Spring Boot 3 - "Whitelabel Error Page" getting in new project

package com.example.demo;

​

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestBody;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestMethod;

import org.springframework.web.bind.annotation.ResponseBody;

​

@Controller

public class MainController {

​

    @RequestMapping(

        value = "/",

        method = RequestMethod.GET

    )

    @ResponseBody

    public String index() {

        return "Hi There!";

    }

}