It seems that you are trying to use @Validated for spring beans, using Spring MVC approach.

First idea

From this article, looks like you need to declare an additional bean.

@Bean
    public static MethodValidationPostProcessor validationPostProcessor() {
        return new MethodValidationPostProcessor();
    }

Second idea

Instead of relying on @ConditionalOnProperty during creation of MyService you can create a @Conditional bean which will validate values of the properties.