402 lines
16 KiB
Plaintext
402 lines
16 KiB
Plaintext
.. _ref-contrib-sites:
|
|
|
|
=====================
|
|
The "sites" framework
|
|
=====================
|
|
|
|
.. module:: django.contrib.sites
|
|
:synopsis: Lets you operate multiple web sites from the same database and
|
|
Django project
|
|
|
|
Django comes with an optional "sites" framework. It's a hook for associating
|
|
objects and functionality to particular Web sites, and it's a holding place for
|
|
the domain names and "verbose" names of your Django-powered sites.
|
|
|
|
Use it if your single Django installation powers more than one site and you
|
|
need to differentiate between those sites in some way.
|
|
|
|
The whole sites framework is based on a simple model:
|
|
|
|
.. class:: django.contrib.sites.models.Site
|
|
|
|
This model has :attr:`~django.contrib.sites.models.Site.domain` and
|
|
:attr:`~django.contrib.sites.models.Site.name` fields. The :setting:`SITE_ID`
|
|
setting specifies the database ID of the
|
|
:class:`~django.contrib.sites.models.Site` object associated with that
|
|
particular settings file.
|
|
|
|
How you use this is up to you, but Django uses it in a couple of ways
|
|
automatically via simple conventions.
|
|
|
|
Example usage
|
|
=============
|
|
|
|
Why would you use sites? It's best explained through examples.
|
|
|
|
Associating content with multiple sites
|
|
---------------------------------------
|
|
|
|
The Django-powered sites LJWorld.com_ and Lawrence.com_ are operated by the
|
|
same news organization -- the Lawrence Journal-World newspaper in Lawrence,
|
|
Kansas. LJWorld.com focuses on news, while Lawrence.com focuses on local
|
|
entertainment. But sometimes editors want to publish an article on *both*
|
|
sites.
|
|
|
|
The brain-dead way of solving the problem would be to require site producers to
|
|
publish the same story twice: once for LJWorld.com and again for Lawrence.com.
|
|
But that's inefficient for site producers, and it's redundant to store
|
|
multiple copies of the same story in the database.
|
|
|
|
The better solution is simple: Both sites use the same article database, and an
|
|
article is associated with one or more sites. In Django model terminology,
|
|
that's represented by a :class:`~django.db.models.ManyToManyField` in the
|
|
``Article`` model::
|
|
|
|
from django.db import models
|
|
from django.contrib.sites.models import Site
|
|
|
|
class Article(models.Model):
|
|
headline = models.CharField(max_length=200)
|
|
# ...
|
|
sites = models.ManyToManyField(Site)
|
|
|
|
This accomplishes several things quite nicely:
|
|
|
|
* It lets the site producers edit all content -- on both sites -- in a
|
|
single interface (the Django admin).
|
|
|
|
* It means the same story doesn't have to be published twice in the
|
|
database; it only has a single record in the database.
|
|
|
|
* It lets the site developers use the same Django view code for both sites.
|
|
The view code that displays a given story just checks to make sure the
|
|
requested story is on the current site. It looks something like this::
|
|
|
|
from django.conf import settings
|
|
|
|
def article_detail(request, article_id):
|
|
try:
|
|
a = Article.objects.get(id=article_id, sites__id__exact=settings.SITE_ID)
|
|
except Article.DoesNotExist:
|
|
raise Http404
|
|
# ...
|
|
|
|
.. _ljworld.com: http://www.ljworld.com/
|
|
.. _lawrence.com: http://www.lawrence.com/
|
|
|
|
Associating content with a single site
|
|
--------------------------------------
|
|
|
|
Similarly, you can associate a model to the :class:`~django.contrib.sites.models.Site`
|
|
model in a many-to-one relationship, using
|
|
:class:`~django.db.models.fields.related.ForeignKey`.
|
|
|
|
For example, if an article is only allowed on a single site, you'd use a model
|
|
like this::
|
|
|
|
from django.db import models
|
|
from django.contrib.sites.models import Site
|
|
|
|
class Article(models.Model):
|
|
headline = models.CharField(max_length=200)
|
|
# ...
|
|
site = models.ForeignKey(Site)
|
|
|
|
This has the same benefits as described in the last section.
|
|
|
|
Hooking into the current site from views
|
|
----------------------------------------
|
|
|
|
On a lower level, you can use the sites framework in your Django views to do
|
|
particular things based on the site in which the view is being called.
|
|
For example::
|
|
|
|
from django.conf import settings
|
|
|
|
def my_view(request):
|
|
if settings.SITE_ID == 3:
|
|
# Do something.
|
|
else:
|
|
# Do something else.
|
|
|
|
Of course, it's ugly to hard-code the site IDs like that. This sort of
|
|
hard-coding is best for hackish fixes that you need done quickly. A slightly
|
|
cleaner way of accomplishing the same thing is to check the current site's
|
|
domain::
|
|
|
|
from django.conf import settings
|
|
from django.contrib.sites.models import Site
|
|
|
|
def my_view(request):
|
|
current_site = Site.objects.get(id=settings.SITE_ID)
|
|
if current_site.domain == 'foo.com':
|
|
# Do something
|
|
else:
|
|
# Do something else.
|
|
|
|
The idiom of retrieving the :class:`~django.contrib.sites.models.Site` object
|
|
for the value of :setting:`settings.SITE_ID <SITE_ID>` is quite common, so
|
|
the :class:`~django.contrib.sites.models.Site` model's manager has a
|
|
``get_current()`` method. This example is equivalent to the previous one::
|
|
|
|
from django.contrib.sites.models import Site
|
|
|
|
def my_view(request):
|
|
current_site = Site.objects.get_current()
|
|
if current_site.domain == 'foo.com':
|
|
# Do something
|
|
else:
|
|
# Do something else.
|
|
|
|
Getting the current domain for display
|
|
--------------------------------------
|
|
|
|
LJWorld.com and Lawrence.com both have e-mail alert functionality, which lets
|
|
readers sign up to get notifications when news happens. It's pretty basic: A
|
|
reader signs up on a Web form, and he immediately gets an e-mail saying,
|
|
"Thanks for your subscription."
|
|
|
|
It'd be inefficient and redundant to implement this signup-processing code
|
|
twice, so the sites use the same code behind the scenes. But the "thank you for
|
|
signing up" notice needs to be different for each site. By using
|
|
:class:`~django.contrib.sites.models.Site`
|
|
objects, we can abstract the "thank you" notice to use the values of the
|
|
current site's :attr:`~django.contrib.sites.models.Site.name` and
|
|
:attr:`~django.contrib.sites.models.Site.domain`.
|
|
|
|
Here's an example of what the form-handling view looks like::
|
|
|
|
from django.contrib.sites.models import Site
|
|
from django.core.mail import send_mail
|
|
|
|
def register_for_newsletter(request):
|
|
# Check form values, etc., and subscribe the user.
|
|
# ...
|
|
|
|
current_site = Site.objects.get_current()
|
|
send_mail('Thanks for subscribing to %s alerts' % current_site.name,
|
|
'Thanks for your subscription. We appreciate it.\n\n-The %s team.' % current_site.name,
|
|
'editor@%s' % current_site.domain,
|
|
[user.email])
|
|
|
|
# ...
|
|
|
|
On Lawrence.com, this e-mail has the subject line "Thanks for subscribing to
|
|
lawrence.com alerts." On LJWorld.com, the e-mail has the subject "Thanks for
|
|
subscribing to LJWorld.com alerts." Same goes for the e-mail's message body.
|
|
|
|
Note that an even more flexible (but more heavyweight) way of doing this would
|
|
be to use Django's template system. Assuming Lawrence.com and LJWorld.com have
|
|
different template directories (:setting:`TEMPLATE_DIRS`), you could simply farm out
|
|
to the template system like so::
|
|
|
|
from django.core.mail import send_mail
|
|
from django.template import loader, Context
|
|
|
|
def register_for_newsletter(request):
|
|
# Check form values, etc., and subscribe the user.
|
|
# ...
|
|
|
|
subject = loader.get_template('alerts/subject.txt').render(Context({}))
|
|
message = loader.get_template('alerts/message.txt').render(Context({}))
|
|
send_mail(subject, message, 'editor@ljworld.com', [user.email])
|
|
|
|
# ...
|
|
|
|
In this case, you'd have to create :file:`subject.txt` and :file:`message.txt` template
|
|
files for both the LJWorld.com and Lawrence.com template directories. That
|
|
gives you more flexibility, but it's also more complex.
|
|
|
|
It's a good idea to exploit the :class:`~django.contrib.sites.models.Site``
|
|
objects as much as possible, to remove unneeded complexity and redundancy.
|
|
|
|
Getting the current domain for full URLs
|
|
----------------------------------------
|
|
|
|
Django's ``get_absolute_url()`` convention is nice for getting your objects'
|
|
URL without the domain name, but in some cases you might want to display the
|
|
full URL -- with ``http://`` and the domain and everything -- for an object.
|
|
To do this, you can use the sites framework. A simple example::
|
|
|
|
>>> from django.contrib.sites.models import Site
|
|
>>> obj = MyModel.objects.get(id=3)
|
|
>>> obj.get_absolute_url()
|
|
'/mymodel/objects/3/'
|
|
>>> Site.objects.get_current().domain
|
|
'example.com'
|
|
>>> 'http://%s%s' % (Site.objects.get_current().domain, obj.get_absolute_url())
|
|
'http://example.com/mymodel/objects/3/'
|
|
|
|
Caching the current ``Site`` object
|
|
===================================
|
|
|
|
.. versionadded:: 1.0
|
|
|
|
As the current site is stored in the database, each call to
|
|
``Site.objects.get_current()`` could result in a database query. But Django is a
|
|
little cleverer than that: on the first request, the current site is cached, and
|
|
any subsequent call returns the cached data instead of hitting the database.
|
|
|
|
If for any reason you want to force a database query, you can tell Django to
|
|
clear the cache using ``Site.objects.clear_cache()``::
|
|
|
|
# First call; current site fetched from database.
|
|
current_site = Site.objects.get_current()
|
|
# ...
|
|
|
|
# Second call; current site fetched from cache.
|
|
current_site = Site.objects.get_current()
|
|
# ...
|
|
|
|
# Force a database query for the third call.
|
|
Site.objects.clear_cache()
|
|
current_site = Site.objects.get_current()
|
|
|
|
The ``CurrentSiteManager``
|
|
==========================
|
|
|
|
.. class:: django.contrib.sites.managers.CurrentSiteManager
|
|
|
|
If :class:`~django.contrib.sites.models.Site`\s play a key role in your application,
|
|
consider using the helpful
|
|
:class:`~django.contrib.sites.managers.CurrentSiteManager` in your model(s).
|
|
It's a model :ref:`manager <topics-db-managers>` that automatically filters
|
|
its queries to include only objects associated with the current
|
|
:class:`~django.contrib.sites.models.Site`.
|
|
|
|
Use :class:`~django.contrib.sites.managers.CurrentSiteManager` by adding it to
|
|
your model explicitly. For example::
|
|
|
|
from django.db import models
|
|
from django.contrib.sites.models import Site
|
|
from django.contrib.sites.managers import CurrentSiteManager
|
|
|
|
class Photo(models.Model):
|
|
photo = models.FileField(upload_to='/home/photos')
|
|
photographer_name = models.CharField(max_length=100)
|
|
pub_date = models.DateField()
|
|
site = models.ForeignKey(Site)
|
|
objects = models.Manager()
|
|
on_site = CurrentSiteManager()
|
|
|
|
With this model, ``Photo.objects.all()`` will return all ``Photo`` objects in
|
|
the database, but ``Photo.on_site.all()`` will return only the ``Photo`` objects
|
|
associated with the current site, according to the :setting:`SITE_ID` setting.
|
|
|
|
Put another way, these two statements are equivalent::
|
|
|
|
Photo.objects.filter(site=settings.SITE_ID)
|
|
Photo.on_site.all()
|
|
|
|
How did :class:`~django.contrib.sites.managers.CurrentSiteManager` know which
|
|
field of ``Photo`` was the :class:`~django.contrib.sites.models.Site`? It
|
|
defaults to looking for a field called
|
|
:class:`~django.contrib.sites.models.Site`. If your model has a
|
|
:class:`~django.db.models.fields.related.ForeignKey` or
|
|
:class:`~django.db.models.fields.related.ManyToManyField` called something
|
|
*other* than :class:`~django.contrib.sites.models.Site`, you need to explicitly
|
|
pass that as the parameter to
|
|
:class:`~django.contrib.sites.managers.CurrentSiteManager`. The following model,
|
|
which has a field called ``publish_on``, demonstrates this::
|
|
|
|
from django.db import models
|
|
from django.contrib.sites.models import Site
|
|
from django.contrib.sites.managers import CurrentSiteManager
|
|
|
|
class Photo(models.Model):
|
|
photo = models.FileField(upload_to='/home/photos')
|
|
photographer_name = models.CharField(max_length=100)
|
|
pub_date = models.DateField()
|
|
publish_on = models.ForeignKey(Site)
|
|
objects = models.Manager()
|
|
on_site = CurrentSiteManager('publish_on')
|
|
|
|
If you attempt to use :class:`~django.contrib.sites.managers.CurrentSiteManager`
|
|
and pass a field name that doesn't exist, Django will raise a :exc:`ValueError`.
|
|
|
|
Finally, note that you'll probably want to keep a normal (non-site-specific)
|
|
``Manager`` on your model, even if you use
|
|
:class:`~django.contrib.sites.managers.CurrentSiteManager`. As explained
|
|
in the :ref:`manager documentation <topics-db-managers>`, if you define a manager
|
|
manually, then Django won't create the automatic ``objects = models.Manager()``
|
|
manager for you.Also, note that certain parts of Django -- namely, the Django admin site and
|
|
generic views -- use whichever manager is defined *first* in the model, so if
|
|
you want your admin site to have access to all objects (not just site-specific
|
|
ones), put ``objects = models.Manager()`` in your model, before you define
|
|
:class:`~django.contrib.sites.managers.CurrentSiteManager`.
|
|
|
|
How Django uses the sites framework
|
|
===================================
|
|
|
|
Although it's not required that you use the sites framework, it's strongly
|
|
encouraged, because Django takes advantage of it in a few places. Even if your
|
|
Django installation is powering only a single site, you should take the two
|
|
seconds to create the site object with your ``domain`` and ``name``, and point
|
|
to its ID in your :setting:`SITE_ID` setting.
|
|
|
|
Here's how Django uses the sites framework:
|
|
|
|
* In the :mod:`redirects framework <django.contrib.redirects>`, each
|
|
redirect object is associated with a particular site. When Django searches
|
|
for a redirect, it takes into account the current :setting:`SITE_ID`.
|
|
|
|
* In the comments framework, each comment is associated with a particular
|
|
site. When a comment is posted, its
|
|
:class:`~django.contrib.sites.models.Site` is set to the current
|
|
:setting:`SITE_ID`, and when comments are listed via the appropriate
|
|
template tag, only the comments for the current site are displayed.
|
|
|
|
* In the :mod:`flatpages framework <django.contrib.flatpages>`, each
|
|
flatpage is associated with a particular site. When a flatpage is created,
|
|
you specify its :class:`~django.contrib.sites.models.Site`, and the
|
|
:class:`~django.contrib.flatpages.middleware.FlatpageFallbackMiddleware`
|
|
checks the current :setting:`SITE_ID` in retrieving flatpages to display.
|
|
|
|
* In the :mod:`syndication framework <django.contrib.syndication>`, the
|
|
templates for ``title`` and ``description`` automatically have access to a
|
|
variable ``{{ site }}``, which is the
|
|
:class:`~django.contrib.sites.models.Site` object representing the current
|
|
site. Also, the hook for providing item URLs will use the ``domain`` from
|
|
the current :class:`~django.contrib.sites.models.Site` object if you don't
|
|
specify a fully-qualified domain.
|
|
|
|
* In the :mod:`authentication framework <django.contrib.auth>`, the
|
|
:func:`django.contrib.auth.views.login` view passes the current
|
|
:class:`~django.contrib.sites.models.Site` name to the template as
|
|
``{{ site_name }}``.
|
|
|
|
* The shortcut view (:func:`django.views.defaults.shortcut`) uses the domain
|
|
of the current :class:`~django.contrib.sites.models.Site` object when
|
|
calculating an object's URL.
|
|
|
|
* In the admin framework, the "view on site" link uses the current
|
|
:class:`~django.contrib.sites.models.Site` to work out the domain for the
|
|
site that it will redirect to.
|
|
|
|
|
|
``RequestSite`` objects
|
|
=======================
|
|
|
|
.. _requestsite-objects:
|
|
|
|
.. versionadded:: 1.0
|
|
|
|
Some :ref:`django.contrib <ref-contrib-index>` applications take advantage of
|
|
the sites framework but are architected in a way that doesn't *require* the
|
|
sites framework to be installed in your database. (Some people don't want to, or
|
|
just aren't *able* to install the extra database table that the sites framework
|
|
requires.) For those cases, the framework provides a
|
|
:class:`~django.contrib.sites.models.RequestSite` class, which can be used as a
|
|
fallback when the database-backed sites framework is not available.
|
|
|
|
A :class:`~django.contrib.sites.models.RequestSite` object has a similar
|
|
interface to a normal :class:`~django.contrib.sites.models.Site` object, except
|
|
its :meth:`~django.contrib.sites.models.RequestSite.__init__()` method takes an
|
|
:class:`~django.http.HttpRequest` object. It's able to deduce the
|
|
:attr:`~django.contrib.sites.models.RequestSite.domain` and
|
|
:attr:`~django.contrib.sites.models.RequestSite.name` by looking at the
|
|
request's domain. It has :meth:`~django.contrib.sites.models.RequestSite.save()`
|
|
and :meth:`~django.contrib.sites.models.RequestSite.delete()` methods to match
|
|
the interface of :class:`~django.contrib.sites.models.Site`, but the methods
|
|
raise :exc:`NotImplementedError`.
|