XML feed generation

For blog reader's search and syndication, a blog needs to produce an RSS feed. RSS is an XML specification that lists blog posts in a specified format as separate items that are simple to process.

To produce the feed for the blog, posts can easily be iterated as we already have a list of IDs. To produce a valid XML feed, the xml package will be used. This is not part of the SDK and is an open source library, which has become a favorite for XML creation and processing in Dart. There was at one time an XML processing package in the SDK, but the xml package was improved so quickly that it made more sense to make it the standard package. Let's have a look at the following code snippet for more information:

  String getRSSFeed() {
    var RssXb = new XmlBuilder();
    RssXb.processing('xml', 'version="1.0"');

    RssXb.element('rss', attributes: {'version': '1.0'}, nest: () {
      RssXb.element('channel', nest: () {
        IDs.forEach((int postID) {
          BlogPost post = getBlogPost(postID);
          RssXb.element('item', nest: () {
            RssXb.element('pubDate', nest: () {
              RssXb.text(post._date);
            });
            RssXb.element('title', nest: () {
              RssXb.text(post._title);
            });
            RssXb.element('link', nest: () {
              RssXb.text("http://127.0.0.1:8080/post${post._id}.html");
            });
          }); //item
        });
      }); //channel
    }); //rss

    var xml = RssXb.build();
    return xml.toXmlString(pretty: true);
  }

Elements are added in a nested fashion here, which reflects the RSS structure. Once the data structure is put together, the build method constructs the XML structure, and finally, it is converted into a string.

As it will be viewed by human beings as well as computers, the optional name parameter option pretty is set to true for a neatly formatted output, as shown in the following example:

<?xml version="1.0"?>
<rss version="1.0">
  <channel>
    <item>
      <pubDate>02/05/2015</pubDate>
      <title>Lemur Facts</title>
      <link>http://127.0.0.1:8080/post6.html</link>
    </item>
...

  void _serveRSSFeed(HttpRequest request) {
    request.response
      ..statusCode = HttpStatus.OK
      ..headers.set('Content-Type', 'application/rss+xml')
      ..write(hostedBlog.getRSSfeed())
      ..close();
  }