@Configuration Annotation

@Configuration
Classes annotated with the @Configuration annotation are eligible for component scanning.
and they can take advantage of @Autowired and @Inject

Classes annotated with @Configuration can be annotated with the @Profile annotation to indicate that they should be processed only 
if a particular profile or profiles are active.

@Profile("development")
@Configuration
public class AppConfigDev {
   @Bean
   public DataSource makeData() { }
}

@Profile("production")
@Configuration
public class AppConfigProd {
   @Bean
   public DataSource makeData() { }
}

You can also nest the @Configuration classes as below
 @Configuration
 public class MyApp {
     @Inject DataSource dataSource;
     @Bean
     public MyBean myBean() {
         return new MyBean(dataSource);
     }

     @Configuration
     static class DatabaseDS {
         @Bean
         DataSource dataSource() {         }
     }
 }