/**
 * Service method call interceptor.
 */
public interface ServiceCallInterceptor {
    /**
     * Invokes before service method invocation.
     *
     * @param mtdName Method name.
     * @param args Method arguments.
     * @param ctx Service request context.
     * @return Listener of the call result or {@code null}.
     */
    public @Nullable ServiceCallListener intercept(String mtdName, Object[] args, Map<String, Object> ctx);
}

/**
 * Listener of the service method invocation.
 */
public interface ServiceCallListener {
    /**
     *
     * @param res Service method call result, if any.
     * @param t Error, if any.
     */
    public void onComplete(@Nullable Object res, @Nullable Throwable t);
}