中间件

Posted 2021-01-16 mlhz

1 中间件的概念

中间件是介于request与response处理之间的一道处理过程，因为改变的时全局，所有需要谨慎使用。

 

2 django默认的Middleware:

1 MIDDLEWARE = [
2     ‘django.middleware.security.SecurityMiddleware‘,
3     ‘django.contrib.sessions.middleware.SessionMiddleware‘,
4     ‘django.middleware.common.CommonMiddleware‘,
5     ‘django.middleware.csrf.CsrfViewMiddleware‘,
6     ‘django.contrib.auth.middleware.AuthenticationMiddleware‘,
7     ‘django.contrib.messages.middleware.MessageMiddleware‘,
8     ‘django.middleware.clickjacking.XFrameOptionsMiddleware‘,
9 ]

默认的middleware

每一个中间件都有具体的方法

 

3 自定义中间件

中间件中一共有四种方法

1 process_request
2 
3 process_view
4 
5 
6 process_exception
7 
8 
9 process_response

四种方法

4 process_request,process_response

当用户发起请求的时候会依次经过所有的中间件，这个时候的请求时的process_request,最后达到views的函数中,views函数处理后，会依次经过中间件，这个时候时process_response,最后返回给请求者

上面的截图的中间件都是在django中的，我们也可以自己定义中间件，我们可以写一个类，但是必须继承MiddlewareMixin

 

需要导入：from django.utils.deprecation import MiddlewareMixin

in views:

1 def index(request):
2    print(‘‘vvvv‘)
3    return HttpResponse(‘ok‘)

View Code

in Mymiddlewares.py:

 1 from django.untils.deprecation import MiddlewareMixin
 2 from django.shortcuts import HttpResponse
 3 
 4 class Md1(MiddlewareMixin):
 5 
 6     def process_request(self,request):
 7         print("Md1请求")
 8  
 9     def process_response(self,request,response):
10         print("Md1返回")
11         return response
12 
13 class Md2(MiddlewareMixin):
14 
15     def process_request(self,request):
16         print("Md2请求")
17         #return HttpResponse("Md2中断")
18     def process_response(self,request,response):
19         print("Md2返回")
20         return response
21 
22 
23 
24 结果：
25 Mdl 请求
26 Md2请求
27 view函数
28 Md2返回
29 Md1 返回

View Code

注意：如果当请求到达请求2时直接不符合条件时返回，程序将把请求直接发给中间件2返回，然后依次返回到请求者，结果如下：

Md1请求

Md2请求

Md2返回

Md1返回

 

5 process_view: 参数如下

process_views(self,request,callback,callback_args,callback_kwargs)

 

Mymiddlewares.py 修改如下

 1 from django.utils.deprecation import MiddlewareMixin
 2 from django.shortcuts import HttpResponse
 3 
 4 class Md1(MiddlewareMixin):
 5 
 6     def process_request(self,request):
 7         print("Md1请求")
 8         #return HttpResponse("Md1中断")
 9     def process_response(self,request,response):
10         print("Md1返回")
11         return response
12 
13     def process_view(self, request, callback, callback_args, callback_kwargs):
14         print("Md1view")
15 
16 class Md2(MiddlewareMixin):
17 
18     def process_request(self,request):
19         print("Md2请求")
20         return HttpResponse("Md2中断")
21     def process_response(self,request,response):
22         print("Md2返回")
23         return response
24 
25     def process_view(self, request, callback, callback_args, callback_kwargs):
26         print("Md2view")

View Code

结果如下：

Md1请求
Md2请求
Md1view
Md2view
view函数...
Md2返回
Md1返回

下图进行分析上面的过程：

 

 

当最后一个中间的process_request到达路由关系映射之后，返回到中间件1的process_view,然后依次往下，到达view函数，最后通过process_response依次返回到用户

 

process_view可以用来调用视图函数：

 1 class Md1(MiddlewareMixin):
 2 
 3     def process_request(self,request):
 4         print("Md1请求")
 5         #return HttpResponse("Md1中断")
 6     def process_response(self,request,response):
 7         print("Md1返回")
 8         return response
 9 
10     def process_view(self, request, callback, callback_args, callback_kwargs):
11 
12         # return HttpResponse("hello")
13 
14         response=callback(request,*callback_args,**callback_kwargs)
15         return response

View Code

注意：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。

 

6 process_exception

process_exception(self, request, exception)

 

实例修改如下：

 1 class Md1(MiddlewareMixin):
 2 
 3     def process_request(self,request):
 4         print("Md1请求")
 5         #return HttpResponse("Md1中断")
 6     def process_response(self,request,response):
 7         print("Md1返回")
 8         return response
 9 
10     def process_view(self, request, callback, callback_args, callback_kwargs):
11 
12         # return HttpResponse("hello")
13 
14         # response=callback(request,*callback_args,**callback_kwargs)
15         # return response
16         print("md1 process_view...")
17 
18     def process_exception(self):
19         print("md1 process_exception...")
20 
21 
22 
23 class Md2(MiddlewareMixin):
24 
25     def process_request(self,request):
26         print("Md2请求")
27         # return HttpResponse("Md2中断")
28     def process_response(self,request,response):
29         print("Md2返回")
30         return response
31     def process_view(self, request, callback, callback_args, callback_kwargs):
32         print("md2 process_view...")
33 
34     def process_exception(self):
35         print("md1 process_exception...")

View Code