HelloRestControllerとApplication.kt

import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.RestController
import org.springframework.boot.SpringApplication
import org.springframework.boot.autoconfigure.EnableAutoConfiguration
import org.springframework.context.annotation.ComponentScan
import org.springframework.context.annotation.Configuration

@RestController
class HelloRestController {
    @RequestMapping("/")
    fun home() = "hello"
}


@Configuration
@EnableAutoConfiguration
@ComponentScan
open class Application {
    companion object {
    @JvmStatic fun main(args: Array<String>) {
      SpringApplication.run(Application::class.java, *args)
    }
}