When using the JAXP XPath interfaces in a multi-classloader environment such as
an application server, the newInstance method on XPathFactory fails to find any
javax.xml.xpath.XPathFactory service files as described in the API documentation
if the service file was loaded in a classloader other than the system classloader.

The reason for this can be found in the javax.xml.xpath.SecuritySupport class in
the getResources method.  The method will always use the getSystemResource
method instead of the getResource method on the context classloader.