Django Restful Framework Authentication HTTP Post Error
<p>I was following the Django restful framework tutorial and I came across a error at the "Authenticating with the API" step. I've retraced myself however can't seem to see where I went wrong. Basically when I go to post to my API i get an error see below. Ideally I would also like to setup permissions which state "access denied" unless object owner - any advice on this would be greatly appreciated.</p>

<pre><code>http -a jimmynos:password POST http://127.0.0.1:8000/snippets/ code="print 789" 
</code></pre>

<p>Some of the error:</p>

<pre><code>IntegrityError at /snippets/
NOT NULL constraint failed: snippets_snippet.owner_id

Request Method: POST
Request URL: http://127.0.0.1:8000/snippets/
Django Version: 1.9.9
Python Executable: /Users/james/Documents/django/tutorialSerialization/env/bin/python
Python Version: 2.7.10
Python Path: ['/Users/james/Documents/django/tutorialSerialization/tutorial', '/Users/james/Documents/django/tutorialSerialization/env/lib/python27.zip', '/User
</code></pre>

<p>views.py</p>

<pre><code>from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from django.http import Http404
from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework import status
from django.contrib.auth.models import User
from snippets.serializers import UserSerializer
from rest_framework import generics
from rest_framework import permissions
from snippets.permissions import IsOwnerOrReadOnly


class UserList(generics.ListAPIView):
    queryset = User.objects.all()
    serializer_class = UserSerializer


class UserDetail(generics.RetrieveAPIView):
    queryset = User.objects.all()
    serializer_class = UserSerializer

class SnippetList(APIView):
    """
    List all snippets, or create a new snippet.
    """
    permission_classes = (permissions.IsAuthenticatedOrReadOnly,IsOwnerOrReadOnly,)

    def get(self, request, format=None):
        #snippets = Snippet.objects.all()
        snippets = Snippet.objects.filter(owner=self.request.user)
        serializer = SnippetSerializer(snippets, many=True)
        return Response(serializer.data)

    def post(self, request, format=None):
        serializer = SnippetSerializer(data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

    def perform_create(self, serializer):
        serializer.save(owner=self.request.user)


class SnippetDetail(APIView):
    """
    Retrieve, update or delete a snippet instance.
    """
    permission_classes = (permissions.IsAuthenticatedOrReadOnly,IsOwnerOrReadOnly,)
    def get_object(self, pk):
        try:
            return Snippet.objects.get(pk=pk)
        except Snippet.DoesNotExist:
            raise Http404

    def get(self, request, pk, format=None):
        snippet = self.get_object(pk)
        serializer = SnippetSerializer(snippet)
        return Response(serializer.data)

    def put(self, request, pk, format=None):
        snippet = self.get_object(pk)
        serializer = SnippetSerializer(snippet, data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

    def delete(self, request, pk, format=None):
        snippet = self.get_object(pk)
        snippet.delete()
        return Response(status=status.HTTP_204_NO_CONTENT)
</code></pre>

<p>serializers.py</p>

<pre><code>from rest_framework import serializers
from snippets.models import Snippet, LANGUAGE_CHOICES, STYLE_CHOICES
from django.contrib.auth.models import User


class SnippetSerializer(serializers.ModelSerializer):
    owner = serializers.ReadOnlyField(source='owner.username')
    class Meta:
        model = Snippet
        #owner = serializers.ReadOnlyField(source='owner.username')
        fields = ('id', 'title', 'code', 'linenos', 'language', 'style', 'owner')


class UserSerializer(serializers.ModelSerializer):
    snippets = serializers.PrimaryKeyRelatedField(many=True, queryset=Snippet.objects.all())

    class Meta:
        model = User
        fields = ('id', 'username', 'snippets')
</code></pre>

<p>permissions.py</p>

<pre><code>from rest_framework import permissions


class IsOwnerOrReadOnly(permissions.BasePermission):
    """
    Custom permission to only allow owners of an object to edit it.
    """

    def has_object_permission(self, request, view, obj):
        # Read permissions are allowed to any request,
        # so we'll always allow GET, HEAD or OPTIONS requests.
        if request.method in permissions.SAFE_METHODS:
            return True

        # Write permissions are only allowed to the owner of the snippet.
        return obj.owner == request.user
</code></pre>

<p>The error must have something to do with</p>

<pre><code>owner = serializers.ReadOnlyField(source='owner.username')
</code></pre>

<p>or</p>

<pre><code>def perform_create(self, serializer):
    serializer.save(owner=self.request.user)
</code></pre>

<p>models.py</p>

<pre><code>from django.db import models
from pygments.lexers import get_all_lexers
from pygments.styles import get_all_styles


LEXERS = [item for item in get_all_lexers() if item[1]]
LANGUAGE_CHOICES = sorted([(item[1][0], item[0]) for item in LEXERS])
STYLE_CHOICES = sorted((item, item) for item in get_all_styles())


class Snippet(models.Model):
    created = models.DateTimeField(auto_now_add=True)
    title = models.CharField(max_length=100, blank=True, default='')
    code = models.TextField()
    linenos = models.BooleanField(default=False)
    language = models.CharField(choices=LANGUAGE_CHOICES, default='python', max_length=100)
    style = models.CharField(choices=STYLE_CHOICES, default='friendly', max_length=100)
    owner = models.ForeignKey('auth.User', related_name='snippets')
    highlighted = models.TextField()

    class Meta:
        ordering = ('created',)
</code></pre>

<p>Enviroment:</p>

<pre><code>Python 2.7.10 on MAC
Django==1.9.9
djangorestframework==3.4.6
Pygments==2.1.3
</code></pre>

<p><a href="http://www.django-rest-framework.org/tutorial/4-authentication-and-permissions/" rel="nofollow">Django Restful Framework API</a></p>

<p>The error should be <code>owner = serializers.ReadOnlyField(source='owner.username')</code></p>

<p>Your serializer need <strong>owner</strong> to create Snippet instance.</p>

<p>If you let owner to be <strong>readonly</strong>, then you will lack the owner field, therefore it failed to create snippet instance. </p>

python django django-rest-framework