Understanding how Spring AOP manages the lifecycle of aspects is essential for building maintainable and predictable applications. Spring AOP weaves cross-cutting concerns—such as logging, security, or transaction management—into your code using aspects. These aspects themselves are managed as beans within the Spring container, and their lifecycle is tightly coupled with the Spring bean lifecycle.

In this chapter, you will explore how Spring determines when and how aspect instances are created, configured, and destroyed. You will also learn how different bean scopes affect aspect behavior, and how these choices can impact performance, thread-safety, and application design. This knowledge will help you make informed decisions about aspect configuration and ensure your aspects behave as expected throughout your application's lifecycle.

Aspect Bean Lifecycle in Spring AOP

Understanding the lifecycle of aspect beans is essential for managing cross-cutting concerns effectively. In Spring AOP, aspects are regular Spring beans, so their lifecycle is controlled by the Spring container.

Instantiation

• When the Spring container starts, it reads the configuration and identifies all beans, including those marked as aspects with the @Aspect annotation;
• Aspect beans are instantiated just like any other Spring bean, either eagerly at container startup or lazily when first needed, depending on their configuration;
• If you use singleton scope (the default), only one instance of the aspect bean is created in the container;
• For prototype-scoped aspects, a new instance is created each time the aspect is needed.

Initialization

• After instantiation, Spring performs dependency injection for the aspect bean, injecting any required collaborators or configuration properties;
• If you define any initialization logic using @PostConstruct or by implementing the InitializingBean interface, Spring calls these after dependencies are set;
• The aspect is now ready to intercept method calls and apply advice as configured.

Destruction

• When the Spring container shuts down, it destroys singleton beans, including aspect beans, by calling their @PreDestroy methods or the DisposableBean interface's destroy() method;
• Prototype-scoped aspect beans are not managed during destruction by the container. You are responsible for cleaning up any resources held by prototype beans.

Key Points

• Aspect beans follow the same lifecycle phases as other Spring beans: instantiation, dependency injection, initialization, and destruction;
• The scope of the aspect bean (singleton or prototype) affects how many instances exist and how they are managed;
• Properly managing your aspect bean's lifecycle ensures efficient resource usage and predictable behavior in your application.