Flask-Security无法正确初始化

Question

在我自己写完登录/注册系统后，我发现了Flask-Security这个工具，并决定把它整合进我的应用里。结果我之前写的所有认证和恢复的代码都没了，但我启动应用时却遇到了一些简单的错误，搞不清楚为什么。

这是我能想到的最简单的例子：

from flask import Flask, render_template_string

from flask.ext.sqlalchemy import SQLAlchemy
from flask.ext.security import Security, SQLAlchemyUserDatastore, UserMixin, RoleMixin, current_user

app = Flask('test')
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/database.db'

db = SQLAlchemy(app)

roles_users = db.Table('roles_users',
    db.Column('user_id', db.Integer, db.ForeignKey('user.id')),
    db.Column('role_id', db.Integer, db.ForeignKey('role.id'))
)

class Role(db.Model, RoleMixin):
    id = db.Column(db.Integer(), primary_key=True)
    name = db.Column(db.String(80), unique=True)
    description = db.Column(db.String(255))

class User(db.Model, UserMixin):
    id = db.Column(db.Integer, primary_key=True)

    username = db.Column(db.String(50), unique=True)
    email = db.Column(db.String(255), unique=True)
    password = db.Column(db.String(255))

    active = db.Column(db.Boolean)
    confirmed_at = db.Column(db.DateTime)
    roles = db.relationship('Role', secondary=roles_users, backref=db.backref('users', lazy='dynamic'))

    def is_authenticated(self):
        return True

    def is_active(self):
        return True

    def is_anonymous(self):
        return False

    def get_id(self):
        return unicode(self.id)

    def __repr__(self):
        return '<User {self.username}>'.format(self=self)

user_datastore = SQLAlchemyUserDatastore(db, User, Role)
security = Security(app)

@app.before_first_request
def create_db():
    db.create_all()

@app.route('/')
def index():
    return render_template_string('''
        {% if current_user.is_authenticated() %}
            You're logged in.
        {% else %}
            You're not logged in.
        {% endif %}
    ''')

if __name__ == '__main__':
    app.run(debug=True)

当我访问http://localhost:5000/时，出现了这个错误：

Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/flask/app.py", line 1701, in __call__
    return self.wsgi_app(environ, start_response)
  File "/usr/lib/python2.7/site-packages/flask/app.py", line 1689, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "/usr/lib/python2.7/site-packages/flask/app.py", line 1687, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/lib/python2.7/site-packages/flask/app.py", line 1360, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/usr/lib/python2.7/site-packages/flask/app.py", line 1358, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/lib/python2.7/site-packages/flask/app.py", line 1344, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/tmp/app.py", line 62, in index
    ''')
  File "/usr/lib/python2.7/site-packages/flask/templating.py", line 140, in render_template_string
    context, ctx.app)
  File "/usr/lib/python2.7/site-packages/flask/templating.py", line 107, in _render
    rv = template.render(context)
  File "/usr/lib/python2.7/site-packages/jinja2/environment.py", line 894, in render
    return self.environment.handle_exception(exc_info, True)
  File "<template>", line 2, in top-level template code

  File "/usr/lib/python2.7/site-packages/jinja2/environment.py", line 372, in getattr
    return getattr(obj, attribute)
UndefinedError: 'current_user' is undefined

我查看了Flask-Security-Example和Flask-Social-Example的源代码，但还是搞不清楚我哪里出错了。

非常感谢大家的帮助。

顺便问一下，为什么这个表格是这样创建的？（更重要的是）它的用途是什么？

roles_users = db.Table('roles_users',
    db.Column('user_id', db.Integer, db.ForeignKey('user.id')),
    db.Column('role_id', db.Integer, db.ForeignKey('role.id'))
)

源代码分析 web开发认证系统错误调试开源工具应用集成用户注册 flask-security

Flask-Security无法正确初始化

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