Changing value passed into custom @Qualifier

Question

Is there a way to change the value passed to a custom @Qualifier, and pass it to the delegating @Qualifier?

I understand that we can create custom qualifiers by

@Qualifier
@Target({ ElementType.FIELD, ElementType.PARAMETER, ElementType.METHOD, ElementType.TYPE })
@Retention(RetentionPolicy.RUNTIME)
public @interface Van {
    String value() default "";
}

And the following would pass the value "green" to @Qualifier and autowire a Vehicle bean named "green".

@Autowired
@Van("green")
Vehicle vehicle;

Let's say I have Vehicle beans created with names "greenVehicle" and "redVehicle".

Is there a way to format the value passed into @Van("green") and autowire the "greenVehicle" Vehicle bean, i.e having @Qualifier("greenVehicle") behind the scene?

retmas · Accepted Answer · 2024-10-04 18:51:25Z

1

Assume you have interface

public interface Vehicle {

    // some methods

}

and its implementation

public class VehicleImpl implements Vehicle {

    // some methods impl

}

Your custom qualifier should be

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

    @AliasFor(annotation = Qualifier.class, attribute = "value")
    String value() default "";

}

Then you can create Vehicle beans like:

@Bean("green")
Vehicle vehicle() {
    return new VehicleImpl();
}

or like:

@Bean
Vehicle green() {
    return new VehicleImpl();
}

and autowire as you expected:

@Van("green")
@Autowired
Vehicle vehicle;

answered Oct 4, 2024 at 18:51

retmas

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1 Comment

Ryan Wong Over a year ago

Thanks! The issue I'm facing is I'm creating the "greenVehicle" and "redVehicle" beans programmatically. So I need a way to convert @Van("green") into @Qualifier("greenVehicle"), in order to autowire the correct bean.

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