code: @SuppressWarnings("deprecation")
      static final void xalanExtensionAware(XPath xpath) {
  
          // Load xalan extensions thread-safely for all of jOOX
          if (!xalanExtensionLoaded) {
              synchronized (Util.class) {
                  if (!xalanExtensionLoaded) {
                      xalanExtensionLoaded = true;
  
                      try {
                          xalanNamespaceContext = (NamespaceContext)
                              Class.forName("org.apache.xalan.extensions.ExtensionNamespaceContext").newInstance();
  
                          xalanFunctionResolver = (XPathFunctionResolver)
                              Class.forName("org.apache.xalan.extensions.XPathFunctionResolverImpl").newInstance();
                      }
                      catch (Exception ignore) {
                      }
                  }
              }
          }
  
          if (xalanNamespaceContext != null && xalanFunctionResolver != null) {
              xpath.setNamespaceContext(xalanNamespaceContext);
              xpath.setXPathFunctionResolver(xalanFunctionResolver);
          }
      }
docs: Make a given {@link XPath} object "xalan-extension aware", if Xalan is on
  the classpath.