9.2.3.2. About Qualifiers
A qualifier is an annotation which ties a bean to a bean type. It allows you to specify exactly which bean you mean to inject. Qualifiers have a retention and a target, which are defined as in the example below.
Example 9.3. Define the @Synchronous and @Asynchronous Qualifiers
@Qualifier
@Retention(RUNTIME)
@Target({TYPE, METHOD, FIELD, PARAMETER})
public @interface Synchronous {}
@Qualifier
@Retention(RUNTIME)
@Target({TYPE, METHOD, FIELD, PARAMETER})
public @interface Asynchronous {}
Example 9.4. Use the @Synchronous and @Asynchronous Qualifiers
@Synchronous
public class SynchronousPaymentProcessor implements PaymentProcessor {
public void process(Payment payment) { ... }
}
@Asynchronous
public class AsynchronousPaymentProcessor implements PaymentProcessor {
public void process(Payment payment) { ... }
}
