LCDUNG.

package com.example.helloWorld;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class HelloWorldController {

    @RequestMapping(value = "/")
    public ResponseEntity<String> hello() {
        return new ResponseEntity<String>("Hello World!", HttpStatus.OK);
    }

}