spring boot 实现helloworld

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
@SpringBootApplication
public class HelloWorldDemoApplication {
  @RequestMapping("/")
  public String home() {
    return "Hello World!";
  }
  public static void main(String[] args) {
    SpringApplication.run(HelloWorldDemoApplication.class, args);
  }
}