Django-djangorestframework-异常模块-源码及自定义异常

    # ...
    def dispatch(self, request, *args, **kwargs):
        """
        `.dispatch()` is pretty much the same as Django's regular dispatch,
        but with extra hooks for startup, finalize, and exception handling.
        """
        self.args = args
        self.kwargs = kwargs
        request = self.initialize_request(request, *args, **kwargs)
        self.request = request
        self.headers = self.default_response_headers  # deprecate?

        try:
            self.initial(request, *args, **kwargs)  # 三大认证

            # Get the appropriate handler method
            if request.method.lower() in self.http_method_names:
                handler = getattr(self, request.method.lower(),
                                  self.http_method_not_allowed)
            else:
                handler = self.http_method_not_allowed

            response = handler(request, *args, **kwargs)

        except Exception as exc:
            response = self.handle_exception(exc)  # 上面 try 代码体内代码出现异常会自动触发这个函数 <---------

        self.response = self.finalize_response(request, response, *args, **kwargs)
        return self.response

    def handle_exception(self, exc):
        """
        Handle any exception that occurs, by returning an appropriate response,
        or re-raising the error.
        """
        if isinstance(exc, (exceptions.NotAuthenticated,
                            exceptions.AuthenticationFailed)):
            # WWW-Authenticate header for 401 responses, else coerce to 403
            auth_header = self.get_authenticate_header(self.request)

            if auth_header:
                exc.auth_header = auth_header
            else:
                exc.status_code = status.HTTP_403_FORBIDDEN

        exception_handler = self.get_exception_handler()  # 获取处理异常的句柄（方法） <---------

        context = self.get_exception_handler_context()
        # 异常处理的结果
        # 自定义异常就是提供 exception_handler 异常处理函数，处理的目的就是让 response 一定有值
        response = exception_handler(exc, context)

        if response is None:
            self.raise_uncaught_exception(exc)  # 乱七八糟的异常就是这里抛出来的

        response.exception = True
        return response

    def get_exception_handler(self):
        """
        Returns the exception handler that this view uses.
        """
        return self.settings.EXCEPTION_HANDLER

    # API policy implementation methods

    # Exception handling
    'EXCEPTION_HANDLER': 'rest_framework.views.exception_handler',

def exception_handler(exc, context):
    """
    Returns the response that should be used for any given exception.

    By default we handle the REST framework `APIException`, and also
    Django's built-in `Http404` and `PermissionDenied` exceptions.

    Any unhandled exceptions may return `None`, which will cause a 500 error
    to be raised.
    """
    if isinstance(exc, Http404):
        exc = exceptions.NotFound()
    elif isinstance(exc, PermissionDenied):
        exc = exceptions.PermissionDenied()

    if isinstance(exc, exceptions.APIException):
        headers = {}
        if getattr(exc, 'auth_header', None):
            headers['WWW-Authenticate'] = exc.auth_header
        if getattr(exc, 'wait', None):
            headers['Retry-After'] = '%d' % exc.wait

        if isinstance(exc.detail, (list, dict)):
            data = exc.detail
        else:
            data = {'detail': exc.detail}

        set_rollback()
        return Response(data, status=exc.status_code, headers=headers)

    return None  # 其他的异常 drf 未处理，返回 None，让其报错（最上面的那种报错）

from rest_framework.views import exception_handler as drf_exception_handler
from rest_framework.views import Response
from rest_framework import status


def exception_handler(exc, context):
    # drf的exception_handler做基础处理
    response = drf_exception_handler(exc, context)
    # 为空，说明 drf 中没有对应的处理，咱们自定义二次处理
    if response is None:
        # print(exc)
        # # Book matching query does not exist
        
        # print(context)
        # # {'view': <api.views.Book object at 0x000001FED29DD860>}, 'args': (), 'kwargs': {'pk': '4'}, 'request': <rest_framework.request.Request object at 0x000001FED2CD9EF0>
        
        # 这里后期应该写成系统日志才对（这只是演示的伪代码）
        print('%s - %s - %s' % (context['view'], context['request'].method, exc))
        # <api.views.Book object at 0x000002505A2A9A90> - GET - Book matching query does not exits.
        return Response({
            'detail': '服务器错误'
        }, status=status.HTTP_500_INTERNAL_SERVER_ERROR, exception=True)
    return response

# 1.确保已注册 drf
INSTALLED_APPS = [
    # ...
    'api.apps.ApiConfig',

    'rest_framework',  # 注册 drf
]

# 2.在 restframework 的配置中配置该自定义异常模块
REST_FRAMEWORK = {
    # ...

    'EXCEPTION_HANDLER': 'api.exception.exception_handler',  # 全局配置异常模块
}