postorder traversal of a DOM tree

From: ravi mannan (ravimannan2002_at_yahoo.com)
Date: 06/27/04 

Date: 26 Jun 2004 15:28:34 -0700

Hello all,

I'm trying to read an xml file and create a nested JPopupMenu from
that. The first thing I want to do is to read in the xml file and put
it in a Document using DOM and then do a post-order traversal of the
DOM tree. This will let me start at the bottom of the tree, which will
be the deepest selections in the menu, and add the leaves(JMenuItem's)
to the parents(JMenu's) and those parents to the root(JPopupMenu). Get
the idea? (Better yet, if you have a better idea of getting a nested
JPopupMenu from an xml documnet please let me know !) The problem I'm
having is that the traversal doesnt start at the deepest level first.
Is there any way of ensuring that I can start at the deepest leaf
node? Or ensuring that not starting at the deepest level wont matter
when I'm building the menu (maybe by using hashtables?) ? Thanks!

here is the XTW.java file:
import java.io.*;
import java.util.*;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.traversal.*; //for treewalker
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Element;

public class XTW
    {
    public Document doc = null;
    private TreeWalker twi = null;

    public XTW(String fileName)
        {
        convert(fileName);

   
        }
     public static void main(String [] av)
        {
        String name = "features-template.xml";

        XTW xtw = new XTW(name);

        try
            {
            DocumentTraversal dt = (DocumentTraversal)xtw.doc;

            xtw.twi = dt.createTreeWalker(xtw.doc,
NodeFilter.SHOW_ALL, null,
                                          false);

            xtw.postOrderTraversal(xtw.twi.firstChild());
            }
        catch (Exception e)
            {
            System.err.println("EXCEPTION:" + e.getMessage());

            e.printStackTrace(System.err);
            }

        }

    /////////////

    public void nodeInfo(Node node)
        {
        System.out.println
                          ("\n =======Start NODE INFO =========");

        System.out.println("node.getNodeValue():" +
node.getNodeValue());

        System.out.println("(node.getParentNode()).getNodeName():"
                               +
(node.getParentNode()).getNodeName());

        System.out.println("============END=========\n");
        }

    //////////////////
    public void postOrderTraversal(Node node)
        {
        int nodeType = node.getNodeType();

        switch (nodeType)
            {
            case Node.DOCUMENT_NODE:
                postOrderTraversal(((Document)node).getDocumentElement());

            case Node.ELEMENT_NODE:
                NodeList children = node.getChildNodes();

                if (children != null)
                    {
                    for (int i = 0; i < children.getLength(); i++)
                        postOrderTraversal(children.item(i));

  nodeInfo(node.getFirstChild());
                    }
            }
        }
    //////////////////////

    /** Convert the file */

    protected void convert(String fileName)
        {
        Reader is;

        try
            {

            // Make the document a URL so relative DTD works.

            String uri = "file:" + new
File(fileName).getAbsolutePath();

            DocumentBuilderFactory
                factory = DocumentBuilderFactory.newInstance();

            DocumentBuilder builder = factory.newDocumentBuilder();

            doc = builder.parse(uri);

            //doRecursive(doc);

            }
        catch (Exception ex)
            {
            System.err.println("Exception is convert method");

            System.err.println(ex.getClass());

            System.err.println(ex.getMessage());
            }
        }
    } //end class

-------------and here is the xml file it reads:features-template.xml
<menu>
        <topmenu> feature ="n"
                <submenu> feature="number"
                        <submenu> feature="sing"
                                <menuitem> feature="sing_text" </menuitem>
                                <menuitem> feature="sing_text_two" </menuitem>
                        </submenu>
                        <submenu> feature="pl"
                                <submenu> feature="sub_pl"
                        <menuitem> feature="sub_pl_text"</menuitem>
                                </submenu>
                        </submenu>
                </submenu>
        </topmenu>
</menu>
----------------------------------------here's the output:
///the deepest would be:
//<menuitem> feature="sub_pl_text"</menuitem>

 =======Start NODE INFO =========
node.getNodeValue(): feature="sing_text"
(node.getParentNode()).getNodeName():menuitem
============END=========

 =======Start NODE INFO =========
node.getNodeValue(): feature="sing_text_two"
(node.getParentNode()).getNodeName():menuitem
============END=========

 =======Start NODE INFO =========
node.getNodeValue(): feature="sing"

(node.getParentNode()).getNodeName():submenu
============END=========

 =======Start NODE INFO =========
node.getNodeValue(): feature="sub_pl_text"
(node.getParentNode()).getNodeName():menuitem
============END=========

 =======Start NODE INFO =========
node.getNodeValue(): feature="sub_pl"

(node.getParentNode()).getNodeName():submenu
============END=========

 =======Start NODE INFO =========
node.getNodeValue(): feature="pl"

(node.getParentNode()).getNodeName():submenu
============END=========

 =======Start NODE INFO =========
node.getNodeValue(): feature="number"

(node.getParentNode()).getNodeName():submenu
============END=========

 =======Start NODE INFO =========
node.getNodeValue(): feature ="n"

(node.getParentNode()).getNodeName():topmenu
============END=========

 =======Start NODE INFO =========
node.getNodeValue():

(node.getParentNode()).getNodeName():menu
============END=========