code: public static void registerUrlProtocolHandler() {
          String handlers = System.getProperty(PROTOCOL_HANDLER, "");
          System.setProperty(PROTOCOL_HANDLER, ("".equals(handlers) ? HANDLERS_PACKAGE
                  : handlers + "|" + HANDLERS_PACKAGE));
          resetCachedUrlHandlers();
      }
docs: Register a {@literal 'java.protocol.handler.pkgs'} property so that a
  {@link URLStreamHandler} will be located to deal with jar URLs.