- February 13, 2009
- 2 (after 2 ratings)
This allows you to host your own URL shortening service for your site's internal urls. By adding this class as a Mixin to your models, any model with a get_absolute_url method will have a get_short_url method also, which either returns an existing redirect or creates a new one and returns that.
Import the class above, add the mixin to your model declaration, and ensure you have declared a get_absolute_url method.
class MyModel = (models.Model, ShortURL):
You must have the django.contrib.redirects app installed, and you must be using the RedirectFallbackMiddleware as a middleware class.
Change the settings in the code above or set them in your settings.py file
SHORTURL_CHARS: the characters to use when creating a shorturl
SHORTURL_CHAR_NO = the number of characters to use in a shorturl
SHORTURL_APPEND_SLASH = whether to append a slash to the end of the shorturl redirect
The default settings will give you about 17 million different unique short URLs, reducing the number of characters used to 4 will give you 600,000 or so. That's enough that collisions will be quite rare for sites of a few thousand pages (collisions just result in a urls being generated until an unused combination is found) but if you've got a big site you'll probably want to explore a more robust solution with a proper hash function.
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from django.conf import settings from django.contrib.sites.models import Site from django.contrib.redirects.models import Redirect from random import choice, seed from os import urandom SHORTURL_CHARS = getattr(settings, "SHORTURL_CHARS", "bcdfghjklmnpqrstvwxyz2346789") SHORTURL_CHAR_NO = getattr(settings, "SHORTURL_CHAR_NO", 5) SHORTURL_APPEND_SLASH = getattr(settings, "SHORTURL_APPEND_SLASH", True) class ShortURLException: pass class ShortURL(object): """ A mixin that sets up short url redirects for models that have a get_absolute_url method. Requires django.contrib.redirects to be installed to create redirects, and django.contrib.redirects.middleware.RedirectFallbackMiddleware to use them. """ def __init__(self, *args, **kwargs): """ Seeds randomiser """ seed(urandom(256)) super(ShortURL, self, *args, **kwargs) def get_short_url(self, *args, **kwargs): """ Finds the short url for the object's absolute url in the Redirects model objects. If it doesn't exist, generate a short url and create a new Redirect object. """ if not hasattr(self, 'get_absolute_url'): return None else: currenturl = self.get_absolute_url() site = Site.objects.get(id=settings.SITE_ID) redirects = Redirect.objects.filter(site=site, new_path=currenturl) for url in redirects: if len(url.old_path) <= SHORTURL_CHAR_NO + 1: #allow for leading slash shorturl = url.old_path break else: shorturl = None if not shorturl: # Check we've got at least a 9 in ten chance of not colliding or throw an exception if Redirect.objects.count() > (len(SHORTURL_CHARS) ** SHORTURL_CHAR_NO) / 10: raise ShortURLException while True: shorturl = '/'+''.join([choice(SHORTURL_CHARS) for char in range(SHORTURL_CHAR_NO)]) if not Redirect.objects.filter(site=site, old_path=shorturl): # save shorturl without trailing slash so redirect middleware will find both forms r = Redirect(site=site, old_path=shorturl, new_path=currenturl) r.save() break shorturl += '/' if SHORTURL_APPEND_SLASH else '' return shorturl
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