Re: Custom Http404 like exception

Hey Serge,

Here is a brief description of how status code is set in request response cycle of Django.

Http404 inherits from Exception defined here - https://github.com/django/django/blob/1.4.3/django/http/__init__.py#L132-L133

get_response() method of django.core.handlers.base.BaseHandler handles Http404 and sets status code here - https://github.com/django/django/blob/stable/1.4.x/django/core/handlers/base.py#L138-L155

django.core.handlers.base.BaseHandler has some code for setting status_code to 403 and 500 as well.

I want to make the same but with for a 401 code and a custom redirection according to the resource to be accessed.

There is really simple way to do this.

    
class HttpResponseUnauthorizedRequest(HttpResponse):
    
    status_code = 401
    

You can use this class similar to HttpResponse

    def protected_view(request):      ## handle authorization      ## if not authorized then return above response      return HttpResponseUnauthorizedRequest("Authorazation is required")

There are similar classes for different status code as well - https://github.com/django/django/blob/stable/1.4.x/django/http/__init__.py#L751-L770

Similar implementation by django-tastypie - https://github.com/toastdriven/django-tastypie/blob/master/tastypie/http.py

So you have set status code, now what

process_response() method of django.middleware.common.CommonMiddleware checks if status code is 404 and sends an email to admins for broken urls - https://github.com/django/django/blob/stable/1.4.x/django/middleware/common.py#L94-L109

You can see status_code based processing of response in other middlewares as well, e.g. cache, http and csrf.

Finally request handlers set status code is response header - 

1. django.core.handlers.wsgi.WSGIHandler sets status code in response header - https://github.com/django/django/blob/stable/1.4.x/django/core/handlers/wsgi.py#L245-L253

2. If you are using modpython then status_code in header is set by django.core.handlers.modpython.ModPythonHandler - https://github.com/django/django/blob/stable/1.4.x/django/core/handlers/wsgi.py#L245-L253

This response is served by Webserver.

Sincerely,

Pankaj Singh

http://about.me/psjinx

On Mon, Feb 18, 2013 at 6:15 PM, Serge G. Spaolonzi <serge@cobalys.com> wrote:

Hi,

How does the Http404 exception works internally?
I want to make the same but with for a 401 code and a custom
redirection according to the resource to be accessed.
I have thought about using a middleware to archive this but I am not
sure if it is standard way used by 'django.http.Http404'.

Thanks

--
Serge G. Spaolonzi
Cobalys Systems
http://www.cobalys.com

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