code: @Override
      public InputSource resolveEntity(final String publicId, final String systemId) throws SAXException, IOException {
          if (!systemId.toLowerCase(Locale.getDefault()).startsWith("http://")) {
              final URL resource = getClass().getResource("flatpack.dtd");
  
              if (resource != null) {
                  return new InputSource(resource.openStream());
              } else {
                  // should probably not happen, this may indicate that the dtd has been
                  // removed from the jar for some reason
                  throw new IOException("could not load dtd resource from jar!!");
              }
          }
  
          // must be pulling from the web, stick with default implementation
          return null;
      }
docs: /*
  (non-Javadoc)
  
  @see org.xml.sax.EntityResolver#resolveEntity(java.lang.String,
  java.lang.String)