Render server side JSON in Django REST Framework - json

Question

I'm trying to make bulk data downloads by serializing my entire database as JSON. The drf documentation on serializers has a section that says you can simply do:
from rest_framework.renderers import JSONRenderer
serializer = CommentSerializer(comment)
json = JSONRenderer().render(serializer.data)
Unfortunately, this doesn't work for HyperLinked relationships. When you try to do it with them, you get something like:
AssertionError: HyperlinkedIdentityField requires the request in the serializer context. Add context={'request': request} when instantiating the serializer.
So, I figured out I can add context attribute, like:
r = Request(request=HttpRequest())
context = dict(request=r)
serializer = CommentSerializer(comment, context=context)
json = JSONRenderer().render(serializer.data)
Which then returns the error:
django.core.exceptions.ImproperlyConfigured: Could not resolve URL for hyperlinked relationship using view name "opinioncluster-detail". You may have failed to include the related model in your API, or incorrectly configured the lookup_field attribute on this field.
I know this API works properly when it's called from the browser, but I can't get past this when I call it as above. Something that's automatic from the browser doesn't happen when you render it manually.
Any ideas?
First edit
Here's another strategy that seemed promising because it would add the path to my request object:
r = Request(request=RequestFactory().get(reverse('comment-list', kwargs={'version': 'v3'})))
context = dict(request=r)
serializer = CommentSerializer(comment, context=context)
json = JSONRenderer().render(serializer.data)
That returns the same problem as if I hadn't defined a path to the request:
django.core.exceptions.ImproperlyConfigured: Could not resolve URL for hyperlinked relationship using view name "opinioncluster-detail". You may have failed to include the related model in your API, or incorrectly configured the lookup_field attribute on this field.
Second Edit
As I said in my comments, I'm fairly certain my serializers and views aren't to blame, since they work perfectly fine via the browser. Nevertheless, here they are. If you're truly generous, the full serializers, filters, and codebase is online.
View:
class OpinionClusterViewSet(LoggingMixin, viewsets.ModelViewSet):
queryset = OpinionCluster.objects.all()
serializer_class = OpinionClusterSerializer
filter_class = OpinionClusterFilter
ordering_fields = (
'date_created', 'date_modified', 'date_filed', 'citation_count',
'date_blocked',
)
Serializer:
class OpinionClusterSerializer(DynamicFieldsModelSerializer,
serializers.HyperlinkedModelSerializer):
absolute_url = serializers.CharField(source='get_absolute_url',
read_only=True)
panel = serializers.HyperlinkedRelatedField(
many=True,
view_name='judge-detail',
read_only=True,
)
non_participating_judges = serializers.HyperlinkedRelatedField(
many=True,
view_name='judge-detail',
read_only=True,
)
docket = serializers.HyperlinkedRelatedField(
many=False,
view_name='docket-detail',
read_only=True,
)
sub_opinions = serializers.HyperlinkedRelatedField(
many=True,
view_name='opinion-detail',
read_only=True,
)
class Meta:
model = OpinionCluster

Answer 1

This management command creates a MockRequest to be used in a non-browser environment and should allow you to create your JSON:
from django.core.management.base import BaseCommand
from django.http import HttpRequest
from rest_framework.renderers import JSONRenderer
from rest_framework.request import Request
from comments.models import Comment
from comments.serializers import CommentSerializer
class MockRequest(HttpRequest):
def __init__(self):
super(MockRequest, self).__init__()
self.setup_host()
def setup_host(self):
# Required to give absolute urls in output
self.META['HTTP_HOST'] = 'localhost:8000'
class Command(BaseCommand):
help = 'Export JSON'
def handle(self, *args, **options):
request = MockRequest()
serializer_context = {
'request': Request(request),
}
comment = Comment.objects.first()
serializer = CommentSerializer(comment, context=serializer_context)
json = JSONRenderer().render(serializer.data)
print(json)
To remove the hard coded domain you could use the Sites framework to power the host name:
def setup_host(self):
from django.contrib.sites.models import Site
site = Site.objects.get_current()
self.META['HTTP_HOST'] = site.domain

Answer 2

After digging quite deeply into the code, I finally figured this out:
r = RequestFactory().request()
r.version = 'v3'
r.versioning_scheme = URLPathVersioning()
context = dict(request=r)
renderer = JSONRenderer()
json_str = renderer.render(
serializer(item, context=context).data,
accepted_media_type='application/json; indent=2',
)
This seems to work, but the HyperLinkRelated values in the JSON that is serialized have the server set to testserver. I could get around that by setting:
r.META['SERVER_NAME']
But I also need to set r.scheme to https, which doesn't seem to be possible (I get an error that r.scheme cannot be set).
I'm pretty close though, so this is going to have to serve as an answer for now.