NOTE
How Spring Autowiring Works
Dependency resolution by type/qualifier/name metadata and the BeanPostProcessor infrastructure behind annotation injection.
This is a historical learning note and may contain outdated or incomplete understanding.
Annotation-based autowiring is implemented by Spring bean post-processing infrastructure that discovers injection metadata and resolves dependencies from the bean factory.
Resolution is primarily type-driven, with qualifiers/primary/name and collection semantics helping disambiguate multiple candidates.
Prefer constructor injection for required dependencies. Field injection hides requirements and makes plain-unit construction harder. Exact processor/internal methods are version-specific; depend on documented dependency-resolution semantics.