Determine if a URL is a Feed

Question

Possible Duplicate:
How To Discover RSS Feeds for a given URL

Given a URL, I'd like to know whether it's a feed or not.

In Zend Framework, it is possible to import a URL as a feed:

try {
    $slashdotRss =
        Zend_Feed::import('http://rss.slashdot.org/Slashdot/slashdot');
} catch (Zend_Feed_Exception $e) {
    // feed import failed
    echo "Exception caught importing feed: {$e->getMessage()}\n";
    exit;
}

And if an exception is thrown, then I know the URL is not a feed.

I would like to do the same algorithm in Java, so my question is: How does Zend know whether a URL is a feed or not ?

Answer 1

What I'd do is get it to rome and try to parse it. If it fails to parse, it will throw a FeedException:

public boolean tryFeed(String feedUrl) throws IOException,MalformedURLException { 
    SyndFeedInput input = new SyndFeedInput();
    SyndFeed feed = null;
    try {
        feed = input.build(new XmlReader(new URL(feedUrl)));
        return true;
    } catch (FeedException e) {
        // Feed's invalid
        return false;
    }

}