changing the document element of a DOM

[Andy Fish]

Hi,

I'm using XML DOM in Java and I have a function like this

Element makeSomeXml(Doc ument doc) {..}

This returns an Element owned by (but not appended to) the specified
document.

Now, when I call this function, sometimes I want to append the result
somewhere in the document, but sometimes I want to have the returned element
as a document in it's own right (i.e. as the root of the XML document). In
principle this seems like a reasonable requirement. I have an XML Element
and it's up to me whether I want to use it as the root element or plug it
into a bigger document.

The problem is that AFAIK a document must always have a root element, and
the root element cannot be replaced. nor can an existing element be
"upgraded" to be a document in it's own right. So I can't see a clean way of
doing what I want.

This seems a bit of a limitation in the way DOM represents the document
element - it seems to treat the root element and the document itself as the
same thing which isn't really the case. If I was editing XML in a file I
could leave all the namespace declarations and other stuff in place and
replace the root element.

Have I misunderstood the way the DOM works at the top level? Is there a
simple clean solution to what I want to do?

Many thanks in advance

Andy

[Martin Honnen]

Andy Fish wrote:

This seems a bit of a limitation in the way DOM represents the document
element - it seems to treat the root element and the document itself as the
same thing which isn't really the case.

The W3C DOM clearly distinguishes Document nodes and Element nodes. I
don't see why you cannot replace the documentElement node of a document:

import javax.xml.parse rs.DocumentBuil derFactory;
import javax.xml.parse rs.DocumentBuil der;

import org.w3c.dom.DOM Implementation;
import org.w3c.dom.Doc ument;
import org.w3c.dom.Ele ment;

public class Test20040703 {
public static void main (String[] args) {
try {
DocumentBuilder Factory documentBuilder Factory =
DocumentBuilder Factory.newInst ance();
documentBuilder Factory.setName spaceAware(true );
DocumentBuilder documentBuilder =
documentBuilder Factory.newDocu mentBuilder();

DOMImplementati on domImplementati on =
documentBuilder .getDOMImplemen tation();

Document xmlDocument = domImplementati on.createDocume nt("",
"gods", null);

Element god = xmlDocument.cre ateElement("god ");

xmlDocument.get DocumentElement ().appendChild( god);

Element devils = xmlDocument.cre ateElement("dev ils");

xmlDocument.rep laceChild(devil s, xmlDocument.get DocumentElement ());

Element devil = xmlDocument.cre ateElement("dev il");

xmlDocument.get DocumentElement ().appendChild( devil);

System.out.prin tln(xmlDocument .getDocumentEle ment().getNodeN ame());
}
catch (Exception e) {
System.out.prin tln("Error: " + e);
}
}
}

--

Martin Honnen
http://JavaScript.FAQTs.com/