Django中间件探索：揭秘中间件在Web应用中的守护角色与实战应用

#settings.py
MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    # 为request/response提供了几种xss脚本过滤的安全改进，无它不安全
    'django.contrib.sessions.middleware.SessionMiddleware',
    # 开启session会话支持，无它无session
    'django.middleware.common.CommonMiddleware',
    # 基于APPEND_SLASH和PREPEND_WWW的设置来重写URL，
    # 如果APPEND_SLASH设为True，并且初始URL 没有以斜线结尾以及在URLconf 中没找到对应定义，这时形成一个斜线结尾的新URL；
    # 如果PREPEND_WWW设为True，前面缺少 www.的url将会被重定向到相同但是以一个www.开头的ur
    
    'django.middleware.csrf.CsrfViewMiddleware',
    # 添加跨站点请求伪造的保护，通过向POST表单添加一个隐藏的表单字段，并检查请求中是否有正确的值，无它无csrf保护
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    # 在视图函数执行前向每个接收到的user对象添加HttpRequest属性，表示当前登录的用户，无它用不了request.user
    'django.contrib.messages.middleware.MessageMiddleware',
    # 开启基于Cookie和会话的消息支持，无它无message
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
    # 对点击劫持的保护
]

1、process_request(self,request) 
2、process_view(self, request, callback, callback_args, callback_kwargs) 
3、process_template_response(self,request,response)
4、process_exception(self, request, exception)
5、process_response(self, request, response) 

# customMiddleware.py
from django.http import HttpResponse
from django.utils.deprecation import MiddlewareMixin
class CustomMiddleware(MiddlewareMixin):
    def process_request(self, request):
        """
        处理请求前: 在每个请求上，request对象产生之后，url匹配之前调用,返回None或HttpResponse对象
        """
        print('before request=====', request)
    def process_view(self, request, view_func, *view_args, **view_kwargs):
        """
        :param view_func: Django即将使用的视图函数,它是实际的函数对象，而不是函数的名称作为字符串
        :param view_args: 将传递给视图的位置参数的列表
        :param view_kwargs: 将传递给视图的关键字参数的字典;
               view_args和view_kwargs都不包含第一个视图参数（request）
        """
        # 处理视图前：在每个请求上，url匹配之后，视图函数调用之前调用，返回None或HttpResponse对象
        print('before view=======')
    def process_template_response(self, request, response):
        # 在视图函数执行完后立即执行的, 执行 该 函数有一个前提条件，那就是视图函数返回的对象是一个 TemplateResponse 对象或等价方法, 直接返回render函数无效）
        print("render template=======")
        return response
    def process_exception(self, request, exception):
        # 这个方法只有在视图函数中出现异常了才执行，它返回的值可以是一个None也可以是一个HttpResponse对象
        print("raise exception=======")
        return HttpResponse(exception)
    def process_response(self, request, response):
        # 处理响应后：视图函数调用之后，所有响应返回浏览器之前被调用，在每个请求上调用，返回HttpResponse对象
        print('after response=======', response)
        return response

from django.utils.encoding import force_str, force_bytes
import json
def process_response(self, request, response):
    if response['Content-Type'] == 'application/json':
        # 解码JSON数据
        data = json.loads(force_str(response.content))
        # 修改数据
        data['modified_key'] = 'modified_value'
        # 重新编码JSON数据
        response.content = force_bytes(json.dumps(data))
    return response

MIDDLEWARE = [
  # 添加自定义的中间件---CustomMiddleware
    'app.customMiddleware.CustomMiddleware',
    'corsheaders.middleware.CorsMiddleware',
    'django.middleware.security.SecurityMiddleware',
    ......
]

# views.py
from rest_framework.views import APIView
from django.http import HttpResponse
# Create your views here.
class IndexView(APIView):
    def get(self, request):
        print("IndexView======================")
        return HttpResponse("Hello Index GET")

before request===== <WSGIRequest: GET '/app/index/'>
before view=======
IndexView======================
after response======= <HttpResponse status_code=200, "text/html; charset=utf-8">
[16/Jun/2024 19:55:45] "GET /app/index/ HTTP/1.1" 200 15

# views.py
from rest_framework.views import APIView
from django.http import HttpResponse
# Create your views here.
class IndexView(APIView):
    def get(self, request):
        print("IndexView======================")
        3/0
        return HttpResponse("Hello Index GET")

before request===== <WSGIRequest: GET '/app/index/'>
before view=======
IndexView======================
raise exception=======
after response======= <HttpResponse status_code=200, "text/html; charset=utf-8">
[16/Jun/2024 19:58:22] "GET /app/index/ HTTP/1.1" 200 16

# views.py
from django.template.response import TemplateResponse
from rest_framework.views import APIView
# Create your views here.
class IndexView(APIView):
    def get(self, request):
        print("IndexView======================")
        return TemplateResponse(request, 'index.html')

before request===== <WSGIRequest: GET '/app/index/'>
before view=======
IndexView======================
render template=======
after response======= <TemplateResponse status_code=200, "text/html; charset=utf-8">
[16/Jun/2024 19:59:20] "GET /app/index/ HTTP/1.1" 200 182