Simple XPath Extraction

[Mark Schmit]

I'm trying what I thought would be a very simple task: given an XPath
and a string containing an XML file's contents, produce a string
containing only the XPath-matching excerpts.  I tried the following,
based heavily on the SimpleXPathAPI and XPathWrapper samples:

================
XMLPlatformUtils::Initialize();
XPathEvaluator::initialize();
XalanNode* context_node = NULL;
{
  XPathEvaluator xpath_evaluator;
  XalanSourceTreeDOMSupport dom_support;
  XalanSourceTreeParserLiaison parser_liaison;
  dom_support.setParserLiaison(&parser_liaison);

  MemBufInputSource input_source(
      reinterpret_cast<const XMLByte*>(full_xml_contents.c_str()),
      full_xml_contents.length(), "what_is_buf_id");

  XalanDocument* doc = parser_liaison.parseXMLStream(input_source);
  ASSERT(doc) << "Failed to create doc";
  XalanDocumentPrefixResolver prefix_resolver(doc);
  context_node = xpath_evaluator.selectSingleNode(dom_support, doc,

XalanDOMString(context).c_str(),
                                                  prefix_resolver);
  if (!context_node) {
    LOG << "Failed to find node for " << context;
  } else {
    const XObjectPtr result(xpath_evaluator.evaluate(dom_support,
                                                     context_node,

XalanDOMString("*").c_str(),
                                                     prefix_resolver));
    ASSERT(!result.null());
    LOG << "Result type: " << result->getTypeString();
    const NodeRefListBase& nodeset = result->nodeset();
    for (int i = 0; i < nodeset.getLength(); ++i) {
      XalanNode* node = nodeset.item(i);
      LOG << "Node " << i << ": " << node->getNodeName();
      XalanDOMString str;
      DOMServices::getNodeData(*node, str);
      LOG << "Node " << i << " contents: " << str;
      // TODO: Append to a single return string
    }
  }
}
XPathEvaluator::terminate();
XMLPlatformUtils::Terminate();
================

This prints each of the nodes' contents, albeit with all of the tags'
contents stripped out.  My problems are that: A) I want to keep all
the XML tags, and B) I want to put them into one aggregated string.
For example, given the the following XML file:

================
<?xml version="1.0" encoding="UTF-8"?>
<GenInfo xmlns="urn:mynamespace">
  <EntityId>ABC123</EntityId>
  <EntityName>My Favorite Entity</EntityName>
  <MembersInfo>
    <Member ID="123456">
      <Name>Bob Smith</Name>
    </Member>
    <Member ID="234567">
      <Name>Jane Doe</Name>
    </Member>
  </MembersInfo>
</GenInfo>
================

I'd like to produce this:
================
<Member ID="123456">
  <Name>Bob Smith</Name>
</Member>
<Member ID="234567">
  <Name>Jane Doe</Name>
</Member>
================

I looked at the DOMServices and DOMSupport classes and couldn't find
anything that produced a string of XML from a given XalanNode.  Do I
need to use the XalanTransformer class in some way?  Should I
essentially be generating an XSL transformation rather than using
XPathEvaluator?

Also, how does the 'urn:mynamespace' aspect figure into this?  Does
that get passed to the prefix resolver?

Finally, is there any documentation online that features descriptions
of the classes or do I need to infer everything from class names?  I
spent a ton of time trying to figure this out from the API docs but
the classes feature almost no descriptions of what role they actually
serve, or how to perform activities that seem to me to be pretty
fundamental (e.g. seeing the XML text representation of a given node
and its children).

Thanks much for any help.

-Mark