我在解析viewset中的 request.data 时遇到问题。我有一个可以根据产品添加多个图像的模型。
我想从传入数据中拆分 图像 ,将 产品数据 发送到ProductSerializer,然后将 图像 与 产品数据 发送到其序列化 器 并保存。
我有两个模型,就像这样:
def Product(models.Model): name = models.CharField(max_length=20) color = models.ForeignKey(Color, on_delete=models.CASCADE) def Color(models.Model): name = models.CharField(max_length=15) def ProductImage(models.Model): product = models.ForeignKey(Product, on_delete=models.CASCADE) image = models.ImageField(upload_to='product_pics/')
我要发送到 产品 的请求(127.0.0.1:8000/products/)就像这样:
{ "name": "strawberry", "color": { "name": "red" }, "productimage_set": [ {"image": "<some_encode_image_data>"} ] }
序列化器没有什么特别的,它只是提取标签链接,所以我没有编写它。如何发送 multipart / form-data 以及如何在视图集中解析它?或有什么解决方案?
我开发了一个解决方案。使用邮递员,我发送了包含多个图像,单个和嵌套数据的multipart / form-data。
在我的模型文件中,我将Tags模型添加为ManyToManyField作为示例,并添加了django-taggit。 表单数据 将如图所示。
和 models.py
models.py
class Product(models.Model): name = models.CharField(max_length=20, blank=True) tags = models.ManyToManyField(Tags) taggit = TaggableManager(blank=True) class ProductImage(models.Model): product = models.ForeignKey(Product, on_delete=models.CASCADE) image = models.ImageField(upload_to='image_path/', null=True, blank=True) class Tags(models.Model): name = models.CharField(max_length=15, blank=True)
首先是第一件事;第一个数据未正确解析。为了解决这个问题,并借助该答案),我创建了这个自定义 解析器 :
class MultipartJsonParser(parsers.MultiPartParser): def parse(self, stream, media_type=None, parser_context=None): result = super().parse( stream, media_type=media_type, parser_context=parser_context ) data = {} for key, value in result.data.items(): if type(value) != str: data[key] = value continue if '{' in value or "[" in value: try: data[key] = json.loads(value) except ValueError: data[key] = value else: data[key] = value return parsers.DataAndFiles(data, result.files)
现在,我们可以使用此解析器和Django REST内置JSONParser解析数据。现在该建立我们的 视图集了 。
class ProductViewSet(ModelViewSet): queryset = Product.objects.all() serializer_class = ProductSerializer parser_classes = [MultipartJsonParser, JSONParser] def get_serializer_context(self): context = super(ProductViewSet, self).get_serializer_context() # appending extra data to context if len(self.request.FILES) > 0: context.update({ 'included_images': self.request.FILES }) return context def create(self, request, *args, **kwargs): # Validating images with its own serializer, but not creating. # The adding process must be through Serializer. try: image_serializer = ProductImageSerializer(data=request.FILES) image_serializer.is_valid(raise_exception=True) except Exception: raise NotAcceptable( detail={ 'message': 'Upload a valid image. The file you uploaded was either not ' 'an image or a corrupted image.'}, code=406) # the rest of method is about the product serialization(with extra context), # validation and creation. serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers) class ProductImageViewSet(ModelViewSet): queryset = ProductImage.objects.all() serializer_class = ProductImageSerializer class TagsViewSet(ModelViewSet): queryset = Tags.objects.all() serializer_class = TagsSerializer
让我们在这里检查。正如我在评论中提到的,图像文件将包含在request.FILES中。因此,我首先将数据发送到 ProductImageSerializer 并进行了验证。如果发生验证错误,该过程将停止,API将发送一条错误消息作为响应。然后,我将数据发送到ProductSerializer,并将图片信息附加到 get_serializer_context 方法中的上下文中。
我们已经完成了 create 方法,其他细节都写在了代码上。
最后, serializer.py
from django.forms import ImageField as DjangoImageField class TagsSerializer(HyperlinkedModelSerializer): class Meta: model = Tags fields = ['url', 'pk', 'name'] class ProductImageSerializer(HyperlinkedModelSerializer): class Meta: model = ProductImage fields = ['url', 'pk', 'product', 'image'] # attention!!! if you not use this bottom line, # it will show error like "product required" and # indirectly our validation at ProductViewSet will raise error. extra_kwargs = { 'product': {'required': False} } # we created Object-level custom validation because validation not working correctly. # when ProductImageSerializer get single image, everything just fine but # when it get multiple image, serializer is just passing all the files. def validate(self, attrs): default_error_messages = { 'invalid_image': 'Upload a valid image. The file you uploaded was either not an image or a corrupted image.', } # in here we're verifying image with using django.forms; Pillow not necessary !! for i in self.initial_data.getlist('image'): django_field = DjangoImageField() django_field.error_messages = default_error_messages django_field.clean(i) return attrs class ProductSerializer(HyperlinkedModelSerializer, TaggitSerializer): tags = TagsSerializer(allow_null=True, many=True, required=False) # you can delete this line. If you delete it, it will appear as url in response. productimage_set = ProductImageSerializer(allow_null=True, many=True, required=False) taggit = TagListSerializerField(allow_null=True, required=False) class Meta: model = Product fields = ['url', 'pk', 'name', 'tags', 'taggit', 'productimage_set'] def create(self, validated_data): # create product try: product_obj = Product.objects.create( name=validated_data['name'] ) except Exception: raise NotAcceptable(detail={'message': 'The request is not acceptable.'}, code=406) if 'included_images' in self.context: # checking if key is in context images_data = self.context['included_images'] for i in images_data.getlist('image'): ProductImage.objects.create( product=product_obj, image=i ) # pop taggit and create if 'taggit' in validated_data: taggit_data = validated_data.pop('taggit') for taggit_data in taggit_data: taggit_obj, created = Tag.objects.get_or_create(name=taggit_data) product_obj.taggit.add(taggit_obj) # pop tags and create if 'tags' in validated_data: tags_data = validated_data.pop('tags') for tags_data in tags_data: for i in tags_data.items(): tags_obj, created = Tags.objects.get_or_create(name=i[1]) product_obj.tags.add(tags_obj) return product_obj
那么这里发生了什么?为什么我们要为图像创建额外的验证?尽管我不知道为什么,但是ImageSerializer仅对单个文件进行正确的验证。如果您尝试上传两个文件,甚至可以在图片旁边放一个电影,验证将无法进行。为了防止这种情况,我们使用django的内置形式依次验证了图片;更改.mp3的格式并将其设置为.jpg,尝试上传高尺寸的文件,但它们均不起作用。进行验证的是纯django。其他细节在代码中。
如果您按照我说的去做,那么响应将是这样的:
我认为这会使大多数 Postman 用户满意。希望对您有所帮助。如果有什么引起您的注意,让我们见面。