Java HTML / XML How to - Traverse the DOM tree using TreeWalker

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Question

We would like to know how to traverse the DOM tree using TreeWalker.

Answer

   //w w w  .ja  va  2s . c  om
import java.io.StringReader;

import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.traversal.DocumentTraversal;
import org.w3c.dom.traversal.NodeFilter;
import org.w3c.dom.traversal.TreeWalker;
import org.xml.sax.InputSource;

public class Main {
  public static String getXMLData() {
    return "<a><person  number='' dept=''><name>myName</name></person></a>";
  }

  public static void main(String[] argv) throws Exception {
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    Document document = factory.newDocumentBuilder().parse(
        new InputSource(new StringReader(getXMLData())));

    DocumentTraversal traversal = (DocumentTraversal) document;

    TreeWalker walker = traversal.createTreeWalker(document.getDocumentElement(),
        NodeFilter.SHOW_ELEMENT, null, true);

    traverseLevel(walker, "");
  }

  private static final void traverseLevel(TreeWalker walker, String indent) {
    Node parend = walker.getCurrentNode();
    System.out.println(indent + "- " + ((Element) parend).getTagName());

    for (Node n = walker.firstChild(); n != null; n = walker.nextSibling()) {
      traverseLevel(walker, indent + '\t');
    }
    walker.setCurrentNode(parend);
  }

}

The code above generates the following result.

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