What is the purpose of the @Autowired annotation?

@Autowired tells the Spring container to automatically resolve and inject a matching bean into a constructor, setter, or field. Spring first tries to match by type; if more than one bean of that type exists, it falls back to matching by the parameter or field name, or you can disambiguate with @Qualifier.

@Component
public class ReportService {
    private final EmailSender sender;

    @Autowired
    public ReportService(EmailSender sender) {
        this.sender = sender;
    }
}

On a single-constructor class, @Autowired is actually optional since Spring 4.3 - the container uses that constructor implicitly. It's still commonly written for clarity, and remains required when a class defines multiple constructors.

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