python学习笔记-flask学习(二)Flask-Login模块-python黑洞网

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python学习笔记-flask学习(二)Flask-Login模块

发布于2019-08-23 16:02 阅读(641) 评论(0) 点赞(24) 收藏(0)

　　Flask-Login模块提供用户状态的管理功能。使用flask-login首先要获取一个loadmanager的实例。

1）当用户登录以后，如果需要记录用户的状态则则可以调用 login_user函数记录当前登录的用户。

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主要的作用就是将user的id加入到session中。getattr(user, current_app.login_manager.id_attribute)其实调用的就是user.get_id()方法所以在定义User类中需要定义get_id()方法。其实Flask-Login提供了一个UserMixin类，这个提供了

所有必要的方法和属性。可以使自定义的类继承这个类来满足需求。UserMixin的定义如下：

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）当中某些操作需要用户登录的时候，就需要用到装饰器login_required。

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

函数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是个函数对象最后调用的Login_Manager的_load_user函数，_load_user中调用了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中获取user的id，然后传入通过user_loader装饰器注册的回调函数，从这个回调中返回用户的实例。注册用户的回调方法如下：

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

如果没有找到则返回一个AnonymousUserMixin的实例。

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