NOTE
Spring IoC Source: BeanFactoryPostProcessor Phase
How BeanFactoryPostProcessor customizes bean definitions/container metadata before ordinary bean instantiation.
This is a historical learning note and may contain outdated or incomplete understanding.
BeanFactoryPostProcessor operates on the bean factory/definitions before ordinary application beans are instantiated.
This is where configuration processors can register/modify definitions, resolve metadata, or otherwise shape what will later be created. Ordering interfaces/annotations may influence processor order when multiple processors participate.
Do not perform arbitrary application business work here; this is container-definition infrastructure time.