Django2.0手册:The flatpages app



Django comes with an optional “flatpages” application. It lets you store simple
“flat” HTML content in a database and handles the management for you via
Django’s admin interface and a Python API.

A flatpage is a simple object with a URL, title and content. Use it for
one-off, special-case pages, such as “About” or “Privacy Policy” pages, that
you want to store in a database but for which you don’t want to develop a
custom Django application.

A flatpage can use a custom template or a default, systemwide flatpage
template. It can be associated with one, or multiple, sites.

The content field may optionally be left blank if you prefer to put your
content in a custom template.

Here are some examples of flatpages on Django-powered sites:

Installation¶

To install the flatpages app, follow these steps:

  1. Install the sites framework by adding
    'django.contrib.sites' to your INSTALLED_APPS setting,
    if it’s not already in there.

    Also make sure you’ve correctly set SITE_ID to the ID of the
    site the settings file represents. This will usually be 1 (i.e.
    SITE_ID = 1, but if you’re using the sites framework to manage
    multiple sites, it could be the ID of a different site.

  2. Add 'django.contrib.flatpages' to your INSTALLED_APPS
    setting.

Then either:

  1. Add an entry in your URLconf. For example:

    urlpatterns = [
        path('pages/', include('django.contrib.flatpages.urls')),
    ]
    

or:

  1. Add 'django.contrib.flatpages.middleware.FlatpageFallbackMiddleware'
    to your MIDDLEWARE setting.
  2. Run the command manage.py migrate.

How it works¶

manage.py migrate creates two tables in your database: django_flatpage
and django_flatpage_sites. django_flatpage is a simple lookup table
that simply maps a URL to a title and bunch of text content.
django_flatpage_sites associates a flatpage with a site.

Using the URLconf¶

There are several ways to include the flat pages in your URLconf. You can
dedicate a particular path to flat pages:

urlpatterns = [
    path('pages/', include('django.contrib.flatpages.urls')),
]

You can also set it up as a “catchall” pattern. In this case, it is important
to place the pattern at the end of the other urlpatterns:

from django.contrib.flatpages import views

# Your other patterns here
urlpatterns += [
    path('<path:url>', views.flatpage),
]

Warning

If you set APPEND_SLASH to False, you must remove the slash
in the catchall pattern or flatpages without a trailing slash will not be
matched.

Another common setup is to use flat pages for a limited set of known pages and
to hard code the urls, so you can reference them with the url template
tag:

from django.contrib.flatpages import views

urlpatterns += [
    path('about-us/', views.flatpage, {'url': '/about-us/'}, name='about'),
    path('license/', views.flatpage, {'url': '/license/'}, name='license'),
]

Using the middleware¶

The FlatpageFallbackMiddleware
can do all of the work.

class FlatpageFallbackMiddleware

Each time any Django application raises a 404 error, this middleware
checks the flatpages database for the requested URL as a last resort.
Specifically, it checks for a flatpage with the given URL with a site ID
that corresponds to the SITE_ID setting.

If it finds a match, it follows this algorithm:

  • If the flatpage has a custom template, it loads that template.
    Otherwise, it loads the template flatpages/default.html.
  • It passes that template a single context variable, flatpage,
    which is the flatpage object. It uses
    RequestContext in rendering the
    template.

The middleware will only add a trailing slash and redirect (by looking
at the APPEND_SLASH setting) if the resulting URL refers to
a valid flatpage. Redirects are permanent (301 status code).

If it doesn’t find a match, the request continues to be processed as usual.

The middleware only gets activated for 404s — not for 500s or responses
of any other status code.

Flatpages will not apply view middleware

Because the FlatpageFallbackMiddleware is applied only after
URL resolution has failed and produced a 404, the response it
returns will not apply any view middleware
methods. Only requests which are successfully routed to a view via
normal URL resolution apply view middleware.

Note that the order of MIDDLEWARE matters. Generally, you can put
FlatpageFallbackMiddleware at the
end of the list. This means it will run first when processing the response, and
ensures that any other response-processing middleware see the real flatpage
response rather than the 404.

For more on middleware, read the middleware docs.

Ensure that your 404 template works

Note that the
FlatpageFallbackMiddleware
only steps in once another view has successfully produced a 404 response.
If another view or middleware class attempts to produce a 404 but ends up
raising an exception instead, the response will become an HTTP 500
(“Internal Server Error”) and the
FlatpageFallbackMiddleware
will not attempt to serve a flat page.

How to add, change and delete flatpages¶

Via the admin interface¶

If you’ve activated the automatic Django admin interface, you should see a
“Flatpages” section on the admin index page. Edit flatpages as you edit any
other object in the system.

The FlatPage model has an enable_comments field that isn’t used by
contrib.flatpages, but that could be useful for your project or third-party
apps. It doesn’t appear in the admin interface, but you can add it by
registering a custom ModelAdmin for FlatPage:

from django.contrib import admin
from django.contrib.flatpages.admin import FlatPageAdmin
from django.contrib.flatpages.models import FlatPage
from django.utils.translation import gettext_lazy as _

# Define a new FlatPageAdmin
class FlatPageAdmin(FlatPageAdmin):
    fieldsets = (
        (None, {'fields': ('url', 'title', 'content', 'sites')}),
        (_('Advanced options'), {
            'classes': ('collapse', ),
            'fields': (
                'enable_comments',
                'registration_required',
                'template_name',
            ),
        }),
    )

# Re-register FlatPageAdmin
admin.site.unregister(FlatPage)
admin.site.register(FlatPage, FlatPageAdmin)

Via the Python API¶

class FlatPage

Flatpages are represented by a standard
Django model,
which lives in django/contrib/flatpages/models.py. You can access
flatpage objects via the Django database API.

Check for duplicate flatpage URLs.

If you add or modify flatpages via your own code, you will likely want to
check for duplicate flatpage URLs within the same site. The flatpage form
used in the admin performs this validation check, and can be imported from
django.contrib.flatpages.forms.FlatpageForm and used in your own
views.

Flatpage templates¶

By default, flatpages are rendered via the template
flatpages/default.html, but you can override that for a
particular flatpage: in the admin, a collapsed fieldset titled
“Advanced options” (clicking will expand it) contains a field for
specifying a template name. If you’re creating a flat page via the
Python API you can simply set the template name as the field
template_name on the FlatPage object.

Creating the flatpages/default.html template is your responsibility;
in your template directory, just create a flatpages directory
containing a file default.html.

Flatpage templates are passed a single context variable, flatpage,
which is the flatpage object.

Here’s a sample flatpages/default.html template:

<!DOCTYPE html>
<html>
<head>
<title>{{ flatpage.title }}</title>
</head>
<body>
{{ flatpage.content }}
</body>
</html>

Since you’re already entering raw HTML into the admin page for a flatpage,
both flatpage.title and flatpage.content are marked as not
requiring automatic HTML escaping in the
template.

Getting a list of FlatPage objects in your templates¶

The flatpages app provides a template tag that allows you to iterate
over all of the available flatpages on the current site.

Like all custom template tags, you’ll need to load its custom
tag library
before you can use
it. After loading the library, you can retrieve all current flatpages
via the get_flatpages tag:

{% load flatpages %}
{% get_flatpages as flatpages %}
<ul>
    {% for page in flatpages %}
        <li><a href="{{ page.url }}">{{ page.title }}</a></li>
    {% endfor %}
</ul>

Displaying registration_required flatpages¶

By default, the get_flatpages template tag will only show
flatpages that are marked registration_required = False. If you
want to display registration-protected flatpages, you need to specify
an authenticated user using a for clause.

For example:

{% get_flatpages for someuser as about_pages %}

If you provide an anonymous user, get_flatpages will behave
the same as if you hadn’t provided a user — i.e., it will only show you
public flatpages.

Limiting flatpages by base URL¶

An optional argument, starts_with, can be applied to limit the
returned pages to those beginning with a particular base URL. This
argument may be passed as a string, or as a variable to be resolved
from the context.

For example:

{% get_flatpages '/about/' as about_pages %}
{% get_flatpages about_prefix as about_pages %}
{% get_flatpages '/about/' for someuser as about_pages %}

Integrating with django.contrib.sitemaps¶

class FlatPageSitemap[source]

The sitemaps.FlatPageSitemap class looks at all
publicly visible flatpages defined for the current
SITE_ID (see the sites documentation) and creates an entry in the sitemap. These entries
include only the location
attribute — not lastmod,
changefreq or
priority.

Example¶

Here’s an example of a URLconf using FlatPageSitemap:

from django.contrib.flatpages.sitemaps import FlatPageSitemap
from django.contrib.sitemaps.views import sitemap
from django.urls import path

urlpatterns = [
    # ...

    # the sitemap
    path('sitemap.xml', sitemap,
        {'sitemaps': {'flatpages': FlatPageSitemap}},
        name='django.contrib.sitemaps.views.sitemap'),
]