Django Database File Storage’s 0.5.0 documentation

Django Database File Storage (PyPI) (GitHub) is a custom file storage system for Django. Use it to save files in your database instead of your file system.

Installing

You can pip-install django-db-file-storage in your environment by typing the following code on your shell:

pip install django-db-file-storage

Settings

On your project’s settings, add 'db_file_storage' to your INSTALLED_APPS list.

How to use (for FileFields on models)

When used for models’ FileFields, django-db-file-storage uses a specific model to hold each FileField.

Settings

On your project’s settings, set DEFAULT_FILE_STORAGE like this:

DEFAULT_FILE_STORAGE = 'db_file_storage.storage.DatabaseFileStorage'

URLs

Add the following URL pattern to your project’s main urlpatterns (/urls.py):

url(r'^files/', include('db_file_storage.urls')),

Models

For each FileField you want to save, you will need a separated model to hold the file in the database. I will refer to this extra model as the FileModel. The FileModel must have at least these fields:

  • a TextField() which will hold the encoded contents of the file
  • a CharField(max_length=255) which will hold the file’s name
  • a CharField(max_length=50) which will hold the file’s MIME type

For example (in a models.py file, inside an app called ‘console’):

from django.db import models

class ConsolePicture(models.Model):
    bytes = models.TextField()
    filename = models.CharField(max_length=255)
    mimetype = models.CharField(max_length=50)

And the class which will have the FileField:

class Console(models.Model):
    name = models.CharField(max_length=100)
    picture = models.ImageField(upload_to='console.ConsolePicture/bytes/filename/mimetype', blank=True, null=True)

In this example, the FileField is actually an ImageField. Its upload_to argument must be a string in the following format:

  1. the FileModel’s app’s name
  2. a dot (.)
  3. the FileModel’s name
  4. a forward slash (/)
  5. the name of the FileModel’s field which will hold the encoded contents of the files
  6. a forward slash
  7. the name of the FileModel’s field which will hold the name of the files
  8. a forward slash
  9. the name of the FileModel’s field which will hold the MIME type of the files

Let’s check it again:

#   1   2       3      4  5  6    7   8    9
'console.ConsolePicture/bytes/filename/mimetype'

Don’t forget to create the necessary tables in your database, if you haven’t yet.

If you want stale files to be deleted when editing and deleting instances, override the save and delete methods of your model, calling db_file_storage.model_utils.delete_file_if_needed and db_file_storage.model_utils.delete_file inside them, respectively:

from db_file_storage.model_utils import delete_file, delete_file_if_needed
from django.db import models

class Console(models.Model):
    name = models.CharField(max_length=100, unique=True)
    picture = models.ImageField(upload_to='console.ConsolePicture/bytes/filename/mimetype', blank=True, null=True)

    def save(self, *args, **kwargs):
        delete_file_if_needed(self, 'picture')
        super(Console, self).save(*args, **kwargs)

    def delete(self, *args, **kwargs):
        super(Console, self).delete(*args, **kwargs)
        delete_file(self, 'picture')

Pay extra attention here to when the methods should be called. delete_file_if_needed should be called before the save method of the super class, and delete_file should be called after the delete method of the super class.

Form widget

At this point, your project already must be saving files in the database when you use Django’s ModelForms.

However, due to Django Database File Storage’s internal logic, Django’s default widget for file inputs won’t show the proper filename when downloading uploaded files. The download itself works perfectly, it’s just the widget that doesn’t show the correct name in its download link.

Django Database File Storage comes with a custom widget to solve this problem: DBClearableFileInput. You just need to use it when defining your form class:

from console.models import Console
from db_file_storage.form_widgets import DBClearableFileInput
from django import forms

class ConsoleForm(forms.ModelForm):
    class Meta:
        model = Console
        exclude = []
        widgets = {
            'picture': DBClearableFileInput
        }

Admin Form widget

In order to solve the same problem in the Django Admin interface, Django Database File Storage comes with another custom widget: DBAdminClearableFileInput. You just need to use it when defining your form class, and then use such form when defining your ModelAdmin class inside your admin.py file:

from console.models import Console
from db_file_storage.form_widgets import DBAdminClearableFileInput
from django import forms
from django.contrib import admin

class ConsoleForm(forms.ModelForm):
    class Meta:
        model = Console
        exclude = []
        widgets = {
            'picture': DBAdminClearableFileInput
        }

class ConsoleAdmin(admin.ModelAdmin):
    form = ConsoleForm

Downloading (and viewing) the files

Django Database File Storage comes with views that you can use to download the files or to just view them (for images, for example). They are accessed through the named url patterns db_file_storage.download_file and db_file_storage.get_file.

Both views must be passed a GET parameter named name, and the value of this parameter must be the value of the filefield of the instance. The template-snippet example below must make it clearer; console is an instance of the Console model defined above:

<!-- The url used to VIEW the file: -->
<img src="{% url 'db_file_storage.get_file' %}?name={{ console.picture }}" />

<br/>

<!-- The url used to DOWNLOAD the file: -->
<a href='{% url "db_file_storage.download_file" %}?name={{ console.picture }}'>
    <i>Click here to download the picture</i>
</a>

How to use (for Form Wizards)

When used this way, django-db-file-storage uses a fixed model to store all the saved files. Just set db_file_storage.storage.FixedModelDatabaseFileStorage as the wizard’s file_storage, passing all the attributes that you would define if you were using a model’s FileField:

from db_file_storage.storage import FixedModelDatabaseFileStorage
from formtools.wizard.views import SessionWizardView

class ExampleFormWizard(SessionWizardView):
    file_storage = FixedModelDatabaseFileStorage(
        model_class_path='form_wizard_example.FormWizardFile',
        content_field='bytes',
        filename_field='filename',
        mimetype_field='mimetype'
    )
    (...)

All the parameters shown above are required for the FixedModelDatabaseFileStorage initialization. The model that will hold the files must be defined as well (in form_wizard_example/models.py, in this case):

class FormWizardFile(models.Model):
    bytes = models.TextField()
    filename = models.CharField(max_length=255)
    mimetype = models.CharField(max_length=50)

In the demo project there is a working example with a Form Wizard.