Spring's AOP primarily uses the Proxy Design Pattern to implement aspects.

AOP create proxies for target objects. These proxies intercept method calls and allow cross-cutting concerns (such as logging, security, or transactions) to be applied dynamically — without modifying the original business logic or class.

if we read Spring documentation, there are two types of proxy configurations.

1. JDK Dynamic Proxies: Used for classes that implement one or more interfaces.

2. CGLIB Proxies: Used for classes that do not implement any interfaces, enabling method interception directly on the class.

Why am I saying no to Decorator Design Pattern? Simple answer IMHO is that both design patterns sounds conceptually similar in this case that they “seems to” adds functionality to a class. Decorator involves explicitly wrapping objects with additional functionality (using existing class/interfaces). While AOP does not explicitly "wrap" objects in the same way but instead uses proxies to transparently intercept method calls and apply additional behaviors. This makes it more appropriate to classify Spring AOP under the Proxy Design Pattern.