Django中间件是一个轻量级的插件系统，可以介入Django的请求和响应处理过程，修改Django的输入或输出。
Django中间件的定义包含四个方法：__init__, process_request, process_view, 和 process_response。
__init__: 用于初始化中间件。process_request: 在请求到达视图函数之前调用。如果返回None，则继续处理；如果返回HttpResponse对象，则中止处理，并返回该响应。process_view: 在请求到达视图函数之前调用。如果返回None，继续处理；如果返回HttpResponse对象，中止处理，并返回该响应。process_response: 在视图函数处理完请求后，返回响应之前调用。返回值必须是HttpResponse对象。
例子：
# middlewares.py
class SimpleMiddleware:
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 other middleware) are called.
response = self.get_response(request)
# Code to be executed for each request/response after
# the view is called.
return response
def process_request(self, request):
# Code to be executed before processing the request.
pass
def process_view(self, request, view_func, view_args, view_kwargs):
# Code to be executed before the view function is called.
pass
def process_response(self, request, response):
# Code to be executed after the view function is called.
return response在settings.py中添加中间件：
MIDDLEWARE = [
# ...
'path.to.middlewares.SimpleMiddleware',
# ...
]以上是一个简单的中间件示例，实现了中间件的基本结构，并展示了如何在Django项目中注册和使用它。