Python Flask：跟踪用户会话？如何获取会话Cookie ID？

Question

我想在学习活动中构建一个简单的Web应用程序。如果遇到首次访问者，Webapp应该要求用户输入他们的email_id，否则它会通过cookie记住用户并自动登录以执行功能。

这是我第一次创建基于用户的Web应用程序。我心中有一个蓝图，但是我无法弄清楚如何实现它。首先，我对收集用户cookie的方式感到困惑。我研究了各种教程和flask_login，但是与flask_login所实现的相比，我想实现的要简单得多。

我也尝试使用，flask.session但是有点难以理解，最终导致实现有缺陷。

这是到目前为止我所拥有的（它是基本的，目的是传达我的用例）：

`from flask import render_template, request, redirect, url_for

@app.route(“/”, methods= [“GET”])
def first_page():
cookie = response.headers[‘cookie’]
if database.lookup(cookie):
user = database.get(cookie) # it returns user_email related to that cookie id
else:
return redirect_url(url_for(‘login’))
data = generateSomeData() # some function
return redirect(url_for(‘do_that’), user_id, data, stats)

@app.route(‘/do_that’, methods =[‘GET’])
def do_that(user_id):
return render_template(‘interface.html’, user_id, stats,data) # it uses Jinja template

@app.route(‘/submit’, methods =[“GET”])
def submit():
# i want to get all the information here
user_id = request.form[‘user_id’]# some data
answer = request.form[‘answer’] # some response to be recorded
data = request.form[‘data’] # same data that I passed in do_that to keep
database.update(data,answer,user_id)
return redirect(url_for(‘/do_that’))

@app.route(‘/login’, methods=[‘GET’])
def login():
return render_template(‘login.html’)

@app.route(‘/loggedIn’, methods =[‘GET’])
def loggedIn():
cookie = response.headers[‘cookie’]
user_email = response.form[‘user_email’]
database.insert(cookie, user_email)
return redirect(url_for(‘first_page’))`

Answer 1

你可以通过request.cookies字典访问请求cookie，并通过使用make_response或仅将调用结果存储render_template在变量中然后调用set_cookie响应对象来设置cookie ：

@app.route("/")
def home():
    user_id = request.cookies.get('YourSessionCookie')
    if user_id:
        user = database.get(user_id)
        if user:
            # Success!
            return render_template('welcome.html', user=user)
        else:
            return redirect(url_for('login'))
    else:
        return redirect(url_for('login'))

@app.route("/login", methods=["GET", "POST"])
def login():
    if request.method == "POST":
        # You should really validate that these fields
        # are provided, rather than displaying an ugly
        # error message, but for the sake of a simple
        # example we'll just assume they are provided

        user_name = request.form["name"]
        password = request.form["password"]
        user = db.find_by_name_and_password(user_name, password)

        if not user:
            # Again, throwing an error is not a user-friendly
            # way of handling this, but this is just an example
            raise ValueError("Invalid username or password supplied")

        # Note we don't *return* the response immediately
        response = redirect(url_for("do_that"))
        response.set_cookie('YourSessionCookie', user.id)
        return response

@app.route("/do-that")
def do_that():
    user_id = request.cookies.get('YourSessionCookie')
    if user_id:
        user = database.get(user_id)
        if user:
            # Success!
            return render_template('do_that.html', user=user)
        else:
            return redirect(url_for('login'))
    else:
        return redirect(url_for('login'))

DRYing up the code

现在，你会注意到和方法中有很多样板，所有这些都与登录有关。你可以通过编写自己的装饰器来避免这种情况（如果你想了解更多关于装饰器的信息，请参阅什么是装饰器）：homedo_that

from functools import wraps
from flask import flash

def login_required(function_to_protect):
    @wraps(function_to_protect)
    def wrapper(*args, **kwargs):
        user_id = request.cookies.get('YourSessionCookie')
        if user_id:
            user = database.get(user_id)
            if user:
                # Success!
                return function_to_protect(*args, **kwargs)
            else:
                flash("Session exists, but user does not exist (anymore)")
                return redirect(url_for('login'))
        else:
            flash("Please log in")
            return redirect(url_for('login'))
    return wrapper

然后，你的home和do_that方法变得更短：

# Note that login_required needs to come before app.route
# Because decorators are applied from closest to furthest
# and we don't want to route and then check login status

@app.route("/")
@login_required
def home():
    # For bonus points we *could* store the user
    # in a thread-local so we don't have to hit
    # the database again (and we get rid of *this* boilerplate too).
    user = database.get(request.cookies['YourSessionCookie'])
    return render_template('welcome.html', user=user)

@app.route("/do-that")
@login_required
def do_that():
    user = database.get(request.cookies['YourSessionCookie'])
    return render_template('welcome.html', user=user)

Using what’s provided

如果你不需要 Cookie来使用特定的名称，我建议你使用flask.session它，因为它已经内置了很多功能（它已签名，因此不能被篡改，可以设置为仅HTTP，等等）。 ）。这会使我们的login_required装饰器更加干燥：

# You have to set the secret key for sessions to work
# Make sure you keep this secret
app.secret_key = 'something simple for now' 

from flask import flash, session

def login_required(function_to_protect):
    @wraps(function_to_protect)
    def wrapper(*args, **kwargs):
        user_id = session.get('user_id')
        if user_id:
            user = database.get(user_id)
            if user:
                # Success!
                return function_to_protect(*args, **kwargs)
            else:
                flash("Session exists, but user does not exist (anymore)")
                return redirect(url_for('login'))
        else:
            flash("Please log in")
            return redirect(url_for('login'))

然后，你的各个方法可以通过以下方式吸引用户：

user = database.get(session['user_id'])