Why SpringBoot example doesn't work like this?

Question

So there is an example from the Spring web-site:

package com.example;

import org.springframework.boot.*;
import org.springframework.boot.autoconfigure.*;
import org.springframework.stereotype.*;
import org.springframework.web.bind.annotation.*;

@RestController
@EnableAutoConfiguration
public class Example {

    @RequestMapping("/")
    String home() {
        return "Hello World!";
    }

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

which works fine. There are notes @RestController is @Controller + @ResponseBody and The @SpringBootApplication annotation is equivalent to using @Configuration, @EnableAutoConfiguration and @ComponentScan.

My question is: Why is there 404 error accessing "/" if I use annotations below?

@ResponseBody
@SpringBootApplication
public class Example { ... }

Answer 1

Using the @ResponseBody annotation alone isn't enough to tell Spring that your class is a MVC controller. You either need to use @RestController:

@RestController
@SpringBootApplication
public class Example { ... }

or @Controller and @ResponseBody:

@Controller
@ResponseBody
@SpringBootApplication
public class Example { ... }