https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/web/bind/annotation/RestController.html
https://www.genuitec.com/spring-frameworkrestcontroller-vs-controller/
https://dzone.com/articles/spring-framework-restcontroller-vs-controller/
https://www.dineshonjava.com/restcontroller-in-spring-40-framework/
https://stackoverflow.com/questions/25242321/difference-between-spring-controller-and-restcontroller-annotation
@RestController is a stereotype annotation that combines @ResponseBody and @Controller. More than that, it gives more meaning to your Controller
and also may carry additional semantics in future releases of the framework.
sample：
https://spring.io/guides/gs/rest-service/
http://www.benchresources.net/spring-mvc-4-0-restful-web-service-using-restcontroller-annotation/
https://viralpatel.net/blogs/spring-4-mvc-rest-example-json/