Overview

| Adapted from https://docs.spring.io/spring-framework/docs/4.0.x/spring-framework-reference/html/aop.html

Concepts

Concept	Description
Aspect	Modularization of a cross-cutting concern e.g. Transaction management
Join Point	A point during the execution of a program
Advice	Action taken by aspect at a join point
Pointcut	Predicate that matches joinpoints
Introduction	Interfaces for Advices
Target Object	Object being advised by one or more object
AOP Proxy	Object created by AOP framework to implement contracts (JDK Dynamic Proxy / CGLib Proxy in Spring)
Weaving	Linking aspects with other application types to create advised object

Advice

Advice	When it is executed
Before	Before a JP (cannot stop execution unless error thrown)
After Return	After JP completes normally
After Throwing	After method exits by throwing an exception
After (finally)	After method exits (regardless of how)
Around	Advice that surrounds a joinpoint during execution

note

Recommended to use the least powerful advice required for implementing an aspect => simpler model will have less potential for errors

AOP Proxies

• (Default) Standard JDK dynamic proxies - for interface
• CGLib Proxies - for classes
• Further Reading

note

It is good practise to use interfaces rather than classes as business class normally implements one or more interfaces

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@AspectJ Support

Enabling AspectJ Support

@Configuration
@EnableAspectJAutoProxy
public class AppConfig{}

Declaring an Aspect

• Aspects cannot target other aspects
• Register Aspect as a bean with @Component

@Aspect
public class someAspect {
}

warning

Not sufficient to just use @Aspect for component scanning, also need @Component

Not possible to target Aspects of advise from other aspects