@Controller and @RestController

Spring MVC provides an annotation-based programming model, where the @Controller and @RestController components use annotations to express query mappings, query entry, exception handling, and more. Annotated controllers have flexible method signatures and are not required to extend base classes or implement specific interfaces. The following example shows a controller defined using annotations:

@Controller
public class HelloController {
    @GetMapping("/hello")
    public String handle(Model model) {
        model.addAttribute("message", "Hello World!");
        return "index";
    }
}

import org.springframework.ui.set
@Controller
class HelloController {
    @GetMapping("/hello")
    fun handle(model: Model): String {
        model["message"] = "Hello World!"
        return "index"
    }
}

In the previous example, the method takes a Model and returns the name of the view as a String, but there are many other options that will be described later in this chapter.