package com.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DemoApplication {

	public static void main(String[] args) {
		SpringApplication.run(DemoApplication.class, args);
	}
}

package com.example;

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;

import java.util.UUID;

@SpringBootApplication
@RestController
public class DemoApplication {
	UUID id = UUID.randomUUID();

	@RequestMapping("/")
	String hello() {
		return "Hello from " + id;
	}

	public static void main(String[] args) {
		SpringApplication.run(DemoApplication.class, args);
	}
}

Add Hello World