Springhard

Spring AOP proxies — what is the self-invocation problem?

Answer

Spring AOP usually works via a proxy around your bean. If a method inside the same class calls another advised method directly (`this.someMethod()`), it bypasses the proxy, so aspects like `@Transactional` may not apply.

Advanced answer

Deep dive

Spring AOP is usually **proxy-based**:

JDK dynamic proxies when you proxy an interface.
CGLIB proxies when you proxy a concrete class (subclassing).

The proxy intercepts calls **made through the proxy**. When code inside the bean calls another method on `this`, it never leaves the target object, so the proxy can’t intercept it.

Example (the issue)

@Service
class BillingService {
  @Transactional
  public void pay() { /* ... */ }

  public void run() {
    this.pay(); // bypasses proxy -> no transaction
  }
}

Fixes

Extract the advised method to another bean and call that bean.
Inject the proxied interface and call through it (be careful with design).
Use AspectJ weaving only if you truly need to advise self-invocations.

Common pitfalls

Annotating private methods with `@Transactional` and expecting it to work.
Calling “helper” advised methods from inside the same class.
Tests that instantiate classes directly (no proxy) and then expecting AOP behavior.