Unlock Spring’s Aware Interfaces: Access ApplicationContext, Environment, and BeanFactory

Environment: Spring 5.3.3 + Java 8

When a bean needs objects such as ApplicationContext, Environment, or BeanFactory, you implement the corresponding *Aware interface; Spring then injects the appropriate instance. This article explores the implementation principle.

Usage example:

@Component
public class BeanAware implements ApplicationContextAware {
    private ApplicationContext ctx;
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.ctx = applicationContext;
        System.out.println(this.ctx);
    }
}

Entry function:

public static void main(String[] args) {
    AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext("com.pack");
    ctx.getBean(BeanAware.class);
    ctx.close();
}

By simply implementing the appropriate *Aware interface, the related object becomes available.

Below is the hierarchy of Aware interfaces (illustrated in the image).

Next, we examine AnnotationConfigApplicationContext 's parent class AbstractApplicationContext. The parent defines several methods (shown in the diagram) that handle Aware‑related processing.

The key class is ApplicationContextAwareProcessor, which implements BeanPostProcessor:

class ApplicationContextAwareProcessor implements BeanPostProcessor

This bean post‑processor runs after a bean is instantiated and dependencies are injected, but before any custom init‑method is invoked, and also after initialization code runs.

During the pre‑initialization phase, Spring checks whether the bean implements an Aware interface; if not, it returns immediately. Otherwise, it proceeds to invokeAwareInterfaces to inject the required objects.

Now you should understand the underlying principle of Spring’s Aware mechanism.

Done!