abstract fun afterSingletonsInstantiated(): Unit
Invoked right at the end of the singleton pre-instantiation phase, with a guarantee that all regular singleton beans have been created already. ListableBeanFactory#getBeansOfType calls within this method won't trigger accidental side effects during bootstrap.
NOTE: This callback won't be triggered for singleton beans lazily initialized on demand after BeanFactory bootstrap, and not for any other bean scope either. Carefully use it for beans with the intended bootstrap semantics only.