ClassLoaderBuilder.java

private ClassLoader buildLoader() throws Exception {
  List<URL> urls = new ArrayList<>();
  urls.addAll(((PluginClassLoader) getClass().getClassLoader()).getUrls());
  urls.addAll(getParent().getUrls());
  return new URLClassLoader(urls.toArray(new URL[urls.size()]));
}

private UrlClassLoader getParent() throws Exception {
  Field parents = PluginClassLoader.class.getDeclaredField("myParents");
  parents.setAccessible(true);
  return (UrlClassLoader) ((ClassLoader[]) parents.get((PluginClassLoader) getClass().getClassLoader()))[0];
}