60 中间件

中间件

功能作用

1.介于request与response处理之间的一道处理过程，并且在全局上改变django的输入与输出。

2.修改请求。例如被传送到view中的HttpRequest对象。 或者想修改view返回的HttpResponse对象，这些都可以通过中间件来实现。

3. 在view执行之前做一些操作，可以用 middleware来实现。

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',
]

中间件中的方法:

process_request  

process_response   

process_view

process_exception

先理解django项目运行流程

django项目
1.wsgiref模块(socket)
报文data--->envision--->request对象
2.中间键，第一层处理业务的流程
3.控制器（路由+视图）
4.models模型层，模板层

5.视图处理后把数据返回给中间件，中间件再将数据返回给客户端

大致的流程如下图：

自定义中间件

注意 ：自定的中间件必须继承   MiddlewareMixin
from django.utils.deprecation import MiddlewareMixin
1.在app 中创建Mymiddlewares.py 的自定义文件
2. 在该文件中导入from django.utils.deprecation import MiddlewareMixin
3.在Mymiddleware.py 中创建中间件  
4.在settings 中添加中间件配置    格式   ：”  app1.自定义中间件文件.中间件名字（类名）”

 

Mymiddlewares.py文件中自定义中间件

from django.utils.deprecation import MiddlewareMixin

from django.shortcuts import HttpResponse


class M1(MiddlewareMixin):

    def process_request(self,request):

        print("process_request  M1....")


    def process_response(self,request,response):
        print("process_response M1 ...")
        return response


class M2(MiddlewareMixin):

    def process_request(self, request):
        print("process_request  M2....")


    def process_response(self, request, response):
        print("process_response M2 ...")
        return response

 

中间件的工作流程：

视图函数：

from django.shortcuts import render,HttpResponse

# Create your views here.
def index(request):

    print("执行index视图函数")

    return HttpResponse("ok")

情况一：

1.自定义中间件M1 和M2  ，process_request都不return ，process_response都return时：

from django.utils.deprecation import MiddlewareMixin

from django.shortcuts import HttpResponse


class M1(MiddlewareMixin):

    def process_request(self,request):

        print("process_request  M1....")


    def process_response(self,request,response):
        print("process_response M1 ...")
        return response


class M2(MiddlewareMixin):

    def process_request(self, request):
        print("process_request  M2....")


    def process_response(self, request, response):
        print("process_response M2 ...")
        return response

服务端打印结果：

process_request  M1....
process_request  M2....
执行index视图函数
process_response M2 ...
process_response M1 ...

流程图：

情况二：

1.如果中间件1中的process_request ,开始就return 结果

那么就不会走中间件2以及视图函数，直接走中间件1的request.response函数，直接返回给用户结果

from django.utils.deprecation import MiddlewareMixin

from django.shortcuts import HttpResponse


class M1(MiddlewareMixin):

    def process_request(self,request):

        print("M1 在process_request 时就return 了")
        return HttpResponse("直接返回给用户的内容") #此处return后可以不让用户进入视图函数


    def process_response(self,request,response):
        print("process_response M1 ...")
        return response


class M2(MiddlewareMixin):

    def process_request(self, request):
        print("process_request  M2....")


    def process_response(self, request, response):
        print("process_response M2 ...")
        return response

服务端打印的结果：

M1 在process_request 时就return 了
[10/Jan/2019 20:38:05] "GET /index/ HTTP/1.1" 200 30
process_response M1 ...

执行流程图：

情况三：process_view

process_view如果有返回值，会越过其他的process_view以及视图函数，但是所有的process_response都还会执行。

1.process_view 中不return 时，如：

Mymiddleware.py 文件中

from django.utils.deprecation import MiddlewareMixin

from django.shortcuts import HttpResponse


class M1(MiddlewareMixin):

    def process_request(self,request):
        print("process_request M1 ...")



    def process_response(self,request,response):
        print("process_response M1 ...")
        return response

    def process_view(self,request,callback, callback_args, callback_kwargs):
　　　　#callback 视图

        print("M1 process_view")


class M2(MiddlewareMixin):

    def process_request(self, request):
        print("process_request  M2....")


    def process_response(self, request, response):
        print("process_response M2 ...")
        return response

    def process_view(self, request, callback, callback_args, callback_kwargs):
        print("M2 process_view")

后端结果：

process_request M1 ...
process_request M2....
M1 process_view
M2 process_view
执行index视图函数
process_response M2 ...
process_response M1 ...

请求过程：

 2. process_view  在M1 中return 出现的情况：

from django.utils.deprecation import MiddlewareMixin

from django.shortcuts import HttpResponse


class M1(MiddlewareMixin):

    def process_request(self,request):
        print("process_request M1 ...")



    def process_response(self,request,response):
        print("process_response M1 ...")
        return response

    def process_view(self,request,callback, callback_args, callback_kwargs):
        print("M1 process_view")

        obj = callback(callback_args) # callback(callback_args) 就是执行对应的视图函数，obj就是视图函数的响应对象
        #callback_args 视图函数的参数 ，obj返回给 M2 的response 
　　　　　return obj


class M2(MiddlewareMixin):

    def process_request(self, request):
        print("process_request  M2....")


    def process_response(self, request, response):
        print("process_response M2 ...")
        return response

    def process_view(self, request, callback, callback_args, callback_kwargs):
        print("M2 process_view")

服务端的打印结果：

process_request M1 ...
process_request  M2....
M1 process_view
执行index视图函数  #为process_view 中callback(callback_args) 提前执行的结果
process_response M2 ...
process_response M1 ...

流程图：

process_exception

Mymiddleware.py:

from django.utils.deprecation import MiddlewareMixin

from django.shortcuts import HttpResponse


class M1(MiddlewareMixin):

    def process_request(self,request):
        print("process_request M1 ...")



    def process_response(self,request,response):
        print("process_response M1 ...")
        return response

    def process_view(self,request,callback, callback_args, callback_kwargs):
        print("M1 process_view")

    def process_exception(self,request,exception):
        print("process_exception M1")
        return HttpResponse("错误的")




class M2(MiddlewareMixin):

    def process_request(self, request):
        print("process_request  M2....")


    def process_response(self, request, response):
        print("process_response M2 ...")
        return response

    def process_view(self, request, callback, callback_args, callback_kwargs):
        print("M2 process_view")
        # obj = callback(callback_args)
        # return obj

    def process_exception(self, request, exception):
        print("process_exception...M2")
        return HttpResponse("error")

视图中：

from django.shortcuts import render,HttpResponse

# Create your views here.
def index(request):

    print("执行index视图函数")
    yun

    return HttpResponse("ok")

后端打印结果：

process_request M1 ...
process_request  M2....
M1 process_view
M2 process_view
执行index视图函数
process_exception...M2
process_response M2 ...
process_response M1 ...

当视图中出现错误时，先执行

M2 process_exception，之后的M1中process_exception 就不执行了，直接去执行process_response