@Qualifier and autowired

We can label the bean given a @Qualifier to it in several ways. take the examples below

@Service
public class RecordsService {

    //(1º)
    @Autowired
    @Qualifier("dbItemsProcessor")
    private ItemsProcessor recordsProcessor;
    //(2º)
    @Autowired
    @Qualifier("file-items-reader")
    private ItemsReader recordsReader;
    //(3º)
    @Autowired
    @Qualifier("db-writer")
    private ItemsWriter recordsWriter;
    //(4º)
    @Autowired
    @ItemValidatorType(FILE)
    private ItemsValidator recordsValidator;
}

1 - Automatic bean generated by spring

The first @Autowired is related to the automatic generated bean name by spring. If you do not define any bean @Qualifier spring automatic generates the name based on the name of the class.

2 - @Component name

Second example is naming your component like below:

@Component("items-reader")
public class ItemsReader {}

3 - @Qualifier in the class

3rd example is using the @Qualifier in the class

@Component
@Qualifier("db-writer")
public class ItemWriter {}

4 - Custom annotation

4th example is using your custom annotation , which you can see also extends @Qualifier and has a enum of 2 possible values.

@Qualifier
@Target({ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface ItemValidatorType {

    ItemValidatorType value();

    enum RecordsValidatorMode {
        DB,
        FILE
    }
}