Question

在django rest框架中使用django-filters时，默认查询过滤表单将为所有字段添加所有查询参数，而空字段最终将作为空字符串传递给后端。空字符串不是None，因此status = self.request.query_params.get('status', None)仍会将空字符串添加到变量中，这将使其进入queryset.filter函数。当要过滤的字段不是字符串时，这非常糟糕。

所以我的问题是我做错了什么吗？有没有办法检查空字符串参数？我不确定自己是否正在正确过滤（我可能无缘无故地进行了两次过滤，但由于要与django-rest-frameworks可浏览API内置集成，因此我想在其中使用django-filters。

我的解决方法是三元运算符在调用query_params.get后检查空字符串

以下是我对该API的查看代码：

class JobList(generics.ListCreateAPIView):
    serializer_class = JobCreateSerializer
    permission_classes = (permissions.IsAuthenticatedOrReadOnly,)

    filter_backends = (filters.OrderingFilter, DjangoFilterBackend)
    filterset_fields = ('status', 'success', 'worker_id', 'owner', 'job_type')
    ordering_fields = ('priority', 'submitted', 'assigned', 'completed')

    def perform_create(self, serializer):
        serializer.save(owner=self.request.user)

    def get(self, request, format=None):
        # IMPORTANT: use self.get_queryset() any place you want filtering to be enabled
        # for built in filtering or ordering you must call self.filter_queryset
        jobs = self.filter_queryset(self.get_queryset())
        serializer = JobSerializer(jobs, context={'request': request}, many=True)

        return Response(serializer.data)

    def get_queryset(self):
        """
        This view should return a list of all the purchases
        for the currently authenticated user.
        """
        queryset = Job.objects.all()

        status = self.request.query_params.get('status', None)
        status = status if not status == '' else None
        success = self.request.query_params.get('success', None)
        success = success if not success == '' else None
        worker_id = self.request.query_params.get('worker_id', None)
        worker_id = worker_id if not worker_id == '' else None
        owner_id = self.request.query_params.get('owner', None)
        owner_id = owner_id if not owner_id == '' else None
        job_type = self.request.query_params.get('job_type', None)
        job_type = job_type if not job_type == '' else None

        if status is not None:
            queryset = queryset.filter(status=status)
        if success is not None:
            queryset = queryset.filter(success=success)
        if worker_id is not None:
            queryset = queryset.filter(worker_id=worker_id)
        if owner_id is not None:
            queryset = queryset.filter(owner=owner_id)
        if job_type is not None:
            queryset = queryset.filter(job_type=job_type)

        return queryset

Answer 1

为什么不将默认值设置为空字符串，而是将其用作保护值而不是None？

status = self.request.query_params.get("status", "")
success = self.request.query_params.get("success", "")
# ...
if status:
    queryset = queryset.filter(status=status)
if success:
    queryset = queryset.filter(success=success)
# ...

Answer 2

如果您使用if status:而不是if status is not None:，则空字符串和None都将得到False。对于整数来说，这样做很危险，因为0将返回false，但这在这里不是问题，因为所有参数都是字符串。

您还可以将''定义为默认值，然后检查非零长度的字符串：

status = self.request.query_params.get('status', '')
# ...
if len(status):

Answer 3

谢谢您的回答，我认为它们是有效的方法，但它们都在进行手动检查。我一直在寻找一种内置的方式来将query_params附带的JSON本机类型转换为Python本机类型（false到False，null到None等）。希望避免手动检查和转换每个query_param。

如果Django Rest框架中没有这样的东西，那真让我大吃一惊。因此，我创建了一个辅助函数，该函数可以从query_params到Python dict进行简单的一级深度转换。我希望这对其他人有帮助，或者如果有人知道DRF中类似的便利功能，我将不胜感激。或者，如果有人可以告诉我为什么这是一种不好的方法，我也将不胜感激！

def query_params_parser(self, fields_list):

        json_values_dict = {}

        for field in fields_list:
            value = '"' + self.request.query_params.get(field) + '"' if not self.query_params.get(field, '') == '' else 'null'
            json_values_dict['"' + field + '"'] = value

        json_string = '{'

        for idx, (key, value) in enumerate(json_values_dict.items()):
            json_string += f'{key}: {value}'

            if idx < len(json_values_dict) - 1:
                json_string += ','

        json_string += '}'

        final_dict = json.loads(json_string)

        return final_dict


def get_queryset(self):
        """
        This view should return a list of all the purchases
        for the currently authenticated user.
        """
        queryset = Job.objects.all()

        # parse json query_params
        # query_params, list of fields
        # returns dict

        params_dict = self.query_params_parser(['status',
                                                'success',
                                                'worker_id',
                                                'owner',
                                                'job_type'])

        status = params_dict['status']
        success = params_dict['success']
        worker_id = params_dict['worker_id']
        owner = params_dict['owner']
        job_type = params_dict['job_type']

        if status is not None:
            queryset = queryset.filter(status=status)
        if success is not None:
            queryset = queryset.filter(success=success)
        if worker_id is not None:
            queryset = queryset.filter(worker_id=worker_id)
        if owner is not None:
            queryset = queryset.filter(owner=owner)
        if job_type is not None:
            queryset = queryset.filter(job_type=job_type)

        return queryset

上面的函数在有限的测试下可以工作，因此它可能有很多错误。

Django过滤器空字符串查询参数导致验证错误

3 个答案: