AOP means Aspect Oriented Programing. Which is a paradigm that complements OOP so it cannot be considered a replacement of OOP. And it is mostly used for Cross-cutting concearns.

What is a cross-cutting concern?

A cross cutting concern is applicable throughout the application, so it means the entire application. Therefore, some requirements take more advantage of AOP.

  • Security
  • Logging
  • Caching
  • Transaction
  • Monitoring

Where you should not apply AOP

You should never apply AOP for the business logic of your domain. This would cause a lot of logic leak and would be really hard to read.

Therefore, the main usage of the AOP is to separate those cross-cutting concerns that are more related to the infrastructure of the application from the Business logic.

Example of aspect

One simple example of usage is creating one Aspect which can be used to log the amount of time spent per execution for the methods with the annotation @LogPerformance


@Aspect
@Component
public class LogPerformanceAspect {

    private Logger logger = Logger.getLogger("performance.log");

    @Around("@annotation(com.spring.examples.annotations.LogPerformance)")
    public Object logPerformance(ProceedingJoinPoint proceedingJoinPoint) throws Throwable {
        long startTime = System.currentTimeMillis();
        try {
            return proceedingJoinPoint.proceed();
        } finally {
            long finishTime = System.currentTimeMillis();
            Duration duration = Duration.ofMillis(finishTime - startTime);

            logger.info(String.format("Duration of %s was %s", proceedingJoinPoint.getSignature(), duration));
        }
    }
}