Spring: Using @Configuration to dynamically return a Bean

Question

Suppose you need to dynamically (at runtime) get an instance of a subtype of a given type.

How would you accomplish that using Spring IoC?

Answer 1

You can also use @Profile to achieve similar functionality in a more declarative way.

@Configuration
@Profile("default")
public class TypeAConfig {
    @Bean
    public Type getType() {
        return new TypeA();
    }
}

@Configuration
@Profile("otherProfile")
public class TypeBConfig() {
    @Bean
    public Type getType() {
        return new TypeB();
    }
}

@Configuration
public class SysConfig {
    @Autowired
    Type type;       

    @Bean Type getType() {
        return type;
    }
}

You can then control which implementation to use by specifying the profiles that Spring should activate, e.g. with the spring.profiles.active system property. More information in the JavaDoc for Profile