postorder traversal of a DOM tree

[ravi mannan]

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(JMenuIte m'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.parse rs.DocumentBuil der;
import javax.xml.parse rs.DocumentBuil derFactory;

import org.w3c.dom.tra versal.*; //for treewalker
import org.w3c.dom.Doc ument;
import org.w3c.dom.Nod e;
import org.w3c.dom.Nod eList;
import org.w3c.dom.Ele ment;

public class XTW
{
public Document doc = null;
private TreeWalker twi = null;
public XTW(String fileName)
{
convert(fileNam e);
}
public static void main(String [] av)
{
String name = "features-template.xml";

XTW xtw = new XTW(name);

try
{
DocumentTravers al dt = (DocumentTraver sal)xtw.doc;

xtw.twi = dt.createTreeWa lker(xtw.doc,
NodeFilter.SHOW _ALL, null,
false);

xtw.postOrderTr aversal(xtw.twi .firstChild());
}
catch (Exception e)
{
System.err.prin tln("EXCEPTION: " + e.getMessage()) ;

e.printStackTra ce(System.err);
}
}

/////////////

public void nodeInfo(Node node)
{
System.out.prin tln
("\n =======Start NODE INFO =========");
System.out.prin tln("node.getNo deValue():" +
node.getNodeVal ue());

System.out.prin tln("(node.getP arentNode()).ge tNodeName():"
+
(node.getParent Node()).getNode Name());
System.out.prin tln("========== ==END=========\ n");
}

//////////////////
public void postOrderTraver sal(Node node)
{
int nodeType = node.getNodeTyp e();

switch (nodeType)
{
case Node.DOCUMENT_N ODE:
postOrderTraver sal(((Document) node).getDocume ntElement());

case Node.ELEMENT_NO DE:
NodeList children = node.getChildNo des();

if (children != null)
{
for (int i = 0; i < children.getLen gth(); i++)
postOrderTraver sal(children.it em(i));

nodeInfo(node.g etFirstChild()) ;
}
}
}
//////////////////////

/** 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 ();

DocumentBuilder Factory
factory = DocumentBuilder Factory.newInst ance();

DocumentBuilder builder = factory.newDocu mentBuilder();

doc = builder.parse(u ri);

//doRecursive(doc );

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

System.err.prin tln(ex.getClass ());

System.err.prin tln(ex.getMessa ge());
}
}
} //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_t ext" </menuitem>
<menuitem> feature="sing_t ext_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.getNodeVal ue(): feature="sing_t ext"
(node.getParent Node()).getNode Name():menuitem
============END =========
=======Start NODE INFO =========
node.getNodeVal ue(): feature="sing_t ext_two"
(node.getParent Node()).getNode Name():menuitem
============END =========
=======Start NODE INFO =========
node.getNodeVal ue(): feature="sing"

(node.getParent Node()).getNode Name():submenu
============END =========
=======Start NODE INFO =========
node.getNodeVal ue(): feature="sub_pl _text"
(node.getParent Node()).getNode Name():menuitem
============END =========
=======Start NODE INFO =========
node.getNodeVal ue(): feature="sub_pl "

(node.getParent Node()).getNode Name():submenu
============END =========
=======Start NODE INFO =========
node.getNodeVal ue(): feature="pl"

(node.getParent Node()).getNode Name():submenu
============END =========
=======Start NODE INFO =========
node.getNodeVal ue(): feature="number "

(node.getParent Node()).getNode Name():submenu
============END =========
=======Start NODE INFO =========
node.getNodeVal ue(): feature ="n"

(node.getParent Node()).getNode Name():topmenu
============END =========
=======Start NODE INFO =========
node.getNodeVal ue():

(node.getParent Node()).getNode Name():menu
============END =========

[Raymond DeCampo]

ravi mannan wrote:

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(JMenuIte m'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!

Personally I would approach the traversal this way (pseudocode):

function visit(JMenu parent, Node current)
{
if (current.hasChi ldren())
{
JMenu curMenu = new JMenu(current);
parent.add(curM enu);
for (child in current.getChil dren())
{
visit(curMenu, child);
}
}
else
{
parent.add(new JMenuItem(curre nt));
}
}

Ray

--
XML is the programmer's duct tape.

[ravi mannan]

Thanks for the help, but i just simply made the xml so that the most
nested portions appear above the least nested. thx again

Raymond DeCampo <rd******@spam. twcny.spam.rr.s pam.com.spam> wrote in message news:<HB******* *************@t wister.nyroc.rr .com>...

ravi mannan wrote:

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(JMenuIte m'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!

Personally I would approach the traversal this way (pseudocode):

function visit(JMenu parent, Node current)
{
if (current.hasChi ldren())
{
JMenu curMenu = new JMenu(current);
parent.add(curM enu);
for (child in current.getChil dren())
{
visit(curMenu, child);
}
}
else
{
parent.add(new JMenuItem(curre nt));
}
}

Ray