BeanNameAware and BeanFactoryAware

Question

What is the use of BeanNameAware and BeanFactoryAware? I was studying spring and came across these two interfaces. I googled them but nothing useful came up. Please tell me what is the functionality of BeanNameAware and BeanFactoryAware interfaces and when to use these?

Answer 1

The xxxAware interface is a common pattern used within the Spring framework. They are typically used to allow a Spring managed bean to be given an object (via the interfaces setXxx method) at Spring bootstrap time.

Springs documentation says this about the Aware interface, which is a super interface to the two you mention:

Marker superinterface indicating that a bean is eligible to be notified by the Spring container of a particular framework object through a callback-style method.

As Sotirious points out, the Aware interface has the feel of the listener, callback, or observer design patterns.

Usage would look like this:

@Component
public MyBean implements BeanFactoryAware {
    private BeanFactory beanFactory;

    @Override
    public void setBeanFactory(final BeanFactory beanFactory) {
        this.beanFactory = beanFactory;
    }

    public void myMethod() {
        //I can now use beanFactory here
    }
}

During bootstrapping, Spring will examine each bean to determine if it implements any of the xxxAware interfaces. When one is found, it invokes the interface method, providing the piece of information that is being asked for. In the example above, Spring calls MyBean#setBeanFactory providing its BeanFactory.

Of course, in many situations, it is not entirely necessary to use these interfaces. For example, the ApplicationContextAware interface can be circumvented by simply @Autowireding an ApplicationContext into a bean.

@Component
public class MyOtherBean {
    @Autowired
    private ApplicationContext applicationContext;

    public void someMethod() {
        //I can use the ApplicationContext here.
    }
}