Fixed #26566 -- Rewrote an incorrect Cache-Control example.

        return response

There are a few other ways to control cache parameters. For example, HTTP

allows applications to do the following:

* Define the maximum time a page should be cached.

* Specify whether a cache should always check for newer versions, only

  delivering the cached content when there are no changes. (Some caches

  might deliver cached content even if the server page changed, simply

  because the cache copy isn't yet expired.)

In Django, use the ``cache_control`` view decorator to specify these cache

parameters. In this example, ``cache_control`` tells caches to revalidate the

cache on every access and to store cached versions for, at most, 3,600 seconds::

You can control downstream caches in other ways as well (see :rfc:`7234` for

details on HTTP caching). For example, even if you don't use Django's

server-side cache framework, you can still tell clients to cache a view for a

certain amount of time with the :rfc:`max-age <7234#section-5.2.2.8>`

directive::

    from django.views.decorators.cache import cache_control

    @cache_control(must_revalidate=True, max_age=3600)

    @cache_control(max_age=3600)

    def my_view(request):

        ...

Any valid ``Cache-Control`` HTTP directive is valid in ``cache_control()``.

Here's a full list:

(If you *do* use the caching middleware, it already sets the ``max-age`` with

the value of the :setting:`CACHE_MIDDLEWARE_SECONDS` setting. In that case,

the custom ``max_age`` from the ``cache_control`` decorator will take

precedence, and the header values will be merged correctly.)

Any valid ``Cache-Control`` response directive is valid in ``cache_control()``.

Here are some more examples:

* ``public=True``

* ``private=True``

* ``no_cache=True``

* ``no_transform=True``

* ``must_revalidate=True``

* ``proxy_revalidate=True``

* ``max_age=num_seconds``

* ``s_maxage=num_seconds``

* ``stale_while_revalidate=num_seconds``

For explanation of Cache-Control HTTP directives, see the :rfc:`Cache-Control

spec <7234#section-5.2>`.

The full list of known directives can be found in the `IANA registry`_

(note that not all of them apply to responses).

(Note that the caching middleware already sets the cache header's max-age with

the value of the :setting:`CACHE_MIDDLEWARE_SECONDS` setting. If you use a custom

``max_age`` in a ``cache_control`` decorator, the decorator will take

precedence, and the header values will be merged correctly.)

.. _IANA registry: http://www.iana.org/assignments/http-cache-directives/http-cache-directives.xhtml

If you want to use headers to disable caching altogether,

:func:`django.views.decorators.cache.never_cache` is a view decorator that adds