Django中的MiddleWare中间件

1. middleware简介

---

Django的middleware的概念相当于SSH框架里面的filter的概念。中间键的作用就是对所有的request，在request前，和在response后做一定的处理。

Django的中间键类型分为五种:

　　 请求(Request)中间件->对应函数process_request
　　视图(View)中间件->对应函数process_view
　　模板(Template)中间件->对应函数process_template_response（不常用）
　　响应(Response)中间件->对应函数process_response
　　异常(Exception)中间件->对应函数process_exception（不常用）

2. middleware中间键函数的执行顺序和过程

---

 （1）请求（Request）中间件和响应（Response）中间件的正常执行顺序

接下来就用程序演示：

m1.py

from django.utils.deprecation import MiddlewareMixin

class ROW1(MiddlewareMixin):
    def process_request(self,request):
        print("朱三")

    def process_response(self,request,response):
        print('赵六')
        return response

class ROW2(MiddlewareMixin):
    def process_request(self,request):
        print("李四")

    def process_response(self,request,response):
        print('薛七')
        return response

class ROW3(MiddlewareMixin):
    def process_request(self,request):
        print("王五")

    def process_response(self,request,response):
        print('宋八')
        return response
 

views.py

def test(request):
    # int("asdsadsad")
    print('小猪->没带钱')
    return HttpResponse("OK")

所以顺序为：朱三-->李四-->王五-->小猪-->没带钱-->宋八-->薛七-->赵六

如果在中间件中发生错误，那么其执行顺序为

 m1.py

from django.utils.deprecation import MiddlewareMixin

class ROW1(MiddlewareMixin):
    def process_request(self,request):
        print("朱三")
    def process_response(self,request,response):
        print('赵六')
        return response
    

from django.shortcuts import HttpResponse
class ROW2(MiddlewareMixin):
    def process_request(self,request):
        print("李四")
        return HttpResponse('离开')

    def process_response(self,request,response):
        print('薛七')
        return response


class ROW3(MiddlewareMixin):
    def process_request(self,request):
        print("王五")

    def process_response(self,request,response):
        print('宋八')
        return response
    

views与上面一样，执行顺序为：朱三-->李四-->薛七-->赵六

 （2）视图中间件执行顺序

from django.utils.deprecation import MiddlewareMixin

class ROW1(MiddlewareMixin):
    def process_request(self,request):
        print("朱三")

    def process_response(self,request,response):
        print('赵六')
        return response

     def process_view(self, request, veiw_func, veiw_func_args, veiw_func_kwargs):
         print('张欣彤')


from django.shortcuts import HttpResponse
class ROW2(MiddlewareMixin):
    def process_request(self,request):
        print("李四")
       

    def process_response(self,request,response):
        print('薛七')
        return response

     def process_view(self, request, veiw_func, veiw_func_args, veiw_func_kwargs):
         print('张需要')


class ROW3(MiddlewareMixin):
    def process_request(self,request):
        print("王五")

    def process_response(self,request,response):
        print('宋八')

        return response
     def process_view(self, request, veiw_func, veiw_func_args, veiw_func_kwargs):
         print('邵林')

    

views.py代码与其最上的views.py代码相同

则执行顺序为：朱三-->李四-->王五-->张欣彤-->张需要-->邵林-->小猪-->没带钱-->宋八-->薛七-->赵六

而模板中间件（函数中出现render才生效）和异常中间价（函数出现错误才生效）因为不常用，默认不生效，所以就不详细介绍了。

3.自定义中间件

---

（1）创建中间件

class RequestExeute(object):
      
    def process_request(self,request):
        pass
    def process_view(self, request, callback, callback_args, callback_kwargs):
        i =1
        pass
    def process_exception(self, request, exception):
        pass
      
    def process_response(self, request, response):
        return response

（2）注册中间件

MIDDLEWARE_CLASSES = (
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
    'wupeiqi.middleware.auth.RequestExeute',
)