How to use xi include and fallback

[Peter A. Kirk]

Hi

I'm new to the Xerces xml parser, and would like some help loading/parsing xml 
documents using Xi Include.

I have two xml files, "mainxml.xml" and "includexml.xml".
MainXml looks like this:
<?xml version="1.0" encoding="utf-8" ?>
<config xmlns:xi="http://www.w3.org/2001/XInclude";>
 <abc>
  <xi:include href="includexml.xml">
   <xi:fallback>
    <str name="fallback include">
      failure include
    </str>
   </xi:fallback>
  </xi:include>
 </abc>
</config>

and IncludeXml looks like:
<str name="include">asd</str>


I'm trying to load the MainXml file like this:

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setNamespaceAware(true);
dbf.setXIncludeAware(true);

DocumentBuilder db = dbf.newDocumentBuilder();

Document doc = db.parse("mainxml.xml");


Which works ok, unless there is an error in "includexml.xml". If there is an 
error, then the fallback is not used - why not? An error could be en empty 
"includexml.xml" file, or if the xml was invalid.

How do I get the fallback to be used?



Thanks,
Peter