Django Middleware

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Middleware是什么？

Middleware is a framework of hooks into Django’s request/response processing. It’s a light, low-level “plugin” system for globally altering Django’s input or output.

工作流程

从浏览器发出一个请求 Request，得到一个响应后的内容 HttpResponse ，这个请求传递到 Django的过程如下：

process_request 被 process_view 替换

每一个请求都是先通过中间件中的 process_view 函数，这个函数返回 None 或者 HttpResponse 对象，如果返回前者，继续处理其它中间件，如果返回一个 HttpResponse，就处理中止，返回结果给浏览器。

process_view: https://docs.djangoproject.com/en/1.11/topics/http/middleware/#process_view

自定义Middleware

开发模式（DEBUG=True）禁用Middleware

在Middleware class的 init() 方法中 raise MiddlewareNotUsed

Django will then remove that middleware from the middleware process and log a debug message to the django.request logger when DEBUG is True.

定义方法

Response类型

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def simple_middleware(get_response):
    # One-time configuration and initialization.

    def middleware(request):
        # Code to be executed for each request before
        # the view (and later middleware) are called.

        response = get_response(request)

        # Code to be executed for each request/response after
        # the view is called.

        return response

    return middleware

定义类

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class SimpleMiddleware(object):
    def __init__(self, get_response):
        self.get_response = get_response
        # One-time configuration and initialization.

    def __call__(self, request):
        # Code to be executed for each request before
        # the view (and later middleware) are called.

        response = self.get_response(request)

        # Code to be executed for each request/response after
        # the view is called.

        return response

Django 1.10 定义类

class django.utils.deprecation.MiddlewareMixin

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class MiddlewareMixin(object):
    def __init__(self, get_response=None):
        self.get_response = get_response
        super(MiddlewareMixin, self).__init__()
 
    def __call__(self, request):
        response = None
        if hasattr(self, 'process_request'):
            response = self.process_request(request)
        if not response:
            response = self.get_response(request)
        if hasattr(self, 'process_response'):
            response = self.process_response(request, response)
        return response

call 方法会先调用 self.process_request(request)，接着执行 self.get_response(request) 然后调用 self.process_response(request, response)

创建一个Middleware基类，后续Middleware直接继承重写即可

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class BaseMiddleware(MiddlewareMixin):
    def process_request(self, request):
        return None

    def get_response(self, request):
        return None

    def process_response(self, request, response):
        return response