The resteasy-client-vertx VertxClientHttpEngine will produce a NullPointerException if the VertxClientHttpEngine(HttpClient) constructor is used. Internally the vertx instance is used, but is null in that constructor.

Internally the method is not used at all. Likewise, it's likely not used elsewhere otherwise the NPE would be thrown. This constructor may need to be removed instead of just deprecated if there is no way to ensure the NPE is not thrown.