  # 此条是新加的 从该项目路径开始写
]

然后执行一个视图函数即可,查看控制台打印

此时自己创建的process_request方法就生效了

多个中间件

此时在之前的py文件中再新建一个类

class MiddlewareShow(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow1 Request')
class MiddlewareShowTwo(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow2 Request')

然后将新建类的路径也放在django主项目的settings的MIDDLEWARE中

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',
'proxy_pro.middleware.MiddlewareShow',
'proxy_pro.middleware.MiddlewareShowTwo'
]

执行视图函数,查看控制台打印

此时定义的两个中间件都生效了,执行顺序是先1后2

2.process_response

分别在刚才的类中添加response方法

from django.utils.deprecation import MiddlewareMixin
from django.http import HttpResponse
class MiddlewareShow(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow1 Request')
def process_response(self, request, response):
print('MiddlewareShow1 Response')
return response
class MiddlewareShowTwo(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow2 Request')
def process_response(self, request, response):
print('MiddlewareShow2 Response')
return response

执行视图函数,查看控制台打印

此时可以看出请求先依次执行了中间件的Request,然后再去执行视图函数,返回是先执行跟后面的中间件再依次往前

这时突然冒出一个想法,如果在request时直接返回了某个东西,还会继续去执行后面的视图函数吗?那我们就来测试一下

from django.utils.deprecation import MiddlewareMixin
from django.http import HttpResponse
class MiddlewareShow(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow1 Request')
return HttpResponse('request1时已返回')
def process_response(self, request, response):
print('MiddlewareShow1 Response')
return response
class MiddlewareShowTwo(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow2 Request')
def process_response(self, request, response):
print('MiddlewareShow2 Response')
return response

执行视图函数,查看控制台

此时可以看出当request中有返回时,直接不执行后面的内容了

3.process_view

分别在刚才的py文件中添加view方法

from django.utils.deprecation import MiddlewareMixin
from django.http import HttpResponse
class MiddlewareShow(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow1 Request')
def process_response(self, request, response):
print('MiddlewareShow1 Response')
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print('MiddlewareShow1 process_view')
class MiddlewareShowTwo(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow2 Request')
def process_response(self, request, response):
print('MiddlewareShow2 Response')
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print('MiddlewareShow2 process_view')

执行视图函数,查看控制台返回

此时可以看出这个process_view方法会在执行完request后执行,执行完再去执行视图函数

这时候就有疑问了,那这个有什么用呢?我们先把它里面的参数打印一下

from django.utils.deprecation import MiddlewareMixin
from django.http import HttpResponse
class MiddlewareShow(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow1 Request')
def process_response(self, request, response):
print('MiddlewareShow1 Response')
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print('MiddlewareShow1 process_view')
print('=====>callback', callback)
print('=====>callback_args', callback_args)
class MiddlewareShowTwo(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow2 Request')
def process_response(self, request, response):
print('MiddlewareShow2 Response')
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print('MiddlewareShow2 process_view')

执行视图函数打印结果

此时可以看到这个view里面的参数callback是视图方法,callback_args是请求参数,那我们试着去请求下看看

class MiddlewareShow(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow1 Request')
def process_response(self, request, response):
print('MiddlewareShow1 Response')
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print('MiddlewareShow1 process_view')
print('=====>callback', callback)
print('=====>callback_args', callback_args)
ret = callback(callback_args)  # 请求
return ret
class MiddlewareShowTwo(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow2 Request')
def process_response(self, request, response):
print('MiddlewareShow2 Response')
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print('MiddlewareShow2 process_view')

查看打印结果

结果显然易见,请求视图函数成功了,返回了以后就没有去执行process_view2了,这边的作用就是可以拦截请求

4.process_exception

分别在刚才的py文件中添加exception方法

from django.utils.deprecation import MiddlewareMixin
from django.http import HttpResponse
class MiddlewareShow(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow1 Request')
def process_response(self, request, response):
print('MiddlewareShow1 Response')
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print('MiddlewareShow1 process_view')
# print('=====>callback', callback)
# print('=====>callback_args', callback_args)
# ret = callback(callback_args)
# return ret
def process_exception(self, request, exception):
print('MiddlewareShow1 process_exception')
return HttpResponse(exception)
class MiddlewareShowTwo(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow2 Request')
def process_response(self, request, response):
print('MiddlewareShow2 Response')
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print('MiddlewareShow2 process_view')
def process_exception(self, request, exception):
print('MiddlewareShow2 process_exception')
return HttpResponse(exception)

执行视图函数,查看控制台

问题来了,为啥没有走这个中间件方法呢?别慌,我们在视图函数中加个错

def middle_show(request):
leo
print('执行了视图函数')
return HttpResponse('hhh')

此时在执行下看看

此时可以看到当process_exception2获取到报错后,就返回了没有执行process_exception1

那如果我们在process_exception1处理呢,我们来测试下

from django.utils.deprecation import MiddlewareMixin
from django.http import HttpResponse
class MiddlewareShow(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow1 Request')
def process_response(self, request, response):
print('MiddlewareShow1 Response')
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print('MiddlewareShow1 process_view')
# print('=====>callback', callback)
# print('=====>callback_args', callback_args)
# ret = callback(callback_args)
# return ret
def process_exception(self, request, exception):
print('MiddlewareShow1 process_exception')
return HttpResponse(exception)
class MiddlewareShowTwo(MiddlewareMixin):
def process_request(self, request):
print('MiddlewareShow2 Request')
def process_response(self, request, response):
print('MiddlewareShow2 Response')
return response
def process_view(self, request, callback, callback_args, callback_kwargs):
print('MiddlewareShow2 process_view')
def process_exception(self, request, exception):
print('MiddlewareShow2 process_exception')

执行视图函数,打印看下

此时还会走到process_exception1哦,然后把错误返回给页面。

以上就是django中间件的介绍,希望和大家多多学习!转载请说明出处,尊重劳动成果!!!

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