Flask闪现消息导致Session不可用

Question

使用官方文档中的确切代码:

@app.route('/', methods=['GET', 'POST'])
def upload_file():
    if request.method == 'POST':
        ...
        if file.filename == '':
            flash('No selected file')
            return redirect(request.url)
        if file and allowed_file(file.filename):
            ..
            flash('File was successfully uploaded')
            return redirect(url_for('uploaded_file', filename=filename))
    return render_template('home.html')

没有flash()一切正常。但是添加时会导致错误 session 不可用，因为没有 secret 。下面是一个痕迹:

> 127.0.0.1 - - [18/Feb/2019 10:16:21] "POST / HTTP/1.1" 500 -
> 127.0.0.1 - - [18/Feb/2019 10:17:16] "GET / HTTP/1.1" 200 - [2019-02-18 10:17:23,999] ERROR in app: Exception on / [POST]
> Traceback (most recent call last):   File
> "/home/dvperv/PycharmProjects/astros/venv/lib/python3.6/site-packages/flask/app.py",
> line 2292, in wsgi_app
>     response = self.full_dispatch_request()   File "/home/dvperv/PycharmProjects/astros/venv/lib/python3.6/site-packages/flask/app.py",
> line 1815, in full_dispatch_request
>     rv = self.handle_user_exception(e)   File "/home/dvperv/PycharmProjects/astros/venv/lib/python3.6/site-packages/flask/app.py",
> line 1718, in handle_user_exception
>     reraise(exc_type, exc_value, tb)   File "/home/dvperv/PycharmProjects/astros/venv/lib/python3.6/site-packages/flask/_compat.py",
> line 35, in reraise
>     raise value   File "/home/dvperv/PycharmProjects/astros/venv/lib/python3.6/site-packages/flask/app.py",
> line 1813, in full_dispatch_request
>     rv = self.dispatch_request()   File "/home/dvperv/PycharmProjects/astros/venv/lib/python3.6/site-packages/flask/app.py",
> line 1799, in dispatch_request
>     return self.view_functions[rule.endpoint](**req.view_args)   File "/home/dvperv/PycharmProjects/astros/app.py", line 39, in upload_file
>     flash('No file part')   File "/home/dvperv/PycharmProjects/astros/venv/lib/python3.6/site-packages/flask/helpers.py",
> line 410, in flash
>     session['_flashes'] = flashes   File "/home/dvperv/PycharmProjects/astros/venv/lib/python3.6/site-packages/werkzeug/local.py",
> line 350, in __setitem__
>     self._get_current_object()[key] = value   File "/home/dvperv/PycharmProjects/astros/venv/lib/python3.6/site-packages/flask/sessions.py",
> line 101, in _fail
>     raise RuntimeError('The session is unavailable because no secret ' RuntimeError: The session is unavailable because no secret key was
> set.  Set the secret_key on the application to something unique and
> secret.
> 127.0.0.1 - - [18/Feb/2019 10:17:24] "POST / HTTP/1.1" 500 -

我读过几篇关于此错误的文章，但它们都与 Flask-Session 扩展有关，我不使用它。

我还尝试在应用程序中添加 app.secret_key = 'super Secret key'，但没有成功。

我应该使用 Flask Session 并进行适当的配置，还是有一种方法只使用普通的 Flask flash() ，它以某种方式在幕后与 session 本身一起工作。

应用程序配置:

app = Flask(__name__)

UPLOAD_FOLDER = ..
ALLOWED_EXTENSIONS = ..

app.config['UPLOAD_FOLDER'] = UPLOAD_FOLDER
app.config['MAX_CONTENT_LENGTH'] = 16 * 1024 * 1024

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

Answer 1

堆栈跟踪中非常清楚地表明未设置 key 。请务必将 key 设置在正确的位置，例如此处:

app = Flask(__name__)
app.secret_key = 'asrtarstaursdlarsn'

UPLOAD_FOLDER = ..