public boolean isProxyDefined() {
        return proxy != null;
    }
Whether a proxy has been defined given the parameters it was constructed with.

For example, if the provided system properties keys resolve null, then this will return {@code false}.

@return true, if a proxy has been defined, otherwise false.
gateway/platforms/vertx3/vertx3/src/main/java/io/apiman/gateway/platforms/vertx3/engine/proxy/JavaSysPropsProxySettings.java