Django.db.utils.IntegrityError:在序列化程序上调用my.save（）函数时，唯一约束失败

Question

因此，我创建了一个singleton类来在我的服务器上存储一个文件，该文件在每次添加新文件时都会被替换，但每当我尝试将一个新文件发布到我的上载端点时，我都会遇到以下错误，并且我将其范围缩小到调用file_serializer.save（）时

sqlite3.IntegrityError: UNIQUE constraint failed: api_app_onixfile.id

Models.py

class SingletonModel(models.Model):

    class Meta:
        abstract = True

    def save(self, *args, **kwargs):
        self.pk = 1
        super(SingletonModel, self).save(*args, **kwargs)

    def delete(self, *args, **kwargs):
        pass

    @classmethod
    def load(cls):
        obj, created = cls.objects.get_or_create(pk=1)
        return obj

class OnixFile(SingletonModel):
    onix_file = models.FileField(blank=False, null=False, validators=[validate_xml])
    def __str__(self):
        return self.onix_file.name 

Views.py

from django.shortcuts import render
from rest_framework.parsers import FileUploadParser
from rest_framework.response import Response
from rest_framework.views import APIView
from rest_framework import status
from .serializers import XMLFileSerializer
from .models import OnixFile
import onixcheck
from .utils import OnixParser
from django.http import JsonResponse


class FileUploadView(APIView):
    parser_class = (FileUploadParser,)

    def post(self, request, *args, **kwargs):


        file_serializer = XMLFileSerializer(data=request.data)

        if(file_serializer.is_valid()):

            onix_file = request.data['onix_file']
            onix_errors = onixcheck.validate(onix_file)
            if len(onix_errors) > 0:
                file_serializer.save()
                print("Onix Errors")
                return Response(onix_errors, status=status.HTTP_400_BAD_REQUEST)

            else:
                file_serializer.save()
                print(OnixFile.load())
                return Response(OnixFile.load().__str__(), status=status.HTTP_201_CREATED)

        else:
            return Response(file_serializer.errors, status=status.HTTP_400_BAD_REQUEST)

序列化程序.py

from rest_framework import serializers
from .models import OnixFile

class XMLFileSerializer(serializers.ModelSerializer):
    class Meta:
        model = OnixFile
        fields = "__all__"

我假设我的SingletonModel保存函数可以处理这样一个事实，即我不能通过用新信息覆盖当前函数来获得唯一的PK

Answer 1

因为您正在向序列化程序发布和传递数据，所以它正在尝试创建一个新的OnixFile。这意味着当序列化程序调用save()时，它试图将这个新的OnixFile实例的id设置为1，这很可能被现有的单例实例所采用

如果您想用新数据更新您的单例，我建议将instance传递到序列化程序中。这样，序列化程序将尝试更新该实例，您可以保存更新，而不是尝试创建新实例：

    def post(self, request, *args, **kwargs):
        # Feel free to use `first()` or do some other check here in case you
        # have a case where the singleton might not exist.
        singleton_instance = OnixFile.objects.get(id=1)
        file_serializer = XMLFileSerializer(instance=singleton_instance, data=request.data)

        if(file_serializer.is_valid()):
            ...