using flask-login with postgresql - postgresql

Question

I'm working on a flask app that needs authentication. I've hooked up flask-login but it doesn't seem very graceful.
First flask-login needs to make sure the user exists:
#login_manager.user_loader
def load_user(id):
return User.query.get(id)
But you also need to use 'login_user' to create the user object
# Some code above
user = User.query.filter_by(email = form.email.data, password = form.password.data).first()
user.login_status = 1
db.session.commit()
login_user(objects.SignedInUser(user.id, user.email, user.login_status == LoginStatus.Active))
# Some code below
In the code above 'User' is a model for postgres and SignedInUser is just an object to be used for flask-login.
Does anyone have an example of flask-login used with postgres?

Answer 1

It looks like you might be misunderstanding what Flask-Login handles. It's there to keep track of everything about the user's session after you tell it authentication was successful (by calling login_user.) The user_loader callback only tells it how to reload the object for a user that has already been authenticated, such as when someone reconnects to a "remember me" session. The docs are not especially clear on that.
There should be no need to keep a flag in the database for the user's login status. Also, the code you included will raise an AttributeError if the credentials are incorrect (user = None).
Here's an example from a Flask-SQLAlchemy application. It uses an external authentication source and a wrapper for the SQLAlchemy User object, but the process is basically the same.
user_loader callback:
#login_manager.user_loader
def load_user(user_id):
user = User.query.get(user_id)
if user:
return DbUser(user)
else:
return None
User class (wrapper for SQLAlchemy object):
# User class
class DbUser(object):
"""Wraps User object for Flask-Login"""
def __init__(self, user):
self._user = user
def get_id(self):
return unicode(self._user.id)
def is_active(self):
return self._user.enabled
def is_anonymous(self):
return False
def is_authenticated(self):
return True
Login handler:
#app.route('/login', methods=['GET', 'POST'])
def login():
error = None
next = request.args.get('next')
if request.method == 'POST':
username = request.form['username']
password = request.form['password']
if authenticate(app.config['AUTH_SERVER'], username, password):
user = User.query.filter_by(username=username).first()
if user:
if login_user(DbUser(user)):
# do stuff
flash("You have logged in")
return redirect(next or url_for('index', error=error))
error = "Login failed"
return render_template('login.html', login=True, next=next, error=error)
Note that login fails if:
external auth fails
user query returns None (user does not exist)
login_user returns False (user.is_active() == False)
Logout
#app.route('/logout')
#login_required
def logout():
logout_user()
flash('You have logged out')
return(redirect(url_for('login')))