烧瓶 SQLAlchemy 更新而不是插入

【问题标题】：Flask SQLAlchely UPDATE instead of INSERT烧瓶 SQLAlchemy 更新而不是插入
【发布时间】：2021-07-19 16:55:45
【问题描述】：

我正在关注 Corey Schafer 的教程系列，用于制作 Flask Web 应用程序，但我做错了。因此，当从用户向数据库发布新帖子时，它会使用表单中的数据写入数据库，但是当我尝试从 same 用户添加另一篇帖子时，我收到错误：

[SQL: UPDATE post SET user_id=? WHERE post.id = ?]
[parameters: (None, 1)]

我的 models.py 中有这个，不应该让 user_id 是 None：

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

登录路径：

@app.route('/login', methods=['GET', 'POST'])
def login():
    if current_user.is_authenticated:
        return redirect(url_for('home'))
    form = LoginForm()
    if form.validate_on_submit():
        user = User.query.filter_by(username=form.username.data).first()
        if user and bcrypt.check_password_hash(user.password, form.password.data):
            login_user(user, remember=form.remember.data)
            flash(f'Success.', category='success')
            next_page = request.args.get('next')
            return redirect(next_page) if next_page else redirect(url_for('home'))
        else:
            flash('Unsuccessful!', category='danger')
    return render_template('login.html', title='Log In', form=form)

这是添加新帖子的路径：

@app.route('/post/new', methods=['GET', 'POST'])
@login_required
def new_product():
    form = PostForm()
    if form.validate_on_submit():
        post = Post(name=form.name.data, content=form.content.data, author=current_user)
        db.session.add(post)
        db.session.commit()
        flash('Created!', category='success')
        return redirect(url_for('home'))
    return render_template('new.html', title='Add Post', form=form, legend='New Post')

这是形式：

class PostForm(FlaskForm):
    name = StringField('Name', validators=[DataRequired()])
    content = StringField('Content', validators=[DataRequired()])

在视频中，他发布了一个新帖子，但来自另一个用户帐户。我怎样才能逃脱呢？

整个错误是这样的：

127.0.0.1 - - [26/Apr/2021 15:00:34] "POST /post/new HTTP/1.1" 500 -
Traceback (most recent call last):
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\engine\base.py", line 1705, in _execute_context
    self.dialect.do_execute(
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\engine\default.py", line 716, in do_execute
    cursor.execute(statement, parameters)
sqlite3.IntegrityError: NOT NULL constraint failed: post.user_id

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "D:\Python\HTML\venv\Lib\site-packages\flask\app.py", line 2464, in __call__
    return self.wsgi_app(environ, start_response)
  File "D:\Python\HTML\venv\Lib\site-packages\flask\app.py", line 2450, in wsgi_app
    response = self.handle_exception(e)
  File "D:\Python\HTML\venv\Lib\site-packages\flask\app.py", line 1867, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "D:\Python\HTML\venv\Lib\site-packages\flask\_compat.py", line 39, in reraise
    raise value
  File "D:\Python\HTML\venv\Lib\site-packages\flask\app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "D:\Python\HTML\venv\Lib\site-packages\flask\app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "D:\Python\HTML\venv\Lib\site-packages\flask\app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "D:\Python\HTML\venv\Lib\site-packages\flask\_compat.py", line 39, in reraise
    raise value
  File "D:\Python\HTML\venv\Lib\site-packages\flask\app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "D:\Python\HTML\venv\Lib\site-packages\flask\app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "D:\Python\HTML\blog\Lib\site-packages\flask_login\utils.py", line 272, in decorated_view
    return func(*args, **kwargs)
  File "D:\Python\HTML\store\routes.py", line 101, in new_product
    db.session.commit()
  File "<string>", line 2, in commit

  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\orm\session.py", line 1423, in commit
    self._transaction.commit(_to_root=self.future)
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\orm\session.py", line 829, in commit
    self._prepare_impl()
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\orm\session.py", line 808, in _prepare_impl
    self.session.flush()
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\orm\session.py", line 3255, in flush
    self._flush(objects)
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\orm\session.py", line 3395, in _flush
    transaction.rollback(_capture_exception=True)
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\util\langhelpers.py", line 70, in __exit__
    compat.raise_(
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\util\compat.py", line 211, in raise_
    raise exception
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\orm\session.py", line 3355, in _flush
    flush_context.execute()
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\orm\unitofwork.py", line 453, in execute
    rec.execute(self)
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\orm\unitofwork.py", line 627, in execute
    util.preloaded.orm_persistence.save_obj(
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\orm\persistence.py", line 234, in save_obj
    _emit_update_statements(
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\orm\persistence.py", line 998, in _emit_update_statements
    c = connection._execute_20(
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\engine\base.py", line 1520, in _execute_20
    return meth(self, args_10style, kwargs_10style, execution_options)
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\sql\elements.py", line 313, in _execute_on_connection
    return connection._execute_clauseelement(
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\engine\base.py", line 1389, in _execute_clauseelement
    ret = self._execute_context(
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\engine\base.py", line 1748, in _execute_context
    self._handle_dbapi_exception(
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\engine\base.py", line 1929, in _handle_dbapi_exception
    util.raise_(
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\util\compat.py", line 211, in raise_
    raise exception
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\engine\base.py", line 1705, in _execute_context
    self.dialect.do_execute(
  File "D:\Python\HTML\venv\Lib\site-packages\sqlalchemy\engine\default.py", line 716, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.IntegrityError: (sqlite3.IntegrityError) NOT NULL constraint failed: post.user_id
[SQL: UPDATE post SET user_id=? WHERE post.id = ?]
[parameters: (None, 1)]
(Background on this error at: http://sqlalche.me/e/14/gkpj)
127.0.0.1 - - [26/Apr/2021 15:00:34] "GET /product/new?__debugger__=yes&cmd=resource&f=style.css HTTP/1.1" 200 -
127.0.0.1 - - [26/Apr/2021 15:00:34] "GET /product/new?__debugger__=yes&cmd=resource&f=jquery.js HTTP/1.1" 200 -
127.0.0.1 - - [26/Apr/2021 15:00:34] "GET /product/new?__debugger__=yes&cmd=resource&f=debugger.js HTTP/1.1" 200 -
127.0.0.1 - - [26/Apr/2021 15:00:35] "GET /product/new?__debugger__=yes&cmd=resource&f=console.png HTTP/1.1" 200 -
127.0.0.1 - - [26/Apr/2021 15:00:35] "GET /product/new?__debugger__=yes&cmd=resource&f=ubuntu.ttf HTTP/1.1" 200 -
127.0.0.1 - - [26/Apr/2021 15:00:35] "GET /product/new?__debugger__=yes&cmd=resource&f=console.png HTTP/1.1" 200 -

解决方案：我在forms.py 中弄乱了导入，是这样的：

from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, SubmitField, BooleanField, TextAreaField
from flask_wtf.file import FileField, FileAllowed
from wtforms.validators import DataRequired, Length, Email, EqualTo, ValidationError
from store.models import User
from flask_login import current_user

不得不改成这样：

from flask_wtf import FlaskForm
from flask_wtf.file import FileField, FileAllowed
from flask_login import current_user
from wtforms import StringField, PasswordField, SubmitField, BooleanField, TextAreaField
from wtforms.validators import DataRequired, Length, Email, EqualTo, ValidationError
from store.models import User

【问题讨论】：

  • 是否 current_user.is_authenticated?
  • 我的意思是用户实际登录了吗？请参阅签入register 和login 路线。此外，对于您的帖子，您只需要 user_id，所以没有理由传递所有对象，只需传递 current_user.id。
  • 您确定与生成此错误消息的路由相同吗？进行一些调试，在代码中添加一些打印以确保。看起来是 PUT 被称为而不是 POST
  • 你能从控制台给出整个错误信息吗？
  • current_user 在会话中吗？ current_user in db.session 显示什么？

标签： python sqlite flask sqlalchemy


【解决方案1】：

更新：感谢@IljaEverilä，我错了，backref 可用于分配，而不仅仅是检索。我的回答解决了作者的问题，但我对教程代码错误的评论不正确，实际问题在另一个地方。有关backref 的更多信息（带有分配示例 - SQLAlchemy docs）

我把它放在那里是因为上面提到的教程中的代码看起来有错误。

问题是你没有传递任何user_id，但你传递了author。我检查了本教程中的代码，注意到 author 字段存在于 Django 模型中，而不是 Flask 中。所以只需将author=current_user 替换为user_id=current_user.id 就可以了

【讨论】：

  • 是的，谢谢，这行得通，但author 在user 模型中是反向引用，如here 所示
  • 是的，但是backref 是一个用于获取相关对象的属性，而不是用于设置它
  • 谢谢。这是有用的信息。
  • 不，relationship backref 用于在另一端创建镜像relationship 属性，通常也应该支持分配。 “backref 是用于获取相关对象的属性，而不是设置它”为 false。
  • @IljaEverilä，你是对的，谢谢你的纠正，我更新了我的答案
猜你喜欢
  • 2013-11-22
  • 2012-12-29
  • 2021-04-10
  • 1970-01-01
  • 2021-06-01
  • 1970-01-01
  • 2020-01-29
  • 1970-01-01
  • 2022-10-21
相关资源
最近更新 更多
热门标签
Java Python linux javascript Mysql C# Docker 算法 前端 SpringBoot Redis Vue spring 设计模式 .net core .net kubernetes c++ 数据库 数据结构 大数据 js 机器学习 微服务 Android Go 程序员 面试 JVM ASP.net core 云原生 人工智能 后端 PHP git CSS golang k8s Nginx Django mybatis 深度学习 多线程 React 架构 devops 爬虫 云计算 Spring Boot LeetCode