We saw in the last two tutorials that in addition to ordinary Configuration classes, @Import annotation can also process ImportSelector and DeferredImportSelector implementations. In this tutorial we are going to see one more option for @Import: ImportBeanDefinitionRegistrar.

The interface ImportBeanDefinitionRegistrar

public interface ImportBeanDefinitionRegistrar {

	public void registerBeanDefinitions(
                            AnnotationMetadata importingClassMetadata,
                            BeanDefinitionRegistry registry);

}

This Interface is to be implemented by types that register additional bean definitions when processing @Configuration classes.

Example:

Implementing ImportBeanDefinitionRegistrar

public class MyBeanRegistrar implements ImportBeanDefinitionRegistrar {

  @Override
  public void registerBeanDefinitions (AnnotationMetadata importingClassMetadata,
                                       BeanDefinitionRegistry registry) {
      GenericBeanDefinition gbd = new GenericBeanDefinition();
      gbd.setBeanClass(AppBean.class);
      gbd.getPropertyValues().addPropertyValue("str", "value set from registrar");
      registry.registerBeanDefinition("appBean", gbd);
  }
}

The configuration class and @Import

@Configuration
@Import(MyBeanRegistrar.class)
public class MyConfig {

  @Bean
  ClientBean clientBean () {
      return new ClientBean();
  }
}

The beans

public class ClientBean {
  @Autowired
  private AppBean appBean;

  public void doSomething () {
      appBean.process();
  }
}

public class AppBean {
  private String str;

  public void setStr (String str) {
      this.str = str;
  }

  public void process () {
      System.out.println(str);
  }
}

The main method

public class ImportBeanDefinitionRegistrarExample {

  public static void main (String[] args) {
      ApplicationContext context =
                new AnnotationConfigApplicationContext(
                          MyConfig.class);
      ClientBean bean = context.getBean(ClientBean.class);
      bean.doSomething();
  }
}

Output

value set from registrar

Example Project

Dependencies and Technologies Used:

• Spring Context 4.3.4.RELEASE: Spring Context.
• JDK 1.8
• Maven 3.3.9