426 lines
16 KiB
Plaintext
426 lines
16 KiB
Plaintext
============================
|
|
Request and response objects
|
|
============================
|
|
|
|
Quick overview
|
|
==============
|
|
|
|
Django uses request and response objects to pass state through the system.
|
|
|
|
When a page is requested, Django creates an ``HttpRequest`` object that
|
|
contains metadata about the request. Then Django loads the appropriate view,
|
|
passing the ``HttpRequest`` as the first argument to the view function. Each
|
|
view is responsible for returning an ``HttpResponse`` object.
|
|
|
|
This document explains the APIs for ``HttpRequest`` and ``HttpResponse``
|
|
objects.
|
|
|
|
HttpRequest objects
|
|
===================
|
|
|
|
Attributes
|
|
----------
|
|
|
|
All attributes except ``session`` should be considered read-only.
|
|
|
|
``path``
|
|
A string representing the full path to the requested page, not including
|
|
the domain.
|
|
|
|
Example: ``"/music/bands/the_beatles/"``
|
|
|
|
``method``
|
|
A string representing the HTTP method used in the request. This is
|
|
guaranteed to be uppercase. Example::
|
|
|
|
if request.method == 'GET':
|
|
do_something()
|
|
elif request.method == 'POST':
|
|
do_something_else()
|
|
|
|
``GET``
|
|
A dictionary-like object containing all given HTTP GET parameters. See the
|
|
``QueryDict`` documentation below.
|
|
|
|
``POST``
|
|
A dictionary-like object containing all given HTTP POST parameters. See the
|
|
``QueryDict`` documentation below.
|
|
|
|
It's possible that a request can come in via POST with an empty ``POST``
|
|
dictionary -- if, say, a form is requested via the POST HTTP method but
|
|
does not include form data. Therefore, you shouldn't use ``if request.POST``
|
|
to check for use of the POST method; instead, check `method`_.
|
|
|
|
Note: ``POST`` does *not* include file-upload information. See ``FILES``.
|
|
|
|
``REQUEST``
|
|
For convenience, a dictionary-like object that searches ``POST`` first,
|
|
then ``GET``. Inspired by PHP's ``$_REQUEST``.
|
|
|
|
For example, if ``GET = {"name": "john"}`` and ``POST = {"age": '34'}``,
|
|
``REQUEST["name"]`` would be ``"john"``, and ``REQUEST["age"]`` would be
|
|
``"34"``.
|
|
|
|
It's strongly suggested that you use ``GET`` and ``POST`` instead of
|
|
``REQUEST``, because the former are more explicit.
|
|
|
|
``COOKIES``
|
|
A standard Python dictionary containing all cookies. Keys and values are
|
|
strings.
|
|
|
|
``FILES``
|
|
A dictionary-like object containing all uploaded files. Each key in
|
|
``FILES`` is the ``name`` from the ``<input type="file" name="" />``. Each
|
|
value in ``FILES`` is a standard Python dictionary with the following three
|
|
keys:
|
|
|
|
* ``filename`` -- The name of the uploaded file, as a Python string.
|
|
* ``content-type`` -- The content type of the uploaded file.
|
|
* ``content`` -- The raw content of the uploaded file.
|
|
|
|
Note that ``FILES`` will only contain data if the request method was POST
|
|
and the ``<form>`` that posted to the request had
|
|
``enctype="multipart/form-data"``. Otherwise, ``FILES`` will be a blank
|
|
dictionary-like object.
|
|
|
|
``META``
|
|
A standard Python dictionary containing all available HTTP headers.
|
|
Available headers depend on the client and server, but here are some
|
|
examples:
|
|
|
|
* ``CONTENT_LENGTH``
|
|
* ``CONTENT_TYPE``
|
|
* ``HTTP_ACCEPT_ENCODING``
|
|
* ``HTTP_ACCEPT_LANGUAGE``
|
|
* ``HTTP_REFERER`` -- The referring page, if any.
|
|
* ``HTTP_USER_AGENT`` -- The client's user-agent string.
|
|
* ``QUERY_STRING`` -- The query string, as a single (unparsed) string.
|
|
* ``REMOTE_ADDR`` -- The IP address of the client.
|
|
* ``REMOTE_HOST`` -- The hostname of the client.
|
|
* ``REQUEST_METHOD`` -- A string such as ``"GET"`` or ``"POST"``.
|
|
* ``SERVER_NAME`` -- The hostname of the server.
|
|
* ``SERVER_PORT`` -- The port of the server.
|
|
|
|
``user``
|
|
A ``django.contrib.auth.models.User`` object representing the currently
|
|
logged-in user. If the user isn't currently logged in, ``user`` will be set
|
|
to an instance of ``django.contrib.auth.models.AnonymousUser``. You
|
|
can tell them apart with ``is_anonymous()``, like so::
|
|
|
|
if request.user.is_anonymous():
|
|
# Do something for anonymous users.
|
|
else:
|
|
# Do something for logged-in users.
|
|
|
|
``user`` is only available if your Django installation has the
|
|
``AuthenticationMiddleware`` activated. For more, see
|
|
`Authentication in Web requests`_.
|
|
|
|
.. _Authentication in Web requests: http://www.djangoproject.com/documentation/authentication/#authentication-in-web-requests
|
|
|
|
``session``
|
|
A readable-and-writable, dictionary-like object that represents the current
|
|
session. This is only available if your Django installation has session
|
|
support activated. See the `session documentation`_ for full details.
|
|
|
|
.. _`session documentation`: http://www.djangoproject.com/documentation/sessions/
|
|
|
|
``raw_post_data``
|
|
The raw HTTP POST data. This is only useful for advanced processing. Use
|
|
``POST`` instead.
|
|
|
|
Methods
|
|
-------
|
|
|
|
``__getitem__(key)``
|
|
Returns the GET/POST value for the given key, checking POST first, then
|
|
GET. Raises ``KeyError`` if the key doesn't exist.
|
|
|
|
This lets you use dictionary-accessing syntax on an ``HttpRequest``
|
|
instance. Example: ``request["foo"]`` would return ``True`` if either
|
|
``request.POST`` or ``request.GET`` had a ``"foo"`` key.
|
|
|
|
``has_key()``
|
|
Returns ``True`` or ``False``, designating whether ``request.GET`` or
|
|
``request.POST`` has the given key.
|
|
|
|
``get_full_path()``
|
|
Returns the ``path``, plus an appended query string, if applicable.
|
|
|
|
Example: ``"/music/bands/the_beatles/?print=true"``
|
|
|
|
QueryDict objects
|
|
-----------------
|
|
|
|
In an ``HttpRequest`` object, the ``GET`` and ``POST`` attributes are instances
|
|
of ``django.http.QueryDict``. ``QueryDict`` is a dictionary-like
|
|
class customized to deal with multiple values for the same key. This is
|
|
necessary because some HTML form elements, notably
|
|
``<select multiple="multiple">``, pass multiple values for the same key.
|
|
|
|
``QueryDict`` instances are immutable, unless you create a ``copy()`` of them.
|
|
That means you can't change attributes of ``request.POST`` and ``request.GET``
|
|
directly.
|
|
|
|
``QueryDict`` implements the all standard dictionary methods, because it's a
|
|
subclass of dictionary. Exceptions are outlined here:
|
|
|
|
* ``__getitem__(key)`` -- Returns the value for the given key. If the key
|
|
has more than one value, ``__getitem__()`` returns the last value.
|
|
|
|
* ``__setitem__(key, value)`` -- Sets the given key to ``[value]``
|
|
(a Python list whose single element is ``value``). Note that this, as
|
|
other dictionary functions that have side effects, can only be called on
|
|
a mutable ``QueryDict`` (one that was created via ``copy()``).
|
|
|
|
* ``__contains__(key)`` -- Returns ``True`` if the given key is set. This
|
|
lets you do, e.g., ``if "foo" in request.GET``.
|
|
|
|
* ``get(key, default)`` -- Uses the same logic as ``__getitem__()`` above,
|
|
with a hook for returning a default value if the key doesn't exist.
|
|
|
|
* ``has_key(key)``
|
|
|
|
* ``setdefault(key, default)`` -- Just like the standard dictionary
|
|
``setdefault()`` method, except it uses ``__setitem__`` internally.
|
|
|
|
* ``update(other_dict)`` -- Takes either a ``QueryDict`` or standard
|
|
dictionary. Just like the standard dictionary ``update()`` method, except
|
|
it *appends* to the current dictionary items rather than replacing them.
|
|
For example::
|
|
|
|
>>> q = QueryDict('a=1')
|
|
>>> q = q.copy() # to make it mutable
|
|
>>> q.update({'a': '2'})
|
|
>>> q.getlist('a')
|
|
['1', '2']
|
|
>>> q['a'] # returns the last
|
|
['2']
|
|
|
|
* ``items()`` -- Just like the standard dictionary ``items()`` method,
|
|
except this uses the same last-value logic as ``__getitem()__``. For
|
|
example::
|
|
|
|
>>> q = QueryDict('a=1&a=2&a=3')
|
|
>>> q.items()
|
|
[('a', '3')]
|
|
|
|
* ``values()`` -- Just like the standard dictionary ``values()`` method,
|
|
except this uses the same last-value logic as ``__getitem()__``. For
|
|
example::
|
|
|
|
>>> q = QueryDict('a=1&a=2&a=3')
|
|
>>> q.values()
|
|
['3']
|
|
|
|
In addition, ``QueryDict`` has the following methods:
|
|
|
|
* ``copy()`` -- Returns a copy of the object, using ``copy.deepcopy()``
|
|
from the Python standard library. The copy will be mutable -- that is,
|
|
you can change its values.
|
|
|
|
* ``getlist(key)`` -- Returns the data with the requested key, as a Python
|
|
list. Returns an empty list if the key doesn't exist. It's guaranteed to
|
|
return a list of some sort.
|
|
|
|
* ``setlist(key, list_)`` -- Sets the given key to ``list_`` (unlike
|
|
``__setitem__()``).
|
|
|
|
* ``appendlist(key, item)`` -- Appends an item to the internal list
|
|
associated with key.
|
|
|
|
* ``setlistdefault(key, default_list)`` -- Just like ``setdefault``, except
|
|
it takes a list of values instead of a single value.
|
|
|
|
* ``lists()`` -- Like ``items()``, except it includes all values, as a list,
|
|
for each member of the dictionary. For example::
|
|
|
|
>>> q = QueryDict('a=1&a=2&a=3')
|
|
>>> q.lists()
|
|
[('a', ['1', '2', '3'])]
|
|
|
|
* ``urlencode()`` -- Returns a string of the data in query-string format.
|
|
Example: ``"a=2&b=3&b=5"``.
|
|
|
|
Examples
|
|
--------
|
|
|
|
Here's an example HTML form and how Django would treat the input::
|
|
|
|
<form action="/foo/bar/" method="post">
|
|
<input type="text" name="your_name" />
|
|
<select multiple="multiple" name="bands">
|
|
<option value="beatles">The Beatles</option>
|
|
<option value="who">The Who</option>
|
|
<option value="zombies">The Zombies</option>
|
|
</select>
|
|
<input type="submit" />
|
|
</form>
|
|
|
|
If the user enters ``"John Smith"`` in the ``your_name`` field and selects both
|
|
"The Beatles" and "The Zombies" in the multiple select box, here's what
|
|
Django's request object would have::
|
|
|
|
>>> request.GET
|
|
{}
|
|
>>> request.POST
|
|
{'your_name': ['John Smith'], 'bands': ['beatles', 'zombies']}
|
|
>>> request.POST['your_name']
|
|
'John Smith'
|
|
>>> request.POST['bands']
|
|
'zombies'
|
|
>>> request.POST.getlist('bands')
|
|
['beatles', 'zombies']
|
|
>>> request.POST.get('your_name', 'Adrian')
|
|
'John Smith'
|
|
>>> request.POST.get('nonexistent_field', 'Nowhere Man')
|
|
'Nowhere Man'
|
|
|
|
Implementation notes
|
|
--------------------
|
|
|
|
The ``GET``, ``POST``, ``COOKIES``, ``FILES``, ``META``, ``REQUEST``,
|
|
``raw_post_data`` and ``user`` attributes are all lazily loaded. That means
|
|
Django doesn't spend resources calculating the values of those attributes until
|
|
your code requests them.
|
|
|
|
HttpResponse objects
|
|
====================
|
|
|
|
In contrast to ``HttpRequest`` objects, which are created automatically by
|
|
Django, ``HttpResponse`` objects are your responsibility. Each view you write
|
|
is responsible for instantiating, populating and returning an ``HttpResponse``.
|
|
|
|
The ``HttpResponse`` class lives at ``django.http.HttpResponse``.
|
|
|
|
Usage
|
|
-----
|
|
|
|
Passing strings
|
|
~~~~~~~~~~~~~~~
|
|
|
|
Typical usage is to pass the contents of the page, as a string, to the
|
|
``HttpResponse`` constructor::
|
|
|
|
>>> response = HttpResponse("Here's the text of the Web page.")
|
|
>>> response = HttpResponse("Text only, please.", mimetype="text/plain")
|
|
|
|
But if you want to add content incrementally, you can use ``response`` as a
|
|
file-like object::
|
|
|
|
>>> response = HttpResponse()
|
|
>>> response.write("<p>Here's the text of the Web page.</p>")
|
|
>>> response.write("<p>Here's another paragraph.</p>")
|
|
|
|
You can add and delete headers using dictionary syntax::
|
|
|
|
>>> response = HttpResponse()
|
|
>>> response['X-DJANGO'] = "It's the best."
|
|
>>> del response['X-PHP']
|
|
>>> response['X-DJANGO']
|
|
"It's the best."
|
|
|
|
Note that ``del`` doesn't raise ``KeyError`` if the header doesn't exist.
|
|
|
|
Passing iterators
|
|
~~~~~~~~~~~~~~~~~
|
|
|
|
Finally, you can pass ``HttpResponse`` an iterator rather than passing it
|
|
hard-coded strings. If you use this technique, follow these guidelines:
|
|
|
|
* The iterator should return strings.
|
|
* If an ``HttpResponse`` has been initialized with an iterator as its
|
|
content, you can't use the ``HttpResponse`` instance as a file-like
|
|
object. Doing so will raise ``Exception``.
|
|
|
|
Methods
|
|
-------
|
|
|
|
``__init__(content='', mimetype=DEFAULT_MIME_TYPE)``
|
|
Instantiates an ``HttpResponse`` object with the given page content (a
|
|
string) and MIME type. The ``DEFAULT_MIME_TYPE`` is ``'text/html'``.
|
|
|
|
``content`` can be an iterator or a string. If it's an iterator, it should
|
|
return strings, and those strings will be joined together to form the
|
|
content of the response.
|
|
|
|
``__setitem__(header, value)``
|
|
Sets the given header name to the given value. Both ``header`` and
|
|
``value`` should be strings.
|
|
|
|
``__delitem__(header)``
|
|
Deletes the header with the given name. Fails silently if the header
|
|
doesn't exist. Case-sensitive.
|
|
|
|
``__getitem__(header)``
|
|
Returns the value for the given header name. Case-sensitive.
|
|
|
|
``has_header(header)``
|
|
Returns ``True`` or ``False`` based on a case-insensitive check for a
|
|
header with the given name.
|
|
|
|
``set_cookie(key, value='', max_age=None, expires=None, path='/', domain=None, secure=None)``
|
|
Sets a cookie. The parameters are the same as in the `cookie Morsel`_
|
|
object in the Python standard library.
|
|
|
|
* ``max_age`` should be a number of seconds, or ``None`` (default) if
|
|
the cookie should last only as long as the client's browser session.
|
|
* ``expires`` should be a string in the format
|
|
``"Wdy, DD-Mon-YY HH:MM:SS GMT"``.
|
|
* Use ``domain`` if you want to set a cross-domain cookie. For example,
|
|
``domain=".lawrence.com"`` will set a cookie that is readable by
|
|
the domains www.lawrence.com, blogs.lawrence.com and
|
|
calendars.lawrence.com. Otherwise, a cookie will only be readable by
|
|
the domain that set it.
|
|
|
|
.. _`cookie Morsel`: http://www.python.org/doc/current/lib/morsel-objects.html
|
|
|
|
``delete_cookie(key)``
|
|
Deletes the cookie with the given key. Fails silently if the key doesn't
|
|
exist.
|
|
|
|
``content``
|
|
Returns the content as a Python string, encoding it from a Unicode object
|
|
if necessary. Note this is a property, not a method, so use ``r.content``
|
|
instead of ``r.content()``.
|
|
|
|
``write(content)``, ``flush()`` and ``tell()``
|
|
These methods make an ``HttpResponse`` instance a file-like object.
|
|
|
|
HttpResponse subclasses
|
|
-----------------------
|
|
|
|
Django includes a number of ``HttpResponse`` subclasses that handle different
|
|
types of HTTP responses. Like ``HttpResponse``, these subclasses live in
|
|
``django.http``.
|
|
|
|
``HttpResponseRedirect``
|
|
The constructor takes a single argument -- the path to redirect to. This
|
|
can be a fully qualified URL (e.g. ``'http://www.yahoo.com/search/'``) or an
|
|
absolute URL with no domain (e.g. ``'/search/'``). Note that this returns
|
|
an HTTP status code 302.
|
|
|
|
``HttpResponsePermanentRedirect``
|
|
Like ``HttpResponseRedirect``, but it returns a permanent redirect (HTTP
|
|
status code 301) instead of a "found" redirect (status code 302).
|
|
|
|
``HttpResponseNotModified``
|
|
The constructor doesn't take any arguments. Use this to designate that a
|
|
page hasn't been modified since the user's last request.
|
|
|
|
``HttpResponseNotFound``
|
|
Acts just like ``HttpResponse`` but uses a 404 status code.
|
|
|
|
``HttpResponseForbidden``
|
|
Acts just like ``HttpResponse`` but uses a 403 status code.
|
|
|
|
``HttpResponseNotAllowed``
|
|
Like ``HttpResponse``, but uses a 405 status code. Takes a single,
|
|
required argument: a list of permitted methods (e.g. ``['GET', 'POST']``).
|
|
|
|
``HttpResponseGone``
|
|
Acts just like ``HttpResponse`` but uses a 410 status code.
|
|
|
|
``HttpResponseServerError``
|
|
Acts just like ``HttpResponse`` but uses a 500 status code.
|