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Django 6.1
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Conas seisiúin a úsáid

Soláthraíonn Django tacaíocht iomlán do sheisiúin gan ainm. Ligeann creat an seisiúin duit sonraí treallach a stóráil agus a aisghabháil ar bhonn cuairteora in aghaidh an láithre Stórálann sé sonraí ar thaobh an fhreastalaí agus déanann sé achoimrí ar sheoladh agus a fháil fianáin. <cookie-session-backend>Tá aitheantas seisiúin i bhfianáin - ní na sonraí féin (mura bhfuil tú ag úsáid an:ref: `backend bhunaithe ar fianáin `).

Seisiúin chumasaithe

Cuirtear seisiúin i bhfeidhm trí phíosa de:doc: middleware </ref/middleware>.

Chun feidhmiúlacht seisiúin a chumasú, déan an méid seo

  • Cuir an socrú:setting: MIDDLEWARE in eagar agus déan cinnte go bhfuil Django.contrib.sessions.middleware.sessionMiddleware'` ann. Tá `SessionMiddleware gníomhachtaithe ag django-admin startproject réamhshocraithe settings.py.

Mura dteastaíonn uait seisiúin a úsáid, b'fhéidir go bhfaighidh tú an líne SessionMiddleware ó:setting: MIDDLEWARE agus ``django.contrib.sessions' ``ó d':setting: `INSTALLED_APPS. Sábhálfaidh sé beagán laochairde duit.

Inneall an seisiúin a chumrú

De réir réamhshocraithe, stórálann Django seisiúin i do bhunachar sonraí (ag baint úsáide as an tsamhail ``Django.Contrib.Sessions.Models.Session ``). Cé go bhfuil sé seo áisiúil, i roinnt socruithe tá sé níos tapúla sonraí seisiúin a stóráil in áiteanna eile, mar sin is féidir Django a chumrú chun sonraí seisiúin a stóráil ar do chóras comhaid nó i do taisce.

Ag baint úsáide as seisiúin tacaithe

Más mian leat seisiún tacaíochta le bunachar sonraí a úsáid, ní mór duit ``django.contrib.sessions'` a chur le do shuíomh: INSTALLED_APPS.

Nuair a bheidh do shuiteáil cumraithe agat, reáchtáil manage.py migrate chun an tábla bunachar sonraí aonair a stóráil sonraí seisiúin a shuiteáil.

Seisiúin taisceáilte a úsáid

Le haghaidh feidhmíochta níos fearr, b'fhéidir gur mhaith leat cúltaca seisiúin bunaithe ar taisce a úsáid.

Chun sonraí seisiúin a stóráil ag baint úsáide as córas taisce Django, beidh ort a chinntiú go bhfuil do taisce cumraithe agat ar dtús; féach an:doc: cáipéisíocht taisceach le haghaidh sonraí </topics/cache>.

Má tá iliomad taisce sainithe agat in:setting: CACHES, úsáidfidh Django an taisce réamhshocraithe. Chun taisce eile a úsáid, socraí:setting: SESSION_CACHE_ALIAS ar ainm an taisce sin.

Nuair a bheidh do taisce cumraithe, caithfidh tú a roghnú idir taisce tacaíochta bunachar sonraí nó taisce neamh-leanúnach.

Úsáideann cúltaca an bhunachar sonraí taisceáilte (cached_db`) taisce scríbhneoireachta - cuirtear scríbhneoireachtaí seisiúin i bhfeidhm ar an mbunachar sonraí agus taisce araon, san ord sin. Má theipeann ar scríobh chuig an taisce, déantar an eisceacht a láimhseáil agus a logáil trí:ref: session logger <django-contrib-sessions-logger>, chun a sheachaint ar oibríocht scríbhneoireachta rathúil ar shlí eile.

Úsáideann léitheanna seisiúin an taisce, nó an bunachar sonraí má dhíothraíodh na sonraí ón taisce. Chun an cúltaca seo a úsáid, socraí:setting: SESSION_ENGINE go "django.contrib.sessions.backends.cached_db", agus lean na treoracha cumraíochta do úsáid seisiúin tacaíochta bunachar sonraí.

Ní stórálann an cúltaca taisce (cache) sonraí seisiúin amháin i do taisce. Tá sé seo níos gasta toisc go seachnaíonn sé marthanacht bunachar sonraí, ach beidh ort machnamh a dhéanamh ar cad a tharlaíonn nuair a dhéantar sonraí taisce a dhíbirt. Is féidir le díothú tarlú má líonann an taisce nó má athosaítear an freastalaí taisce, agus ciallaíonn sé go gcailltear sonraí seisiúin, lena n-áirítear úsáideoirí logáil amach. Chun an cúltaca seo a úsáid, socraí:setting: SESSION_ENGINE go "django.contrib.sessions.backends.cache".

Is féidir an cúltaca taisce a dhéanamh leanúnach trí taisce leanúnach a úsáid, mar shampla Redis le cumraíocht chuí. Ach mura bhfuil do taisce cumraithe cinnte le haghaidh marthanacht leordhóthanach, roghnaigh cúltaca an bhunachar sonraí taisceáilte. Seachnaíonn sé seo cásanna imeall de bharr stóráil sonraí neamhiontaofa sa táirge

Ag baint úsáide as seisiúin comhad

Chun seisiúin comhadbhunaithe a úsáid, socraigh an socrú:setting: SESSION_ENGINE go "django.contrib.sessions.backends.file".

B'fhéidir gur mhaith leat an socrú: setting: SESSION_FILE_PATH a shocrú (a réamhshocraíonn aschur ó tempfile.gettempdir () `, is dóichí /tmp) chun rialú a dhéanamh ar an áit a stórálann Django comhaid seisiúin. Bí cinnte a sheiceáil go bhfuil ceadanna ag do fhreastalaí gréasáin chun léamh agus scríobh chuig an áit seo.

Seisiúin a úsáid i radhairc

Nuair a chuirtear SessionMiddleWare` i ngníomh, beidh tréith seisiúna ag gach rud: ~django.http.httpRequest - an chéad argóint d'aon fheidhm amharc Django -- tréith seisiú, ar réad cosúil le foclóir é.

Is féidir leat é a léamh agus scríobh chuig `request.session ``ag aon phointe i do thuairim. Is féidir leat é a chur in eagar arís agus arís eile.

class backends.base.SessionBase

Is é seo an bunaicme do gach réad seisiúin. Tá na modhanna caighdeánacha foclóra seo a leanas aige:

__getitem__(key)

Sampla: ``fav_color = iarrat.session ['fav_color'] ``

__setitem__(key, value)

Sampla: ``request.session ['fav_color'] = 'blue' ``

__delitem__(key)

Example: del request.session['fav_color']. This raises KeyError if the given key isn't already in the session.

__contains__(key)

Example: 'fav_color' in request.session

__bool__()

Returns the inverse of is_empty(). This allows checking if a session has data:

Code
if request.session:
    # Session has data or a key
    pass
get(key, default=None)
aget(key, default=None)

Leagan asincrón: ``aget () ``

Example: fav_color = request.session.get('fav_color', 'red')

aset(key, value)

Example: await request.session.aset('fav_color', 'red')

update(dict)
aupdate(dict)

Asynchronous version: aupdate()

Example: request.session.update({'fav_color': 'red'})

pop(key, default=__not_given)
apop(key, default=__not_given)

Asynchronous version: apop()

Example: fav_color = request.session.pop('fav_color', 'blue')

keys()
akeys()

Asynchronous version: akeys()

values()
avalues()

Asynchronous version: avalues()

has_key(key)
ahas_key(key)

Asynchronous version: ahas_key()

items()
aitems()

Asynchronous version: aitems()

setdefault()
asetdefault()

Asynchronous version: asetdefault()

clear()

It also has these methods:

flush()
aflush()

Asynchronous version: aflush()

Deletes the current session data from the session and deletes the session cookie. This is used if you want to ensure that the previous session data can't be accessed again from the user's browser (for example, the django.contrib.auth.logout() function calls it).

is_empty()

Returns True if the session does not have a key and is empty.

Asynchronous version: aset_test_cookie()

Sets a test cookie to determine whether the user's browser supports cookies. Due to the way cookies work, you won't be able to test this until the user's next page request. See Setting test cookies below for more information.

Asynchronous version: atest_cookie_worked()

Returns either True or False, depending on whether the user's browser accepted the test cookie. Due to the way cookies work, you'll have to call set_test_cookie() or aset_test_cookie() on a previous, separate page request. See Setting test cookies below for more information.

Asynchronous version: adelete_test_cookie()

Deletes the test cookie. Use this to clean up after yourself.

Returns the value of the setting SESSION_COOKIE_AGE. This can be overridden in a custom session backend.

set_expiry(value)
aset_expiry(value)

Asynchronous version: aset_expiry()

Sets the expiration time for the session. You can pass a number of different values:

  • If value is an integer, the session will expire after that many seconds of inactivity. For example, calling request.session.set_expiry(300) would make the session expire in 5 minutes.

  • If value is a datetime or timedelta object, the session will expire at that specific date/time.

  • If value is 0, the user's session cookie will expire when the user's web browser is closed.

  • If value is None, the session reverts to using the global session expiry policy.

Reading a session is not considered activity for expiration purposes. Session expiration is computed from the last time the session was modified.

get_expiry_age()
aget_expiry_age()

Asynchronous version: aget_expiry_age()

Returns the number of seconds until this session expires. For sessions with no custom expiration (or those set to expire at browser close), this will equal SESSION_COOKIE_AGE.

This function accepts two optional keyword arguments:

  • modification: last modification of the session, as a datetime object. Defaults to the current time.

  • expiry: expiry information for the session, as a datetime object, an int (in seconds), or None. Defaults to the value stored in the session by set_expiry()/aset_expiry(), if there is one, or None.

get_expiry_date()
aget_expiry_date()

Asynchronous version: aget_expiry_date()

Returns the date this session will expire. For sessions with no custom expiration (or those set to expire at browser close), this will equal the date SESSION_COOKIE_AGE seconds from now.

This function accepts the same keyword arguments as get_expiry_age(), and similar notes on usage apply.

get_expire_at_browser_close()
aget_expire_at_browser_close()

Asynchronous version: aget_expire_at_browser_close()

Returns either True or False, depending on whether the user's session cookie will expire when the user's web browser is closed.

clear_expired()
aclear_expired()

Asynchronous version: aclear_expired()

Removes expired sessions from the session store. This class method is called by clearsessions.

cycle_key()
acycle_key()

Asynchronous version: acycle_key()

Creates a new session key while retaining the current session data. django.contrib.auth.login() calls this method to mitigate against session fixation.

Session serialization

By default, Django serializes session data using JSON. You can use the SESSION_SERIALIZER setting to customize the session serialization format. Even with the caveats described in Write your own serializer, we highly recommend sticking with JSON serialization especially if you are using the cookie backend.

For example, here's an attack scenario if you use pickle to serialize session data. If you're using the signed cookie session backend and SECRET_KEY (or any key of SECRET_KEY_FALLBACKS) is known by an attacker (there isn't an inherent vulnerability in Django that would cause it to leak), the attacker could insert a string into their session which, when unpickled, executes arbitrary code on the server. The technique for doing so is simple and easily available on the internet. Although the cookie session storage signs the cookie-stored data to prevent tampering, a SECRET_KEY leak immediately escalates to a remote code execution vulnerability.

Bundled serializers

class serializers.JSONSerializer

A wrapper around the JSON serializer from django.core.signing. Can only serialize basic data types.

In addition, as JSON supports only string keys, note that using non-string keys in request.session won't work as expected:

Python console
>>> # initial assignment
>>> request.session[0] = "bar"
>>> # subsequent requests following serialization & deserialization
>>> # of session data
>>> request.session[0]  # KeyError
>>> request.session["0"]
'bar'

Similarly, data that can't be encoded in JSON, such as non-UTF8 bytes like '\xd9' (which raises UnicodeDecodeError), can't be stored.

See the Write your own serializer section for more details on limitations of JSON serialization.

Write your own serializer

Note that the JSONSerializer cannot handle arbitrary Python data types. As is often the case, there is a trade-off between convenience and security. If you wish to store more advanced data types including datetime and Decimal in JSON backed sessions, you will need to write a custom serializer (or convert such values to a JSON serializable object before storing them in request.session). While serializing these values is often straightforward (DjangoJSONEncoder may be helpful), writing a decoder that can reliably get back the same thing that you put in is more fragile. For example, you run the risk of returning a datetime that was actually a string that just happened to be in the same format chosen for datetimes.

Your serializer class must implement two methods, dumps(self, obj) and loads(self, data), to serialize and deserialize the dictionary of session data, respectively.

Session object guidelines

  • Use normal Python strings as dictionary keys on request.session. This is more of a convention than a hard-and-fast rule.

  • Session dictionary keys that begin with an underscore are reserved for internal use by Django.

  • Don't override request.session with a new object, and don't access or set its attributes. Use it like a Python dictionary.

Samplaí

This simplistic view sets a has_commented variable to True after a user posts a comment. It doesn't let a user post a comment more than once:

Code
def post_comment(request, new_comment):
    if request.session.get("has_commented", False):
        return HttpResponse("You've already commented.")
    c = comments.Comment(comment=new_comment)
    c.save()
    request.session["has_commented"] = True
    return HttpResponse("Thanks for your comment!")

This simplistic view logs in a "member" of the site:

Code
def login(request):
    m = Member.objects.get(username=request.POST["username"])
    if m.check_password(request.POST["password"]):
        request.session["member_id"] = m.id
        return HttpResponse("You're logged in.")
    else:
        return HttpResponse("Your username and password didn't match.")

...And this one logs a member out, according to login() above:

Code
def logout(request):
    try:
        del request.session["member_id"]
    except KeyError:
        pass
    return HttpResponse("You're logged out.")

The standard django.contrib.auth.logout() function actually does a bit more than this to prevent inadvertent data leakage. It calls the flush() method of request.session. We are using this example as a demonstration of how to work with session objects, not as a full logout() implementation.

Setting test cookies

As a convenience, Django provides a way to test whether the user's browser accepts cookies. Call the set_test_cookie() method of request.session in a view, and call test_cookie_worked() in a subsequent view -- not in the same view call.

This awkward split between set_test_cookie() and test_cookie_worked() is necessary due to the way cookies work. When you set a cookie, you can't actually tell whether a browser accepted it until the browser's next request.

It's good practice to use delete_test_cookie() to clean up after yourself. Do this after you've verified that the test cookie worked.

Here's a typical usage example:

Code
from django.http import HttpResponse
from django.shortcuts import render


def login(request):
    if request.method == "POST":
        if request.session.test_cookie_worked():
            request.session.delete_test_cookie()
            return HttpResponse("You're logged in.")
        else:
            return HttpResponse("Please enable cookies and try again.")
    request.session.set_test_cookie()
    return render(request, "foo/login_form.html")

Using sessions out of views

An API is available to manipulate session data outside of a view:

Python console
>>> from django.contrib.sessions.backends.db import SessionStore
>>> s = SessionStore()
>>> # stored as seconds since epoch since datetimes are not serializable in JSON.
>>> s["last_login"] = 1376587691
>>> s.create()
>>> s.session_key
'2b1189a188b44ad18c35e113ac6ceead'
>>> s = SessionStore(session_key="2b1189a188b44ad18c35e113ac6ceead")
>>> s["last_login"]
1376587691

SessionStore.create() is designed to create a new session (i.e. one not loaded from the session store and with session_key=None). save() is designed to save an existing session (i.e. one loaded from the session store). Calling save() on a new session may also work but has a small chance of generating a session_key that collides with an existing one. create() calls save() and loops until an unused session_key is generated.

If you're using the django.contrib.sessions.backends.db backend, each session is a normal Django model. The Session model is defined in django/contrib/sessions/models.py. Because it's a normal model, you can access sessions using the normal Django database API:

Python console
>>> from django.contrib.sessions.models import Session
>>> s = Session.objects.get(pk="2b1189a188b44ad18c35e113ac6ceead")
>>> s.expire_date
datetime.datetime(2005, 8, 20, 13, 35, 12)

Note that you'll need to call get_decoded() to get the session dictionary. This is necessary because the dictionary is stored in an encoded format:

Python console
>>> s.session_data
'KGRwMQpTJ19hdXRoX3VzZXJfaWQnCnAyCkkxCnMuMTExY2ZjODI2Yj...'
>>> s.get_decoded()
{'user_id': 42}

When sessions are saved

By default, Django only saves to the session database when the session has been modified -- that is if any of its dictionary values have been assigned or deleted:

Code
# Session is modified.
request.session["foo"] = "bar"

# Session is modified.
del request.session["foo"]

# Session is modified.
request.session["foo"] = {}

# Gotcha: Session is NOT modified, because this alters
# request.session['foo'] instead of request.session.
request.session["foo"]["bar"] = "baz"

In the last case of the above example, we can tell the session object explicitly that it has been modified by setting the modified attribute on the session object:

Code
request.session.modified = True

To change this default behavior, set the SESSION_SAVE_EVERY_REQUEST setting to True. When set to True, Django will save the session to the database on every single request.

Note that the session cookie is only sent when a session has been created or modified. If SESSION_SAVE_EVERY_REQUEST is True, the session cookie will be sent on every request.

Similarly, the expires part of a session cookie is updated each time the session cookie is sent.

The session is not saved if the response's status code is 500.

Browser-length sessions vs. persistent sessions

You can control whether the session framework uses browser-length sessions vs. persistent sessions with the SESSION_EXPIRE_AT_BROWSER_CLOSE setting.

By default, SESSION_EXPIRE_AT_BROWSER_CLOSE is set to False, which means session cookies will be stored in users' browsers for as long as SESSION_COOKIE_AGE. Use this if you don't want people to have to log in every time they open a browser.

If SESSION_EXPIRE_AT_BROWSER_CLOSE is set to True, Django will use browser-length cookies -- cookies that expire as soon as the user closes their browser. Use this if you want people to have to log in every time they open a browser.

This setting is a global default and can be overwritten at a per-session level by explicitly calling the set_expiry() method of request.session as described above in using sessions in views.

Clearing the session store

As users create new sessions on your website, session data can accumulate in your session store. If you're using the database backend, the django_session database table will grow. If you're using the file backend, your temporary directory will contain an increasing number of files.

To understand this problem, consider what happens with the database backend. When a user logs in, Django adds a row to the django_session database table. Django updates this row each time the session data changes. If the user logs out manually, Django deletes the row. But if the user does not log out, the row never gets deleted. A similar process happens with the file backend.

Django does not provide automatic purging of expired sessions. Therefore, it's your job to purge expired sessions on a regular basis. Django provides a clean-up management command for this purpose: clearsessions. It's recommended to call this command on a regular basis, for example as a daily cron job.

Note that the cache backend isn't vulnerable to this problem, because caches automatically delete stale data. Neither is the cookie backend, because the session data is stored by the users' browsers.

Socruithe

A few Django settings give you control over session behavior:

Session security

Subdomains within a site are able to set cookies on the client for the whole domain. This makes session fixation possible if cookies are permitted from subdomains not controlled by trusted users.

For example, an attacker could log into good.example.com and get a valid session for their account. If the attacker has control over bad.example.com, they can use it to send their session key to you since a subdomain is permitted to set cookies on *.example.com. When you visit good.example.com, you'll be logged in as the attacker and might inadvertently enter your sensitive personal data (e.g. credit card info) into the attacker's account.

Another possible attack would be if good.example.com sets its SESSION_COOKIE_DOMAIN to "example.com" which would cause session cookies from that site to be sent to bad.example.com.

Technical details

  • The session dictionary accepts any json serializable value when using JSONSerializer.

  • Session data is stored in a database table named django_session .

  • Django only sends a cookie if it needs to. If you don't set any session data, it won't send a session cookie.

The SessionStore object

When working with sessions internally, Django uses a session store object from the corresponding session engine. By convention, the session store object class is named SessionStore and is located in the module designated by SESSION_ENGINE.

All SessionStore subclasses available in Django implement the following data manipulation methods:

An asynchronous interface for these methods is provided by wrapping them with sync_to_async(). They can be implemented directly if an async-native implementation is available:

In order to build a custom session engine or to customize an existing one, you may create a new class inheriting from SessionBase or any other existing SessionStore class.

You can extend the session engines, but doing so with database-backed session engines generally requires some extra effort (see the next section for details).

Extending database-backed session engines

Creating a custom database-backed session engine built upon those included in Django (namely db and cached_db) may be done by inheriting AbstractBaseSession and either SessionStore class.

AbstractBaseSession and BaseSessionManager are importable from django.contrib.sessions.base_session so that they can be imported without including django.contrib.sessions in INSTALLED_APPS.

class base_session.AbstractBaseSession

The abstract base session model.

session_key

Primary key. The field itself may contain up to 40 characters. The current implementation generates a 32-character string (a random sequence of digits and lowercase ASCII letters).

session_data

A string containing an encoded and serialized session dictionary.

expire_date

A datetime designating when the session expires.

Expired sessions are not available to a user, however, they may still be stored in the database until the clearsessions management command is run.

classmethod get_session_store_class()

Returns a session store class to be used with this session model.

get_decoded()

Returns decoded session data.

Decoding is performed by the session store class.

You can also customize the model manager by subclassing BaseSessionManager:

class base_session.BaseSessionManager
encode(session_dict)

Returns the given session dictionary serialized and encoded as a string.

Encoding is performed by the session store class tied to a model class.

save(session_key, session_dict, expire_date)

Saves session data for a provided session key, or deletes the session in case the data is empty.

Customization of SessionStore classes is achieved by overriding methods and properties described below:

class backends.db.SessionStore

Implements database-backed session store.

classmethod get_model_class()

Override this method to return a custom session model if you need one.

create_model_instance(data)

Returns a new instance of the session model object, which represents the current session state.

Overriding this method provides the ability to modify session model data before it's saved to database.

class backends.cached_db.SessionStore

Implements cached database-backed session store.

cache_key_prefix

A prefix added to a session key to build a cache key string.

Sampla

The example below shows a custom database-backed session engine that includes an additional database column to store an account ID (thus providing an option to query the database for all active sessions for an account):

Code
from django.contrib.sessions.backends.db import SessionStore as DBStore
from django.contrib.sessions.base_session import AbstractBaseSession
from django.db import models


class CustomSession(AbstractBaseSession):
    account_id = models.IntegerField(null=True, db_index=True)

    @classmethod
    def get_session_store_class(cls):
        return SessionStore


class SessionStore(DBStore):
    @classmethod
    def get_model_class(cls):
        return CustomSession

    def create_model_instance(self, data):
        obj = super().create_model_instance(data)
        try:
            account_id = int(data.get("_auth_user_id"))
        except (ValueError, TypeError):
            account_id = None
        obj.account_id = account_id
        return obj

If you are migrating from the Django's built-in cached_db session store to a custom one based on cached_db, you should override the cache key prefix in order to prevent a namespace clash:

Code
class SessionStore(CachedDBStore):
    cache_key_prefix = "mysessions.custom_cached_db_backend"

    # ...

Session IDs in URLs

The Django sessions framework is entirely, and solely, cookie-based. It does not fall back to putting session IDs in URLs as a last resort, as PHP does. This is an intentional design decision. Not only does that behavior make URLs ugly, it makes your site vulnerable to session-ID theft via the "Referer" header.

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