中间件

流程

客户端请求 -> 
    -> M1.process_request -> M2.process_request -> ... -> Mn.process_request
    -> M1.process_view -> M2.process_view -> ... -> Mn.process_view
    -> view函数 
    有异常
        ->Mn.process_exception -> ... -> M2.process_exception -> M1.process_response
    无异常
        -> Mn.process_response -> ... -> M2.process_response -> M1.process_response 
-> 客户端

自定义中间件

在app中创建middleware.py文件

from django.utils.deprecation import MiddlewareMixin
class M1(MiddlewareMixin):
    def process_request(self, request):
        """
        如果此处直接return 则不执行view函数
        从当前中间件的process_response 开始执行返回
        """
        return HttpResponse('hehe')
    def process_view(self,request, callback, callback_args, callback_kwargs):
        """
            callback: views函数
            callback_args:
            callback_kwargs: views函数参数
            如果执行callback函数即执行view函数 则将跳过后面的process_view函数
        接着执行 process_response 函数
        """
        return callback(request, *callback_args, **callback_kwargs) 
    def process_response(self, request, response):
        return response
    def process_exception(self, request, exception):
        """
        view有异常时才出发
        如果处理的异常则不继续执行后面的process_exception
        """
        pass
    def process_template_response(self, request, response):
        """
        视图函数中有render返回时才会执行
        """
        pass

'''
settings.py中注册
 --------------------------
中间件的顺序按照list中顺序执行
'''
MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
    # ... 
]

上下文渲染器

可解决在多个template中都需要显示相同的数据，无需在每个view中都传一次值

自定义上下文渲染器

在项目同名的目录中(即settings.py同级目录中)创建context_processor.py文件

def myuser(request):
    """
        返回字典，key名即可在template中直接调用
    """
    return {'key1': 'value1'}

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
                # 添加配置
                'projectname.context_processor.myuser',
            ],
        },
    },
]