code: @Override
      protected PippoFilter createPippoFilter() {
          try {
              // try to load a class from jetty.websocket
              Class.forName("org.eclipse.jetty.websocket.api.WebSocketListener");
          } catch (ClassNotFoundException e) {
              return super.createPippoFilter();
          }
  
          try {
              // create an instance of JettyWebSocketFilter
              Class<?> pippoFilterClass = Class.forName("ro.pippo.jetty.websocket.JettyWebSocketFilter");
              return (PippoFilter) pippoFilterClass.newInstance();
          } catch (ClassNotFoundException | IllegalAccessException | InstantiationException e) {
              throw new PippoRuntimeException(e);
          }
      }
docs: Check the existence of {@code org.eclipse.jetty.websocket} as dependency
  and add {@link ro.pippo.jetty.websocket.JettyWebSocketFilter} instead of {@link PippoFilter}.
  
  @return