title: what will happen if we didn't define @Bean under @Configuration class in spring boot
body: <p>so usually when we write a class and add @Configuration to the class, we will define bean in that class for example:</p>
  <pre><code>@Configuration
  public class AppConfig {
      @Bean
      public DemoClass service() 
      {
          
      }
  }
  </code></pre>
  <p>but we I review some codes, I saw some class didn't define @bean method in inside these class,like:</p>
  <pre><code>@Configuration
  public class AutoRefreshConfig {
      @Scheduled(fixedRate = 60000)
      public void update(){
        // update something with a fix rate
  
      }
  }
  
  </code></pre>
  <p>so is this correct? actually it works well. but I am wondering what will happen when I start running the project. what kind of behavior of will spring boot act? Is it just like a normal java class?</p>