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@Bean methods may also be declared within classes that are not annotated with @Configuration. For example, bean methods may be declared in a @Component class or even in a plain old class. In such cases, a @Bean method will get processed in a so-called 'lite' mode.
One of the most important annotations in spring is @Configuration annotation which indicates that the class has @Bean definition methods. So Spring container can process the class and generate Spring Beans to be used in the application. This annotation is part of the spring core framework.
1. Declaring a bean. To declare a bean, simply annotate a method with the @Bean annotation. When JavaConfig encounters such a method, it will execute that method and register the return value as a bean within a BeanFactory .
@Configuration & @Bean Annotations.
Yes, Spring does some magic. Check the Spring Docs:
This is where the magic comes in: All
@Configurationclasses are subclassed at startup-time with CGLIB. In the subclass, the child method checks the container first for any cached (scoped) beans before it calls the parent method and creates a new instance.
This means that the calls to @Bean methods are proxied via CGLIB and therefore the cached version of the bean is returned (a new one is not created).
The default scope of @Beans is SINGLETON, if you specify a different scope such as PROTOTYPE the call will be passed to the original method.
Please note that this is not valid for static methods. As per the spring docs:
Calls to static
@Beanmethods never get intercepted by the container, not even within@Configurationclasses (as described earlier in this section), due to technical limitations: CGLIB subclassing can override only non-static methods. As a consequence, a direct call to another@Beanmethod has standard Java semantics, resulting in an independent instance being returned straight from the factory method itself.
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