spring Creating and using beans Declaring Bean
Example
To declare a bean, simply annotate a method with the @Bean annotation or annotate a class with the @Component annotation (annotations @Service, @Repository, @Controller could be used as well).
When JavaConfig encounters such a method, it will execute that method and register the return value as a bean within a BeanFactory. By default, the bean name will be that of the method name.
We can create bean using one of three ways:
-
Using Java based Configuration: In Configuration file we need to declare bean using @bean annotation
@Configuration public class AppConfig { @Bean public TransferService transferService() { return new TransferServiceImpl(); } } -
Using XML based configuration: For XML based configuration we need to create declare bean in application configuration XML i.e.
<beans> <bean name="transferService" class="com.acme.TransferServiceImpl"/> </beans> -
Annotation-Driven Component: For annotation-driven components, we need to add the @Component annotation to the class we want to declare as bean.
@Component("transferService") public class TransferServiceImpl implements TransferService { ... }
Now all three beans with name transferService are available in BeanFactory or ApplicationContext.
