Enhance PersistentApplicationEventMulticaster to support externalization configuration and add warning for events published outside transaction context.

Signed-off-by: yunhobb <a01049048063@gmail.com>

Author: yunhobb

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/config/EventPublicationAutoConfiguration.java

@@ -39,6 +39,7 @@
 import org.springframework.context.annotation.Import;
 import org.springframework.context.annotation.Role;
 import org.springframework.core.env.Environment;
+import org.springframework.modulith.events.EventExternalizationConfiguration;
 import org.springframework.modulith.events.config.EventPublicationAutoConfiguration.AsyncEnablingConfiguration;
 import org.springframework.modulith.events.core.DefaultEventPublicationRegistry;
 import org.springframework.modulith.events.core.EventPublicationRegistry;
@@ -74,9 +75,11 @@ DefaultEventPublicationRegistry eventPublicationRegistry(EventPublicationReposit
 	@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
 	@ConditionalOnBean(EventPublicationRegistry.class)
 	static PersistentApplicationEventMulticaster applicationEventMulticaster(
-			ObjectFactory<EventPublicationRegistry> eventPublicationRegistry, ObjectFactory<Environment> environment) {
+			ObjectFactory<EventPublicationRegistry> eventPublicationRegistry, ObjectFactory<Environment> environment,
+			ObjectProvider<EventExternalizationConfiguration> externalizationConfiguration) {
 
-		return EventPublicationConfiguration.applicationEventMulticaster(eventPublicationRegistry, environment);
+		return EventPublicationConfiguration.applicationEventMulticaster(eventPublicationRegistry, environment,
+				externalizationConfiguration);
 	}
 
 	@Bean

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/config/EventPublicationConfiguration.java

@@ -24,6 +24,7 @@
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Role;
 import org.springframework.core.env.Environment;
+import org.springframework.modulith.events.EventExternalizationConfiguration;
 import org.springframework.modulith.events.core.DefaultEventPublicationRegistry;
 import org.springframework.modulith.events.core.EventPublicationRegistry;
 import org.springframework.modulith.events.core.EventPublicationRepository;
@@ -51,10 +52,12 @@ DefaultEventPublicationRegistry eventPublicationRegistry(EventPublicationReposit
 	@Bean
 	@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
 	static PersistentApplicationEventMulticaster applicationEventMulticaster(
-			ObjectFactory<EventPublicationRegistry> eventPublicationRegistry, ObjectFactory<Environment> environment) {
+			ObjectFactory<EventPublicationRegistry> eventPublicationRegistry, ObjectFactory<Environment> environment,
+			ObjectProvider<EventExternalizationConfiguration> externalizationConfiguration) {
 
 		return new PersistentApplicationEventMulticaster(() -> eventPublicationRegistry.getObject(),
-				() -> environment.getObject());
+				() -> environment.getObject(),
+				() -> externalizationConfiguration.getIfAvailable(EventExternalizationConfiguration::disabled));
 	}
 
 	@Bean

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/support/PersistentApplicationEventMulticaster.java

@@ -37,6 +37,7 @@
 import org.springframework.core.ResolvableType;
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
 import org.springframework.core.env.Environment;
+import org.springframework.modulith.events.EventExternalizationConfiguration;
 import org.springframework.modulith.events.EventPublication;
 import org.springframework.modulith.events.FailedEventPublications;
 import org.springframework.modulith.events.IncompleteEventPublications;
@@ -47,6 +48,7 @@
 import org.springframework.modulith.events.core.TargetEventPublication;
 import org.springframework.transaction.event.TransactionPhase;
 import org.springframework.transaction.event.TransactionalApplicationListener;
+import org.springframework.transaction.support.TransactionSynchronizationManager;
 import org.springframework.util.Assert;
 
 /**
@@ -58,6 +60,7 @@
  * for incomplete publications.
  *
  * @author Oliver Drotbohm
+ * @author Yunho Jung
  * @see CompletionRegisteringAdvisor
  */
 public class PersistentApplicationEventMulticaster extends AbstractApplicationEventMulticaster
@@ -70,21 +73,26 @@ public class PersistentApplicationEventMulticaster extends AbstractApplicationEv
 
 	private final @NonNull Supplier<EventPublicationRegistry> registry;
 	private final @NonNull Supplier<Environment> environment;
+	private final @NonNull Supplier<EventExternalizationConfiguration> externalizationConfiguration;
 
 	/**
 	 * Creates a new {@link PersistentApplicationEventMulticaster} for the given {@link EventPublicationRegistry}.
 	 *
 	 * @param registry must not be {@literal null}.
 	 * @param environment must not be {@literal null}.
+	 * @param externalizationConfiguration must not be {@literal null}.
 	 */
 	public PersistentApplicationEventMulticaster(Supplier<EventPublicationRegistry> registry,
-			Supplier<Environment> environment) {
+			Supplier<Environment> environment,
+			Supplier<EventExternalizationConfiguration> externalizationConfiguration) {
 
 		Assert.notNull(registry, "EventPublicationRegistry must not be null!");
 		Assert.notNull(environment, "Environment must not be null!");
+		Assert.notNull(externalizationConfiguration, "EventExternalizationConfiguration must not be null!");
 
 		this.registry = registry;
 		this.environment = environment;
+		this.externalizationConfiguration = externalizationConfiguration;
 	}
 
 	/*
@@ -111,8 +119,13 @@ public void multicastEvent(ApplicationEvent event, @Nullable ResolvableType even
 			return;
 		}
 
-		new TransactionalEventListeners(listeners)
-				.ifPresent(it -> storePublications(it, getEventToPersist(event)));
+		var eventToPersist = getEventToPersist(event);
+		var transactionalListeners = new TransactionalEventListeners(listeners);
+
+		// Detect events configured for externalization published outside transaction context
+		detectEventPublishedOutsideTransaction(transactionalListeners, eventToPersist);
+
+		transactionalListeners.ifPresent(it -> storePublications(it, eventToPersist));
 
 		for (ApplicationListener listener : listeners) {
 			listener.onApplicationEvent(event);
@@ -273,6 +286,41 @@ private static boolean invokeShouldHandle(ApplicationListener<?> candidate, Appl
 		return true;
 	}
 
+	/**
+	 * Detects if an event selected for externalization is published outside a transaction context.
+	 * If detected, logs a warning message to help developers identify the problem.
+	 *
+	 * @param transactionalListeners the transactional event listeners
+	 * @param event the event being published
+	 */
+	private void detectEventPublishedOutsideTransaction(TransactionalEventListeners transactionalListeners,
+			Object event) {
+
+		// Transaction is active, no problem
+		if (TransactionSynchronizationManager.isActualTransactionActive()) {
+			return;
+		}
+
+		// No transactional listeners, nothing to check
+		if (!transactionalListeners.hasListeners()) {
+			return;
+		}
+
+		// Check if the event is configured for externalization
+		var config = externalizationConfiguration.get();
+		if (!config.supports(event)) {
+			return;
+		}
+
+		// Issue a warning log hinting at the problem
+		LOGGER.warn(
+				"Event {} is configured for externalization but published outside a transaction context. "
+						+ "Event externalization requires a transactional context to work properly. "
+						+ "The event will not be persisted to the event publication registry and externalization will not be triggered. "
+						+ "Consider publishing this event from a @Transactional method.",
+				event.getClass().getName());
+	}
+
 	/**
 	 * First-class collection to work with transactional event listeners, i.e. {@link ApplicationListener} instances that
 	 * implement {@link TransactionalApplicationListener}.

spring-modulith-events/spring-modulith-events-core/src/test/java/org/springframework/modulith/events/support/PersistentApplicationEventMulticasterUnitTests.java

@@ -31,6 +31,7 @@
 import org.springframework.core.ResolvableType;
 import org.springframework.core.env.MapPropertySource;
 import org.springframework.core.env.StandardEnvironment;
+import org.springframework.modulith.events.EventExternalizationConfiguration;
 import org.springframework.modulith.events.core.EventPublicationRegistry;
 import org.springframework.stereotype.Component;
 import org.springframework.transaction.event.TransactionPhase;
@@ -51,7 +52,8 @@ class PersistentApplicationEventMulticasterUnitTests {
 
 	@BeforeEach
 	void setUp() {
-		this.multicaster = new PersistentApplicationEventMulticaster(() -> registry, () -> environment);
+		this.multicaster = new PersistentApplicationEventMulticaster(() -> registry, () -> environment,
+				EventExternalizationConfiguration::disabled);
 	}
 
 	@Test // GH-240, GH-251