Enterprise Java

HOW-TO: Register components using @Conditional and Condition in Spring

@Profile annotation in Spring can be used on any Spring components (e.g. @Component, @Service, @Configuration etc.) that are candidates for auto-detection. @Profile annotation accepts a single profile or a set of profiles that must be active in order to make the annotated component eligible for auto-detection. For a given @Profile({"p1", "!p2"}), registration will occur if profile p1 is active or if profile p2 is not active. The or is crucial here.

But how to achieve this with @Profile: we want to activate a given component if profile p1 is active and if profiles p2 and p3 are both inactive?

Let’s assume the following situation: we have aNotificationSender interface that is implemented by:

  • SendGridNotificationSender – active only if sendgrid profile is active,
  • EmailNotificationSender – active only if email profile is active.
  • NoOpNotificationSender – active only if development profile is active and none of sendgrid and email are active.

In addition: only one NotificationSender can be registered at a time and development profile can be used in conjunction with sendgrid and email profiles.

In the above situation using the @Profile annotation seems not enough. Maybe I am complicating things a bit, but actually I really wanted to achieve the above without introducing another profile. And how I did it?

I used Spring’s 4 @Conditional annotation. @Conditional allow registration of component when all specified Condition(s) match:

@Component
@Conditional(value = NoOpNotificationSender.ProfilesCondition.class)
class NoOpNotificationSender extends NotificationSenderAdapter {

}

ProfilesCondition implements org.springframework.context.annotation.Condition interface:

public static class ProfilesCondition implements Condition {
    @Override
    public boolean matches(ConditionContext c, AnnotatedTypeMetadata m) {

    }
}

The whole solution to the problem:

@Component
@Conditional(value = NoOpNotificationSender.ProfilesCondition.class)
class NoOpNotificationSender extends NotificationSenderAdapter {

    static class ProfilesCondition implements Condition {
        @Override
        public boolean matches(ConditionContext c, AnnotatedTypeMetadata m) {
            return accepts(c, Profiles.DEVELOPMENT)
                && !accepts(c, Profiles.MAIL)
                && !accepts(c, Profiles.SEND_GRID);
        }

        private boolean accepts(ConditionContext c, String profile) {
            return c.getEnvironment().acceptsProfiles(profile);
        }
    }
}

The other components will be activated when appropriate profile is active:

@Component
@Profile(value = Profiles.SEND_GRID)
public class SendGridNotificationSender extends NotificationSenderAdapter {

}

@Component
@Profile(value = Profiles.MAIL)
class EmailNotificationSender extends NotificationSenderAdapter {

}

Usage examples:

Active profiles Bean
development NoOpNotificationSender
development,sendgrid SendGridNotificationSender
development,mail EmailNotificationSender
sendgrid SendGridNotificationSender
mail EmailNotificationSender

 
What do you think? How would you solve this problem?

Rafal Borowiec

Software developer, Team Leader, Agile practitioner, occasional blogger, lecturer. Open Source enthusiast, quality oriented and open-minded.
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