AOP and Proxies

Cert Focus

You should understand why Spring uses proxies and how AOP relates to transactions, security, caching, and async behavior.

Must Know

• AOP separates cross-cutting concerns from business logic.
• An aspect contains advice and pointcuts.
• Advice is code that runs at a matched join point.
• A pointcut selects where advice applies.
• Spring AOP is proxy-based.
• JDK proxies proxy interfaces.
• CGLIB proxies classes.
• Self-invocation bypasses the proxy.

Direct Book Links

• Spring AOP Mental Model
• Spring Events
• Scheduling and Async

Exam Trap

Proxy-based features only apply when the call goes through the Spring proxy.

Self-Check

• Can I explain aspect, advice, pointcut, and join point?
• Can I explain JDK proxy vs CGLIB proxy?
• Can I explain self-invocation?
• Can I name Spring features that commonly depend on proxies?

Model Answers

An aspect contains cross-cutting behavior. Advice is the code that runs. A pointcut selects where the advice applies. A join point is a point in execution where advice can apply.

JDK dynamic proxies proxy interfaces. CGLIB proxies classes by creating subclasses.

Self-invocation means one method in a class calls another method on the same object. That call bypasses the Spring proxy, so proxy-based behavior may not run.

Common proxy-based features include @Transactional, method security, @Cacheable, @Async, and many AOP advices.

Memory Sentence

Spring AOP works when methods are called through a proxy.