mongodb GridFS django FileFiled 默认 widget 只有一个文件上传框显示不了字段内容，重写widget

首先，定位到：FileFiled 默认 widget 源码：mongoadmin包options.py中，如下：

# Defaults for formfield_overrides. ModelAdmin subclasses can change this
# by adding to ModelAdmin.formfield_overrides.
FORMFIELD_FOR_DBFIELD_DEFAULTS = {
    DateTimeField: {
        'form_class': forms.SplitDateTimeField,
        'widget'    : widgets.AdminSplitDateTime
        },
    URLField     : {'widget': widgets.AdminURLFieldWidget},
    IntField     : {'widget': widgets.AdminIntegerFieldWidget},
    ImageField   : {'widget': widgets.AdminFileWidget},
    FileField    : {'widget': widgets.AdminFileWidget},
    }

_fieldgenerator = load_field_generator()()

然后，根据注释部分：

# Defaults for formfield_overrides. ModelAdmin subclasses can change this
# by adding to ModelAdmin.formfield_overrides.

重写widget如下：

from django.contrib.admin.widgets import AdminFileWidget
class FileWidget(AdminFileWidget):
    """
    A FileField Widget that shows its current value if it has one.
    """

    def __init__(self, attrs={}):
        super(FileWidget, self).__init__(attrs)

    def render(self, name, value, attrs=None):
        output = []
        output.append(super(FileWidget, self).render(name, value, attrs))
        output.append('<p class="help"><textarea name="%s" id="id_%s" rows="10" cols="40" class="vLargeTextField"> %s </textarea></p>' % (name, name, value.read()))
        return mark_safe(u''.join(output))

引入widget如下：

from mongoengine import Document
class AbstractDocument(Document):

    ModelAdmin.formfield_overrides = {
        FileField: {'widget': FileWidget},
    }

    meta = {
        'abstract': True,
    }