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Custom complex filters for selecting nodes |
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Except bit-masks identifying the node-types to shows during traverse the DOM-tree,
both iterator and walker allows to use user-defined node filters.
Such a filters can performs more complex actions in order to decide should the node
be passed or not.
The sample below shows element-name based filter usage:
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.traversal.DocumentTraversal;
import org.w3c.dom.traversal.NodeFilter;
import org.w3c.dom.traversal.NodeIterator;
import org.w3c.dom.*;
/**
* This sample program using tree-walker for
* non-linear traverse of DOM-document.
*/
public class Test {
public static void main(String[] args) {
try {
// load the document from a file:
DocumentBuilderFactory factory =
DocumentBuilderFactory.newInstance();
DocumentBuilder loader = factory.newDocumentBuilder();
Document document = loader.parse("sample.xml");
// get the traversal:
DocumentTraversal traversal = (DocumentTraversal) document;
NodeIterator iterator = traversal.createNodeIterator(
document.getDocumentElement(), NodeFilter.SHOW_ALL,
new ItemFilter(), true);
for (Node n = iterator.nextNode(); n != null; n = iterator.nextNode()) {
System.out.println("Element: " + ((Element) n).getTagName());
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
// accepts only DOM-element with tag-name 'item':
private static final class ItemFilter implements NodeFilter {
// this will be applied to each specified node in order to indicate
// should it be visible in the logical view:
public short acceptNode(Node n) {
if (n instanceof Element) {
if (((Element) n).getTagName().equals("item")) {
return NodeFilter.FILTER_ACCEPT;
}
}
return NodeFilter.FILTER_REJECT;
}
}
}
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