Reading and Writing RSS Feeds - Java 6 - page 516

The Builder() and Builder(true) constructors both use the default parser—most likely
a version of Xerces. The presence of the Boolean argument true in the second construc-
tor configures the parser to be validating. It would be nonvalidating otherwise. A validat-
ing parser throws a nu.xom.ValidityException if the XML document doesn't validate
according to the rules of its document type definition.
The Builder object's build() method loads an XML document from a source and
returns a Document object:
Builder builder = new Builder();
File xmlFile = new File(“feed.rss”);
Document doc = builder.build(xmlFile);
These statements load an XML document from the file feed.rss barring one of two
problems: A nu.xom.ParseException is thrown if the file does not contain well-formed
XML, and a java.io.IOException is thrown if the input operation fails.
Elements are retrieved from the tree by calling a method of their parent node.
A Document object's getRootElement() method returns the root element of the docu-
ment:
Element root = doc.getRootElement();
In the XML document feed.rss , the root element is domains .
Elements with names can be retrieved by calling their parent node's
getFirstChildElement() method with the name as a String argument:
Element channel = root.getFirstChildElement(“channel”);
This statement retrieves the channel element contained in the rss element (or null if
that element could not be found). Like other examples, this is simplified by the lack of a
namespace in the document; there are also methods where a name and namespace are
arguments.
When several elements within a parent have the same name, the parent node's
getChildElements() method can be used instead:
Elements children = channel.getChildElements()
The getChildElements() method returns an Elements object containing each of the ele-
ments. This object is a read-only list and does not change automatically if the parent
node's contents change after getChildElements() is called.
Elements has a size() method containing an integer count of the elements it holds. This
can be used in a loop to cycle through each element in turn beginning with the one at