4.SpringBoot : Qualifier Annotation in Spring boot | Interview Question
Qualifier :
Certainly! In Spring Boot, the `@Qualifier` annotation is used to provide additional identification for a bean when there are multiple beans of the same type. This is particularly useful when you have multiple implementations of the same interface or abstract class, and you want to specify which implementation to use in a particular context.
Here's how the `@Qualifier` annotation works:
Multiple Implementations:
Imagine you have an interface `MyService` with multiple implementations, e.g., `MyServiceA` and `MyServiceB`. If you don't use `@Qualifier`, Spring will not know which implementation to use when you try to inject `MyService` into another bean.
Disambiguation :
By using the `@Qualifier` annotation, you can explicitly specify which implementation of `MyService` you want to use. For example, you can annotate `MyServiceA` with `@Qualifier("serviceA")` and `MyServiceB` with `@Qualifier("serviceB")`
Injection :
When you need to use a specific implementation of `MyService`, you can use the `@Qualifier` annotation in the constructor, method, or field where you're injecting the service. For example, `@Autowired @Qualifier("serviceA") MyService myServiceA`.