Trying to understand how the retries are implemented, I'd expect to see something like threads in the source of Spring Retry - but don't. I'd like to know how retrying is implemented, if not as per threads.
Additionally I didn't find an @Aspect that would wrap the method to be retried. Since AOP is a dependency of Spring Retry - I would also expect to see some AOP-stuff. Where is that 'hidden'?
There is no threading; retries are invoked on the calling thread.
Spring Retry can be used in two modes:
In Imperative Mode you programmatically invoke the target code using a RetryTemplate.
In Declarative Mode you annotate public methods with @Retryable.
In this mode, @EnableRetry registers 2 beans RetryConfiguration (extends AbstractPointcutAdvisor) and AnnotationAwareAspectJAutoProxyCreator.
RetryConfiguration creates an Advice (AnnotationAwareRetryOperationsInterceptor) and AnnotationClassOrMethodPointcut.
Using these beans, Spring AOP uses the auto proxy creator to wrap beans with @Retryable annotations in a proxy with the interceptor advice.