Spring Boot Qualifiers

Qualifier Overview

Qualifiers are a Spring feature rather than a Spring Boot-specific feature. Spring provides qualifiers similar to CDI qualifiers.

Specifying a Qualifier Name

Use @Qualifier to specify a Bean name.
Combine @Autowired and @Qualifier to inject a specific Bean.
This is similar to using @Named in CDI.

Writing the Code

public interface MyInterface {
}

@Component
@Qualifier("hoge")
public class Hoge implements MyInterface {
}

@Component
@Qualifier("fuga")
public class Fuga implements MyInterface {
}

@SpringBootApplication
public class Main {
    public static void main(String[] args) {
        try (ConfigurableApplicationContext context = SpringApplication.run(Main.class, args)) {
            Main m = context.getBean(Main.class);
            System.out.println("hoge = " + m.hoge.getClass());
            System.out.println("fuga = " + m.fuga.getClass());
        }
    }

    @Autowired @Qualifier("hoge")
    private MyInterface hoge;

    @Autowired @Qualifier("fuga")
    private MyInterface fuga;
}

Result

hoge = class sample.springboot.Hoge
fuga = class sample.springboot.Fuga

Creating a Qualifier

Create a qualifier by annotating a custom annotation with @Qualifier.
This works like a custom CDI qualifier.

@Qualifier
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.TYPE})
public @interface MyQualifier {
    MyType value();
}

public enum MyType {
    HOGE,
    FUGA,
}

@Component
@MyQualifier(MyType.HOGE)
public class Hoge implements MyInterface {
}

@Component
@MyQualifier(MyType.FUGA)
public class Fuga implements MyInterface {
}

@Autowired @MyQualifier(MyType.HOGE)
private MyInterface hoge;

@Autowired @MyQualifier(MyType.FUGA)
private MyInterface fuga;

The result is the same: each field receives the Bean with the matching custom qualifier.