Merging Documents while preserving xsi:type

Question

I have 2 Document objects with documents that contain similiar XML's. For example:

<tt:root xmlns:tt="http://myurl.com/">
  <tt:child/>
  <tt:child/>
</tt:root>

And the other one:

<ns1:root xmlns:ns1="http://myurl.com/" xmlns:ns2="http://myotherurl.com/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <ns1:child/>
  <ns1:child xsi:type="ns2:SomeType"/>
</ns1:root>

I need to merge them to 1 document with 1 root element and 4 child elements. Problem is, if I use document.importNode function to do the merging, it properly handles the namespaces everywhere BUT xsi:type element. So what I'm getting in result is this:

<tt:root xmlns:tt="http://myurl.com/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <tt:child/>
  <tt:child/>
  <ns1:child xmlns:ns1="http://myurl.com/"/>
  <ns1:child xmlns:ns1="http://myurl.com/" xsi:type="ns2:SomeType"/>
</tt:root>

As you can see, ns2 is used in xsi:type but is not defined anywhere. Is there any automated way to solve this problem?

Thanks.

ADDED:

If this task is impossible to complete using the default java DOM libraries, maybe there is some other library I can use to complete my task?

Answer 1

A single-line of XQuery could do the job: construct a new node named as the context root element, then import its children together with those from the other document:

declare variable $other external; element {node-name(*)} {*/*, $other/*/*}

Though in XQuery you don't have full control over namespace nodes (at least in XQuery 1.0), it has a copy-namespaces mode setting that can be used to ask for keeping the namespace context intact, in case the implementation does preserve it by default.

If XQuery is a viable option, then saxon9he.jar could be the "magic xml library" that you are after.

Here is sample code exposing some context, using the s9api API:

import javax.xml.parsers.DocumentBuilderFactory;
import net.sf.saxon.s9api.*;
import org.w3c.dom.Document;

...

  Document merge(Document context, Document other) throws Exception
  {
    Processor processor = new Processor(false);
    XQueryExecutable executable = processor.newXQueryCompiler().compile(
      "declare variable $other external; element {node-name(*)} {*/*, $other/*/*}");
    XQueryEvaluator evaluator = executable.load();    
    DocumentBuilder db = processor.newDocumentBuilder();
    evaluator.setContextItem(db.wrap(context));
    evaluator.setExternalVariable(new QName("other"), db.wrap(other));
    Document doc =
      DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
    processor.writeXdmValue(evaluator.evaluate(), new DOMDestination(doc));
    return doc;
  }