django.contrib.auth 登錄註銷學習

備註： 內容基於django1.9版本

auth模塊實現功能

經過入口url.py文件中定義的urlpatterns能夠看出，auth模塊共定義了8個url，分別用於：

• 登陸
• 註銷
• 修改密碼
• 修改密碼完成
• 密碼重置
• 密碼重置完成
• 密碼重置驗證
• 密碼重置結束

from django.conf.urls import url
from django.contrib.auth import views

# urlpatterns直接是一個list便可
urlpatterns = [
    url(r'^login/$', views.login, name='login'),
    url(r'^logout/$', views.logout, name='logout'),
    url(r'^password_change/$', views.password_change, name='password_change'),
    url(r'^password_change/done/$', views.password_change_done, name='password_change_done'),
    url(r'^password_reset/$', views.password_reset, name='password_reset'),
    url(r'^password_reset/done/$', views.password_reset_done, name='password_reset_done'),
    url(r'^reset/(?P<uidb64>[0-9A-Za-z_\-]+)/(?P<token>[0-9A-Za-z]{1,13}-[0-9A-Za-z]{1,20})/$',
        views.password_reset_confirm, name='password_reset_confirm'),
    url(r'^reset/done/$', views.password_reset_complete, name='password_reset_complete'),
]

如下僅對登錄, 註銷進行了學習.

login 登陸

def login(request, template_name='registration/login.html',
          redirect_field_name=REDIRECT_FIELD_NAME,
          authentication_form=AuthenticationForm,
          extra_context=None):
    """
    Displays the login form and handles the login action.
    """
    redirect_to = request.POST.get(redirect_field_name,
                                   request.GET.get(redirect_field_name, ''))

    if request.method == "POST":
        form = authentication_form(request, data=request.POST)
        if form.is_valid():

            # Ensure the user-originating redirection url is safe.
            if not is_safe_url(url=redirect_to, host=request.get_host()):
                redirect_to = resolve_url(settings.LOGIN_REDIRECT_URL)

            # Okay, security check complete. Log the user in.
            auth_login(request, form.get_user())

            return HttpResponseRedirect(redirect_to)
    else:
        form = authentication_form(request)

    current_site = get_current_site(request)

    context = {
        'form': form,
        redirect_field_name: redirect_to,
        'site': current_site,
        'site_name': current_site.name,
    }
    if extra_context is not None:
        context.update(extra_context)

    return TemplateResponse(request, template_name, context)

登陸處理視圖函數依據功能分爲：

• 展現登陸頁面供用戶提供認證信息進行登陸操做(request.method == "GET")
• 對用戶提交的認證信息進行認證，並作出相應反映(request.method == "POST")

request.method == "GET"

1. 實例化一個authentication_form實例(經過傳入request將request綁定到form實例上)，供用戶輸入認證信息
2. 獲取站點信息，供頁面顯示
3. 生成context，並使用關鍵詞參數extra_context進行拓展
4. 返回頁面(TemplateResponse)

此場景處理邏輯較簡單

request.method == "POST"

1. 經過獲取到的用戶數據(request.POST)實例化authentication_form
2. 判斷用戶輸入數據是否有效合理(檢查是否有輸入傳入；而且調用full_clean方法來進行驗證)。默認的AuthenticationForm中的clean方法中會調用django.contrib.auth.authenticate方法對用戶提供的認證信息進行校驗。而authenticate方法會遍歷settings中定義的AUTHENTICATION_BACKENDS模塊，並調用模塊的authenticate方法進行認證，直到成功，不然出發user_login_failed singnal
3. 調用django.contrib.auth.login方法使得用戶登陸成功，並返回HttpResponseRedirect響應，重定向到redirect_field_name指向地址。

step2 form.is_valid()調用過程
# django.forms.forms.py
class BaseForm(object):
    ....
    @property
    def errors(self):
        "Returns an ErrorDict for the data provided for the form"
        if self._errors is None:
            self.full_clean()
        return self._errors

    def is_valid(self):
        """
        Returns True if the form has no errors. Otherwise, False. If errors are
        being ignored, returns False.
        """
        return self.is_bound and not self.errors
    
    def full_clean(self):
        """
        Cleans all of self.data and populates self._errors and
        self.cleaned_data.
        """
        self._errors = ErrorDict()
        if not self.is_bound:  # Stop further processing.
            return
        self.cleaned_data = {}
        # If the form is permitted to be empty, and none of the form data has
        # changed from the initial data, short circuit any validation.
        if self.empty_permitted and not self.has_changed():
            return

        self._clean_fields()
        self._clean_form()
        self._post_clean()
        
    def _clean_fields(self):
        for name, field in self.fields.items():
            # value_from_datadict() gets the data from the data dictionaries.
            # Each widget type knows how to retrieve its own data, because some
            # widgets split data over several HTML fields.
            if field.disabled:
                value = self.initial.get(name, field.initial)
            else:
                value = field.widget.value_from_datadict(self.data, self.files, self.add_prefix(name))
            try:
                if isinstance(field, FileField):
                    initial = self.initial.get(name, field.initial)
                    value = field.clean(value, initial)
                else:
                    value = field.clean(value)
                self.cleaned_data[name] = value
                ## 若是有clean_filedname方法的話，調用之
                if hasattr(self, 'clean_%s' % name):
                    value = getattr(self, 'clean_%s' % name)()
                    self.cleaned_data[name] = value
            except ValidationError as e:
                self.add_error(name, e)

    def _clean_form(self):
        try:
            cleaned_data = self.clean()
        except ValidationError as e:
            self.add_error(None, e)
        else:
            if cleaned_data is not None:
                self.cleaned_data = cleaned_data

    def _post_clean(self):
        """
        An internal hook for performing additional cleaning after form cleaning
        is complete. Used for model validation in model forms.
        """
        pass

step2 django.contrib.auth.authenticate方法
def load_backend(path):
    return import_string(path)()

def _get_backends(return_tuples=False):
    backends = []
    for backend_path in settings.AUTHENTICATION_BACKENDS:
        backend = load_backend(backend_path)
        backends.append((backend, backend_path) if return_tuples else backend)
    if not backends:
        raise ImproperlyConfigured(
            'No authentication backends have been defined. Does '
            'AUTHENTICATION_BACKENDS contain anything?'
        )
    return backends

def authenticate(**credentials):
    """
    If the given credentials are valid, return a User object.
    """
    for backend, backend_path in _get_backends(return_tuples=True):
        try:
            inspect.getcallargs(backend.authenticate, **credentials)
        except TypeError:
            # This backend doesn't accept these credentials as arguments. Try the next one.
            continue

        try:
            user = backend.authenticate(**credentials)
        except PermissionDenied:
            # This backend says to stop in our tracks - this user should not be allowed in at all.
            return None
        if user is None:
            continue
        # Annotate the user object with the path of the backend.
        user.backend = backend_path
        return user

    # The credentials supplied are invalid to all backends, fire signal
    user_login_failed.send(sender=__name__,
            credentials=_clean_credentials(credentials))

step3 django.contrib.auth.login方法

1. request.user = user
2. 觸發user_logged_in singnal

def login(request, user):
    """
    Persist a user id and a backend in the request. This way a user doesn't
    have to reauthenticate on every request. Note that data set during
    the anonymous session is retained when the user logs in.
    """
    session_auth_hash = ''
    if user is None:
        user = request.user
    if hasattr(user, 'get_session_auth_hash'):
        session_auth_hash = user.get_session_auth_hash()

    if SESSION_KEY in request.session:
        if _get_user_session_key(request) != user.pk or (
                session_auth_hash and
                request.session.get(HASH_SESSION_KEY) != session_auth_hash):
            # To avoid reusing another user's session, create a new, empty
            # session if the existing session corresponds to a different
            # authenticated user.
            request.session.flush()
    else:
        request.session.cycle_key()
    request.session[SESSION_KEY] = user._meta.pk.value_to_string(user)
    request.session[BACKEND_SESSION_KEY] = user.backend
    request.session[HASH_SESSION_KEY] = session_auth_hash
    if hasattr(request, 'user'):
        request.user = user
    rotate_token(request)
    user_logged_in.send(sender=user.__class__, request=request, user=user)
    ```
    
    ## logout 註銷
    
    ```
@deprecate_current_app
def logout(request, next_page=None,
           template_name='registration/logged_out.html',
           redirect_field_name=REDIRECT_FIELD_NAME,
           extra_context=None):
    """
    Logs out the user and displays 'You are logged out' message.
    """
    auth_logout(request)

    if next_page is not None:
        next_page = resolve_url(next_page)

    if (redirect_field_name in request.POST or
            redirect_field_name in request.GET):
        next_page = request.POST.get(redirect_field_name,
                                     request.GET.get(redirect_field_name))
        # Security check -- don't allow redirection to a different host.
        if not is_safe_url(url=next_page, host=request.get_host()):
            next_page = request.path

    if next_page:
        # Redirect to this page until the session has been cleared.
        return HttpResponseRedirect(next_page)

    current_site = get_current_site(request)
    context = {
        'site': current_site,
        'site_name': current_site.name,
        'title': _('Logged out')
    }
    if extra_context is not None:
        context.update(extra_context)

    return TemplateResponse(request, template_name, context)

實現了登出用戶，並跳轉到指定(next_page或者request.GET, request.POST中攜帶的redicted_field_name)頁面功能

登出用戶 django.contrib.auth.logout

1. 出發user_logged_out　singnal
2. request.session.flush()
3. request.user = AnonymousUser() if hasattr(request, 'user')

def logout(request):
    """
    Removes the authenticated user's ID from the request and flushes their
    session data.
    """
    # Dispatch the signal before the user is logged out so the receivers have a
    # chance to find out *who* logged out.
    user = getattr(request, 'user', None)
    if hasattr(user, 'is_authenticated') and not user.is_authenticated():
        user = None
    user_logged_out.send(sender=user.__class__, request=request, user=user)

    # remember language choice saved to session
    language = request.session.get(LANGUAGE_SESSION_KEY)

    request.session.flush()

    if language is not None:
        request.session[LANGUAGE_SESSION_KEY] = language

    if hasattr(request, 'user'):
        from django.contrib.auth.models import AnonymousUser
        request.user = AnonymousUser()