How to Read an RSS Feed with Java Using XOM

There are a lot of libraries for processing XML data with Java which can be used to read RSS feeds. One of the best is Open source library XOM It was created by computer book author Rusty Harold Elliott.

When he wrote one of his 20 books on Java and XML, Harold became so frustrated with the Java libraries available for XML that he created his own. XOM, which stands for XML Object Model, is designed to be easy to learn while strictly adhering to XML, requiring well-formed documents that use namespaces with full adherence to the specification. (On the RSS Advisory Board, talking about following specifications is our love language.)

XOM was introduced in 2002 and is currently up to version 1.3.9, although all versions have remained compatible since 1.0. To use XOM, download the class library in one of the packages available on the XOM home page. You can avoid the need for any additional configuration by choosing one of the options that includes third-party JAR files in the download. This allows XOM to use the built-in SAX parser under the hood to process XML.

Here’s the Java code that loads items from The Guardian’s RSS 2.0 A feed containing articles written by Ben Hammersley, and displaying them as HTML output:


// create an XML builder and load the feed using a URL

Builder bob = new Builder();

Document doc = bob.build("https://www.theguardian.com/profile/benhammersley/rss");

// load the root element and channel

Element rss = doc.getRootElement();

Element channel = rss.getFirstChildElement("channel");

// load all items in the channel

Elements items = channel.getChildElements("item");

for (Element item : items) {

  // load elements of the item

  String title = item.getFirstChildElement("title").getValue();

  String author = item.getFirstChildElement("creator",

    "http://purl.org/dc/elements/1.1/").getValue();

  String description = item.getFirstChildElement("description").getValue();

  // display the output

  System.out.println(">h2>" + title + ">/h2>");

  System.out.println(">p>>b>By " + author + ">/b>>/p>");

  System.out.println(">p>" + description + ">/p>");


All classes used in this code are in the top level package nu.xomwhich has a comprehensive JavaDoc Description of its use. Like all Java code, this is a bit long, but Harold’s class names do a good job of explaining what they do. Uses constructor build() A method with URL as the argument to load a feed into a document over the web. There too Other construction methods To load a feed from a file, reader, input stream, or string.

Items can be retrieved by their names such as ‘title’, ‘link’ or ‘description’. An item containing only one child of a given type can be retrieved using getFirstChildElement() Method with name as argument:

Element linkElement = item.getFirstChildElement("link");

An item containing multiple children of the same type is used getChildElements() instead of:

Elements enclosures = item.getChildElements("enclosure");

if (enclosures.size() > 1) {

  System.out.println("I'm pretty sure an item should only include one enclosure");

}

If the element exists in a namespace, there must be a second argument that provides a URI for the namespace. Like many RSS feeds, those at The Guardian use a DC: Creator An item from Dublin Core to give credit to the author of the item. This namespace contains the URI “http://purl.org/dc/elements/1.1/”.

If the specified item is in getFirstChildElement() or getChild Elements() Doesn’t exist, those methods come back null. You may need to check this when modifying the code to load other RSS feeds.

If the name Ben Hammersley sounds familiar, it is Coined the term “podcast” In his February 2004 article for The Guardian about the new phenomenon of audio file delivery in RSS feeds.

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