django/docs/topics/http/decorators.txt

===============
View decorators
===============

.. module:: django.views.decorators.http

Django provides several decorators that can be applied to views to support
various HTTP features.

See :ref:`decorating-class-based-views` for how to use these decorators with
class-based views.

Allowed HTTP methods
====================

The decorators in :mod:`django.views.decorators.http` can be used to restrict
access to views based on the request method. These decorators will return
a :class:`django.http.HttpResponseNotAllowed` if the conditions are not met.

.. function:: require_http_methods(request_method_list)

    Decorator to require that a view only accepts particular request
    methods. Usage::

        from django.views.decorators.http import require_http_methods


        @require_http_methods(["GET", "POST"])
        def my_view(request):
            # I can assume now that only GET or POST requests make it this far
            # ...
            pass

    Note that request methods should be in uppercase.

.. function:: require_GET()

    Decorator to require that a view only accepts the GET method.

.. function:: require_POST()

    Decorator to require that a view only accepts the POST method.

.. function:: require_safe()

    Decorator to require that a view only accepts the GET and HEAD methods.
    These methods are commonly considered "safe" because they should not have
    the significance of taking an action other than retrieving the requested
    resource.

    .. note::
        Web servers should automatically strip the content of responses to HEAD
        requests while leaving the headers unchanged, so you may handle HEAD
        requests exactly like GET requests in your views. Since some software,
        such as link checkers, rely on HEAD requests, you might prefer
        using ``require_safe`` instead of ``require_GET``.

Conditional view processing
===========================

The following decorators in :mod:`django.views.decorators.http` can be used to
control caching behavior on particular views.

.. function:: condition(etag_func=None, last_modified_func=None)

.. function:: conditional_page()

    This decorator provides the conditional GET operation handling of
    :class:`~django.middleware.http.ConditionalGetMiddleware` to a view.

.. function:: etag(etag_func)

.. function:: last_modified(last_modified_func)

    These decorators can be used to generate ``ETag`` and ``Last-Modified``
    headers; see
    :doc:`conditional view processing </topics/conditional-view-processing>`.

.. module:: django.views.decorators.gzip

GZip compression
================

The decorators in :mod:`django.views.decorators.gzip` control content
compression on a per-view basis.

.. function:: gzip_page()

    This decorator compresses content if the browser allows gzip compression.
    It sets the ``Vary`` header accordingly, so that caches will base their
    storage on the ``Accept-Encoding`` header.

.. module:: django.views.decorators.vary

Vary headers
============

The decorators in :mod:`django.views.decorators.vary` can be used to control
caching based on specific request headers.

.. function:: vary_on_cookie(func)

.. function:: vary_on_headers(*headers)

    The ``Vary`` header defines which request headers a cache mechanism should take
    into account when building its cache key.

    See :ref:`using vary headers <using-vary-headers>`.

.. module:: django.views.decorators.cache

Caching
=======

The decorators in :mod:`django.views.decorators.cache` control server and
client-side caching.

.. function:: cache_control(**kwargs)

    This decorator patches the response's ``Cache-Control`` header by adding
    all of the keyword arguments to it. See
    :func:`~django.utils.cache.patch_cache_control` for the details of the
    transformation.

.. function:: never_cache(view_func)

    This decorator adds an ``Expires`` header to the current date/time.

    This decorator adds a ``Cache-Control: max-age=0, no-cache, no-store,
    must-revalidate, private`` header to a response to indicate that a page
    should never be cached.

    Each header is only added if it isn't already set.

.. module:: django.views.decorators.common

Common
======

The decorators in :mod:`django.views.decorators.common` allow per-view
customization of :class:`~django.middleware.common.CommonMiddleware` behavior.

.. function:: no_append_slash()

    This decorator allows individual views to be excluded from
    :setting:`APPEND_SLASH` URL normalization.