Kapil Kaushik Kapil Kaushik - 4 years ago 179
AngularJS Question

Django CORS API from AngularJS

I have enabled CORS in Django, with "django-cors":

https://github.com/ottoyiu/django-cors-headers

After following the installation steps here, I have set the following:

CORS_ORIGIN_ALLOW_ALL = False

CORS_ORIGIN_WHITELIST = (
'http://localhost:8000'
)


The django app runs on http://locahost:3000

My frontend is an Angular app, which runs on "http:/localhost:8000", and I have done the following changes to communicate with the django app.

RestangularProvider.setBaseUrl('http://localhost:3000/');


[Using Restangular for resource APIs]

When I call the GET API, the "OPTIONS" pre-flight call happens, and I get the following error:

XMLHttpRequest cannot load http://localhost:3000/users. Credentials flag is 'true', but the 'Access-Control-Allow-Credentials' header is ''. It must be 'true' to allow credentials. Origin 'http://localhost:8000' is therefore not allowed access.

Looking at the documentation, I understood that I needed to set certain headers which the server would expect as a part of the call. So, I added the following:
RestangularProvider.setDefaultHeaders({"x-requested-with" : 'XMLHttpRequest'});

However, on making this change, I am getting another error, which I am unable to resolve:
XMLHttpRequest cannot load http://localhost:3000/users. Response for preflight is invalid (redirect)

Note: The request/response headers are as follows:

General:
Remote Address:127.0.0.1:3000
Request URL:http://localhost:3000/users
Request Method:OPTIONS
Status Code:301 MOVED PERMANENTLY

Response Headers
Access-Control-Allow-Headers:x-requested-with, content-type, accept, origin, authorization, x-csrftoken, user-agent, accept-encoding
Access-Control-Allow-Methods:GET, POST, PUT, PATCH, DELETE, OPTIONS
Access-Control-Allow-Origin:http://localhost:8000
Access-Control-Max-Age:86400
Content-Type:text/html; charset=utf-8
Date:Thu, 17 Dec 2015 11:10:16 GMT
Location:http://localhost:3000/users/
Server:WSGIServer/0.1 Python/2.7.10
X-Frame-Options:SAMEORIGIN

Request Headers
Accept:*/*
Accept-Encoding:gzip, deflate, sdch
Accept-Language:en-US,en;q=0.8
Access-Control-Request-Headers:accept, x-requested-with
Access-Control-Request-Method:GET
Cache-Control:no-cache
Connection:keep-alive
Host:localhost:3000
Origin:http://localhost:8000
Pragma:no-cache
Referer:http://localhost:8000/
User-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2490.86 Safari/537.36

Answer Source

I finally managed to resolve the problem. The problem was because of improper API naming.

My colleague had named the API as follows:

url(r'^users/', views.user_details)

And when I would call "/users", then because of django's "APPEND_SLASH" setting, it was doing a permanent redirect to "/users/". Here's what the django documentation says about APPEND_SLASH:

When set to True, if the request URL does not match any of the patterns 
in the URLconf and it doesn’t end in a slash, an HTTP redirect is issued 
to the same URL with a slash appended. Note that the redirect 
may cause any data submitted in a POST request to be lost.

The APPEND_SLASH setting is only used if CommonMiddleware 
is installed.

Of course, the simplest (and best) way of resolving this problem, is to update the API url by removing the slash, i.e.

url(r'^users', views.user_details)

Then it would match the URL directly, and no redirect will be issued.

However, in case someone really wants to keep the trailing slash in the API, then you can still make it work, by adding the following code in AngularJS:

resourceProvider.defaults.stripTrailingSlashes = false;
RestangularProvider.setRequestSuffix('/'); 

The above is however not recommended, but since it came out of my experiments, I am sharing it anyways.

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