Django带有一个高聚合的框架让创造RSS 和 Atom更容易。
创建聚合feed，你要做的仅仅是写一个简短的Python类。你想要创造多少，就能创造多少feeds。
Django 也带有一个低等级的生成feed的API。如果你想要生成一个外部的Web内容或者其他普通的方式，你可以使用它。
一个 Feed类就是一个提供聚合种子的Python类。一个简单的种子（例如新闻的信息种子，或者只展示博客最新消息）更多功能的种子（例如展示博客中允许展示的特定类别的条目）。
Feed类继承自django.contrib.syndication.views.Feed。它们可以在你代码中的任意一处。
这个简单的示例，演示了某站点的最近五条新闻的记录：
from django.contrib.syndication.views import Feed
from django.core.urlresolvers import reverse
from policebeat.models import NewsItem
class LatestEntriesFeed(Feed):
title = "Police beat site news"
link = "/sitenews/"
description = "Updates on changes and additions to police beat central."
def items(self):
return NewsItem.objects.order_by('-pub_date')[:5]
def item_title(self, item):
return item.title
def item_description(self, item):
return item.description
# item_link is only needed if NewsItem has no get_absolute_url method.
def item_link(self, item):
return reverse('news-item', args=[item.pk])
配置一个URL到这个feed，在URLconf中配置一个入口。例如:
from django.conf.urls import url
from myproject.feeds import LatestEntriesFeed
urlpatterns = [
# ...
url(r'^latest/feed/$', LatestEntriesFeed()),
# ...
]
注意:
还有一件事没做。在一个 RSS feed中, 每一个 <item> 都有一个<title>, <link> 和<description>. 我们需要告诉框架那些数据放进这些对象中。
在 <title>和<description>的内容中，Django尝试着在Feed类中召集item_title()和item_description()方法。他们会传入一个自己内部的单独的参数 item。这些都是可选的; 默认的是，unicode表示的对象都被使用了
如果你想要做一些特殊的格式化title或者description，Django templates可以帮助你。他们的路径会被Feed类中的title_template和description_template 参数做特殊处理。会通过模板内容的两个变量来返回每一条记录到模板中：
从下方的 a complex example 使用一个描述的模板。
There is also a way to pass additional information to title and description templates, if you need to supply more than the two variables mentioned before. You can provide your implementation of get_context_data method in your Feed subclass. 例如:
from mysite.models import Article
from django.contrib.syndication.views import Feed
class ArticlesFeed(Feed):
title = "My articles"
description_template = "feeds/articles.html"
def items(self):
return Article.objects.order_by('-pub_date')[:5]
def get_context_data(self, **kwargs):
context = super(ArticlesFeed, self).get_context_data(**kwargs)
context['foo'] = 'bar'
return context
And the template:
Something about {{ foo }}: {{ obj.description }}
This method will be called once per each item in the list returned by items() with the following keyword arguments:
The behavior of get_context_data() mimics that of generic views - you’re supposed to call super() to retrieve context data from parent class, add your data and return the modified dictionary.
To specify the contents of <link>, you have two options. For each item in items(), Django first tries calling the item_link() method on the Feed class. In a similar way to the title and description, it is passed it a single parameter, item. If that method doesn’t exist, Django tries executing a get_absolute_url() method on that object. Both get_absolute_url() and item_link() should return the item’s URL as a normal Python string. As with get_absolute_url(), the result of item_link() will be included directly in the URL, so you are responsible for doing all necessary URL quoting and conversion to ASCII inside the method itself.
The framework also supports more complex feeds, via arguments.
For example, a website could offer an RSS feed of recent crimes for every police beat in a city. It’d be silly to create a separate Feed class for each police beat; that would violate the DRY principle and would couple data to programming logic. Instead, the syndication framework lets you access the arguments passed from your URLconf so feeds can output items based on information in the feed’s URL.
The police beat feeds could be accessible via URLs like this:
These can be matched with a URLconf line such as:
url(r'^beats/(?P<beat_id>[0-9]+)/rss/$', BeatFeed()),
Like a view, the arguments in the URL are passed to the get_object() method along with the request object.
Here’s the code for these beat-specific feeds:
from django.contrib.syndication.views import FeedDoesNotExist
from django.shortcuts import get_object_or_404
class BeatFeed(Feed):
description_template = 'feeds/beat_description.html'
def get_object(self, request, beat_id):
return get_object_or_404(Beat, pk=beat_id)
def title(self, obj):
return "Police beat central: Crimes for beat %s" % obj.beat
def link(self, obj):
return obj.get_absolute_url()
def description(self, obj):
return "Crimes recently reported in police beat %s" % obj.beat
def items(self, obj):
return Crime.objects.filter(beat=obj).order_by('-crime_date')[:30]
To generate the feed’s <title>, <link> and <description>, Django uses the title(), link() and description() methods. In the previous example, they were simple string class attributes, but this example illustrates that they can be either strings or methods. For each of title, link and description, Django follows this algorithm:
Also note that items() also follows the same algorithm – first, it tries items(obj), then items(), then finally an items class attribute (which should be a list).
We are using a template for the item descriptions. It can be very simple:
{{ obj.description }}
However, you are free to add formatting as desired.
The ExampleFeed class below gives full documentation on methods and attributes of Feed classes.
By default, feeds produced in this framework use RSS 2.0.
To change that, add a feed_type attribute to your Feed class, like so:
from django.utils.feedgenerator import Atom1Feed
class MyFeed(Feed):
feed_type = Atom1Feed
Note that you set feed_type to a class object, not an instance.
Currently available feed types are:
To specify enclosures, such as those used in creating podcast feeds, use the item_enclosure_url, item_enclosure_length and item_enclosure_mime_type hooks. See the ExampleFeed class below for usage examples.
Feeds created by the syndication framework automatically include the appropriate <language> tag (RSS 2.0) or xml:lang attribute (Atom). This comes directly from your LANGUAGE_CODE setting.
The link method/attribute can return either an absolute path (e.g. "/blog/") or a URL with the fully-qualified domain and protocol (e.g. "http://www.example.com/blog/"). If link doesn’t return the domain, the syndication framework will insert the domain of the current site, according to your SITE_ID setting.
Atom feeds require a <link rel="self"> that defines the feed’s current location.
Some developers like to make available both Atom and RSS versions of their feeds. That’s easy to do with Django: Just create a subclass of your Feed class and set the feed_type to something different. Then update your URLconf to add the extra versions.
Here’s a full example:
from django.contrib.syndication.views import Feed
from policebeat.models import NewsItem
from django.utils.feedgenerator import Atom1Feed
class RssSiteNewsFeed(Feed):
title = "Police beat site news"
link = "/sitenews/"
description = "Updates on changes and additions to police beat central."
def items(self):
return NewsItem.objects.order_by('-pub_date')[:5]
class AtomSiteNewsFeed(RssSiteNewsFeed):
feed_type = Atom1Feed
subtitle = RssSiteNewsFeed.description
Note
In this example, the RSS feed uses a description while the Atom feed uses a subtitle. That’s because Atom feeds don’t provide for a feed-level “description,” but they do provide for a “subtitle.”
If you provide a description in your Feed class, Django will not automatically put that into the subtitle element, because a subtitle and description are not necessarily the same thing. Instead, you should define a subtitle attribute.
In the above example, we simply set the Atom feed’s subtitle to the RSS feed’s description, because it’s quite short already.
And the accompanying URLconf:
from django.conf.urls import url
from myproject.feeds import RssSiteNewsFeed, AtomSiteNewsFeed
urlpatterns = [
# ...
url(r'^sitenews/rss/$', RssSiteNewsFeed()),
url(r'^sitenews/atom/$', AtomSiteNewsFeed()),
# ...
]
This example illustrates all possible attributes and methods for a Feed class:
from django.contrib.syndication.views import Feed
from django.utils import feedgenerator
class ExampleFeed(Feed):
# FEED TYPE -- Optional. This should be a class that subclasses
# django.utils.feedgenerator.SyndicationFeed. This designates
# which type of feed this should be: RSS 2.0, Atom 1.0, etc. If
# you don't specify feed_type, your feed will be RSS 2.0. This
# should be a class, not an instance of the class.
feed_type = feedgenerator.Rss201rev2Feed
# TEMPLATE NAMES -- Optional. These should be strings
# representing names of Django templates that the system should
# use in rendering the title and description of your feed items.
# Both are optional. If a template is not specified, the
# item_title() or item_description() methods are used instead.
title_template = None
description_template = None
# TITLE -- One of the following three is required. The framework
# looks for them in this order.
def title(self, obj):
"""
Takes the object returned by get_object() and returns the
feed's title as a normal Python string.
"""
def title(self):
"""
Returns the feed's title as a normal Python string.
"""
title = 'foo' # Hard-coded title.
# LINK -- One of the following three is required. The framework
# looks for them in this order.
def link(self, obj):
"""
# Takes the object returned by get_object() and returns the URL
# of the HTML version of the feed as a normal Python string.
"""
def link(self):
"""
Returns the URL of the HTML version of the feed as a normal Python
string.
"""
link = '/blog/' # Hard-coded URL.
# FEED_URL -- One of the following three is optional. The framework
# looks for them in this order.
def feed_url(self, obj):
"""
# Takes the object returned by get_object() and returns the feed's
# own URL as a normal Python string.
"""
def feed_url(self):
"""
Returns the feed's own URL as a normal Python string.
"""
feed_url = '/blog/rss/' # Hard-coded URL.
# GUID -- One of the following three is optional. The framework looks
# for them in this order. This property is only used for Atom feeds
# (where it is the feed-level ID element). If not provided, the feed
# link is used as the ID.
def feed_guid(self, obj):
"""
Takes the object returned by get_object() and returns the globally
unique ID for the feed as a normal Python string.
"""
def feed_guid(self):
"""
Returns the feed's globally unique ID as a normal Python string.
"""
feed_guid = '/foo/bar/1234' # Hard-coded guid.
# DESCRIPTION -- One of the following three is required. The framework
# looks for them in this order.
def description(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
description as a normal Python string.
"""
def description(self):
"""
Returns the feed's description as a normal Python string.
"""
description = 'Foo bar baz.' # Hard-coded description.
# AUTHOR NAME --One of the following three is optional. The framework
# looks for them in this order.
def author_name(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
author's name as a normal Python string.
"""
def author_name(self):
"""
Returns the feed's author's name as a normal Python string.
"""
author_name = 'Sally Smith' # Hard-coded author name.
# AUTHOR EMAIL --One of the following three is optional. The framework
# looks for them in this order.
def author_email(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
author's email as a normal Python string.
"""
def author_email(self):
"""
Returns the feed's author's email as a normal Python string.
"""
author_email = 'test@example.com' # Hard-coded author email.
# AUTHOR LINK --One of the following three is optional. The framework
# looks for them in this order. In each case, the URL should include
# the "http://" and domain name.
def author_link(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
author's URL as a normal Python string.
"""
def author_link(self):
"""
Returns the feed's author's URL as a normal Python string.
"""
author_link = 'http://www.example.com/' # Hard-coded author URL.
# CATEGORIES -- One of the following three is optional. The framework
# looks for them in this order. In each case, the method/attribute
# should return an iterable object that returns strings.
def categories(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
categories as iterable over strings.
"""
def categories(self):
"""
Returns the feed's categories as iterable over strings.
"""
categories = ("python", "django") # Hard-coded list of categories.
# COPYRIGHT NOTICE -- One of the following three is optional. The
# framework looks for them in this order.
def feed_copyright(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
copyright notice as a normal Python string.
"""
def feed_copyright(self):
"""
Returns the feed's copyright notice as a normal Python string.
"""
feed_copyright = 'Copyright (c) 2007, Sally Smith' # Hard-coded copyright notice.
# TTL -- One of the following three is optional. The framework looks
# for them in this order. Ignored for Atom feeds.
def ttl(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
TTL (Time To Live) as a normal Python string.
"""
def ttl(self):
"""
Returns the feed's TTL as a normal Python string.
"""
ttl = 600 # Hard-coded Time To Live.
# ITEMS -- One of the following three is required. The framework looks
# for them in this order.
def items(self, obj):
"""
Takes the object returned by get_object() and returns a list of
items to publish in this feed.
"""
def items(self):
"""
Returns a list of items to publish in this feed.
"""
items = ('Item 1', 'Item 2') # Hard-coded items.
# GET_OBJECT -- This is required for feeds that publish different data
# for different URL parameters. (See "A complex example" above.)
def get_object(self, request, *args, **kwargs):
"""
Takes the current request and the arguments from the URL, and
returns an object represented by this feed. Raises
django.core.exceptions.ObjectDoesNotExist on error.
"""
# ITEM TITLE AND DESCRIPTION -- If title_template or
# description_template are not defined, these are used instead. Both are
# optional, by default they will use the unicode representation of the
# item.
def item_title(self, item):
"""
Takes an item, as returned by items(), and returns the item's
title as a normal Python string.
"""
def item_title(self):
"""
Returns the title for every item in the feed.
"""
item_title = 'Breaking News: Nothing Happening' # Hard-coded title.
def item_description(self, item):
"""
Takes an item, as returned by items(), and returns the item's
description as a normal Python string.
"""
def item_description(self):
"""
Returns the description for every item in the feed.
"""
item_description = 'A description of the item.' # Hard-coded description.
def get_context_data(self, **kwargs):
"""
Returns a dictionary to use as extra context if either
description_template or item_template are used.
Default implementation preserves the old behavior
of using {'obj': item, 'site': current_site} as the context.
"""
# ITEM LINK -- One of these three is required. The framework looks for
# them in this order.
# First, the framework tries the two methods below, in
# order. Failing that, it falls back to the get_absolute_url()
# method on each item returned by items().
def item_link(self, item):
"""
Takes an item, as returned by items(), and returns the item's URL.
"""
def item_link(self):
"""
Returns the URL for every item in the feed.
"""
# ITEM_GUID -- The following method is optional. If not provided, the
# item's link is used by default.
def item_guid(self, obj):
"""
Takes an item, as return by items(), and returns the item's ID.
"""
# ITEM_GUID_IS_PERMALINK -- The following method is optional. If
# provided, it sets the 'isPermaLink' attribute of an item's
# GUID element. This method is used only when 'item_guid' is
# specified.
def item_guid_is_permalink(self, obj):
"""
Takes an item, as returned by items(), and returns a boolean.
"""
item_guid_is_permalink = False # Hard coded value
# ITEM AUTHOR NAME -- One of the following three is optional. The
# framework looks for them in this order.
def item_author_name(self, item):
"""
Takes an item, as returned by items(), and returns the item's
author's name as a normal Python string.
"""
def item_author_name(self):
"""
Returns the author name for every item in the feed.
"""
item_author_name = 'Sally Smith' # Hard-coded author name.
# ITEM AUTHOR EMAIL --One of the following three is optional. The
# framework looks for them in this order.
#
# If you specify this, you must specify item_author_name.
def item_author_email(self, obj):
"""
Takes an item, as returned by items(), and returns the item's
author's email as a normal Python string.
"""
def item_author_email(self):
"""
Returns the author email for every item in the feed.
"""
item_author_email = 'test@example.com' # Hard-coded author email.
# ITEM AUTHOR LINK -- One of the following three is optional. The
# framework looks for them in this order. In each case, the URL should
# include the "http://" and domain name.
#
# If you specify this, you must specify item_author_name.
def item_author_link(self, obj):
"""
Takes an item, as returned by items(), and returns the item's
author's URL as a normal Python string.
"""
def item_author_link(self):
"""
Returns the author URL for every item in the feed.
"""
item_author_link = 'http://www.example.com/' # Hard-coded author URL.
# ITEM ENCLOSURE URL -- One of these three is required if you're
# publishing enclosures. The framework looks for them in this order.
def item_enclosure_url(self, item):
"""
Takes an item, as returned by items(), and returns the item's
enclosure URL.
"""
def item_enclosure_url(self):
"""
Returns the enclosure URL for every item in the feed.
"""
item_enclosure_url = "/foo/bar.mp3" # Hard-coded enclosure link.
# ITEM ENCLOSURE LENGTH -- One of these three is required if you're
# publishing enclosures. The framework looks for them in this order.
# In each case, the returned value should be either an integer, or a
# string representation of the integer, in bytes.
def item_enclosure_length(self, item):
"""
Takes an item, as returned by items(), and returns the item's
enclosure length.
"""
def item_enclosure_length(self):
"""
Returns the enclosure length for every item in the feed.
"""
item_enclosure_length = 32000 # Hard-coded enclosure length.
# ITEM ENCLOSURE MIME TYPE -- One of these three is required if you're
# publishing enclosures. The framework looks for them in this order.
def item_enclosure_mime_type(self, item):
"""
Takes an item, as returned by items(), and returns the item's
enclosure MIME type.
"""
def item_enclosure_mime_type(self):
"""
Returns the enclosure MIME type for every item in the feed.
"""
item_enclosure_mime_type = "audio/mpeg" # Hard-coded enclosure MIME type.
# ITEM PUBDATE -- It's optional to use one of these three. This is a
# hook that specifies how to get the pubdate for a given item.
# In each case, the method/attribute should return a Python
# datetime.datetime object.
def item_pubdate(self, item):
"""
Takes an item, as returned by items(), and returns the item's
pubdate.
"""
def item_pubdate(self):
"""
Returns the pubdate for every item in the feed.
"""
item_pubdate = datetime.datetime(2005, 5, 3) # Hard-coded pubdate.
# ITEM UPDATED -- It's optional to use one of these three. This is a
# hook that specifies how to get the updateddate for a given item.
# In each case, the method/attribute should return a Python
# datetime.datetime object.
def item_updateddate(self, item):
"""
Takes an item, as returned by items(), and returns the item's
updateddate.
"""
def item_updateddate(self):
"""
Returns the updateddated for every item in the feed.
"""
item_updateddate = datetime.datetime(2005, 5, 3) # Hard-coded updateddate.
# ITEM CATEGORIES -- It's optional to use one of these three. This is
# a hook that specifies how to get the list of categories for a given
# item. In each case, the method/attribute should return an iterable
# object that returns strings.
def item_categories(self, item):
"""
Takes an item, as returned by items(), and returns the item's
categories.
"""
def item_categories(self):
"""
Returns the categories for every item in the feed.
"""
item_categories = ("python", "django") # Hard-coded categories.
# ITEM COPYRIGHT NOTICE (only applicable to Atom feeds) -- One of the
# following three is optional. The framework looks for them in this
# order.
def item_copyright(self, obj):
"""
Takes an item, as returned by items(), and returns the item's
copyright notice as a normal Python string.
"""
def item_copyright(self):
"""
Returns the copyright notice for every item in the feed.
"""
item_copyright = 'Copyright (c) 2007, Sally Smith' # Hard-coded copyright notice.
Behind the scenes, the high-level RSS framework uses a lower-level framework for generating feeds’ XML. This framework lives in a single module: django/utils/feedgenerator.py.
You use this framework on your own, for lower-level feed generation. You can also create custom feed generator subclasses for use with the feed_type Feed option.
The feedgenerator module contains a base class:
and several subclasses:
Each of these three classes knows how to render a certain type of feed as XML. They share this interface:
Initialize the feed with the given dictionary of metadata, which applies to the entire feed. Required keyword arguments are:
There’s also a bunch of other optional keywords:
Any extra keyword arguments you pass to __init__ will be stored in self.feed for use with custom feed generators.
All parameters should be Unicode objects, except categories, which should be a sequence of Unicode objects.
Add an item to the feed with the given parameters.
Required keyword arguments are:
Optional keyword arguments are:
Extra keyword arguments will be stored for custom feed generators.
All parameters, if given, should be Unicode objects, except:
The optional updateddate argument was added.
For example, to create an Atom 1.0 feed and print it to standard output:
>>> from django.utils import feedgenerator
>>> from datetime import datetime
>>> f = feedgenerator.Atom1Feed(
... title="My Weblog",
... link="http://www.example.com/",
... description="In which I write about what I ate today.",
... language="en",
... author_name="Myself",
... feed_url="http://example.com/atom.xml")
>>> f.add_item(title="Hot dog today",
... link="http://www.example.com/entries/1/",
... pubdate=datetime.now(),
... description="<p>Today I had a Vienna Beef hot dog. It was pink, plump and perfect.</p>")
>>> print(f.writeString('UTF-8'))
<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en">
...
</feed>
If you need to produce a custom feed format, you’ve got a couple of options.
If the feed format is totally custom, you’ll want to subclass SyndicationFeed and completely replace the write() and writeString() methods.
However, if the feed format is a spin-off of RSS or Atom (i.e. GeoRSS, Apple’s iTunes podcast format, etc.), you’ve got a better choice. These types of feeds typically add extra elements and/or attributes to the underlying format, and there are a set of methods that SyndicationFeed calls to get these extra attributes. Thus, you can subclass the appropriate feed generator class (Atom1Feed or Rss201rev2Feed) and extend these callbacks. They are:
Warning
If you override any of these methods, be sure to call the superclass methods since they add the required elements for each feed format.
For example, you might start implementing an iTunes RSS feed generator like so:
class iTunesFeed(Rss201rev2Feed):
def root_attributes(self):
attrs = super(iTunesFeed, self).root_attributes()
attrs['xmlns:itunes'] = 'http://www.itunes.com/dtds/podcast-1.0.dtd'
return attrs
def add_root_elements(self, handler):
super(iTunesFeed, self).add_root_elements(handler)
handler.addQuickElement('itunes:explicit', 'clean')
Obviously there’s a lot more work to be done for a complete custom feed class, but the above example should demonstrate the basic idea.
May 13, 2015