Reading and Writing RSS Feeds - Java 6 - page 513

This statement creates an object for the root element of the document, rss . Element 's
one-argument constructor can be used because the document does not employ a feature
of XML called namespaces; if it did, a second argument would be necessary: the name-
space uniform resource identifier (URI) of the element. The other classes in the XOM
library support namespaces in a similar manner.

In the XML document in Listing 19.2, the rss element includes an attribute named ver-
sion with the value “2.0”. An attribute can be created by specifying its name and value
in consecutive arguments:

Attribute version = new Attribute(“version”, “2.0”);

Attributes are added to an element by calling its addAttribute() method with the
attribute as the only argument:

rss.addAttribute(version);

The text contained within an element is represented by the Text class, which is con-
structed by specifying the text as a String argument:

Text titleText = new Text(“Workbench”);

When composing an XML document, all of its elements end up inside a root element
that is used to create a Document object—a Document constructor is called with the root
element as an argument. In the RssStarter application, this element is called rss . Any
Element object can be the root of a document:

Document doc = new Document(rss);

In XOM's tree structure, the classes representing an XML document and its constituent
parts are organized into a hierarchy below the generic superclass nu.xom.Node . This
class has three subclasses in the same package: Attribute , LeafNode , and ParentNode .

19

To add a child to a parent node, call the parent's appendChild() method with the node to
add as the only argument. The following code creates three elements—a parent called
domain and two of its children, name and dns :

Element channel = new Element(“channel”);
Element link = new Element(“link”);
Text linkText = new Text(“http://www.cadenhead.org/workbench/”);
link.appendChild(linkText);
channel.appendChild(link);