HHH-17966 EAGER collections in StatelessSession (#8186)

hibernate-core/src/main/java/org/hibernate/engine/spi/SharedSessionDelegatorBaseImpl.java

@@ -26,7 +26,6 @@ import org.hibernate.engine.jdbc.LobCreator;
 import org.hibernate.engine.jdbc.connections.spi.JdbcConnectionAccess;
 import org.hibernate.engine.jdbc.spi.JdbcCoordinator;
 import org.hibernate.engine.jdbc.spi.JdbcServices;
-import org.hibernate.event.spi.AutoFlushEvent;
 import org.hibernate.event.spi.EventManager;
 import org.hibernate.graph.RootGraph;
 import org.hibernate.jdbc.ReturningWork;

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

@@ -48,7 +48,7 @@ public abstract class AbstractCollectionEvent extends AbstractEvent {
 
 	protected static CollectionPersister getLoadedCollectionPersister( PersistentCollection<?> collection, EventSource source ) {
 		CollectionEntry ce = source.getPersistenceContextInternal().getCollectionEntry( collection );
-		return ( ce == null ? null : ce.getLoadedPersister() );		
+		return ce == null ? null : ce.getLoadedPersister();
 	}
 
 	protected static Object getLoadedOwnerOrNull( PersistentCollection<?> collection, EventSource source ) {
@@ -68,19 +68,24 @@ public abstract class AbstractCollectionEvent extends AbstractEvent {
 			CollectionPersister collectionPersister,
 			Object affectedOwner,
 			EventSource source ) {
-
-		// collectionPersister should not be null, but we don't want to throw
-		// an exception if it is null
-		String entityName = collectionPersister == null
-				? null
-				: collectionPersister.getOwnerEntityPersister().getEntityName();
 		if ( affectedOwner != null ) {
-			EntityEntry ee = source.getPersistenceContextInternal().getEntry( affectedOwner );
+			final EntityEntry entry =
-			if ( ee != null && ee.getEntityName() != null) {
+					source.getPersistenceContextInternal()
-				entityName = ee.getEntityName();
+							.getEntry( affectedOwner );
+			if ( entry != null && entry.getEntityName() != null ) {
+				return entry.getEntityName();
 			}
 		}
-		return entityName;
+
+		if ( collectionPersister != null ) {
+			return collectionPersister.getOwnerEntityPersister().getEntityName();
+		}
+		else {
+			// collectionPersister should not be null,
+			// but we don't want to throw an exception
+			// if it is null
+			return null;
+		}
 	}
 
 	public PersistentCollection<?> getCollection() {

hibernate-core/src/main/java/org/hibernate/internal/StatelessSessionImpl.java

@@ -23,6 +23,7 @@ import org.hibernate.cache.spi.access.EntityDataAccess;
 import org.hibernate.collection.spi.CollectionSemantics;
 import org.hibernate.collection.spi.PersistentCollection;
 import org.hibernate.engine.internal.StatefulPersistenceContext;
+import org.hibernate.engine.spi.CollectionEntry;
 import org.hibernate.engine.spi.EffectiveEntityGraph;
 import org.hibernate.engine.spi.EntityHolder;
 import org.hibernate.engine.spi.EntityKey;
@@ -71,6 +72,7 @@ import static org.hibernate.engine.internal.Versioning.setVersion;
 import static org.hibernate.event.internal.DefaultInitializeCollectionEventListener.handlePotentiallyEmptyCollection;
 import static org.hibernate.generator.EventType.INSERT;
 import static org.hibernate.internal.util.NullnessUtil.castNonNull;
+import static org.hibernate.pretty.MessageHelper.collectionInfoString;
 import static org.hibernate.pretty.MessageHelper.infoString;
 import static org.hibernate.proxy.HibernateProxy.extractLazyInitializer;
 
@@ -529,16 +531,35 @@ public class StatelessSessionImpl extends AbstractSharedSessionContract implemen
 	}
 
 	@Override
-	public void initializeCollection(
+	public void initializeCollection(PersistentCollection<?> collection, boolean writing)
-			PersistentCollection<?> collection,
+			throws HibernateException {
-			boolean writing) throws HibernateException {
+		final PersistenceContext persistenceContext = getPersistenceContextInternal();
-		throw new SessionException( "collections cannot be fetched by a stateless session" );
+		final CollectionEntry ce = persistenceContext.getCollectionEntry( collection );
+		if ( ce == null ) {
+			throw new HibernateException( "no entry for collection" );
+		}
+		if ( !collection.wasInitialized() ) {
+			final CollectionPersister loadedPersister = ce.getLoadedPersister();
+			final Object loadedKey = ce.getLoadedKey();
+			if ( LOG.isTraceEnabled() ) {
+				LOG.tracev( "Initializing collection {0}",
+						collectionInfoString( loadedPersister, collection, loadedKey, this ) );
+			}
+			loadedPersister.initialize( loadedKey, this );
+			handlePotentiallyEmptyCollection( collection, persistenceContext, loadedKey, loadedPersister );
+			if ( LOG.isTraceEnabled() ) {
+				LOG.trace( "Collection initialized" );
+			}
+			//TODO: statistics!
+//			final StatisticsImplementor statistics = getFactory().getStatistics();
+//			if ( statistics.isStatisticsEnabled() ) {
+//				statistics.fetchCollection( loadedPersister.getRole() );
+//			}
+		}
 	}
 
 	@Override
-	public Object instantiate(
+	public Object instantiate(String entityName, Object id) throws HibernateException {
-			String entityName,
-			Object id) throws HibernateException {
 		return instantiate( getEntityPersister( entityName ), id );
 	}
 

hibernate-core/src/test/java/org/hibernate/orm/test/stateless/EagerCollectionInStatelessTest.java

@@ -0,0 +1,63 @@
+package org.hibernate.orm.test.stateless;
+
+import jakarta.persistence.ElementCollection;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import org.hibernate.Hibernate;
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.junit.jupiter.api.Test;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import static jakarta.persistence.FetchType.EAGER;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+@SessionFactory
+@DomainModel(annotatedClasses = EagerCollectionInStatelessTest.WithEagerCollection.class)
+public class EagerCollectionInStatelessTest {
+	@Test
+	void test(SessionFactoryScope scope) {
+		scope.inStatelessTransaction(s-> {
+			WithEagerCollection entity = new WithEagerCollection();
+			entity.eager.add("Hello");
+			entity.eager.add("World");
+			entity.lazy.add("Goodbye");
+			entity.lazy.add("World");
+			s.insert(entity);
+		});
+		scope.inStatelessSession(s-> {
+			WithEagerCollection entity = s.get(WithEagerCollection.class, 69L);
+			assertTrue(Hibernate.isInitialized(entity.eager));
+			assertFalse(Hibernate.isInitialized(entity.lazy));
+			s.fetch(entity.lazy);
+			assertTrue(Hibernate.isInitialized(entity.lazy));
+			assertEquals(2, entity.eager.size());
+			assertEquals(2, entity.lazy.size());
+		});
+		scope.inStatelessSession(s-> {
+			WithEagerCollection entity =
+					s.createSelectionQuery("where id= 69L", WithEagerCollection.class)
+							.getSingleResult();
+			assertTrue(Hibernate.isInitialized(entity.eager));
+			assertFalse(Hibernate.isInitialized(entity.lazy));
+			s.fetch(entity.lazy);
+			assertTrue(Hibernate.isInitialized(entity.lazy));
+			assertEquals(2, entity.eager.size());
+			assertEquals(2, entity.lazy.size());
+		});
+	}
+
+	@Entity
+	static class WithEagerCollection {
+		@Id long id = 69L;
+		@ElementCollection(fetch = EAGER)
+		Set<String> eager = new HashSet<>();
+		@ElementCollection
+		Set<String> lazy = new HashSet<>();
+	}
+}