授權事件

每當授權被拒絕時，會觸發一個 AuthorizationDeniedEvent 事件。此外，對於已授予的授權，也可能觸發一個 AuthorizationGrantedEvent 事件。

要監聽這些事件，必須先發佈一個 AuthorizationEventPublisher。

Spring Security 的 SpringAuthorizationEventPublisher 可能就足夠了。它使用 Spring 的 ApplicationEventPublisher 釋出授權事件。

Java
Kotlin

@Bean
public AuthorizationEventPublisher authorizationEventPublisher
        (ApplicationEventPublisher applicationEventPublisher) {
    return new SpringAuthorizationEventPublisher(applicationEventPublisher);
}

@Bean
fun authorizationEventPublisher
        (applicationEventPublisher: ApplicationEventPublisher?): AuthorizationEventPublisher {
    return SpringAuthorizationEventPublisher(applicationEventPublisher)
}

然後，可以使用 Spring 的 @EventListener 支援。

Java
Kotlin

@Component
public class AuthenticationEvents {

    @EventListener
    public void onFailure(AuthorizationDeniedEvent failure) {
		// ...
    }
}

@Component
class AuthenticationEvents {

    @EventListener
    fun onFailure(failure: AuthorizationDeniedEvent?) {
        // ...
    }
}

授權已授予事件

由於 AuthorizationGrantedEvent 可能非常頻繁，預設情況下不釋出它們。

實際上，釋出這些事件可能需要您編寫一些業務邏輯，以確保您的應用程式不會被頻繁的授權事件淹沒。

您可以建立自己的事件釋出者來過濾成功事件。例如，以下發布者只發布那些需要 ROLE_ADMIN 的授權授予事件。

Java
Kotlin

@Component
public class MyAuthorizationEventPublisher implements AuthorizationEventPublisher {
    private final ApplicationEventPublisher publisher;
    private final AuthorizationEventPublisher delegate;

    public MyAuthorizationEventPublisher(ApplicationEventPublisher publisher) {
        this.publisher = publisher;
        this.delegate = new SpringAuthorizationEventPublisher(publisher);
    }

    @Override
    public <T> void publishAuthorizationEvent(Supplier<Authentication> authentication,
            T object, AuthorizationDecision decision) {
        if (decision == null) {
            return;
        }
        if (!decision.isGranted()) {
            this.delegate.publishAuthorizationEvent(authentication, object, decision);
            return;
        }
        if (shouldThisEventBePublished(decision)) {
            AuthorizationGrantedEvent granted = new AuthorizationGrantedEvent(
                    authentication, object, decision);
            this.publisher.publishEvent(granted);
        }
    }

    private boolean shouldThisEventBePublished(AuthorizationDecision decision) {
        if (!(decision instanceof AuthorityAuthorizationDecision)) {
            return false;
        }
        Collection<GrantedAuthority> authorities = ((AuthorityAuthorizationDecision) decision).getAuthorities();
        for (GrantedAuthority authority : authorities) {
            if ("ROLE_ADMIN".equals(authority.getAuthority())) {
                return true;
            }
        }
        return false;
    }
}

@Component
class MyAuthorizationEventPublisher(val publisher: ApplicationEventPublisher,
    val delegate: SpringAuthorizationEventPublisher = SpringAuthorizationEventPublisher(publisher)):
    AuthorizationEventPublisher {

    override fun <T : Any?> publishAuthorizationEvent(
        authentication: Supplier<Authentication>?,
        `object`: T,
        decision: AuthorizationDecision?
    ) {
        if (decision == null) {
            return
        }
        if (!decision.isGranted) {
            this.delegate.publishAuthorizationEvent(authentication, `object`, decision)
            return
        }
        if (shouldThisEventBePublished(decision)) {
            val granted = AuthorizationGrantedEvent(authentication, `object`, decision)
            this.publisher.publishEvent(granted)
        }
    }

    private fun shouldThisEventBePublished(decision: AuthorizationDecision): Boolean {
        if (decision !is AuthorityAuthorizationDecision) {
            return false
        }
        val authorities = decision.authorities
        for (authority in authorities) {
            if ("ROLE_ADMIN" == authority.authority) {
                return true
            }
        }
        return false
    }
}