HHH-19056 prevent NPE when using @mapsid on an embeddable

Author: robwgreenjr

hibernate-core/src/main/java/org/hibernate/id/CompositeNestedGeneratedValueGenerator.java

@@ -18,6 +18,7 @@
 import org.hibernate.type.CompositeType;
 
 import static org.hibernate.generator.EventType.INSERT;
+import static org.hibernate.internal.util.ReflectHelper.getDefaultSupplier;
 
 /**
  * For composite identifiers, defines a number of "nested" generations that
@@ -131,9 +132,12 @@ public void addGeneratedValuePlan(GenerationPlan plan) {
 
 	@Override
 	public Object generate(SharedSessionContractImplementor session, Object object) {
-		final Object context = generationContextLocator.locateGenerationContext( session, object );
+		Object context = generationContextLocator.locateGenerationContext( session, object );
+		if ( context == null ) {
+			context = getDefaultSupplier( compositeType.getReturnedClass() ).get();
+		}
 		final List<Object> generatedValues = generatedValues( session, object, context );
-		if ( generatedValues != null) {
+		if ( generatedValues != null ) {
 			final Object[] values = compositeType.getPropertyValues( context );
 			for ( int i = 0; i < generatedValues.size(); i++ ) {
 				values[generationPlans.get( i ).getPropertyIndex()] = generatedValues.get( i );

hibernate-core/src/test/java/org/hibernate/orm/test/annotations/mapsid/MapsEmbeddedIdNullTest.java

@@ -0,0 +1,105 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.orm.test.annotations.mapsid;
+
+import jakarta.persistence.CascadeType;
+import jakarta.persistence.EmbeddedId;
+import jakarta.persistence.Entity;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.Id;
+import jakarta.persistence.ManyToOne;
+import jakarta.persistence.MapsId;
+import jakarta.persistence.OneToMany;
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.Jira;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+
+
+@SessionFactory
+@DomainModel(
+		annotatedClasses = {
+				MapsEmbeddedIdNullTest.Level0.class,
+				MapsEmbeddedIdNullTest.Level1.class,
+				MapsEmbeddedIdNullTest.Level2.class
+		})
+@Jira("https://hibernate.atlassian.net/browse/HHH-19056")
+public class MapsEmbeddedIdNullTest {
+
+	@Test
+	void test(SessionFactoryScope scope) {
+		scope.inTransaction( s -> {
+			Level0 level0 = new Level0();
+			Level2 level2 = new Level2();
+			Level1 level1 = new Level1( level0, level2 );
+			level0.level1s.add( level1 );
+			s.persist( level0 );
+		} );
+	}
+
+	@Entity(name = "Level0")
+	public static class Level0 {
+		@Id
+		@GeneratedValue
+		private Integer id;
+		@OneToMany(mappedBy = "level0", cascade = CascadeType.ALL)
+		private List<Level1> level1s = new ArrayList<>();
+	}
+
+	@Entity(name = "Level1")
+	public static class Level1 {
+		@EmbeddedId
+		Level1PK id;
+		@MapsId("level0Id")
+		@ManyToOne
+		private Level0 level0;
+		@MapsId("level2Id")
+		@ManyToOne(cascade = CascadeType.ALL)
+		private Level2 level2;
+
+		public Level1() {
+		}
+
+		public Level1(Level0 level0, Level2 level2) {
+			super();
+			this.level0 = level0;
+			this.level2 = level2;
+		}
+	}
+
+	@Entity(name = "Level2")
+	public static class Level2 {
+		@Id
+		@GeneratedValue
+		private Integer id;
+	}
+
+	public static class Level1PK {
+		private Integer level0Id;
+		private Integer level2Id;
+
+		@Override
+		public final boolean equals(Object o) {
+			if ( !(o instanceof Level1PK level1PK) ) {
+				return false;
+			}
+
+			return Objects.equals( level0Id, level1PK.level0Id )
+				&& Objects.equals( level2Id, level1PK.level2Id );
+		}
+
+		@Override
+		public int hashCode() {
+			int result = Objects.hashCode( level0Id );
+			result = 31 * result + Objects.hashCode( level2Id );
+			return result;
+		}
+	}
+}