Flask-WTForms FileField 未验证

Question

我正在尝试构建一个应用程序，以使用 Flask 和 WTForms 的 FileField 表单字段将文件上传到 Web 服务器。这篇文章正在成功通过，但我很好奇为什么 form.validate_on_submit() 每次都失败，即使特定的验证器都成功了。这是我的表单 (forms.py)、应用程序 (main.py) 和 html 模板 (upload.html) 的代码。

### forms.py   

from flask.ext.wtf import Form
from flask.ext.wtf.html5 import EmailField
from flask.ext.wtf.file import FileField, FileRequired, FileAllowed
from wtforms import validators, ValidationError, SubmitField

class UploadForm(Form):
  presentation = FileField('Presentation in Image Format', validators=[FileRequired(), FileAllowed(['jpg', 'png'], 'Images only!')])
  submit = SubmitField("Send")



### main.py

from forms import UploadForm
from flask import render_template, url_for, redirect, send_from_directory

@app.route('/upload/', methods=('GET', 'POST'))
  def upload():
    form = UploadForm()
    if form.validate_on_submit():
      filename = secure_filename(form.presentation.file.filename)
      print filename
      form.presentation.file.save(os.path.join('uploads/', filename))
      return redirect(url_for('uploads', filename=filename))
    filename = None
    return render_template('upload.html', form=form, filename=filename)

@app.route('/uploads/<filename>')
  def uploaded_file(filename):
    return send_from_directory(app.config['UPLOAD_FOLDER'], filename)



### upload.html
   {% for message in form.presentation.errors %}
     <div class="flash">{{ message }}</div>
   {% endfor %}
   <form action="/upload/" method="POST" enctype="multipart/form-data">
     {{ form.presentation.label }}
     {{ form.presentation }}
     {{ form.submit}}
   </form>

有谁知道为什么这可能无法验证？或者我不应该使用validate_on_submit()？

Answer 1

Flask-WTF 默认启用 CRSF，如果您打印form.errors，您将收到一条消息，告诉您需要 csrf 令牌。

解决办法很简单，把{{ form.csrf_token }}你的模板放进去，或者禁用表单的CSRF，但你真的不应该这样做。

<form action="/upload/" method="POST" enctype="multipart/form-data">
 {{ form.presentation.label }}
 {{ form.presentation }}
 {{ form.csrf_token }}
 {{ form.submit}}
</form>

还有一种将每个隐藏字段添加到表单的快速方法hidden_tags：

<form action="/upload/" method="POST" enctype="multipart/form-data">
 {{ form.presentation.label }}
 {{ form.presentation }}
 {{ form.hidden_tag() }}
 {{ form.submit}}
</form>