private final SignalResolver resolver;

    private ArrayList rooms = new ArrayList();

    @Bean
    public void addCustomJoinHandler() {
        Signal join_exist = Signal.fromString("join_exist");
        resolver.addCustomHandler(join_exist, (msg) ->
            InternalMessage.create()
                    .to(msg.getFrom())
                    .content(msg.getContent())
                    .signal(rooms.contains(msg.getContent()) ? Signal.JOIN : Signal.EMPTY)
                    .build()
                    .send()
        );
    }

    @Bean
    public void addCustomCreateHandler() {
        Signal join_exist = Signal.fromString("create_exist");
        resolver.addCustomHandler(join_exist, (msg) ->
                InternalMessage.create()
                        .to(msg.getFrom())
                        .content(msg.getContent())
                        .signal(rooms.contains(msg.getContent()) ? Signal.EMPTY : create(msg.getContent()))
                        .build()
                        .send()
        );
    }

    private Signal create(String content) {
        rooms.add(content);

        return Signal.CREATE;
    }