# Django 2.2.9.dev20191202104323 文档

# The redirects app

Django comes with an optional redirects application. It lets you store simple redirects in a database and handles the redirecting for you. It uses the HTTP response status code `301 Moved Permanently` by default.

## 安装

To install the redirects app, follow these steps:

1. Ensure that the `django.contrib.sites` framework is installed.
2. Add `'django.contrib.redirects'` to your `INSTALLED_APPS` setting.
3. Add `'django.contrib.redirects.middleware.RedirectFallbackMiddleware'` to your `MIDDLEWARE` setting.
4. Run the command `manage.py migrate`.

## How it works

`manage.py migrate` creates a `django_redirect` table in your database. This is a simple lookup table with `site_id`, `old_path` and `new_path` fields.

The `RedirectFallbackMiddleware` does all of the work. Each time any Django application raises a 404 error, this middleware checks the redirects database for the requested URL as a last resort. Specifically, it checks for a redirect with the given `old_path` with a site ID that corresponds to the `SITE_ID` setting.

- If it finds a match, and `new_path` is not empty, it redirects to `new_path` using a 301 ("Moved Permanently") redirect. You can subclass `RedirectFallbackMiddleware` and set `response_redirect_class` to `django.http.HttpResponseRedirect` to use a `302 Moved Temporarily` redirect instead.
- If it finds a match, and `new_path` is empty, it sends a 410 ("Gone") HTTP header and empty (content-less) response.
- 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.

Note that the order of `MIDDLEWARE` matters. Generally, you can put `RedirectFallbackMiddleware` at the end of the list, because it's a last resort.

For more on middleware, read the middleware docs.

## How to add, change and delete redirects

### Via the admin interface

If you've activated the automatic Django admin interface, you should see a "Redirects" section on the admin index page. Edit redirects as you edit any other object in the system.

### Via the Python API

class `models.``Redirect`

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

## 中间件

class `middleware.``RedirectFallbackMiddleware`

  You can change the `HttpResponse` classes used by the middleware by creating a subclass of `RedirectFallbackMiddleware` and overriding `response_gone_class` and/or `response_redirect_class`.

  `response_gone_class`

    The `HttpResponse` class used when a `Redirect` is not found for the requested path or has a blank `new_path` value.

    Defaults to `HttpResponseGone`.

  `response_redirect_class`

    The `HttpResponse` class that handles the redirect.

    Defaults to `HttpResponsePermanentRedirect`.