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！！！