python - Django REST 框架 : return 404 (not 400) on POST if related field does not exist?

Question

我正在开发一个 REST API，它从一些无法 PATCH 或其他任何东西的真正脑残软件接收 POST 请求。 POST 用于更新数据库中已存在的模型对象。

具体来说，我正在为具有相关字段(SlugRelatedField，因为 POSTer 知道“名称”属性但不知道“pk”)的对象发布数据。但是，如果 POSTer 发送数据，其中“名称”在 SlugRelatedField 上不返回任何内容(例如，相关对象不存在)，我需要返回 404。我已经通过调试器完成了这个，但 DRF 似乎使用了一些 Django 信号魔术来完成 DRF Does It™ 的方式，即返回 400 BAD REQUEST。我不知道如何修改它 - 仅当它是上述条件而不是真正的 400-worthy POST - 到 404。

顺便说一句，在我看来，pre_save() 在失败测试的执行过程中并未执行。

这是序列化程序:

class CharacterizationSerializer(serializers.ModelSerializer):
    """
    Work-in-progress for django-rest-framework use.  This handles (de)serialization
    of data into a Characterization object and vice versa.

    See: http://www.django-rest-framework.org/tutorial/1-serialization
    """
    creator = serializers.Field(source='owner.user.username')
    sample = serializers.SlugRelatedField(slug_field='name',
                                          required=True,
                                          many=False,
                                          read_only=False)

    class Meta:
        model = Characterization
        # leaving 'request' out because it's been decided to deprecate it. (...maybe?)
        fields = ('sample', 'date', 'creator', 'comments', 'star_volume', 'solvent_volume',
                  'solution_center', 'solution_var', 'solution_minimum', 'solution_min_stddev',
                  'solution_test_len',)

这是 pre_save 未在给定测试中运行的 View (但在其他一些测试中运行):

class CharacterizationList(generics.ListCreateAPIView):
    queryset = Characterization.objects.all()
    serializer_class = CharacterizationSerializer
    permission_classes = (AnonPostAllowed,)   # @todo XXX hack for braindead POSTer

    def pre_save(self, obj):
        # user isn't sent as part of the serialized representation,
        # but is instead a property of the incoming request.
        if not self.request.user.is_authenticated():
            obj.owner = get_dummy_proxyuser()   # this is done for CharacterizationList so unauthed users can POST. @todo XXX hack
        else:
            obj.owner = ProxyUser.objects.get(pk=self.request.user.pk)

        # here, we're fed a string sample name, but we need to look up
        # the actual sample model.
        # @TODO: Are we failing properly if it doesn't exist?  Should
        # throw 404, not 400 or 5xx.
        # except, this code doesn't seem to be run directly when debugging.
        # a 400 is thrown; DRF must be bombing out before pre_save?
        obj.sample = Sample.objects.get(name=self.request.DATA['sample'])

为了更好的衡量，这是失败的测试:

def test_bad_post_single_missing_sample(self):
    url = reverse(self._POST_ONE_VIEW_NAME)

    my_sample_postdict = self.dummy_plqy_postdict.copy()
    my_sample_postdict["sample"] = "I_DONT_EXIST_LUL"
    response = self.rest_client.post(url, my_sample_postdict)
    self.assertTrue(response.status_code == 404,
                    "Expected 404 status code, got %d (%s). Content: %s" % (response.status_code, response.reason_phrase, response.content))

如果我在 self.rest_client.post() 调用中放置一个断点，那时候响应中已经有一个 400。

Answer 1

您可以为此使用 Django 快捷方式，获取 obj.sample:

from django.shortcuts import get_object_or_404
obj.sample = get_object_or_404(Sample, name=self.request.DATA['sample'])