allow an EntityCopyObserverFactory in MERGE_ENTITY_COPY_OBSERVER setting

Author: gavinking

hibernate-core/src/main/java/org/hibernate/event/internal/EntityCopyNotAllowedObserver.java

@@ -45,12 +45,9 @@ public void entityCopyDetected(
 	}
 
 	private String getManagedOrDetachedEntityString(Object managedEntity, Object entity ) {
-		if ( entity == managedEntity) {
-			return  "Managed: [" + entity + "]";
-		}
-		else {
-			return "Detached: [" + entity + "]";
-		}
+		return entity == managedEntity
+				? "Managed: [" + entity + "]"
+				: "Detached: [" + entity + "]";
 	}
 
 	public void clear() {

hibernate-core/src/main/java/org/hibernate/event/internal/EntityCopyObserverFactoryInitiator.java

@@ -18,7 +18,7 @@
 
 /**
  * Looks for the configuration property {@value AvailableSettings#MERGE_ENTITY_COPY_OBSERVER} and registers
- * the matching {@link EntityCopyObserverFactory} based on the configuration value.
+ * the matching {@link EntityCopyObserverFactory} based on the configuration observerClass.
  * <p>
  * For known implementations some optimisations are possible, such as reusing a singleton for the stateless
  * implementations. When a user plugs in a custom {@link EntityCopyObserver} we take a defensive approach.
@@ -32,7 +32,10 @@ public class EntityCopyObserverFactoryInitiator implements StandardServiceInitia
 	@Override
 	public EntityCopyObserverFactory initiateService(final Map<String, Object> configurationValues, final ServiceRegistryImplementor registry) {
 		final Object value = getConfigurationValue( configurationValues );
-		if ( value.equals( EntityCopyNotAllowedObserver.SHORT_NAME )
+		if ( value instanceof EntityCopyObserverFactory factory ) {
+			return factory;
+		}
+		else if ( value.equals( EntityCopyNotAllowedObserver.SHORT_NAME )
 				|| value.equals( EntityCopyNotAllowedObserver.class.getName() ) ) {
 			LOG.debugf( "Configured EntityCopyObserver strategy: %s", EntityCopyNotAllowedObserver.SHORT_NAME );
 			return EntityCopyNotAllowedObserver.FACTORY_OF_SELF;
@@ -48,15 +51,16 @@ else if ( value.equals( EntityCopyAllowedLoggedObserver.SHORT_NAME )
 			return EntityCopyAllowedLoggedObserver.FACTORY_OF_SELF;
 		}
 		else {
-			//We load an "example instance" just to get its Class;
-			//this might look excessive, but it also happens to test eagerly (at boot) that we can actually construct these
-			//and that they are indeed of the right type.
+			// We load an "example instance" just to get its Class;
+			// this might look excessive, but it also happens to test eagerly
+			// (at boot) that we can actually construct these and that they
+			// are indeed of the right type.
 			final EntityCopyObserver exampleInstance =
 					registry.requireService( StrategySelector.class )
 							.resolveStrategy( EntityCopyObserver.class, value );
-			final Class<?> observerType = exampleInstance.getClass();
-			LOG.debugf( "Configured EntityCopyObserver is a custom implementation of type %s", observerType.getName() );
-			return new EntityObserversFactoryFromClass( observerType );
+			final Class<? extends EntityCopyObserver> observerType = exampleInstance.getClass();
+			LOG.debugf( "Configured EntityCopyObserver is a custom implementation of type '%s'", observerType.getName() );
+			return new EntityCopyObserverFactoryFromClass( observerType );
 		}
 	}
 
@@ -78,23 +82,17 @@ public Class<EntityCopyObserverFactory> getServiceInitiated() {
 		return EntityCopyObserverFactory.class;
 	}
 
-	private static class EntityObserversFactoryFromClass implements EntityCopyObserverFactory {
-
-		private final Class<?> value;
-
-		public EntityObserversFactoryFromClass(Class<?> value) {
-			this.value = value;
-		}
+	private record EntityCopyObserverFactoryFromClass(Class<? extends EntityCopyObserver> observerClass)
+			implements EntityCopyObserverFactory {
 
 		@Override
-		public EntityCopyObserver createEntityCopyObserver() {
-			try {
-				return (EntityCopyObserver) value.newInstance();
-			}
-			catch (Exception e) {
-				throw new HibernateException( "Could not instantiate class of type " + value.getName() );
+			public EntityCopyObserver createEntityCopyObserver() {
+				try {
+					return observerClass.newInstance();
+				}
+				catch (Exception e) {
+					throw new HibernateException( "Could not instantiate class of type " + observerClass.getName() );
+				}
 			}
 		}
-	}
-
 }

hibernate-core/src/main/java/org/hibernate/event/spi/EntityCopyObserver.java

@@ -24,14 +24,14 @@ public interface EntityCopyObserver {
 	void entityCopyDetected(Object managedEntity, Object mergeEntity1, Object mergeEntity2, EventSource session);
 
 	/**
-	 * Called when the top-level merge operation is complete.
+	 * Called when the toplevel merge operation is complete.
 	 *
 	 * @param session The session
 	 */
 	void topLevelMergeComplete(EventSource session);
 
 	/**
-	 * Called to clear any data stored in this EntityCopyObserver.
+	 * Called to clear any data stored in this {@code EntityCopyObserver}.
 	 */
 	void clear();
 }

hibernate-core/src/main/java/org/hibernate/event/spi/EntityCopyObserverFactory.java

@@ -6,6 +6,9 @@
 
 import org.hibernate.service.Service;
 
+/**
+ * A {@linkplain Service service} which creates new instances of {@link EntityCopyObserver}.
+ */
 @FunctionalInterface
 public interface EntityCopyObserverFactory extends Service {
 	EntityCopyObserver createEntityCopyObserver();