Django Rest Framework File Upload

Question

I'm using the same stack and was also looking for an example of file upload, but my case is simpler since I use the ModelViewSet instead of APIView. The key turned out to be the pre_save hook. I ended up using it together with the angular-file-upload module like so:

# Django
class ExperimentViewSet(ModelViewSet):
    queryset = Experiment.objects.all()
    serializer_class = ExperimentSerializer

    def pre_save(self, obj):
        obj.samplesheet = self.request.FILES.get('file')

class Experiment(Model):
    notes = TextField(blank=True)
    samplesheet = FileField(blank=True, default='')
    user = ForeignKey(User, related_name='experiments')

class ExperimentSerializer(ModelSerializer):
    class Meta:
        model = Experiment
        fields = ('id', 'notes', 'samplesheet', 'user')

// AngularJS
controller('UploadExperimentCtrl', function($scope, $upload) {
    $scope.submit = function(files, exp) {
        $upload.upload({
            url: '/api/experiments/' + exp.id + '/',
            method: 'PUT',
            data: {user: exp.user.id},
            file: files[0]
        });
    };
});

Use the FileUploadParser, it's all in the request. Use a put method instead, you'll find an example in the docs :)

class FileUploadView(views.APIView):
    parser_classes = (FileUploadParser,)

    def put(self, request, filename, format=None):
        file_obj = request.FILES['file']
        # do some stuff with uploaded file
        return Response(status=204)

Finally I am able to upload image using Django. Here is my working code

views.py

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

    def post(self, request, format='jpg'):
        up_file = request.FILES['file']
        destination = open('/Users/Username/' + up_file.name, 'wb+')
        for chunk in up_file.chunks():
            destination.write(chunk)
        destination.close()  # File should be closed only after all chuns are added

        # ...
        # do some stuff with uploaded file
        # ...
        return Response(up_file.name, status.HTTP_201_CREATED)

urls.py

urlpatterns = patterns('', 
url(r'^imageUpload', views.FileUploadView.as_view())

curl request to upload

curl -X POST -S -H -u "admin:password" -F "[email protected];type=image/jpg" 127.0.0.1:8000/resourceurl/imageUpload

From my experience, you don't need to do anything particular about file fields, you just tell it to make use of the file field:

from rest_framework import routers, serializers, viewsets

class Photo(django.db.models.Model):
    file = django.db.models.ImageField()

    def __str__(self):
        return self.file.name

class PhotoSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.Photo
        fields = ('id', 'file')   # <-- HERE

class PhotoViewSet(viewsets.ModelViewSet):
    queryset = models.Photo.objects.all()
    serializer_class = PhotoSerializer

router = routers.DefaultRouter()
router.register(r'photos', PhotoViewSet)

api_urlpatterns = ([
    url('', include(router.urls)),
], 'api')
urlpatterns += [
    url(r'^api/', include(api_urlpatterns)),
]

and you're ready to upload files:

curl -sS http://example.com/api/photos/ -F 'file=@/path/to/file'

Add -F field=value for each extra field your model has. And don't forget to add authentication.

After spending 1 day on this, I figured out that ...

For someone who needs to upload a file and send some data, there is no straight fwd way you can get it to work. There is an open issue in json api specs for this. One possibility i have seen is to use multipart/related as shown here, but i think its very hard to implement it in drf.

Finally what i had implemented was to send the request as formdata. You would send each file as file and all other data as text. Now for sending the data as text you have two choices. case 1) you can send each data as key value pair or case 2) you can have a single key called data and send the whole json as string in value.

The first method would work out of the box if you have simple fields, but will be a issue if you have nested serializes. The multipart parser wont be able to parse the nested fields.

Below i am providing the implementation for both the cases

Models.py

class Posts(models.Model):
    id = models.UUIDField(default=uuid.uuid4, primary_key=True, editable=False)
    caption = models.TextField(max_length=1000)
    media = models.ImageField(blank=True, default="", upload_to="posts/")
    tags = models.ManyToManyField('Tags', related_name='posts')

serializers.py -> no special changes needed, not showing my serializer here as its too lengthy because of the writable ManyToMany Field implimentation.

views.py

class PostsViewset(viewsets.ModelViewSet):
    serializer_class = PostsSerializer
    #parser_classes = (MultipartJsonParser, parsers.JSONParser) use this if you have simple key value pair as data with no nested serializers
    #parser_classes = (parsers.MultipartParser, parsers.JSONParser) use this if you want to parse json in the key value pair data sent
    queryset = Posts.objects.all()
    lookup_field = 'id'

Now, if you are following the first method and is only sending non-Json data as key value pairs, you don't need a custom parser class. DRF'd MultipartParser will do the job. But for the second case or if you have nested serializers (like i have shown) you will need custom parser as shown below.

utils.py

from django.http import QueryDict
import json
from rest_framework import parsers

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 case1 with nested serializers
        # parse each field with json
        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

        # for case 2
        # find the data field and parse it
        data = json.loads(result.data["data"])

        qdict = QueryDict('', mutable=True)
        qdict.update(data)
        return parsers.DataAndFiles(qdict, result.files)

This serializer would basically parse any json content in the values.

The request example in post man for both cases: case 1 ,

Case 2

If anyone interested in the easiest example with ModelViewset for Django Rest Framework.

The Model is,

class MyModel(models.Model):
    name = models.CharField(db_column='name', max_length=200, blank=False, null=False, unique=True)
    imageUrl = models.FileField(db_column='image_url', blank=True, null=True, upload_to='images/')

    class Meta:
        managed = True
        db_table = 'MyModel'

The Serializer,

class MyModelSerializer(serializers.ModelSerializer):
    class Meta:
        model = MyModel
        fields = "__all__"

And the View is,

class MyModelView(viewsets.ModelViewSet):
    queryset = MyModel.objects.all()
    serializer_class = MyModelSerializer

Test in Postman,

models.py

from django.db import models

import uuid

class File(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    file = models.FileField(blank=False, null=False)
    
    def __str__(self):
        return self.file.name

serializers.py

from rest_framework import serializers
from .models import File

class FileSerializer(serializers.ModelSerializer):
    class Meta:
        model = File
        fields = "__all__"

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 FileSerializer


class FileUploadView(APIView):
    permission_classes = []
    parser_class = (FileUploadParser,)

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

      file_serializer = FileSerializer(data=request.data)

      if file_serializer.is_valid():
          file_serializer.save()
          return Response(file_serializer.data, status=status.HTTP_201_CREATED)
      else:
          return Response(file_serializer.errors, status=status.HTTP_400_BAD_REQUEST)

urls.py

from apps.files import views as FileViews

urlpatterns = [
    path('api/files', FileViews.FileUploadView.as_view()),
]

settings.py

# file uload parameters
MEDIA_URL =  '/media/'
MEDIA_ROOT = os.path.join(BASE_DIR, 'media')

Send a post request to api/files with a your file attached to a form-data field file. The file will be uploaded to /media folder and a db record will be added with id and file name.