For what purposes is aspect-oriented programming used?

Aspect-Oriented Programming (AOP) is used to separate cross-cutting concerns that affect multiple parts of a program but are not directly related to business logic. These tasks include logging, transaction management, security, caching, and error handling.

AOP allows these concerns to be modularized into separate modules (aspects), which are automatically woven into the necessary parts of the program without modifying the core code. This enhances modularity, simplifies maintenance, and promotes code reuse.

An example in Java using Spring AOP:

@Aspect
@Component
public class LoggingAspect {
    @Before("execution(* com.example.service.*.*(..))")
    public void logBeforeMethod(JoinPoint joinPoint) {
        System.out.println("Method call: " + joinPoint.getSignature().getName());
    }
}

Here, the aspect adds logging before the invocation of service layer methods without changing their code.