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