Category Archives: Syndication

Interface Design, Syndication, XML

RSS, Processing Instructions and Firefox 2.0

Leave a comment

A couple weeks ago I posted an article that describes how you can use XML stylesheets with ROME to create RSS / Atom feeds that are ‘user friendly’ (like the ones that FeedBurner produces). Firefox 2.0, released just this past week, has a new feature which renders my article moot. The “Previewing and subscribing to Web feeds” feature, is a good one for most non technical users: click on a link that results in an RSS feed and Firefox will recognize the RSS content type and show you the RSS styled with their own style sheet even if the feed has provided a style sheet. The current workaround, should you want your visitors to see your style sheet instead of the default Firefox 2.0 stylesheet, is to

“…put in a comment ranting about the evils of sniffing web content and overriding the desires of web developers which is long enough to move “<rss” or “<feed” out of the first 512 bytes, since that’s all we sniff.”
(source)

There’s an extremely lively discussion going on in the mozilla.dev.apps.firefox newsgroup and on bugzilla about this behavior.

More here, here, here, here and here.

Blogs, Interface Design, J2EE, Syndication, XML

XSL / CSS Processing Instructions using ROME

3 Comments

Have you seen the way that the smart guys at FeedBurner display RSS feeds in a browser (here’s a sample if you haven’t)? If you’re like me, the first time you see a feed they manage, you’ll probably think that you’re viewing a page that contains a link to an RSS or ATOM feed, not the actual feed. In fact what you’re seeing is the feed transformed by your browser using XSL and CSS. Take a peek at the source and you’ll see that the XSL and CSS transformations are produced by what are technically called processing instructions. I won’t go into the work that they’ve done to create that look (but if you poke around the source it’s not trivial), but the inclusion of the processing instruction… now that’s something I can help you out with. I’ve used ROME on a couple different projects now because it is trivial to create RSS, RSS2 or ATOM feeds with only a couple lines of code. There are a number of tutorials up on the ROME site that show you how to create a feed and then write to a String, a File or a Writer which you should check out if you don’t have any experience with ROME. Assuming that you do however and given that you have a feed (technically a SyndFeed in ROME), you would write it out in a servlet like this:

SyndFeedOutput output = new SyndFeedOutput();
output.output(feed, response.getWriter());

ROME abstracts you from having to work directly with an XML document, which is handy most of the time. But if you want to add a processing instruction to style your feed, it takes a little fiddling with the source. If you peek at the source of SyndFeedOutput, you’ll see that it wraps WireFeedOutput. WireFeedOutput uses a JDOM Document and the XMLOutputter class to create write the feed. Conveniently, the Document class has methods for adding processing instructions, in fact it has a ProcessingInstruction class. Putting all these things together, you’d get this if you were creating the RSS feeds for FeedBurner using ROME:

WireFeedOutput feedOutput = new WireFeedOutput();
Document doc = feedOutput.outputJDom(feed.createWireFeed());
// create the XSL processing instruction
Map xsl = new HashMap();
xsl.put("href", "http://feeds.feedburner.com/~d/styles/rss2full.xsl");
xsl.put("type", "text/xsl");
xsl.put("media", "screen");
ProcessingInstruction pXsl = new ProcessingInstruction("xml-stylesheet", xsl);
doc.addContent(0, pXsl);
// create the CSS processing instruction
Map css = new HashMap();
css.put("href", "http://feeds.feedburner.com/~d/styles/itemcontent.css");
css.put("type", "text/css");
css.put("media", "screen");
ProcessingInstruction pCss = new ProcessingInstruction("xml-stylesheet", css);
doc.addContent(1, pCss);
// write the document to the servlet response
XMLOutputter outputter = new XMLOutputter(format);
outputter.output(doc,response.getWriter());

So now that I’ve made that easy for you, who’s going to show me the website that has a bunch of easy to use CSS and XSL templates for transforming RSS and ATOM feeds? Better yet, when are browsers going to have this kind of logic baked in so that my mom doesn’t have to look at an RSS feed that looks like a bunch of gobbly gook XML?