python學習筆記-flask學習(二)Flask-Login模塊

　　Flask-Login模塊提供用戶狀態的管理功能。使用flask-login首先要獲取一個loadmanager的實例。

   1） 當用戶登錄以后，如果需要記錄用戶的狀態則則可以調用 login_user函數記錄當前登錄的用戶。

def login_user(user, remember=False, force=False, fresh=True):
  
    if not force and not user.is_active:
        return False

    user_id = getattr(user, current_app.login_manager.id_attribute)()
    session['user_id'] = user_id
    session['_fresh'] = fresh
    session['_id'] = _create_identifier()

    if remember:
        session['remember'] = 'set'

    _request_ctx_stack.top.user = user
    user_logged_in.send(current_app._get_current_object(), user=_get_user())
    return True

login_user主要的作用就是將user的id加入到session中。getattr(user, current_app.login_manager.id_attribute)其實調用的就是user.get_id()方法所以在定義User類中需要定義get_id()方法。其實Flask-Login提供了一個UserMixin類，這個提供了

所有必要的方法和屬性。可以使自定義的類繼承這個類來滿足需求。UserMixin的定義如下：

class UserMixin(object):

    if not PY2:  # pragma: no cover
        # Python 3 implicitly set __hash__ to None if we override __eq__
        # We set it back to its default implementation
        __hash__ = object.__hash__

    @property
    def is_active(self):
        return True

    @property
    def is_authenticated(self):
        return True

    @property
    def is_anonymous(self):
        return False

    def get_id(self):
        try:
            return text_type(self.id)
        except AttributeError:
            raise NotImplementedError('No `id` attribute - override `get_id`')

    def __eq__(self, other):
        '''
        Checks the equality of two `UserMixin` objects using `get_id`.
        '''
        if isinstance(other, UserMixin):
            return self.get_id() == other.get_id()
        return NotImplemented

    def __ne__(self, other):
        '''
        Checks the inequality of two `UserMixin` objects using `get_id`.
        '''
        equal = self.__eq__(other)
        if equal is NotImplemented:
            return NotImplemented
        return not equal

2）當中某些操作需要用戶登錄的時候，就需要用到裝飾器login_required。

        @app.route('/post')
        @login_required
        def post():
            pass

函數login_required：

def login_required(func):
 
    @wraps(func)
    def decorated_view(*args, **kwargs):
        if request.method in EXEMPT_METHODS:
            return func(*args, **kwargs)
        elif current_app.login_manager._login_disabled:
            return func(*args, **kwargs)
        elif not current_user.is_authenticated:
            return current_app.login_manager.unauthorized()
        return func(*args, **kwargs)
    return decorated_view

current_user是個函數對象最后調用的Login_Manager的_load_user函數，_load_user中調用了reload_user。

    def reload_user(self, user=None):
        ctx = _request_ctx_stack.top

        if user is None:
            user_id = session.get('user_id')
            if user_id is None:
                ctx.user = self.anonymous_user()
            else:
                if self.user_callback is None:
                    raise Exception(
                        "No user_loader has been installed for this "
                        "LoginManager. Add one with the "
                        "'LoginManager.user_loader' decorator.")
                user = self.user_callback(user_id)
                if user is None:
                    ctx.user = self.anonymous_user()
                else:
                    ctx.user = user
        else:
            ctx.user = user

reload_user在Session中獲取user的id，然后傳入通過user_loader裝飾器注冊的回調函數，從這個回調中返回用戶的實例。注冊用戶的回調方法如下：

@loginManager.user_loader
def load_user(user_id):
    return User.query.get(int(user_id))

如果沒有找到則返回一個AnonymousUserMixin的實例。

class AnonymousUserMixin(object):
    '''
    This is the default object for representing an anonymous user.
    '''
    @property
    def is_authenticated(self):
        return False

    @property
    def is_active(self):
        return False

    @property
    def is_anonymous(self):
        return True

    def get_id(self):
        return

如果user類繼承自UserMixin則current_user.is_authenticated的值為Ture表示用戶已經登錄認證了。

flak-login管理登錄認證的流程大致就如上所述