5 Aspect Oriented Programming

Aspect-Oriented Programming (AOP) historically has had many incarnations and some very complicated implementations. Generally AOP can be thought of as a way to define cross cutting concerns (logging, transactions, tracing etc.) separate from application code in the form of aspects that define advice.

There are typically two forms of advice:

• Around Advice - decorates a method or class

• Introduction Advice - introduces new behaviour to a class.

In modern Java applications declaring advice typically takes the form of an annotation. The most well-known annotation advice in the Java world is probably @Transactional which is used to demarcate transaction boundaries in Spring and Grails applications.

The disadvantage of traditional approaches to AOP is the heavy reliance on runtime proxy creation and reflection, which slows application performance, makes debugging harder and increases memory consumption.

Micronaut tries to address these concerns by providing a simple compile time AOP API that does not use reflection.