Callback interface triggered at the end of the singleton pre-instantiation phase during BeanFactory bootstrap. This interface can be implemented by singleton beans in order to perform some initialization after the regular singleton instantiation algorithm, avoiding side effects with accidental early initialization (e.g. from ListableBeanFactory#getBeansOfType calls). In that sense, it is an alternative to InitializingBean which gets triggered right at the end of a bean's local construction phase.

This callback variant is somewhat similar to org.springframework.context.event.ContextRefreshedEvent but doesn't require an implementation of org.springframework.context.ApplicationListener, with no need to filter context references across a context hierarchy etc. It also implies a more minimal dependency on just the beans package and is being honored by standalone ListableBeanFactory implementations, not just in an org.springframework.context.ApplicationContext environment.