Currently StandardWebSocketClient supports SSL using user properties:
standardWebSocketClient.setUserProperties(Map.of(Constants.SSL_CONTEXT_PROPERTY, sslContext));

Unfortunately this support ends with Tomcat 11. New way to go:
ClientEndpointConfig endpointConfig = ClientEndpointConfig.Builder.create().sslContext(sslContext).build();

But the creation of ClientEndpointConfig is capsulated in the class StandardWebSocketClient, so sslContext(...) can not be inserted there. Would it be possible to enable that?