HHH-18909 fix NPE for READ_ONLY cached entity with array

Author: gavinking

hibernate-core/src/main/java/org/hibernate/sql/results/internal/ResultsHelper.java

@@ -77,14 +77,18 @@ public static void finalizeCollectionLoading(
 		}
 
 		if ( collectionDescriptor.getCollectionType().hasHolder() ) {
-			// in case of PersistentArrayHolder we have to realign the EntityEntry loaded state with
-			// the entity values
+			// in case of PersistentArrayHolder we have to realign
+			// the EntityEntry loaded state with the entity values
 			final Object owner = collectionInstance.getOwner();
 			final EntityEntry entry = persistenceContext.getEntry( owner );
-			final PluralAttributeMapping mapping = collectionDescriptor.getAttributeMapping();
-			final int propertyIndex = mapping.getStateArrayPosition();
 			final Object[] loadedState = entry.getLoadedState();
-			loadedState[propertyIndex] = mapping.getValue( owner );
+			if ( loadedState != null ) {
+				final PluralAttributeMapping mapping = collectionDescriptor.getAttributeMapping();
+				final int propertyIndex = mapping.getStateArrayPosition();
+				loadedState[propertyIndex] = mapping.getValue( owner );
+			}
+			// else it must be an immutable entity or loaded in read-only mode,
+			// but unfortunately we have no way to reliably determine that here
 			persistenceContext.addCollectionHolder( collectionInstance );
 		}
 

hibernate-core/src/test/java/org/hibernate/orm/test/cache/CachedReadOnlyArrayTest.java

@@ -0,0 +1,41 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.orm.test.cache;
+
+import jakarta.persistence.ElementCollection;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import org.hibernate.annotations.Cache;
+import org.hibernate.annotations.Immutable;
+import org.hibernate.testing.orm.junit.EntityManagerFactoryScope;
+import org.hibernate.testing.orm.junit.Jpa;
+import org.junit.jupiter.api.Test;
+
+import static org.hibernate.annotations.CacheConcurrencyStrategy.READ_ONLY;
+
+@Jpa(annotatedClasses = CachedReadOnlyArrayTest.Publication.class)
+class CachedReadOnlyArrayTest {
+
+	@Test
+	void testReadFromCache(EntityManagerFactoryScope scope) {
+		scope.inTransaction(em -> {
+			Publication entity1 = new Publication();
+			entity1.id = "123l";
+			em.persist(entity1);
+		});
+		scope.inTransaction(em -> em.find(Publication.class, "123l"/*, ReadOnlyMode.READ_ONLY*/));
+
+	}
+
+	@Immutable
+	@Entity
+	@Cache(usage = READ_ONLY)
+	static class Publication {
+		@Id
+		String id;
+		@ElementCollection
+		String[] topics;
+	}
+}