Json parse error using POST in django rest api

Question

I am trying to implement a simple GET/POST api via Django REST framework

views.py

class cuser(APIView):
def post(self, request):
   stream  = BytesIO(request.DATA)
    json = JSONParser().parse(stream)
    return Response()

urls.py

from django.conf.urls import patterns, url
from app import views
urlpatterns = patterns('',

           url(r'^challenges/',views.getall.as_view() ),
           url(r'^cuser/' , views.cuser.as_view() ),
      )

I am trying to POST some json to /api/cuser/ (api is namespace in my project's urls.py ) , the JSON

{
"username" : "abhishek",
"email" : "john@doe.com",
"password" : "secretpass"
}

I tried from both Browseable API page and httpie ( A python made tool similar to curl)

httpie command

http --json POST http://localhost:58601/api/cuser/ username=abhishek email=john@doe.com password=secretpass

but I am getting JSON parse error :

JSON parse error - Expecting property name enclosed in double quotes: line 1 column 2 (char 1)

Whole Debug message using --verbose --debug

    POST /api/cuser/ HTTP/1.1

Content-Length: 75

Accept-Encoding: gzip, deflate

Host: localhost:55392

Accept: application/json

User-Agent: HTTPie/0.8.0

Connection: keep-alive

Content-Type: application/json; charset=utf-8



{"username": "abhishek", "email": "john@doe.com", "password": "aaezaakmi1"}

HTTP/1.0 400 BAD REQUEST

Date: Sat, 24 Jan 2015 09:40:03 GMT

Server: WSGIServer/0.1 Python/2.7.9

Vary: Accept, Cookie

Content-Type: application/json

Allow: POST, OPTIONS



{"detail":"JSON parse error - Expecting property name enclosed in double quotes: line 1 column 2 (char 1)"}

Answer 1

I arrived at this post via Google for

"detail": "JSON parse error - Expecting property name enclosed in double-quotes": Turns out you CANNOT have a trailing comma in JSON.

So if you are getting this error you may need to change a post like this:

{
    "username" : "abhishek",
    "email" : "john@doe.com",
    "password" : "secretpass",
}

to this:

{
    "username" : "abhishek",
    "email" : "john@doe.com",
    "password" : "secretpass"
}

Note the removed comma after the last property in the JSON object.

Answer 2

Basically, whenever you are trying to make a post request with requests lib, This library also contains json argument which is ignored in the case when data argument is set to files or data. So basically when json argument is set with json data. Headers are set asContent-Type: application/json. Json argument basically encodes data sends into a json format. So that at DRF particularly is able to parse json data. Else in case of only data argument it is been treated as form-encoded

requests.post(url, json={"key1":"value1"})

you can find more here request.post complicated post methods

Answer 3

The problem that you are running into is that your request is already being parsed, and you are trying to parse it a second time.

From "How the parser is determined"

The set of valid parsers for a view is always defined as a list of classes. When request.data is accessed, REST framework will examine the Content-Type header on the incoming request, and determine which parser to use to parse the request content.

In your code you are accessing request.DATA, which is the 2.4.x equaivalent of request.data. So your request is being parsed as soon as you call that, and request.DATA is actually returning the dictionary that you were expecting to parse.

json = request.DATA

is really all you need to parse the incoming JSON data. You were really passing a Python dictionary into json.loads, which does not appear to be able to parse it, and that is why you were getting your error.