Using "Content-Type:application/json" to post in curl gives HTTP/1.1 400 BAD REQUEST - django

Question

When I make a post request using the following
curl -i -d "username=rock&password=rock" http://my_VM_IP/api/1.1/json/my_login/
it generates the required response generating a token like this(abridged):
HTTP/1.1 200 OK
Date: Mon, 22 Oct 2012 08:37:39 GMT
Vary: Authorization,Accept-Language,Cookie,Accept-Encoding
Content-Type: text/plain
Transfer-Encoding: chunked
OK{"success": {"my_token": "required_token"}}
But when I try the same including a header as:
curl -i -H "Content-Type:application/json" -d "username=rock&password=rock" http://my_VM_IP/api/1.1/json/my_login/
it gives me the following error:
HTTP/1.1 400 BAD REQUEST
Date: Mon, 22 Oct 2012 11:12:04 GMT
Vary: Authorization,Accept-Language,Cookie,Accept-Encoding
***Content-Type: text/plain***
Content-Language: en-us
Connection: close
Transfer-Encoding: chunked
Bad Request
I dont understand why this happens. And also why does the content-Type show text/plain, I also tried looking at some other questions like Why Setting POST Content-type:"Application/Json" causes a "Bad Request" on REST WebService? . It also addresses the same problem I have. Following the answer in that I tried giving the data in various formats as
{"username":"rock", "password":"rock"}
but without success. Thanks in advance.

Answer 1

By using -H "Content-Type:application/json" you're setting the Content-Type header for your request. The response will still return whatever your view tells it to return.
To return a response with Content-Type application/json, use something along these lines:
import json
from django.http import HttpResponse
def json_response(return_vars):
'JSON-encodes return_vars returns it in an HttpResponse with a JSON mimetype'
return HttpResponse(json.dumps(return_vars), content_type = "application/json")
#Usage: return json_response({'admin_token': admin_api_token.token})

Answer 2

You were close, but you need to send it as a JSON format via curl:
curl -i -H "Content-Type:application/json" -d '{"username":"rock", "password":"rock"}'
("password","admin" should be "password":"admin")
If that's not working, try:
curl --dump-header - -H "Accept:application/json" -H "Content-Type:application/json" -X POST --data '{"username": "admin", "password": "admin"}' http://my_VM_IP/api/1.1/json/my_login/

Answer 3

When you set -H parameter of curl command, you specify content type of request. Content type of response, that you see in response, is set on the server. In WSGI application you need to specify 'content-type' and 'content-length' manually. Some of framework provide utility method to return JSON responses (for example, jsonify method in Flask).