HHH-18060 - HbXmlTransformer work

* non-aggregated composite id
* extends

hibernate-core/src/main/java/org/hibernate/boot/MetadataSources.java

@@ -22,9 +22,11 @@ import org.hibernate.HibernateException;
 import org.hibernate.Internal;
 import org.hibernate.boot.archive.spi.InputStreamAccess;
 import org.hibernate.boot.internal.MetadataBuilderImpl;
+import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmHibernateMapping;
 import org.hibernate.boot.jaxb.internal.XmlSources;
-import org.hibernate.boot.jaxb.spi.JaxbBindableMappingDescriptor;
+import org.hibernate.boot.jaxb.mapping.spi.JaxbEntityMappingsImpl;
 import org.hibernate.boot.jaxb.spi.Binding;
+import org.hibernate.boot.jaxb.spi.JaxbBindableMappingDescriptor;
 import org.hibernate.boot.jaxb.spi.XmlSource;
 import org.hibernate.boot.registry.BootstrapServiceRegistry;
 import org.hibernate.boot.registry.BootstrapServiceRegistryBuilder;
@@ -37,6 +39,8 @@ import org.hibernate.internal.CoreMessageLogger;
 import org.hibernate.service.ServiceRegistry;
 import org.hibernate.type.SerializationException;
 
+import static org.hibernate.internal.util.collections.CollectionHelper.arrayList;
+
 /**
  * Entry point for working with sources of O/R mapping metadata, either
  * in the form of annotated classes, or as XML mapping documents.
@@ -65,7 +69,9 @@ public class MetadataSources implements Serializable {
 
 	private XmlMappingBinderAccess xmlMappingBinderAccess;
 
-	private List<Binding<JaxbBindableMappingDescriptor>> xmlBindings;
+	private List<Binding<JaxbEntityMappingsImpl>> mappingXmlBindings;
+	private List<Binding<JaxbHbmHibernateMapping>> hbmXmlBindings;
+
 	private LinkedHashSet<Class<?>> annotatedClasses;
 	private LinkedHashSet<String> annotatedClassNames;
 	private LinkedHashSet<String> annotatedPackages;
@@ -121,8 +127,36 @@ public class MetadataSources implements Serializable {
 		return xmlMappingBinderAccess;
 	}
 
+	/**
+	 * @deprecated Prefer {@linkplain #getMappingXmlBindings()} and/or {@linkplain #getHbmXmlBindings()}
+	 */
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	@Deprecated(since = "7.0")
 	public List<Binding<JaxbBindableMappingDescriptor>> getXmlBindings() {
-		return xmlBindings == null ? Collections.emptyList() : xmlBindings;
+		if ( mappingXmlBindings == null && hbmXmlBindings == null ) {
+			return Collections.emptyList();
+		}
+
+		if ( hbmXmlBindings == null ) {
+			return (List) mappingXmlBindings;
+		}
+
+		if ( mappingXmlBindings == null ) {
+			return (List) hbmXmlBindings;
+		}
+
+		final ArrayList<Binding<JaxbBindableMappingDescriptor>> combined = arrayList( mappingXmlBindings.size() + hbmXmlBindings.size() );
+		combined.addAll( (List) mappingXmlBindings );
+		combined.addAll( (List) hbmXmlBindings );
+		return combined;
+	}
+
+	public List<Binding<JaxbEntityMappingsImpl>> getMappingXmlBindings() {
+		return mappingXmlBindings == null ? Collections.emptyList() : mappingXmlBindings;
+	}
+
+	public List<Binding<JaxbHbmHibernateMapping>> getHbmXmlBindings() {
+		return hbmXmlBindings == null ? Collections.emptyList() : hbmXmlBindings;
 	}
 
 	public Collection<String> getAnnotatedPackages() {
@@ -329,7 +363,7 @@ public class MetadataSources implements Serializable {
 	public MetadataSources addResource(String name) {
 		final XmlSource xmlSource = XmlSources.fromResource( name, classLoaderService );
 		final XmlMappingBinderAccess binderAccess = getXmlMappingBinderAccess();
-		getXmlBindingsForWrite().add( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
+		addXmlBinding( xmlSource.doBind( binderAccess.getMappingBinder() ) );
 		return this;
 	}
 
@@ -359,7 +393,7 @@ public class MetadataSources implements Serializable {
 	public MetadataSources addFile(File file) {
 		final XmlSource xmlSource = XmlSources.fromFile( file );
 		final XmlMappingBinderAccess binderAccess = getXmlMappingBinderAccess();
-		getXmlBindingsForWrite().add( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
+		addXmlBinding( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
 		return this;
 	}
 
@@ -372,8 +406,45 @@ public class MetadataSources implements Serializable {
 	 * @return this (for method chaining purposes)
 	 */
 	public MetadataSources addXmlBinding(Binding<?> binding) {
+		if ( binding.getRoot() instanceof JaxbEntityMappingsImpl ) {
 			//noinspection unchecked
-		getXmlBindingsForWrite().add( (Binding<JaxbBindableMappingDescriptor>) binding );
+			return addMappingXmlBinding( (Binding<JaxbEntityMappingsImpl>) binding );
+		}
+		else if ( binding.getRoot() instanceof JaxbHbmHibernateMapping ) {
+			//noinspection unchecked
+			return addHbmXmlBinding( (Binding<JaxbHbmHibernateMapping>) binding );
+		}
+
+		throw new UnsupportedOperationException( "Unknown type of binding : " + binding.getRoot() );
+	}
+
+	/**
+	 * Add a {@linkplain Binding binding} for {@linkplain JaxbEntityMappingsImpl mapping.xsd} document
+	 *
+	 * @param binding The binding
+	 *
+	 * @return this (for method chaining purposes)
+	 */
+	public MetadataSources addMappingXmlBinding(Binding<JaxbEntityMappingsImpl> binding) {
+		if ( mappingXmlBindings == null ) {
+			mappingXmlBindings = new ArrayList<>();
+		}
+		mappingXmlBindings.add( binding );
+		return this;
+	}
+
+	/**
+	 * Add a {@linkplain Binding binding} for {@linkplain JaxbHbmHibernateMapping hbm.xsd} document
+	 *
+	 * @param binding The binding
+	 *
+	 * @return this (for method chaining purposes)
+	 */
+	public MetadataSources addHbmXmlBinding(Binding<JaxbHbmHibernateMapping> binding) {
+		if ( hbmXmlBindings == null ) {
+			hbmXmlBindings = new ArrayList<>();
+		}
+		hbmXmlBindings.add( binding );
 		return this;
 	}
 
@@ -444,7 +515,7 @@ public class MetadataSources implements Serializable {
 	public MetadataSources addCacheableFile(File file, File cacheDirectory) {
 		final XmlSource xmlSource = XmlSources.fromCacheableFile( file, cacheDirectory );
 		final XmlMappingBinderAccess binderAccess = getXmlMappingBinderAccess();
-		getXmlBindingsForWrite().add( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
+		addXmlBinding( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
 		return this;
 	}
 
@@ -464,7 +535,7 @@ public class MetadataSources implements Serializable {
 	public MetadataSources addCacheableFileStrictly(File file) throws SerializationException {
 		final XmlSource xmlSource = XmlSources.fromCacheableFile( file, true );
 		final XmlMappingBinderAccess binderAccess = getXmlMappingBinderAccess();
-		getXmlBindingsForWrite().add( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
+		addXmlBinding( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
 		return this;
 	}
 
@@ -484,7 +555,7 @@ public class MetadataSources implements Serializable {
 	public MetadataSources addCacheableFileStrictly(File file, File cacheDir) throws SerializationException {
 		final XmlSource xmlSource = XmlSources.fromCacheableFile( file, cacheDir, true );
 		final XmlMappingBinderAccess binderAccess = getXmlMappingBinderAccess();
-		getXmlBindingsForWrite().add( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
+		addXmlBinding( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
 		return this;
 	}
 
@@ -498,7 +569,7 @@ public class MetadataSources implements Serializable {
 	public MetadataSources addInputStream(InputStreamAccess xmlInputStreamAccess) {
 		final XmlSource xmlSource = XmlSources.fromStream( xmlInputStreamAccess );
 		final XmlMappingBinderAccess binderAccess = getXmlMappingBinderAccess();
-		getXmlBindingsForWrite().add( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
+		addXmlBinding( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
 		return this;
 	}
 
@@ -512,7 +583,7 @@ public class MetadataSources implements Serializable {
 	public MetadataSources addInputStream(InputStream xmlInputStream) {
 		final XmlSource xmlSource = XmlSources.fromStream( xmlInputStream );
 		final XmlMappingBinderAccess binderAccess = getXmlMappingBinderAccess();
-		getXmlBindingsForWrite().add( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
+		addXmlBinding( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
 		return this;
 	}
 
@@ -526,7 +597,7 @@ public class MetadataSources implements Serializable {
 	public MetadataSources addURL(URL url) {
 		final XmlSource xmlSource = XmlSources.fromUrl( url );
 		final XmlMappingBinderAccess binderAccess = getXmlMappingBinderAccess();
-		getXmlBindingsForWrite().add( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
+		addXmlBinding( xmlSource.doBind( binderAccess.getMappingBinder()  ) );
 		return this;
 	}
 
@@ -544,18 +615,11 @@ public class MetadataSources implements Serializable {
 		final XmlMappingBinderAccess binderAccess = getXmlMappingBinderAccess();
 		XmlSources.fromJar(
 				jar,
-				xmlSource -> getXmlBindingsForWrite().add( xmlSource.doBind( binderAccess.getMappingBinder() ) )
+				xmlSource -> addXmlBinding( xmlSource.doBind( binderAccess.getMappingBinder() ) )
 		);
 		return this;
 	}
 
-	private List<Binding<JaxbBindableMappingDescriptor>> getXmlBindingsForWrite() {
-		if ( xmlBindings == null ) {
-			xmlBindings = new ArrayList<>();
-		}
-		return xmlBindings;
-	}
-
 	/**
 	 * Read all {@code .hbm.xml} mapping documents from a directory tree.
 	 * <p>

hibernate-core/src/main/java/org/hibernate/boot/jaxb/hbm/transform/HbmXmlTransformer.java

@@ -83,6 +83,7 @@ import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmRootEntityType;
 import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmSecondaryTableType;
 import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmSetType;
 import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmSimpleIdType;
+import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmSubclassEntityBaseDefinition;
 import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmSynchronizeType;
 import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmTimestampAttributeType;
 import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmUnionSubclassEntityType;
@@ -155,6 +156,7 @@ import org.hibernate.boot.jaxb.mapping.spi.JaxbTableImpl;
 import org.hibernate.boot.jaxb.mapping.spi.JaxbTransientImpl;
 import org.hibernate.boot.jaxb.mapping.spi.JaxbUserTypeImpl;
 import org.hibernate.boot.jaxb.mapping.spi.JaxbVersionImpl;
+import org.hibernate.boot.jaxb.spi.Binding;
 import org.hibernate.internal.util.StringHelper;
 import org.hibernate.internal.util.collections.CollectionHelper;
 
@@ -170,54 +172,65 @@ import jakarta.xml.bind.JAXBException;
 import jakarta.xml.bind.Marshaller;
 
 import static org.hibernate.boot.jaxb.hbm.transform.HbmTransformationLogging.TRANSFORMATION_LOGGER;
-import static org.hibernate.internal.util.StringHelper.coalesce;
 import static org.hibernate.internal.util.StringHelper.isNotEmpty;
 
 /**
- * Transforms a JAXB binding of a hbm.xml file into a unified orm.xml representation
+ * Transforms {@code hbm.xml} {@linkplain JaxbHbmHibernateMapping JAXB} bindings into
+ * {@code mapping.xml} {@linkplain JaxbEntityMappingsImpl JAXB} bindings
  *
  * @author Steve Ebersole
  * @author Brett Meyer
- *
- * @implNote This transformation happens on the JAXB model level creating
- * a {@link JaxbEntityMappingsImpl} "copy" of the {@link JaxbHbmHibernateMapping}
- * representation
  */
 public class HbmXmlTransformer {
 	/**
-	 * Main entry into hbm.xml transformation
+	 * Transforms a list of {@code hbm.xml} JAXB bindings into a list of {@code mapping.xml} JAXB bindings
 	 *
-	 * @param hbmXmlMapping The hbm.xml mapping to be transformed
+	 * @param hbmXmlBindings The list of {@code hbm.xml} JAXB bindings
-	 * @param origin The origin of the hbm.xml mapping
+	 * @param unsupportedFeatureHandling How to handle {@code hbm.xml} features we don't transform
-	 * @return The transformed representation
+	 *
+	 * @return The list of {@code mapping.xml} JAXB bindings
 	 */
-	public static JaxbEntityMappingsImpl transform(JaxbHbmHibernateMapping hbmXmlMapping, Origin origin, Options options) {
+	public static List<Binding<JaxbEntityMappingsImpl>> transform(
-		return new HbmXmlTransformer( hbmXmlMapping, origin, options ).doTransform();
+			List<Binding<JaxbHbmHibernateMapping>> hbmXmlBindings,
+			UnsupportedFeatureHandling unsupportedFeatureHandling) {
+		final TransformationState transformationState = new TransformationState( hbmXmlBindings );
+		TransformationPreprocessor.preprocessHbmXml( hbmXmlBindings, transformationState );
+
+		for ( int i = 0; i < hbmXmlBindings.size(); i++ ) {
+			final Binding<JaxbHbmHibernateMapping> hbmJaxbBinding = hbmXmlBindings.get( i );
+			final Binding<JaxbEntityMappingsImpl> mappingJaxbBinding = transformationState.getMappingBindings().get( i );
+			final HbmXmlTransformer hbmXmlTransformer = new HbmXmlTransformer(
+					hbmJaxbBinding,
+					mappingJaxbBinding,
+					transformationState,
+					unsupportedFeatureHandling
+			);
+			hbmXmlTransformer.doTransform();
 		}
 
-	public interface Options {
+		return transformationState.getMappingBindings();
-		UnsupportedFeatureHandling unsupportedFeatureHandling();
 	}
 
 	private final Origin origin;
 	private final JaxbHbmHibernateMapping hbmXmlMapping;
 	private final JaxbEntityMappingsImpl ormRoot;
+	private final TransformationState transformationState;
+	private final UnsupportedFeatureHandling unsupportedFeatureHandling;
 
-	private final Options options;
-
-	public HbmXmlTransformer(JaxbHbmHibernateMapping hbmXmlMapping, Origin origin, Options options) {
-		this.origin = origin;
-		this.hbmXmlMapping = hbmXmlMapping;
-		this.options = options;
-
-		this.ormRoot = new JaxbEntityMappingsImpl();
-		this.ormRoot.setDescription(
-				"mapping.xml document auto-generated from legacy hbm.xml format via transformation - " + origin.getName()
-		);
 
+	private HbmXmlTransformer(
+			Binding<JaxbHbmHibernateMapping> hbmJaxbBinding,
+			Binding<JaxbEntityMappingsImpl> mappingJaxbBinding,
+			TransformationState transformationState,
+			UnsupportedFeatureHandling unsupportedFeatureHandling) {
+		this.origin = hbmJaxbBinding.getOrigin();
+		this.hbmXmlMapping = hbmJaxbBinding.getRoot();
+		this.ormRoot = mappingJaxbBinding.getRoot();
+		this.transformationState = transformationState;
+		this.unsupportedFeatureHandling = unsupportedFeatureHandling;
 	}
 
-	private JaxbEntityMappingsImpl doTransform() {
+	private void doTransform() {
 		TRANSFORMATION_LOGGER.tracef(
 				"Starting hbm.xml transformation - `%s`",
 				origin
@@ -247,7 +260,6 @@ public class HbmXmlTransformer {
 		if ( TRANSFORMATION_LOGGER.isDebugEnabled() ) {
 			dumpTransformed( origin, ormRoot );
 		}
-		return ormRoot;
 	}
 
 	private static void dumpTransformed(Origin origin, JaxbEntityMappingsImpl ormRoot) {
@@ -293,7 +305,7 @@ public class HbmXmlTransformer {
 	}
 
 	private void handleUnsupported(PickHandler pickHandler, String message, Object... messageArgs) {
-		switch ( options.unsupportedFeatureHandling() ) {
+		switch ( unsupportedFeatureHandling ) {
 			case ERROR -> throw new UnsupportedOperationException(
 					String.format(
 							Locale.ROOT,
@@ -807,32 +819,28 @@ public class HbmXmlTransformer {
 		//		2) ?? Have abstract hbm class mappings become MappedSuperclass mappings ??
 
 		for ( JaxbHbmRootEntityType hbmClass : hbmXmlMapping.getClazz() ) {
-			final JaxbEntityImpl entity = new JaxbEntityImpl();
+			final JaxbEntityImpl entity = transformationState.getEntityXref().get( hbmClass );
-			ormRoot.getEntities().add( entity );
 			transferRootEntity( hbmClass, entity );
 		}
 
 		for ( JaxbHbmDiscriminatorSubclassEntityType hbmSubclass : hbmXmlMapping.getSubclass() ) {
-			final JaxbEntityImpl entity = new JaxbEntityImpl();
+			final JaxbEntityImpl entity = transformationState.getEntityXref().get( hbmSubclass );
-			ormRoot.getEntities().add( entity );
 			transferDiscriminatorSubclass( hbmSubclass, entity );
 		}
 
 		for ( JaxbHbmJoinedSubclassEntityType hbmSubclass : hbmXmlMapping.getJoinedSubclass() ) {
-			final JaxbEntityImpl entity = new JaxbEntityImpl();
+			final JaxbEntityImpl entity = transformationState.getEntityXref().get( hbmSubclass );
-			ormRoot.getEntities().add( entity );
 			transferJoinedSubclass( hbmSubclass, entity );
 		}
 
 		for ( JaxbHbmUnionSubclassEntityType hbmSubclass : hbmXmlMapping.getUnionSubclass() ) {
-			final JaxbEntityImpl entity = new JaxbEntityImpl();
+			final JaxbEntityImpl entity = transformationState.getEntityXref().get( hbmSubclass );
-			ormRoot.getEntities().add( entity );
 			transferUnionSubclass( hbmSubclass, entity );
 		}
 
 	}
 
-	private String extractEntityName(EntityInfo entityInfo) {
+	private static String extractEntityName(EntityInfo entityInfo) {
 		if ( entityInfo.getEntityName() != null ) {
 			return entityInfo.getEntityName();
 		}
@@ -901,12 +909,12 @@ public class HbmXmlTransformer {
 		entity.setSqlRestriction( hbmClass.getWhere() );
 
 		if ( !hbmClass.getTuplizer().isEmpty() ) {
-			if ( options.unsupportedFeatureHandling() == UnsupportedFeatureHandling.ERROR ) {
+			if ( unsupportedFeatureHandling == UnsupportedFeatureHandling.ERROR ) {
 				throw new MappingException( "HBM transformation: Tuplizer not supported", origin );
 			}
 
 			TRANSFORMATION_LOGGER.logf(
-					options.unsupportedFeatureHandling() == UnsupportedFeatureHandling.WARN
+					unsupportedFeatureHandling == UnsupportedFeatureHandling.WARN
 							? Logger.Level.WARN
 							: Logger.Level.DEBUG,
 					"Transformation of <tuplizer/> is not supported - `%s`",
@@ -950,26 +958,17 @@ public class HbmXmlTransformer {
 		}
 		
 		for ( JaxbHbmJoinedSubclassEntityType hbmSubclass : hbmClass.getJoinedSubclass() ) {
-			entity.setInheritance( new JaxbInheritanceImpl() );
+			final JaxbEntityImpl subclassEntity = transformationState.getEntityXref().get( hbmSubclass );
-			entity.getInheritance().setStrategy( InheritanceType.JOINED );
-
-			final JaxbEntityImpl subclassEntity = new JaxbEntityImpl();
-			ormRoot.getEntities().add( subclassEntity );
 			transferJoinedSubclass( hbmSubclass, subclassEntity );
 		}
 		
 		for (JaxbHbmUnionSubclassEntityType hbmSubclass : hbmClass.getUnionSubclass() ) {
-			entity.setInheritance( new JaxbInheritanceImpl() );
+			final JaxbEntityImpl subclassEntity = transformationState.getEntityXref().get( hbmSubclass );
-			entity.getInheritance().setStrategy( InheritanceType.TABLE_PER_CLASS );
-
-			final JaxbEntityImpl subclassEntity = new JaxbEntityImpl();
-			ormRoot.getEntities().add( subclassEntity );
 			transferUnionSubclass( hbmSubclass, subclassEntity );
 		}
 		
 		for ( JaxbHbmDiscriminatorSubclassEntityType hbmSubclass : hbmClass.getSubclass() ) {
-			final JaxbEntityImpl subclassEntity = new JaxbEntityImpl();
+			final JaxbEntityImpl subclassEntity = transformationState.getEntityXref().get( hbmSubclass );
-			ormRoot.getEntities().add( subclassEntity );
 			transferDiscriminatorSubclass( hbmSubclass, subclassEntity );
 		}
 		
@@ -1023,6 +1022,19 @@ public class HbmXmlTransformer {
 		transfer( hbmClass::getEntityName, entity::setName );
 		transfer( hbmClass::getName, entity::setClazz );
 
+		if ( StringHelper.isEmpty( entity.getExtends() ) ) {
+			if ( hbmClass instanceof JaxbHbmSubclassEntityBaseDefinition hbmSubclass ) {
+				if ( StringHelper.isNotEmpty( hbmSubclass.getExtends() ) ) {
+					entity.setExtends( TransformationState.requireEntityReferenceName(
+							hbmSubclass.getExtends(),
+							hbmXmlMapping,
+							transformationState.getEntityMap(),
+							origin
+					) );
+				}
+			}
+		}
+
 		if ( hbmClass instanceof Discriminatable discriminatable ) {
 			transfer( discriminatable::getDiscriminatorValue, entity::setDiscriminatorValue );
 		}
@@ -1081,6 +1093,13 @@ public class HbmXmlTransformer {
 		transferBaseEntityInformation( hbmSubclass, subclassEntity );
 
 		transferEntityElementAttributes( hbmSubclass, subclassEntity );
+
+		if ( !hbmSubclass.getSubclass().isEmpty() ) {
+			for ( JaxbHbmDiscriminatorSubclassEntityType nestedHbmSubclass : hbmSubclass.getSubclass() ) {
+				final JaxbEntityImpl nestedSubclassEntity = transformationState.getEntityXref().get( nestedHbmSubclass );
+				transferDiscriminatorSubclass( nestedHbmSubclass, nestedSubclassEntity );
+			}
+		}
 	}
 
 	private void transferJoinedSubclass(JaxbHbmJoinedSubclassEntityType hbmSubclass, JaxbEntityImpl subclassEntity) {
@@ -1113,11 +1132,8 @@ public class HbmXmlTransformer {
 		}
 		
 		if ( !hbmSubclass.getJoinedSubclass().isEmpty() ) {
-			subclassEntity.setInheritance( new JaxbInheritanceImpl() );
-			subclassEntity.getInheritance().setStrategy( InheritanceType.JOINED );
 			for ( JaxbHbmJoinedSubclassEntityType nestedHbmSubclass : hbmSubclass.getJoinedSubclass() ) {
-				final JaxbEntityImpl nestedSubclassEntity = new JaxbEntityImpl();
+				final JaxbEntityImpl nestedSubclassEntity = transformationState.getEntityXref().get( nestedHbmSubclass );
-				ormRoot.getEntities().add( nestedSubclassEntity );
 				transferJoinedSubclass( nestedHbmSubclass, nestedSubclassEntity );
 			}
 		}
@@ -1284,7 +1300,15 @@ public class HbmXmlTransformer {
 				attributes.getEmbeddedAttributes().add( transformEmbedded( jaxbEmbeddable, hbmComponent ) );
 			}
 			else if ( hbmAttributeMapping instanceof JaxbHbmPropertiesType hbmProperties ) {
-				transferAttributes( hbmProperties.getAttributes(), attributes );
+				// while we could simply "unwrap" the <properties/> itself and inline the attributes,
+				// <properties/> is most often used to create a target for property-ref mappings - that
+				// we could not support without a new sort of annotation - e.g.
+				//
+				// @interface PropertyGroup {
+				// 		String name();
+				//		String[] propertyNames();
+				// }
+				handleUnsupported( "<properties/> mappings not supported for transformation [name=%s]", hbmProperties.getName() );
 			}
 			else if ( hbmAttributeMapping instanceof JaxbHbmDynamicComponentType ) {
 				final String name = ( (JaxbHbmDynamicComponentType) hbmAttributeMapping ).getName();
@@ -2401,11 +2425,8 @@ public class HbmXmlTransformer {
 		}
 
 		if ( !hbmSubclass.getUnionSubclass().isEmpty() ) {
-			subclassEntity.setInheritance( new JaxbInheritanceImpl() );
-			subclassEntity.getInheritance().setStrategy( InheritanceType.TABLE_PER_CLASS );
 			for ( JaxbHbmUnionSubclassEntityType nestedHbmSubclass : hbmSubclass.getUnionSubclass() ) {
-				final JaxbEntityImpl nestedSubclassEntity = new JaxbEntityImpl();
+				final JaxbEntityImpl nestedSubclassEntity = transformationState.getEntityXref().get( nestedHbmSubclass );
-				ormRoot.getEntities().add( nestedSubclassEntity );
 				transferUnionSubclass( nestedHbmSubclass, nestedSubclassEntity );
 			}
 		}

hibernate-core/src/main/java/org/hibernate/boot/jaxb/hbm/transform/TransformationPreprocessor.java

@@ -0,0 +1,368 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+ */
+package org.hibernate.boot.jaxb.hbm.transform;
+
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+
+import org.hibernate.boot.MappingException;
+import org.hibernate.boot.jaxb.Origin;
+import org.hibernate.boot.jaxb.hbm.spi.EntityInfo;
+import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmDiscriminatorSubclassEntityType;
+import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmEntityBaseDefinition;
+import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmHibernateMapping;
+import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmJoinedSubclassEntityType;
+import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmSubclassEntityBaseDefinition;
+import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmUnionSubclassEntityType;
+import org.hibernate.boot.jaxb.mapping.spi.JaxbEntityImpl;
+import org.hibernate.boot.jaxb.mapping.spi.JaxbEntityMappingsImpl;
+import org.hibernate.boot.jaxb.mapping.spi.JaxbInheritanceImpl;
+import org.hibernate.boot.jaxb.spi.Binding;
+import org.hibernate.internal.util.StringHelper;
+import org.hibernate.internal.util.collections.CollectionHelper;
+
+import jakarta.persistence.InheritanceType;
+
+/**
+ * @author Steve Ebersole
+ */
+public class TransformationPreprocessor {
+	static void preprocessHbmXml(
+			List<Binding<JaxbHbmHibernateMapping>> hbmXmlBindings,
+			TransformationState transformationState) {
+		final EntityMappingConsumer entityMappingConsumer = new EntityMappingConsumer( transformationState );
+		final Map<String, JaxbEntityImpl> rootClassesMap = new HashMap<>();
+
+		processStructuredHierarchies( hbmXmlBindings, rootClassesMap, entityMappingConsumer );
+		processSeparatedHierarchies( hbmXmlBindings, rootClassesMap, entityMappingConsumer );
+	}
+
+	private static void processStructuredHierarchies(
+			Collection<Binding<JaxbHbmHibernateMapping>> hbmXmlBindings,
+			Map<String, JaxbEntityImpl> rootClassesMap,
+			EntityMappingConsumer entityMappingConsumer) {
+		hbmXmlBindings.forEach( (hbmBinding) -> {
+			processStructuredHierarchies( rootClassesMap, entityMappingConsumer, hbmBinding );
+		} );
+	}
+
+	private static void processStructuredHierarchies(
+			Map<String, JaxbEntityImpl> rootClassesMap,
+			EntityMappingConsumer entityMappingConsumer,
+			Binding<JaxbHbmHibernateMapping> hbmBinding) {
+		final JaxbHbmHibernateMapping hibernateMapping = hbmBinding.getRoot();
+		hibernateMapping.getClazz().forEach( (hbmRoot) -> {
+			final JaxbEntityImpl rootJaxbEntity = makeJaxbEntity( hbmRoot, hibernateMapping );
+			final String entityName = determineEntityName( hbmRoot, hibernateMapping );
+
+			entityMappingConsumer.accept( hbmBinding, entityName, hbmRoot, rootJaxbEntity );
+			rootClassesMap.put( entityName, rootJaxbEntity );
+
+			if ( CollectionHelper.isNotEmpty( hbmRoot.getSubclass() ) ) {
+				applyInheritanceStrategy( entityName, rootJaxbEntity, InheritanceType.SINGLE_TABLE );
+				processStructuredDiscriminatorSubclasses(
+						hbmRoot.getSubclass(),
+						entityName,
+						hbmBinding,
+						entityMappingConsumer
+				);
+			}
+
+			if ( CollectionHelper.isNotEmpty( hbmRoot.getJoinedSubclass() ) ) {
+				applyInheritanceStrategy( entityName, rootJaxbEntity, InheritanceType.JOINED );
+				processStructuredJoinedSubclasses(
+						hbmRoot.getJoinedSubclass(),
+						entityName,
+						hbmBinding,
+						entityMappingConsumer
+				);
+			}
+
+			if ( CollectionHelper.isNotEmpty( hbmRoot.getUnionSubclass() ) ) {
+				applyInheritanceStrategy( entityName, rootJaxbEntity, InheritanceType.TABLE_PER_CLASS );
+				processStructuredUnionSubclasses(
+						hbmRoot.getUnionSubclass(),
+						entityName,
+						hbmBinding,
+						entityMappingConsumer
+				);
+			}
+		} );
+	}
+
+	private static void applyInheritanceStrategy(String entityName, JaxbEntityImpl rootJaxbEntity, InheritanceType strategy) {
+		final JaxbInheritanceImpl existing = rootJaxbEntity.getInheritance();
+		if ( existing != null ) {
+			if ( existing.getStrategy() != null && existing.getStrategy() != strategy ) {
+				throw new IllegalStateException( String.format(
+						Locale.ROOT,
+						"Root entity `%s` defined a mix of inheritance strategies; at least %s and %s",
+						entityName,
+						strategy,
+						existing.getStrategy()
+				) );
+			}
+			existing.setStrategy( strategy );
+		}
+		else {
+			final JaxbInheritanceImpl created = new JaxbInheritanceImpl();
+			created.setStrategy( strategy );
+			rootJaxbEntity.setInheritance( created );
+		}
+	}
+
+	private static void processStructuredDiscriminatorSubclasses(
+			List<JaxbHbmDiscriminatorSubclassEntityType> hbmSubclasses,
+			String superEntityName,
+			Binding<JaxbHbmHibernateMapping> hbmBinding,
+			EntityMappingConsumer entityMappingConsumer) {
+		hbmSubclasses.forEach( (hbmSubclass) -> {
+			final JaxbEntityImpl subclassJaxbEntity = makeJaxbEntity( hbmSubclass, hbmBinding.getRoot() );
+			final String subclassEntityName = determineEntityName( hbmSubclass, hbmBinding.getRoot() );
+			entityMappingConsumer.accept( hbmBinding, subclassEntityName, hbmSubclass, subclassJaxbEntity );
+
+			subclassJaxbEntity.setExtends( superEntityName );
+
+			if ( CollectionHelper.isNotEmpty( hbmSubclass.getSubclass() ) ) {
+				processStructuredDiscriminatorSubclasses(
+						hbmSubclass.getSubclass(),
+						subclassEntityName,
+						hbmBinding,
+						entityMappingConsumer
+				);
+			}
+		} );
+	}
+
+	private static void processStructuredJoinedSubclasses(
+			List<JaxbHbmJoinedSubclassEntityType> hbmSubclasses,
+			String superEntityName,
+			Binding<JaxbHbmHibernateMapping> hbmBinding,
+			EntityMappingConsumer entityMappingConsumer) {
+		hbmSubclasses.forEach( (hbmSubclass) -> {
+			final JaxbEntityImpl subclassJaxbEntity = makeJaxbEntity( hbmSubclass, hbmBinding.getRoot() );
+			final String subclassEntityName = determineEntityName( hbmSubclass, hbmBinding.getRoot() );
+			entityMappingConsumer.accept( hbmBinding, subclassEntityName, hbmSubclass, subclassJaxbEntity );
+
+			subclassJaxbEntity.setExtends( superEntityName );
+
+			if ( CollectionHelper.isNotEmpty( hbmSubclass.getJoinedSubclass() ) ) {
+				processStructuredJoinedSubclasses(
+						hbmSubclass.getJoinedSubclass(),
+						subclassEntityName,
+						hbmBinding,
+						entityMappingConsumer
+				);
+			}
+		} );
+	}
+
+	private static void processStructuredUnionSubclasses(
+			List<JaxbHbmUnionSubclassEntityType> hbmSubclasses,
+			String superEntityName,
+			Binding<JaxbHbmHibernateMapping> hbmBinding,
+			EntityMappingConsumer entityMappingConsumer) {
+		hbmSubclasses.forEach( (hbmSubclass) -> {
+			final JaxbEntityImpl subclassJaxbEntity = makeJaxbEntity( hbmSubclass, hbmBinding.getRoot() );
+			final String subclassEntityName = determineEntityName( hbmSubclass, hbmBinding.getRoot() );
+			entityMappingConsumer.accept( hbmBinding, subclassEntityName, hbmSubclass, subclassJaxbEntity );
+
+			subclassJaxbEntity.setExtends( superEntityName );
+
+			if ( CollectionHelper.isNotEmpty( hbmSubclass.getUnionSubclass() ) ) {
+				processStructuredUnionSubclasses(
+						hbmSubclass.getUnionSubclass(),
+						subclassEntityName,
+						hbmBinding,
+						entityMappingConsumer
+				);
+			}
+		} );
+	}
+
+	private static void processSeparatedHierarchies(
+			Collection<Binding<JaxbHbmHibernateMapping>> hbmXmlBindings,
+			Map<String, JaxbEntityImpl> rootClassesMap,
+			EntityMappingConsumer entityMappingConsumer) {
+		hbmXmlBindings.forEach( (hbmBinding) -> {
+			processSeparatedHierarchies( rootClassesMap, entityMappingConsumer, hbmBinding );
+
+		} );
+	}
+
+	private static void processSeparatedHierarchies(
+			Map<String, JaxbEntityImpl> rootClassesMap,
+			EntityMappingConsumer entityMappingConsumer,
+			Binding<JaxbHbmHibernateMapping> hbmBinding) {
+		final JaxbHbmHibernateMapping hibernateMapping = hbmBinding.getRoot();
+
+		processTopLevelDiscriminatedSubclasses( rootClassesMap, entityMappingConsumer, hbmBinding, hibernateMapping );
+		processTopLevelJoinedSubclasses( rootClassesMap, entityMappingConsumer, hbmBinding, hibernateMapping );
+		processTopLevelUnionSubclasses( rootClassesMap, entityMappingConsumer, hbmBinding, hibernateMapping );
+	}
+
+	private static void processTopLevelDiscriminatedSubclasses(
+			Map<String, JaxbEntityImpl> rootClassesMap,
+			EntityMappingConsumer entityMappingConsumer,
+			Binding<JaxbHbmHibernateMapping> hbmBinding,
+			JaxbHbmHibernateMapping hibernateMapping) {
+		hibernateMapping.getSubclass().forEach( (hbmSubclass) -> {
+			final String entityName = determineEntityName( hbmSubclass, hibernateMapping );
+			applyExtendedInheritanceStrategy(
+					entityName,
+					InheritanceType.SINGLE_TABLE,
+					hbmSubclass,
+					hibernateMapping,
+					rootClassesMap,
+					hbmBinding.getOrigin()
+			);
+
+			final JaxbEntityImpl jaxbEntity = makeJaxbEntity( hbmSubclass, hibernateMapping );
+			entityMappingConsumer.accept( hbmBinding, entityName, hbmSubclass, jaxbEntity );
+
+			if ( CollectionHelper.isNotEmpty( hbmSubclass.getSubclass() ) ) {
+				processStructuredDiscriminatorSubclasses(
+						hbmSubclass.getSubclass(),
+						entityName,
+						hbmBinding,
+						entityMappingConsumer
+				);
+			}
+		} );
+	}
+
+	private static void processTopLevelJoinedSubclasses(
+			Map<String, JaxbEntityImpl> rootClassesMap,
+			EntityMappingConsumer entityMappingConsumer,
+			Binding<JaxbHbmHibernateMapping> hbmBinding,
+			JaxbHbmHibernateMapping hibernateMapping) {
+		hibernateMapping.getJoinedSubclass().forEach( (hbmSubclass) -> {
+			final String entityName = determineEntityName( hbmSubclass, hibernateMapping );
+			applyExtendedInheritanceStrategy(
+					entityName,
+					InheritanceType.JOINED,
+					hbmSubclass,
+					hibernateMapping,
+					rootClassesMap,
+					hbmBinding.getOrigin()
+			);
+
+			final JaxbEntityImpl jaxbEntity = makeJaxbEntity( hbmSubclass, hibernateMapping );
+			entityMappingConsumer.accept( hbmBinding, entityName, hbmSubclass, jaxbEntity );
+
+			if ( CollectionHelper.isNotEmpty( hbmSubclass.getJoinedSubclass() ) ) {
+				processStructuredJoinedSubclasses(
+						hbmSubclass.getJoinedSubclass(),
+						entityName,
+						hbmBinding,
+						entityMappingConsumer
+				);
+			}
+		} );
+	}
+
+	private static void processTopLevelUnionSubclasses(
+			Map<String, JaxbEntityImpl> rootClassesMap,
+			EntityMappingConsumer entityMappingConsumer,
+			Binding<JaxbHbmHibernateMapping> hbmBinding,
+			JaxbHbmHibernateMapping hibernateMapping) {
+		hibernateMapping.getUnionSubclass().forEach( (hbmSubclass) -> {
+			final String entityName = determineEntityName( hbmSubclass, hibernateMapping );
+			applyExtendedInheritanceStrategy(
+					entityName,
+					InheritanceType.TABLE_PER_CLASS,
+					hbmSubclass,
+					hibernateMapping,
+					rootClassesMap,
+					hbmBinding.getOrigin()
+			);
+
+			final JaxbEntityImpl jaxbEntity = makeJaxbEntity( hbmSubclass, hibernateMapping );
+			entityMappingConsumer.accept( hbmBinding, entityName, hbmSubclass, jaxbEntity );
+
+			if ( CollectionHelper.isNotEmpty( hbmSubclass.getUnionSubclass() ) ) {
+				processStructuredUnionSubclasses(
+						hbmSubclass.getUnionSubclass(),
+						entityName,
+						hbmBinding,
+						entityMappingConsumer
+				);
+			}
+		} );
+	}
+
+	private static void applyExtendedInheritanceStrategy(
+			String entityName,
+			InheritanceType strategy,
+			JaxbHbmSubclassEntityBaseDefinition hbmSubclass,
+			JaxbHbmHibernateMapping hibernateMapping,
+			Map<String, JaxbEntityImpl> rootClassesMap,
+			Origin origin) {
+		if ( StringHelper.isEmpty( hbmSubclass.getExtends() ) ) {
+			throw new MappingException( "Separated inheritance mapping did not specify extends", origin );
+		}
+
+		// we only have something to do here if the extends names a root entity
+		final JaxbEntityImpl superRoot = TransformationState.resolveEntityReference(
+				hbmSubclass.getExtends(),
+				hibernateMapping,
+				rootClassesMap
+		);
+
+		if ( superRoot != null ) {
+			applyInheritanceStrategy( entityName, superRoot, strategy );
+		}
+	}
+
+	private static JaxbEntityImpl makeJaxbEntity(
+			JaxbHbmEntityBaseDefinition hbmEntity,
+			JaxbHbmHibernateMapping hibernateMapping) {
+		final JaxbEntityImpl jaxbEntity = new JaxbEntityImpl();
+		if ( StringHelper.isNotEmpty( hbmEntity.getName() ) ) {
+			jaxbEntity.setClazz( StringHelper.qualifyConditionallyIfNot( hibernateMapping.getPackage(), hbmEntity.getName() ) );
+		}
+		if ( StringHelper.isNotEmpty( hbmEntity.getEntityName() ) ) {
+			jaxbEntity.setName( hbmEntity.getEntityName() );
+		}
+		return jaxbEntity;
+	}
+
+	private static String determineEntityName(EntityInfo entityInfo, JaxbHbmHibernateMapping hibernateMapping) {
+		if ( entityInfo.getEntityName() != null ) {
+			return entityInfo.getEntityName();
+		}
+		return StringHelper.qualifyConditionallyIfNot( hibernateMapping.getPackage(), entityInfo.getName() );
+	}
+
+
+	private record EntityMappingConsumer(TransformationState transformationState) {
+
+		public void accept(
+					Binding<JaxbHbmHibernateMapping> hbmBinding,
+					String registrationName,
+					JaxbHbmEntityBaseDefinition hbmEntity,
+					JaxbEntityImpl mappingEntity) {
+				final Binding<JaxbEntityMappingsImpl> mappingBinding = resolveMappingBinding( hbmBinding );
+				mappingBinding.getRoot().getEntities().add( mappingEntity );
+				transformationState.getEntityXref().put( hbmEntity, mappingEntity );
+				transformationState.getEntityMap().put( registrationName, mappingEntity );
+			}
+
+			private Binding<JaxbEntityMappingsImpl> resolveMappingBinding(Binding<JaxbHbmHibernateMapping> hbmBinding) {
+				for ( int i = 0; i < transformationState.getHbmBindings().size(); i++ ) {
+					if ( hbmBinding == transformationState.getHbmBindings().get( i ) ) {
+						return transformationState.getMappingBindings().get( i );
+					}
+				}
+
+				throw new IllegalStateException( "Could not resolve corresponding mapping binding : " + hbmBinding );
+			}
+		}
+}

hibernate-core/src/main/java/org/hibernate/boot/jaxb/hbm/transform/TransformationState.java

@@ -0,0 +1,137 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+ */
+package org.hibernate.boot.jaxb.hbm.transform;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+
+import org.hibernate.boot.jaxb.Origin;
+import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmEntityBaseDefinition;
+import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmHibernateMapping;
+import org.hibernate.boot.jaxb.mapping.spi.JaxbEntityImpl;
+import org.hibernate.boot.jaxb.mapping.spi.JaxbEntityMappingsImpl;
+import org.hibernate.boot.jaxb.spi.Binding;
+import org.hibernate.internal.util.StringHelper;
+import org.hibernate.internal.util.collections.CollectionHelper;
+
+/**
+ * @author Steve Ebersole
+ */
+class TransformationState {
+	private final List<Binding<JaxbHbmHibernateMapping>> hbmBindings;
+	private final List<Binding<JaxbEntityMappingsImpl>> mappingBindings;
+
+	private final Map<String, JaxbEntityImpl> entityMap = new HashMap<>();
+	private final Map<JaxbHbmEntityBaseDefinition, JaxbEntityImpl> entityXref = new HashMap<>();
+
+	public TransformationState(List<Binding<JaxbHbmHibernateMapping>> hbmBindings) {
+		this.hbmBindings = hbmBindings;
+		this.mappingBindings = CollectionHelper.arrayList( hbmBindings.size() );
+		for ( Binding<JaxbHbmHibernateMapping> hbmBinding : this.hbmBindings ) {
+			final JaxbEntityMappingsImpl mappingRoot = new JaxbEntityMappingsImpl();
+			mappingRoot.setDescription( String.format(
+					Locale.ROOT,
+					"Generated by Hibernate HbmXmlTransformer from %s (%s)",
+					hbmBinding.getOrigin().getName(),
+					hbmBinding.getOrigin().getType()
+			) );
+			mappingBindings.add( new Binding<>( mappingRoot, hbmBinding.getOrigin() ) );
+		}
+	}
+
+	public static String resolveEntityReferenceName(
+			String referenceName,
+			JaxbHbmHibernateMapping hibernateMapping,
+			Map<String,JaxbEntityImpl> entityMap) {
+
+		// First try it as a direct key reference; this covers the case of:
+		// 		1. entity-name
+		//		2. fully-qualified name
+		final JaxbEntityImpl byDirectName = entityMap.get( referenceName );
+		if ( byDirectName != null ) {
+			return referenceName;
+		}
+
+		// Next, try as an implicitly qualified name
+		if ( StringHelper.isNotEmpty( hibernateMapping.getPackage() ) ) {
+			final String qualifiedName = StringHelper.qualify( hibernateMapping.getPackage(), referenceName );
+			final JaxbEntityImpl byQualifiedName = entityMap.get( qualifiedName );
+			if ( byQualifiedName != null ) {
+				return qualifiedName;
+			}
+		}
+
+		return null;
+	}
+
+	public static String requireEntityReferenceName(
+			String referenceName,
+			JaxbHbmHibernateMapping hibernateMapping,
+			Map<String,JaxbEntityImpl> entityMap,
+			Origin origin) {
+		final String resolved = resolveEntityReferenceName( referenceName, hibernateMapping, entityMap );
+		if ( resolved == null ) {
+			throw new UnknownEntityReferenceException( referenceName, origin );
+		}
+		return resolved;
+	}
+
+	public static JaxbEntityImpl resolveEntityReference(
+			String referenceName,
+			JaxbHbmHibernateMapping hibernateMapping,
+			Map<String,JaxbEntityImpl> entityMap) {
+
+		// First try it as a direct key reference; this covers the case of:
+		// 		1. entity-name
+		//		2. fully-qualified name
+		final JaxbEntityImpl byDirectName = entityMap.get( referenceName );
+		if ( byDirectName != null ) {
+			return byDirectName;
+		}
+
+		// Next, try as an implicitly qualified name
+		if ( StringHelper.isNotEmpty( hibernateMapping.getPackage() ) ) {
+			final String qualifiedName = StringHelper.qualify( hibernateMapping.getPackage(), referenceName );
+			final JaxbEntityImpl byQualifiedName = entityMap.get( qualifiedName );
+			if ( byQualifiedName != null ) {
+				return byQualifiedName;
+			}
+		}
+
+		return null;
+	}
+
+	public static JaxbEntityImpl requireEntityReference(
+			String referenceName,
+			JaxbHbmHibernateMapping hibernateMapping,
+			Map<String,JaxbEntityImpl> entityMap,
+			Origin origin) {
+		final JaxbEntityImpl resolved = resolveEntityReference( referenceName, hibernateMapping, entityMap );
+		if ( resolved == null ) {
+			throw new UnknownEntityReferenceException( referenceName, origin );
+		}
+		return resolved;
+	}
+
+	public List<Binding<JaxbHbmHibernateMapping>> getHbmBindings() {
+		return hbmBindings;
+	}
+
+	public List<Binding<JaxbEntityMappingsImpl>> getMappingBindings() {
+		return mappingBindings;
+	}
+
+	public Map<String, JaxbEntityImpl> getEntityMap() {
+		return entityMap;
+	}
+
+	public Map<JaxbHbmEntityBaseDefinition, JaxbEntityImpl> getEntityXref() {
+		return entityXref;
+	}
+}

hibernate-core/src/main/java/org/hibernate/boot/jaxb/hbm/transform/UnknownEntityReferenceException.java

@@ -0,0 +1,29 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+ */
+package org.hibernate.boot.jaxb.hbm.transform;
+
+import java.util.Locale;
+
+import org.hibernate.MappingException;
+import org.hibernate.boot.jaxb.Origin;
+
+/**
+ * We encountered a reference to an entity by name which we cannot resolve
+ *
+ * @author Steve Ebersole
+ */
+public class UnknownEntityReferenceException extends MappingException {
+	public UnknownEntityReferenceException(String name, Origin origin) {
+		super( String.format(
+				Locale.ROOT,
+				"Could not resolve entity name `%s` : %s (%s)",
+				name,
+				origin.getName(),
+				origin.getType()
+		) );
+	}
+}

hibernate-core/src/main/java/org/hibernate/boot/jaxb/internal/MappingBinder.java

@@ -15,22 +15,19 @@ import javax.xml.stream.events.StartElement;
 import org.hibernate.Internal;
 import org.hibernate.boot.ResourceStreamLocator;
 import org.hibernate.boot.UnsupportedOrmXsdVersionException;
-import org.hibernate.boot.jaxb.JaxbLogger;
 import org.hibernate.boot.jaxb.Origin;
 import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmHibernateMapping;
-import org.hibernate.boot.jaxb.hbm.transform.HbmXmlTransformer;
 import org.hibernate.boot.jaxb.hbm.transform.UnsupportedFeatureHandling;
 import org.hibernate.boot.jaxb.internal.stax.HbmEventReader;
 import org.hibernate.boot.jaxb.internal.stax.JpaOrmXmlEventReader;
 import org.hibernate.boot.jaxb.internal.stax.MappingEventReader;
 import org.hibernate.boot.jaxb.mapping.spi.JaxbEntityMappingsImpl;
-import org.hibernate.boot.jaxb.spi.JaxbBindableMappingDescriptor;
 import org.hibernate.boot.jaxb.spi.Binding;
+import org.hibernate.boot.jaxb.spi.JaxbBindableMappingDescriptor;
 import org.hibernate.boot.registry.classloading.spi.ClassLoaderService;
 import org.hibernate.boot.xsd.MappingXsdSupport;
 import org.hibernate.cfg.AvailableSettings;
 import org.hibernate.engine.config.spi.ConfigurationService;
-import org.hibernate.internal.log.DeprecationLogger;
 import org.hibernate.internal.util.config.ConfigurationException;
 import org.hibernate.service.ServiceRegistry;
 import org.hibernate.service.spi.ServiceRegistryImplementor;
@@ -62,8 +59,6 @@ public class MappingBinder extends AbstractBinder<JaxbBindableMappingDescriptor>
 
 	public interface Options {
 		boolean validateMappings();
-
-		boolean transformHbmMappings();
 	}
 
 	public static final Options VALIDATING = new Options() {
@@ -71,11 +66,6 @@ public class MappingBinder extends AbstractBinder<JaxbBindableMappingDescriptor>
 		public boolean validateMappings() {
 			return true;
 		}
-
-		@Override
-		public boolean transformHbmMappings() {
-			return false;
-		}
 	};
 
 	public static final Options NON_VALIDATING = new Options() {
@@ -83,11 +73,6 @@ public class MappingBinder extends AbstractBinder<JaxbBindableMappingDescriptor>
 		public boolean validateMappings() {
 			return true;
 		}
-
-		@Override
-		public boolean transformHbmMappings() {
-			return false;
-		}
 	};
 
 	/**
@@ -131,15 +116,6 @@ public class MappingBinder extends AbstractBinder<JaxbBindableMappingDescriptor>
 					}
 					return BOOLEAN.convert( setting );
 				}
-
-				@Override
-				public boolean transformHbmMappings() {
-					final Object setting = settingsAccess.apply( AvailableSettings.TRANSFORM_HBM_XML );
-					if ( setting == null ) {
-						return false;
-					}
-					return BOOLEAN.convert( setting );
-				}
 			};
 
 			this.unsupportedHandlingAccess = () -> {
@@ -178,11 +154,6 @@ public class MappingBinder extends AbstractBinder<JaxbBindableMappingDescriptor>
 					public boolean validateMappings() {
 						return false;
 					}
-
-					@Override
-					public boolean transformHbmMappings() {
-						return false;
-					}
 				},
 				unsupportedHandling
 		);
@@ -219,13 +190,6 @@ public class MappingBinder extends AbstractBinder<JaxbBindableMappingDescriptor>
 					origin
 			);
 
-			if ( optionsAccess.get().transformHbmMappings() ) {
-				JaxbLogger.JAXB_LOGGER.tracef( "Performing on-the-fly hbm.xml -> mapping.xml transformation - %s ", origin );
-				//noinspection unchecked
-				return new Binding<>( (X) HbmXmlTransformer.transform( hbmBindings, origin, unsupportedHandlingAccess::get ), origin );
-			}
-
-			DeprecationLogger.DEPRECATION_LOGGER.logDeprecatedHbmXmlProcessing( origin.getType(), origin.getName() );
 			//noinspection unchecked
 			return new Binding<>( (X) hbmBindings, origin );
 		}
@@ -241,6 +205,7 @@ public class MappingBinder extends AbstractBinder<JaxbBindableMappingDescriptor>
 						mappingJaxbContext(),
 						origin
 				);
+
 				//noinspection unchecked
 				return new Binding<>( (X) bindingRoot, origin );
 			}

hibernate-core/src/main/java/org/hibernate/boot/model/process/internal/ManagedResourcesImpl.java

@@ -16,15 +16,27 @@ import java.util.Map;
 import java.util.Set;
 
 import org.hibernate.Internal;
+import org.hibernate.boot.BootLogging;
 import org.hibernate.boot.MetadataSources;
-import org.hibernate.boot.jaxb.spi.JaxbBindableMappingDescriptor;
+import org.hibernate.boot.jaxb.Origin;
+import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmHibernateMapping;
+import org.hibernate.boot.jaxb.hbm.transform.HbmXmlTransformer;
+import org.hibernate.boot.jaxb.hbm.transform.UnsupportedFeatureHandling;
+import org.hibernate.boot.jaxb.mapping.spi.JaxbEntityMappingsImpl;
 import org.hibernate.boot.jaxb.spi.Binding;
+import org.hibernate.boot.jaxb.spi.JaxbBindableMappingDescriptor;
 import org.hibernate.boot.model.convert.spi.ConverterDescriptor;
 import org.hibernate.boot.model.process.spi.ManagedResources;
 import org.hibernate.boot.spi.BootstrapContext;
+import org.hibernate.cfg.AvailableSettings;
+import org.hibernate.cfg.MappingSettings;
+import org.hibernate.engine.config.spi.ConfigurationService;
+import org.hibernate.internal.log.DeprecationLogger;
 
 import jakarta.persistence.AttributeConverter;
 
+import static org.hibernate.engine.config.spi.StandardConverters.BOOLEAN;
+
 /**
  * @author Steve Ebersole
  */
@@ -42,11 +54,53 @@ public class ManagedResourcesImpl implements ManagedResources {
 		impl.annotatedClassReferences.addAll( sources.getAnnotatedClasses() );
 		impl.annotatedClassNames.addAll( sources.getAnnotatedClassNames() );
 		impl.annotatedPackageNames.addAll( sources.getAnnotatedPackages() );
-		impl.mappingFileBindings.addAll( sources.getXmlBindings() );
+		handleXmlMappings( sources, impl, bootstrapContext );
 		impl.extraQueryImports = sources.getExtraQueryImports();
 		return impl;
 	}
 
+	@SuppressWarnings({ "rawtypes", "unchecked" })
+	private static void handleXmlMappings(
+			MetadataSources sources,
+			ManagedResourcesImpl impl,
+			BootstrapContext bootstrapContext) {
+		impl.mappingFileBindings.addAll( (List) sources.getMappingXmlBindings() );
+
+		if ( !bootstrapContext.getMetadataBuildingOptions().isXmlMappingEnabled() ) {
+			BootLogging.BOOT_LOGGER.debugf(
+					"Ignoring %s XML mappings due to `%s`",
+					sources.getMappingXmlBindings().size(),
+					MappingSettings.XML_MAPPING_ENABLED
+			);
+			return;
+		}
+
+		final ConfigurationService configurationService = bootstrapContext.getServiceRegistry().getService( ConfigurationService.class );
+		// NOTE : the configurationService nullness checking is here for a few tests using mocks
+		final boolean transformHbm = configurationService != null
+				&& configurationService.getSetting( MappingSettings.TRANSFORM_HBM_XML, BOOLEAN,false );
+
+		if ( !transformHbm ) {
+			// we are not transforming hbm.xml to mapping.xml, so just add the hbm.xml bindings as-is
+			impl.mappingFileBindings.addAll( (List) sources.getHbmXmlBindings() );
+			for ( Binding<JaxbHbmHibernateMapping> hbmXmlBinding : sources.getHbmXmlBindings() ) {
+				final Origin origin = hbmXmlBinding.getOrigin();
+				DeprecationLogger.DEPRECATION_LOGGER.logDeprecatedHbmXmlProcessing( origin.getType(), origin.getName() );
+			}
+		}
+		else {
+			// do the transformations
+			final List<Binding<JaxbEntityMappingsImpl>> transformed = HbmXmlTransformer.transform(
+					sources.getHbmXmlBindings(),
+					UnsupportedFeatureHandling.fromSetting(
+							configurationService.getSettings().get( AvailableSettings.TRANSFORM_HBM_XML_FEATURE_HANDLING ),
+							UnsupportedFeatureHandling.ERROR
+					)
+			);
+			impl.mappingFileBindings.addAll( (List) transformed );
+		}
+	}
+
 	public ManagedResourcesImpl() {
 	}
 

hibernate-core/src/main/java/org/hibernate/boot/model/process/spi/MetadataBuildingProcess.java

@@ -576,11 +576,6 @@ public class MetadataBuildingProcess {
 						public boolean validateMappings() {
 							return false;
 						}
-
-						@Override
-						public boolean transformHbmMappings() {
-							return false;
-						}
 					}
 			);
 		}

hibernate-core/src/main/java/org/hibernate/boot/model/source/internal/annotations/AdditionalManagedResourcesImpl.java

@@ -9,11 +9,15 @@ package org.hibernate.boot.model.source.internal.annotations;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 
 import org.hibernate.boot.jaxb.Origin;
 import org.hibernate.boot.jaxb.SourceType;
+import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmHibernateMapping;
+import org.hibernate.boot.jaxb.hbm.transform.HbmXmlTransformer;
+import org.hibernate.boot.jaxb.hbm.transform.UnsupportedFeatureHandling;
 import org.hibernate.boot.jaxb.internal.MappingBinder;
 import org.hibernate.boot.jaxb.mapping.spi.JaxbEntityMappingsImpl;
 import org.hibernate.boot.jaxb.spi.Binding;
@@ -85,6 +89,7 @@ public class AdditionalManagedResourcesImpl implements ManagedResources {
 
 	public static class Builder {
 		private final MappingBinder mappingBinder;
+		private final boolean transformHbmMappings;
 
 		private List<Class<?>> classes;
 		private List<ClassDetails> classDetails;
@@ -92,35 +97,26 @@ public class AdditionalManagedResourcesImpl implements ManagedResources {
 		private Collection<Binding<JaxbBindableMappingDescriptor>> xmlMappings;
 
 		public Builder(boolean validateMappings, boolean transformHbmMappings) {
-			this( new MappingBinder.Options() {
+			this( transformHbmMappings, new MappingBinder.Options() {
 				@Override
 				public boolean validateMappings() {
 					return validateMappings;
 				}
-
-				@Override
-				public boolean transformHbmMappings() {
-					return transformHbmMappings;
-				}
 			} );
 		}
 
 		public Builder() {
-			this( new MappingBinder.Options() {
+			this( false, new MappingBinder.Options() {
 				@Override
 				public boolean validateMappings() {
 					return false;
 				}
-
-				@Override
-				public boolean transformHbmMappings() {
-					return false;
-				}
 			} );
 		}
 
-		public Builder(MappingBinder.Options options) {
+		public Builder(boolean transformHbmMappings, MappingBinder.Options options) {
-			mappingBinder = new MappingBinder(
+			this.transformHbmMappings = transformHbmMappings;
+			this.mappingBinder = new MappingBinder(
 					(resourceName) -> Builder.class.getClassLoader().getResourceAsStream( resourceName ),
 					options
 			);
@@ -163,6 +159,28 @@ public class AdditionalManagedResourcesImpl implements ManagedResources {
 		}
 
 		public ManagedResources build() {
+			if ( CollectionHelper.isNotEmpty( xmlMappings ) ) {
+				if ( transformHbmMappings ) {
+					final List<Binding<JaxbHbmHibernateMapping>> hbmBindings = new ArrayList<>();
+					final Iterator<Binding<JaxbBindableMappingDescriptor>> iterator = xmlMappings.iterator();
+					while ( iterator.hasNext() ) {
+						final Binding<JaxbBindableMappingDescriptor> xmlBinding = iterator.next();
+						if ( xmlBinding.getRoot() instanceof JaxbHbmHibernateMapping ) {
+							//noinspection rawtypes,unchecked
+							hbmBindings.add( (Binding) xmlBinding );
+							iterator.remove();
+						}
+					}
+					if ( !hbmBindings.isEmpty() ) {
+						final List<Binding<JaxbEntityMappingsImpl>> transformed = HbmXmlTransformer.transform(
+								hbmBindings,
+								UnsupportedFeatureHandling.ERROR
+						);
+						//noinspection rawtypes,unchecked
+						xmlMappings.addAll( (List) transformed );
+					}
+				}
+			}
 			return new AdditionalManagedResourcesImpl( classes, classDetails, packageNames, xmlMappings );
 		}
 

hibernate-core/src/main/java/org/hibernate/boot/model/source/internal/annotations/AnnotationMetadataSourceProcessorImpl.java

@@ -12,6 +12,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Set;
 
+import org.hibernate.MappingException;
 import org.hibernate.boot.internal.MetadataBuildingContextRootImpl;
 import org.hibernate.boot.jaxb.mapping.spi.JaxbEntityMappingsImpl;
 import org.hibernate.boot.model.convert.internal.ClassBasedConverterDescriptor;
@@ -229,6 +230,14 @@ public class AnnotationMetadataSourceProcessorImpl implements MetadataSourceProc
 		List<XClass> clazzHierarchy = new ArrayList<>();
 
 		for ( ClassDetails clazz : classes ) {
+			if ( clazz.isInterface() ) {
+				if ( clazz.hasDirectAnnotationUsage( Entity.class ) ) {
+					throw new MappingException( "Only classes (not interfaces) may be mapped as @Entity : " + clazz.getName() );
+				}
+				if ( clazz.hasDirectAnnotationUsage( MappedSuperclass.class ) ) {
+					throw new MappingException( "Only classes (not interfaces) may be mapped as @MappedSuperclass : " + clazz.getName() );
+				}
+			}
 			if ( clazz.hasDirectAnnotationUsage( MappedSuperclass.class ) ) {
 				if ( debug ) {
 					log.debugf(

hibernate-core/src/main/java/org/hibernate/boot/models/xml/internal/ManagedTypeProcessor.java

@@ -10,6 +10,7 @@ import java.lang.reflect.Modifier;
 import java.util.List;
 import java.util.function.Supplier;
 
+import org.hibernate.MappingException;
 import org.hibernate.annotations.CacheConcurrencyStrategy;
 import org.hibernate.boot.jaxb.mapping.spi.JaxbAttributesContainer;
 import org.hibernate.boot.jaxb.mapping.spi.JaxbAttributesContainerImpl;
@@ -59,7 +60,9 @@ import org.hibernate.property.access.spi.BuiltInPropertyAccessStrategies;
 import jakarta.persistence.Access;
 import jakarta.persistence.AccessType;
 import jakarta.persistence.EmbeddedId;
+import jakarta.persistence.Entity;
 import jakarta.persistence.Id;
+import jakarta.persistence.MappedSuperclass;
 
 import static org.hibernate.boot.models.xml.XmlProcessLogging.XML_PROCESS_LOGGER;
 import static org.hibernate.internal.util.NullnessHelper.coalesce;
@@ -123,6 +126,9 @@ public class ManagedTypeProcessor {
 					defaultAccessTypeFromDefaultAccessor( xmlDocumentContext ),
 					AccessType.PROPERTY
 			);
+			if ( classDetails.isInterface() ) {
+				throw new MappingException( "Only classes (not interfaces) may be mapped as @Entity : " + classDetails.getName() );
+			}
 		}
 
 		classDetails.clearMemberAnnotationUsages();

hibernate-core/src/main/java/org/hibernate/jpa/boot/internal/EntityManagerFactoryBuilderImpl.java

@@ -351,10 +351,9 @@ public class EntityManagerFactoryBuilderImpl implements EntityManagerFactoryBuil
 					if ( classLoader == null ) {
 						throw persistenceException( "Enhancement requires a temp class loader, but none was given." );
 					}
-					for ( Binding<JaxbBindableMappingDescriptor> binding : metadataSources.getXmlBindings() ) {
+
-						final JaxbBindableMappingDescriptor root = binding.getRoot();
+					for ( Binding<JaxbHbmHibernateMapping> binding : metadataSources.getHbmXmlBindings() ) {
-						if ( root instanceof JaxbHbmHibernateMapping ) {
+						final JaxbHbmHibernateMapping hibernateMapping = binding.getRoot();
-							final JaxbHbmHibernateMapping hibernateMapping = (JaxbHbmHibernateMapping) root;
 						final String packageName = hibernateMapping.getPackage();
 						for ( JaxbHbmRootEntityType clazz : hibernateMapping.getClazz() ) {
 							final String className;
@@ -372,7 +371,6 @@ public class EntityManagerFactoryBuilderImpl implements EntityManagerFactoryBuil
 							}
 						}
 					}
-					}
 					for ( String annotatedClassName : metadataSources.getAnnotatedClassNames() ) {
 						classTransformer.discoverTypes( classLoader, annotatedClassName );
 					}

hibernate-core/src/test/java/org/hibernate/orm/test/boot/jaxb/hbm/TransformationHelper.java

@@ -10,6 +10,8 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.StringReader;
 import java.io.StringWriter;
+import java.util.Collections;
+import java.util.List;
 
 import javax.xml.stream.XMLEventFactory;
 import javax.xml.stream.XMLEventReader;
@@ -21,6 +23,7 @@ import org.hibernate.boot.jaxb.hbm.transform.HbmXmlTransformer;
 import org.hibernate.boot.jaxb.hbm.transform.UnsupportedFeatureHandling;
 import org.hibernate.boot.jaxb.internal.stax.HbmEventReader;
 import org.hibernate.boot.jaxb.mapping.spi.JaxbEntityMappingsImpl;
+import org.hibernate.boot.jaxb.spi.Binding;
 import org.hibernate.boot.registry.classloading.spi.ClassLoaderService;
 import org.hibernate.boot.xsd.MappingXsdSupport;
 import org.hibernate.orm.test.boot.jaxb.JaxbHelper;
@@ -57,11 +60,12 @@ public class TransformationHelper {
 					assertThat( hbmMapping ).isNotNull();
 					assertThat( hbmMapping.getClazz() ).hasSize( 1 );
 
-					return HbmXmlTransformer.transform(
+					final List<Binding<JaxbEntityMappingsImpl>> transformed = HbmXmlTransformer.transform(
-							hbmMapping,
+							Collections.singletonList( new Binding<>( hbmMapping, new Origin( SourceType.RESOURCE, resourceName ) ) ),
-							new Origin( SourceType.RESOURCE, resourceName ),
+							UnsupportedFeatureHandling.ERROR
-							() -> UnsupportedFeatureHandling.ERROR
 					);
+
+					return transformed.get(0).getRoot();
 				}
 				catch (JAXBException e) {
 					throw new RuntimeException( "Error during JAXB processing", e );

hibernate-core/src/test/java/org/hibernate/orm/test/boot/jaxb/mapping/HbmTransformationJaxbTests.java

@@ -8,6 +8,8 @@ package org.hibernate.orm.test.boot.jaxb.mapping;
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.util.Collections;
+import java.util.List;
 import javax.xml.stream.XMLEventFactory;
 import javax.xml.stream.XMLEventReader;
 
@@ -19,6 +21,7 @@ import org.hibernate.boot.jaxb.hbm.transform.UnsupportedFeatureHandling;
 import org.hibernate.boot.jaxb.internal.stax.HbmEventReader;
 import org.hibernate.boot.jaxb.mapping.spi.JaxbEntityImpl;
 import org.hibernate.boot.jaxb.mapping.spi.JaxbEntityMappingsImpl;
+import org.hibernate.boot.jaxb.spi.Binding;
 import org.hibernate.boot.registry.classloading.spi.ClassLoaderService;
 import org.hibernate.boot.xsd.MappingXsdSupport;
 import org.hibernate.orm.test.boot.jaxb.JaxbHelper;
@@ -56,11 +59,11 @@ public class HbmTransformationJaxbTests {
 					assertThat( hbmMapping ).isNotNull();
 					assertThat( hbmMapping.getClazz() ).hasSize( 1 );
 
-					final JaxbEntityMappingsImpl transformed = HbmXmlTransformer.transform(
+					final List<Binding<JaxbEntityMappingsImpl>> transformedBindingList = HbmXmlTransformer.transform(
-							hbmMapping,
+							Collections.singletonList( new Binding<>( hbmMapping, new Origin( SourceType.RESOURCE, resourceName ) ) ),
-							new Origin( SourceType.RESOURCE, resourceName ),
+							UnsupportedFeatureHandling.ERROR
-							() -> UnsupportedFeatureHandling.ERROR
 					);
+					final JaxbEntityMappingsImpl transformed = transformedBindingList.get( 0 ).getRoot();
 
 					assertThat( transformed ).isNotNull();
 					assertThat( transformed.getEntities() ).hasSize( 1 );

hibernate-core/src/test/java/org/hibernate/orm/test/boot/models/hbm/_extends/ExtendsTests.java

@@ -0,0 +1,73 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+ */
+package org.hibernate.orm.test.boot.models.hbm._extends;
+
+import org.hibernate.boot.jaxb.mapping.spi.JaxbEntityImpl;
+import org.hibernate.boot.jaxb.mapping.spi.JaxbEntityMappingsImpl;
+import org.hibernate.cfg.MappingSettings;
+import org.hibernate.orm.test.boot.jaxb.hbm.TransformationHelper;
+
+import org.hibernate.testing.orm.junit.ServiceRegistry;
+import org.hibernate.testing.orm.junit.ServiceRegistryScope;
+import org.hibernate.testing.orm.junit.Setting;
+import org.junit.jupiter.api.Test;
+
+import jakarta.persistence.InheritanceType;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Steve Ebersole
+ */
+@SuppressWarnings("JUnitMalformedDeclaration")
+public class ExtendsTests {
+	@ServiceRegistry(settings = @Setting(name = MappingSettings.TRANSFORM_HBM_XML, value = "true"))
+	@Test
+	void testDiscriminatedStructured(ServiceRegistryScope registryScope) {
+		final JaxbEntityMappingsImpl transformed = TransformationHelper.transform(
+				"mappings/models/hbm/extends/discriminated-structured.xml",
+				registryScope.getRegistry()
+		);
+		verifyHierarchy( transformed, InheritanceType.SINGLE_TABLE );
+	}
+
+	@ServiceRegistry(settings = @Setting(name = MappingSettings.TRANSFORM_HBM_XML, value = "true"))
+	@Test
+	void testDiscriminatedSeparated(ServiceRegistryScope registryScope) {
+		final JaxbEntityMappingsImpl transformed = TransformationHelper.transform(
+				"mappings/models/hbm/extends/discriminated-separate.xml",
+				registryScope.getRegistry()
+		);
+		verifyHierarchy( transformed, InheritanceType.SINGLE_TABLE );
+	}
+
+	private void verifyHierarchy(JaxbEntityMappingsImpl transformed, InheritanceType inheritanceType) {
+		assertThat( transformed ).isNotNull();
+		assertThat( transformed.getEntities() ).hasSize( 3 );
+
+		for ( JaxbEntityImpl jaxbEntity : transformed.getEntities() ) {
+			if ( "org.hibernate.test.hbm._extends.Root".equals( jaxbEntity.getClazz() ) ) {
+				assertThat( jaxbEntity.getInheritance() ).isNotNull();
+				assertThat( jaxbEntity.getInheritance().getStrategy() ).isEqualTo( inheritanceType );
+				assertThat( jaxbEntity.getExtends() ).isNull();
+				assertThat( jaxbEntity.getDiscriminatorColumn().getName() ).isEqualTo( "the_type" );
+				assertThat( jaxbEntity.getDiscriminatorValue() ).isEqualTo( "R" );
+			}
+			else if ( "org.hibernate.test.hbm._extends.Branch".equals( jaxbEntity.getName() ) ) {
+				assertThat( jaxbEntity.getInheritance() ).isNull();
+				assertThat( jaxbEntity.getDiscriminatorValue() ).isEqualTo( "B" );
+				assertThat( jaxbEntity.getExtends() ).isEqualTo( "org.hibernate.test.hbm._extends.Root" );
+			}
+			else if ( "org.hibernate.test.hbm._extends.Leaf".equals( jaxbEntity.getName() ) ) {
+				assertThat( jaxbEntity.getInheritance() ).isNull();
+				assertThat( jaxbEntity.getDiscriminatorValue() ).isEqualTo( "L" );
+				assertThat( jaxbEntity.getExtends() ).isEqualTo( "org.hibernate.test.hbm._extends.Branch" );
+
+			}
+		}
+	}
+}

hibernate-core/src/test/java/org/hibernate/orm/test/boot/models/hbm/ecid/EmbeddedCompositeIdentifierOnAbstractClassTests.java

@@ -1,59 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
- * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
- */
-package org.hibernate.orm.test.boot.models.hbm.ecid;
-
-import org.hibernate.cfg.MappingSettings;
-import org.hibernate.orm.test.abstractembeddedcomponents.cid.AbstractCompositeIdTest;
-import org.hibernate.orm.test.abstractembeddedcomponents.cid.MyInterfaceImpl;
-
-import org.hibernate.testing.orm.junit.DomainModel;
-import org.hibernate.testing.orm.junit.FailureExpected;
-import org.hibernate.testing.orm.junit.ServiceRegistry;
-import org.hibernate.testing.orm.junit.SessionFactory;
-import org.hibernate.testing.orm.junit.SessionFactoryScope;
-import org.hibernate.testing.orm.junit.Setting;
-import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.Test;
-
-/**
- * @see AbstractCompositeIdTest
- *
- * @author Steve Ebersole
- */
-@SuppressWarnings("JUnitMalformedDeclaration")
-@ServiceRegistry(settings = @Setting(name= MappingSettings.TRANSFORM_HBM_XML, value="true"))
-@DomainModel( xmlMappings = "org/hibernate/orm/test/abstractembeddedcomponents/cid/Mappings.hbm.xml" )
-@SessionFactory
-@FailureExpected
-public class EmbeddedCompositeIdentifierOnAbstractClassTests {
-
-	@Test
-	public void testTransformedHbmXml(SessionFactoryScope scope) {
-		MyInterfaceImpl myInterface = new MyInterfaceImpl();
-		myInterface.setKey1( "key1" );
-		myInterface.setKey2( "key2" );
-		myInterface.setName( "test" );
-
-		scope.inTransaction(
-				session -> {
-					// test persistence
-					session.persist( myInterface );
-					session.flush();
-
-					// test loading
-					session.createQuery( "from MyInterface" ).list();
-				}
-		);
-	}
-
-	@AfterEach
-	void dropTestData(SessionFactoryScope scope) {
-		scope.inTransaction( (session) -> {
-			session.createMutationQuery( "delete MyInterface" ).executeUpdate();
-		} );
-	}
-}

hibernate-core/src/test/java/org/hibernate/orm/test/boot/models/hbm/ecid/Login.java

@@ -1,49 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
- * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
- */
-package org.hibernate.orm.test.boot.models.hbm.ecid;
-
-/**
- * @author Steve Ebersole
- */
-public class Login {
-	private String system;
-	private String username;
-	private String email;
-
-	public Login() {
-	}
-
-	public Login(String system, String username, String email) {
-		this.system = system;
-		this.username = username;
-		this.email = email;
-	}
-
-	public String getSystem() {
-		return system;
-	}
-
-	public void setSystem(String system) {
-		this.system = system;
-	}
-
-	public String getUsername() {
-		return username;
-	}
-
-	public void setUsername(String username) {
-		this.username = username;
-	}
-
-	public String getEmail() {
-		return email;
-	}
-
-	public void setEmail(String email) {
-		this.email = email;
-	}
-}

hibernate-core/src/test/java/org/hibernate/orm/test/boot/models/hbm/ecid/StandardNonAggregatedIdTests.java

@@ -1,40 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
- * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
- */
-package org.hibernate.orm.test.boot.models.hbm.ecid;
-
-import java.util.List;
-
-import org.hibernate.cfg.MappingSettings;
-
-import org.hibernate.testing.orm.junit.DomainModel;
-import org.hibernate.testing.orm.junit.ServiceRegistry;
-import org.hibernate.testing.orm.junit.SessionFactory;
-import org.hibernate.testing.orm.junit.SessionFactoryScope;
-import org.hibernate.testing.orm.junit.Setting;
-import org.junit.jupiter.api.Test;
-
-import static org.assertj.core.api.Assertions.assertThat;
-
-/**
- * @author Steve Ebersole
- */
-@SuppressWarnings("JUnitMalformedDeclaration")
-@ServiceRegistry(settings = @Setting(name= MappingSettings.TRANSFORM_HBM_XML, value="true"))
-@DomainModel(xmlMappings = "mappings/models/hbm/ecid/standard-ecid.hbm.xml")
-@SessionFactory
-public class StandardNonAggregatedIdTests {
-	@Test
-	void simpleTest(SessionFactoryScope scope) {
-		final Login login = new Login( "prod", "john", "john@doe.com" );
-		scope.inTransaction( (session) -> session.persist( login ) );
-
-		scope.inTransaction( (session) -> {
-			final List<Login> logins = session.createSelectionQuery( "from Login", Login.class ).list();
-			assertThat( logins ).hasSize( 1 );
-		} );
-	}
-}

hibernate-core/src/test/java/org/hibernate/orm/test/boot/models/hbm/intf/IPerson.java

@@ -0,0 +1,21 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+ */
+package org.hibernate.orm.test.boot.models.hbm.intf;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+
+/**
+ * @author Steve Ebersole
+ */
+@Entity
+public interface IPerson {
+	@Id
+	Integer getId();
+	String getName();
+	void setName(String name);
+}

hibernate-core/src/test/java/org/hibernate/orm/test/boot/models/hbm/intf/InterfaceMappingTests.java

@@ -0,0 +1,59 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+ */
+package org.hibernate.orm.test.boot.models.hbm.intf;
+
+import org.hibernate.MappingException;
+import org.hibernate.boot.Metadata;
+import org.hibernate.boot.MetadataSources;
+import org.hibernate.boot.registry.StandardServiceRegistry;
+import org.hibernate.cfg.MappingSettings;
+
+import org.hibernate.testing.orm.junit.ServiceRegistry;
+import org.hibernate.testing.orm.junit.ServiceRegistryScope;
+import org.hibernate.testing.orm.junit.Setting;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for mapping interfaces as managed classes.
+ *
+ * @implNote This is something {@code hbm.xml} supported, and we want to make sure it fails in
+ * a consistent manner.
+ *
+ * @author Steve Ebersole
+ */
+@SuppressWarnings("JUnitMalformedDeclaration")
+public class InterfaceMappingTests {
+	@ServiceRegistry
+	@Test
+	void testInterfaceAsEntity(ServiceRegistryScope registryScope) {
+		try (StandardServiceRegistry serviceRegistry = registryScope.getRegistry()) {
+			final Metadata metadata = new MetadataSources( serviceRegistry )
+					.addAnnotatedClasses( IPerson.class, Person.class )
+					.buildMetadata();
+		}
+		catch (MappingException expected) {
+			assertThat( expected.getMessage() ).startsWith( "Only classes (not interfaces) may be mapped as @Entity :" );
+			assertThat( expected.getMessage() ).endsWith( IPerson.class.getName() );
+		}
+	}
+
+	@ServiceRegistry(settings = @Setting(name = MappingSettings.TRANSFORM_HBM_XML, value = "true"))
+	@Test
+	void testTransformedHbmXml(ServiceRegistryScope registryScope) {
+		try (StandardServiceRegistry serviceRegistry = registryScope.getRegistry()) {
+			final Metadata metadata = new MetadataSources( serviceRegistry )
+					.addResource( "mappings/models/hbm/intf/mapped-interface.hbm.xml" )
+					.buildMetadata();
+		}
+		catch (MappingException expected) {
+			assertThat( expected.getMessage() ).startsWith( "Only classes (not interfaces) may be mapped as @Entity :" );
+			assertThat( expected.getMessage() ).endsWith( IPerson.class.getName() );
+		}
+	}
+}

hibernate-core/src/test/java/org/hibernate/orm/test/boot/models/hbm/intf/Person.java

@@ -0,0 +1,41 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+ */
+package org.hibernate.orm.test.boot.models.hbm.intf;
+
+import jakarta.persistence.Entity;
+
+/**
+ * @author Steve Ebersole
+ */
+@Entity
+public class Person implements IPerson {
+	private Integer id;
+	private String name;
+
+	public Person() {
+	}
+
+	public Person(Integer id, String name) {
+		this.id = id;
+		this.name = name;
+	}
+
+	@Override
+	public Integer getId() {
+		return id;
+	}
+
+	@Override
+	public String getName() {
+		return name;
+	}
+
+	@Override
+	public void setName(String name) {
+		this.name = name;
+	}
+}

hibernate-core/src/test/java/org/hibernate/orm/test/boot/models/hbm/properties/Address.java

@@ -0,0 +1,13 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+ */
+package org.hibernate.orm.test.boot.models.hbm.properties;
+
+/**
+ * @author Steve Ebersole
+ */
+public class Address {
+}

hibernate-core/src/test/java/org/hibernate/orm/test/boot/models/hbm/properties/PropertiesGroupingTests.java

@@ -0,0 +1,15 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+ */
+package org.hibernate.orm.test.boot.models.hbm.properties;
+
+/**
+ * Tests for {@code hbm.xml} {@code <properties/>} grouping element
+ *
+ * @author Steve Ebersole
+ */
+public class PropertiesGroupingTests {
+}

hibernate-core/src/test/java/org/hibernate/orm/test/boot/models/hbm/properties/Server.java

@@ -0,0 +1,13 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+ */
+package org.hibernate.orm.test.boot.models.hbm.properties;
+
+/**
+ * @author Steve Ebersole
+ */
+public class Server {
+}

hibernate-core/src/test/java/org/hibernate/orm/test/boot/models/hbm/propertyref/GroupedPropertyRefTests.java

@@ -0,0 +1,160 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+ */
+package org.hibernate.orm.test.boot.models.hbm.propertyref;
+
+import java.util.List;
+
+import org.hibernate.boot.InvalidMappingException;
+import org.hibernate.boot.MetadataSources;
+import org.hibernate.boot.registry.StandardServiceRegistry;
+import org.hibernate.cfg.MappingSettings;
+import org.hibernate.mapping.PersistentClass;
+import org.hibernate.mapping.Property;
+import org.hibernate.mapping.ToOne;
+
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.DomainModelScope;
+import org.hibernate.testing.orm.junit.ServiceRegistry;
+import org.hibernate.testing.orm.junit.ServiceRegistryScope;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.hibernate.testing.orm.junit.Setting;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@code hbm.xml} {@code <properties/>} grouping element
+ *
+ * @author Steve Ebersole
+ */
+@SuppressWarnings("JUnitMalformedDeclaration")
+public class GroupedPropertyRefTests {
+	@Test
+	@DomainModel(annotatedClasses = {Person.class, Account.class}, xmlMappings = "mappings/models/hbm/propertyref/properties.hbm.xml" )
+	@SessionFactory
+	void testHbmXml(DomainModelScope domainModelScope, SessionFactoryScope sessionFactoryScope) {
+		// baseline test for straight hbm.xml handling
+		try {
+			verify( domainModelScope, sessionFactoryScope );
+		}
+		finally {
+			sessionFactoryScope.inTransaction( (session) -> {
+				session.createMutationQuery( "delete GroupedPropertyRefTests$Account" ).executeUpdate();
+				session.createMutationQuery( "delete GroupedPropertyRefTests$Person" ).executeUpdate();
+			} );
+		}
+	}
+
+	private void verify(DomainModelScope domainModelScope, SessionFactoryScope sessionFactoryScope) {
+		final PersistentClass accountMapping = domainModelScope.getEntityBinding( Account.class );
+
+		final Property ownerProperty = accountMapping.getProperty( "owner" );
+		final ToOne ownerPropertyValue = (ToOne) ownerProperty.getValue();
+		assertThat( ownerPropertyValue.getReferencedPropertyName() ).isEqualTo( "name" );
+
+		sessionFactoryScope.inTransaction( (session) -> {
+			final Person john = new Person( 1, "John", "Doe" );
+			final Account account = new Account( 1, "savings", john );
+			session.persist( john );
+			session.persist( account );
+		} );
+
+		sessionFactoryScope.inTransaction( (session) -> {
+			final List<Account> accounts = session.createSelectionQuery(
+					"from GroupedPropertyRefTests$Account a join fetch a.owner",
+					Account.class ).list();
+			assertThat( accounts ).hasSize( 1 );
+		} );
+	}
+
+	@Test
+	@ServiceRegistry(settings = @Setting(name= MappingSettings.TRANSFORM_HBM_XML, value="true"))
+	void testTransformed(ServiceRegistryScope registryScope) {
+		// test the transformation - should be an error as this is unsupported
+		try {
+			final StandardServiceRegistry serviceRegistry = registryScope.getRegistry();
+			final MetadataSources metadataSources = new MetadataSources( serviceRegistry );
+			metadataSources.addResource( "mappings/models/hbm/propertyref/properties.hbm.xml" );
+		}
+		catch (InvalidMappingException expected) {
+			assertThat( expected.getCause() ).isInstanceOf( UnsupportedOperationException.class );
+			assertThat( expected.getCause().getMessage() ).startsWith( "<properties/>" );
+		}
+	}
+
+	public static class Person {
+		private Integer id;
+		private String firstName;
+		private String lastName;
+
+		public Person() {
+		}
+
+		public Person(Integer id, String firstName, String lastName) {
+			this.id = id;
+			this.firstName = firstName;
+			this.lastName = lastName;
+		}
+
+		public Integer getId() {
+			return id;
+		}
+
+		public String getFirstName() {
+			return firstName;
+		}
+
+		public void setFirstName(String firstName) {
+			this.firstName = firstName;
+		}
+
+		public String getLastName() {
+			return lastName;
+		}
+
+		public void setLastName(String lastName) {
+			this.lastName = lastName;
+		}
+	}
+
+	public static class Account {
+		private Integer id;
+		private String name;
+		private Person owner;
+
+		public Account() {
+		}
+
+		public Account(Integer id, String name, Person owner) {
+			this.id = id;
+			this.name = name;
+			this.owner = owner;
+		}
+
+		public Integer getId() {
+			return id;
+		}
+
+		public String getName() {
+			return name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+
+		public Person getOwner() {
+			return owner;
+		}
+
+		public void setOwner(Person owner) {
+			this.owner = owner;
+		}
+	}
+
+}

hibernate-core/src/test/java/org/hibernate/orm/test/boot/models/xml/column/transform/ModelTests.java

@@ -12,6 +12,7 @@ import org.hibernate.boot.internal.MetadataBuilderImpl;
 import org.hibernate.boot.model.process.spi.ManagedResources;
 import org.hibernate.boot.model.source.internal.annotations.AdditionalManagedResourcesImpl;
 import org.hibernate.boot.registry.StandardServiceRegistry;
+import org.hibernate.cfg.MappingSettings;
 import org.hibernate.mapping.Column;
 import org.hibernate.mapping.Property;
 import org.hibernate.models.spi.ClassDetails;
@@ -22,6 +23,7 @@ import org.hibernate.testing.orm.junit.DomainModel;
 import org.hibernate.testing.orm.junit.DomainModelScope;
 import org.hibernate.testing.orm.junit.ServiceRegistry;
 import org.hibernate.testing.orm.junit.ServiceRegistryScope;
+import org.hibernate.testing.orm.junit.Setting;
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -59,7 +61,7 @@ public class ModelTests {
 		assertThat( transformerAnn.write() ).isEqualTo( "? * 100.00" );
 	}
 
-	@ServiceRegistry
+	@ServiceRegistry(settings = @Setting(name = MappingSettings.TRANSFORM_HBM_XML, value = "true"))
 	@Test
 	void testHbmXml(ServiceRegistryScope scope) {
 		final ManagedResources managedResources = new AdditionalManagedResourcesImpl.Builder( true, true )

hibernate-core/src/test/java/org/hibernate/orm/test/bootstrap/scanning/ScanningCoordinatorTest.java

@@ -35,12 +35,18 @@ import org.hibernate.boot.registry.StandardServiceRegistry;
 import org.hibernate.boot.registry.classloading.spi.ClassLoaderService;
 import org.hibernate.boot.registry.classloading.spi.ClassLoadingException;
 import org.hibernate.boot.spi.BootstrapContext;
+import org.hibernate.boot.spi.MetadataBuildingOptions;
 import org.hibernate.boot.spi.XmlMappingBinderAccess;
+import org.hibernate.cfg.Environment;
+import org.hibernate.engine.config.internal.ConfigurationServiceInitiator;
+import org.hibernate.engine.config.spi.ConfigurationService;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.orm.junit.Logger;
 import org.hibernate.testing.orm.junit.MessageKeyInspection;
 import org.hibernate.testing.orm.junit.MessageKeyWatcher;
+import org.hibernate.testing.orm.junit.ServiceRegistry;
+import org.hibernate.testing.orm.junit.ServiceRegistryScope;
 
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -70,6 +76,7 @@ public class ScanningCoordinatorTest {
 	private BootstrapContext bootstrapContext = Mockito.mock( BootstrapContext.class );
 	private ClassmateContext classmateContext = new ClassmateContext();
 	private XmlMappingBinderAccess xmlMappingBinderAccess = Mockito.mock( XmlMappingBinderAccess.class );
+	private MetadataBuildingOptions metadataBuildingOptions = Mockito.mock( MetadataBuildingOptions.class );
 
 	private ScanEnvironment scanEnvironment = Mockito.mock( ScanEnvironment.class );
 	private StandardServiceRegistry serviceRegistry = Mockito.mock( StandardServiceRegistry.class );
@@ -87,8 +94,12 @@ public class ScanningCoordinatorTest {
 		when( bootstrapContext.getScanEnvironment() ).thenReturn( scanEnvironment );
 		when( bootstrapContext.getClassmateContext() ).thenReturn( classmateContext );
 		when( bootstrapContext.getServiceRegistry() ).thenReturn( serviceRegistry );
+		when( bootstrapContext.getMetadataBuildingOptions() ).thenReturn( metadataBuildingOptions );
+
 		when( serviceRegistry.requireService( ClassLoaderService.class ) ).thenReturn( classLoaderService );
 
+		when( metadataBuildingOptions.isXmlMappingEnabled() ).thenReturn( true );
+
 		when( scanEnvironment.getExplicitlyListedClassNames() ).thenReturn(
 				Arrays.asList( "a.b.C" ) );
 

hibernate-core/src/test/resources/hibernate.properties

@@ -16,6 +16,8 @@ hibernate.connection.autocommit false
 hibernate.connection.initial_pool_size 0
 hibernate.connection.pool_size 5
 
+hibernate.transform_hbm_xml.enabled true
+
 hibernate.show_sql true
 hibernate.format_sql true
 hibernate.highlight_sql true

hibernate-core/src/test/resources/mappings/models/hbm/ecid/standard-ecid.hbm.xml

@@ -1,22 +0,0 @@
-<?xml version="1.0"?>
-<!--
-  ~ Hibernate, Relational Persistence for Idiomatic Java
-  ~
-  ~ License: GNU Lesser General Public License (LGPL), version 2.1 or later.
-  ~ See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
-  -->
-<!DOCTYPE hibernate-mapping PUBLIC
-        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
-        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
-
-<hibernate-mapping>
-
-    <class name="org.hibernate.orm.test.boot.models.hbm.ecid.Login" table="user_logins">
-        <composite-id>
-            <key-property name="system"/>
-            <key-property name="username"/>
-        </composite-id>
-        <property name="email"/>
-    </class>
-
-</hibernate-mapping>

hibernate-core/src/test/resources/mappings/models/hbm/extends/discriminated-separate.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0"?>
+<!--
+  ~ Hibernate, Relational Persistence for Idiomatic Java
+  ~
+  ~ License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+  ~ See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+  -->
+<!DOCTYPE hibernate-mapping PUBLIC
+        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
+        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
+
+<hibernate-mapping package="org.hibernate.test.hbm._extends">
+    <subclass entity-name="Leaf" discriminator-value="L" extends="Branch">
+    </subclass>
+
+    <subclass entity-name="Branch" discriminator-value="B" extends="Root">
+    </subclass>
+
+    <class entity-name="Root" discriminator-value="R">
+        <id/>
+        <discriminator column="the_type"/>
+        <property name="name"/>
+    </class>
+</hibernate-mapping>

hibernate-core/src/test/resources/mappings/models/hbm/extends/discriminated-structured.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0"?>
+<!--
+  ~ Hibernate, Relational Persistence for Idiomatic Java
+  ~
+  ~ License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+  ~ See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+  -->
+<!DOCTYPE hibernate-mapping PUBLIC
+        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
+        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
+
+<hibernate-mapping package="org.hibernate.test.hbm._extends">
+    <class entity-name="Root" discriminator-value="R">
+        <id/>
+        <discriminator column="the_type"/>
+        <property name="name"/>
+        <subclass entity-name="Branch" discriminator-value="B">
+            <subclass entity-name="Leaf" discriminator-value="L">
+            </subclass>
+        </subclass>
+    </class>
+</hibernate-mapping>

hibernate-core/src/test/resources/mappings/models/hbm/intf/mapped-interface.hbm.xml

@@ -0,0 +1,20 @@
+<?xml version="1.0"?>
+<!--
+  ~ Hibernate, Relational Persistence for Idiomatic Java
+  ~
+  ~ License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+  ~ See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+  -->
+<!DOCTYPE hibernate-mapping PUBLIC
+        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
+        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
+
+<hibernate-mapping package="org.hibernate.orm.test.boot.models.hbm.intf">
+    <class name="IPerson" abstract="true">
+        <id/>
+        <discriminator/>
+        <property name="name"/>
+
+        <subclass name="Person" discriminator-value="P"/>
+    </class>
+</hibernate-mapping>

hibernate-core/src/test/resources/mappings/models/hbm/properties/standard.hbm.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0"?>
+<!--
+  ~ Hibernate, Relational Persistence for Idiomatic Java
+  ~
+  ~ License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+  ~ See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+  -->
+<!DOCTYPE hibernate-mapping PUBLIC
+        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
+        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
+
+<hibernate-mapping>
+    <class name="Address" table="addresses">
+        <id name="id"/>
+        <properties name="uniqueAddress">
+            <property name="addressType" column="ADDRESS_TYPE" type="string" insert="false" update="false" length="30"/>
+            <many-to-one name="server" column="SERVER_ID" class="Server" not-null="true"/>
+        </properties>
+    </class>
+
+    <class name="Server" table="servers">
+        <id name="id"/>
+        <property name="serverType" type="string" column="SERVER_TYPE" length="10" update="false" insert="false"/>
+        <many-to-one name="address"
+                     class="Address"
+                     property-ref="uniqueAddress"
+                     cascade="all"
+                     unique="true"
+                     update="false"
+                     insert="false">
+            <column name="address_type"/>
+            <column name="server_id"/>
+        </many-to-one>
+    </class>
+</hibernate-mapping>

hibernate-core/src/test/resources/mappings/models/hbm/propertyref/properties.hbm.xml

@@ -0,0 +1,33 @@
+<?xml version="1.0"?>
+<!--
+  ~ Hibernate, Relational Persistence for Idiomatic Java
+  ~
+  ~ License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+  ~ See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+  -->
+<!DOCTYPE hibernate-mapping PUBLIC
+        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
+        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
+
+<hibernate-mapping
+        package="org.hibernate.orm.test.boot.models.hbm.propertyref"
+        default-access="field">
+
+    <class name="GroupedPropertyRefTests$Person" table="persons">
+        <id name="id"/>
+        <properties name="name">
+            <property name="firstName" column="fname"/>
+            <property name="lastName" column="lname"/>
+        </properties>
+    </class>
+
+    <class name="GroupedPropertyRefTests$Account" table="accounts">
+        <id name="id"/>
+        <property name="name"/>
+        <many-to-one name="owner" property-ref="name">
+            <column name="owner_name_first"/>
+            <column name="owner_name_last"/>
+        </many-to-one>
+    </class>
+
+</hibernate-mapping>

migration-guide.adoc

@@ -179,6 +179,15 @@ Hibernate can use the persistence-unit name for binding into JNDI as well, but `
 must be explicitly set to true.
 
 
+[[hbm-transform]]
+== hbm.xml Transformation
+
+Previous versions of Hibernate performed transformations of `hbm.xml` files (with `` enabled)
+one file at a time.  This is now done across the entire set of `hbm.xml` files at once.
+While most users will never see this change, it might impact integrations which tie-in to
+XML processing.
+
+
 [[todo]]
 == Todos (dev)
 

settings.gradle

@@ -72,7 +72,7 @@ dependencyResolutionManagement {
             def byteBuddyVersion = version "byteBuddy", "1.14.18"
             def classmateVersion = version "classmate", "1.5.1"
             def geolatteVersion = version "geolatte", "1.9.1"
-            def hibernateModelsVersion = version "hibernateModels", "0.8.4"
+            def hibernateModelsVersion = version "hibernateModels", "0.8.5"
             def jandexVersion = version "jandex", "3.2.0"
 			def hcannVersion = version "hcann", "7.0.1.Final"
             def jacksonVersion = version "jackson", "2.17.0"

tooling/hibernate-gradle-plugin/src/main/java/org/hibernate/orm/tooling/gradle/misc/OriginImpl.java

@@ -0,0 +1,28 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html.
+ */
+package org.hibernate.orm.tooling.gradle.misc;
+
+import java.io.File;
+
+import org.hibernate.boot.jaxb.Origin;
+import org.hibernate.boot.jaxb.SourceType;
+
+/**
+ * @author Steve Ebersole
+ */
+public class OriginImpl extends Origin {
+	private final File hbmXmlFile;
+
+	public OriginImpl(File hbmXmlFile) {
+		super( SourceType.FILE, hbmXmlFile.getAbsolutePath() );
+		this.hbmXmlFile = hbmXmlFile;
+	}
+
+	public File getHbmXmlFile() {
+		return hbmXmlFile;
+	}
+}

tooling/hibernate-gradle-plugin/src/main/java/org/hibernate/orm/tooling/gradle/misc/TransformHbmXmlTask.java

@@ -9,9 +9,12 @@ package org.hibernate.orm.tooling.gradle.misc;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
 
 import org.gradle.api.file.DirectoryProperty;
 import org.gradle.api.provider.Property;
+import org.gradle.api.tasks.CacheableTask;
 import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.Nested;
 import org.gradle.api.tasks.OutputDirectory;
@@ -19,7 +22,6 @@ import org.gradle.api.tasks.SourceTask;
 import org.gradle.api.tasks.TaskAction;
 
 import org.hibernate.boot.jaxb.Origin;
-import org.hibernate.boot.jaxb.SourceType;
 import org.hibernate.boot.jaxb.hbm.spi.JaxbHbmHibernateMapping;
 import org.hibernate.boot.jaxb.hbm.transform.HbmXmlTransformer;
 import org.hibernate.boot.jaxb.hbm.transform.UnsupportedFeatureHandling;
@@ -53,6 +55,7 @@ import jakarta.xml.bind.Marshaller;
  * 		replacing the original (destructive).
  * @see org.hibernate.boot.jaxb.hbm.transform.HbmXmlTransformer
  */
+@CacheableTask
 public abstract class TransformHbmXmlTask extends SourceTask {
 	private final Property<TransformationNaming> renaming;
 	private final Property<UnsupportedFeatureHandling> unsupportedFeatures;
@@ -127,15 +130,24 @@ public abstract class TransformHbmXmlTask extends SourceTask {
 			throw new RuntimeException( "Unable to create JAXB Marshaller", e );
 		}
 
-		getSource().forEach( (hbmXmlFile) -> transformFile( mappingBinder, marshaller, hbmXmlFile ) );
+		final List<Binding<JaxbHbmHibernateMapping>> hbmBindings = new ArrayList<>();
-	}
+		getSource().forEach( (hbmXmlFile) -> {
+			final Origin origin = new OriginImpl( hbmXmlFile );
+			final Binding<JaxbHbmHibernateMapping> hbmBinding = bindMapping( mappingBinder, hbmXmlFile, origin );
+			hbmBindings.add( hbmBinding );
+		} );
 
-	private void transformFile(MappingBinder mappingBinder, Marshaller marshaller, File hbmXmlFile) {
+		final List<Binding<JaxbEntityMappingsImpl>> transformedBindings = HbmXmlTransformer.transform(
-		final Origin origin = new Origin( SourceType.FILE, hbmXmlFile.getAbsolutePath() );
+				hbmBindings,
-		final Binding<JaxbHbmHibernateMapping> binding = bindMapping( mappingBinder, hbmXmlFile, origin );
+				unsupportedFeatures.get()
-		if ( binding == null ) {
+		);
-			return;
+
-		}
+		for ( int i = 0; i < hbmBindings.size(); i++ ) {
+			final Binding<JaxbHbmHibernateMapping> hbmBinding = hbmBindings.get( i );
+			final Binding<JaxbEntityMappingsImpl> transformedBinding = transformedBindings.get( i );
+
+			final OriginImpl origin = (OriginImpl) hbmBinding.getOrigin();
+			final File hbmXmlFile = origin.getHbmXmlFile();
 
 			if ( deleteHbmFiles.getOrElse( false ) ) {
 				final boolean deleted = hbmXmlFile.delete();
@@ -144,16 +156,12 @@ public abstract class TransformHbmXmlTask extends SourceTask {
 				}
 			}
 
-		final HbmXmlTransformer.Options transformationOptions = unsupportedFeatures::get;
-
-		final JaxbEntityMappingsImpl transformed = HbmXmlTransformer.transform( binding.getRoot(), origin, transformationOptions );
-
 			final String copyName = determineCopyName( hbmXmlFile );
 			final File copyFile = determineCopyFile( copyName, hbmXmlFile );
 			//noinspection ResultOfMethodCallIgnored
 			copyFile.getParentFile().mkdirs();
 			try {
-			marshaller.marshal( transformed, copyFile );
+				marshaller.marshal( transformedBinding.getRoot(), copyFile );
 			}
 			catch (JAXBException e) {
 				throw new RuntimeException(
@@ -162,6 +170,7 @@ public abstract class TransformHbmXmlTask extends SourceTask {
 				);
 			}
 		}
+	}
 
 	private Binding<JaxbHbmHibernateMapping> bindMapping(MappingBinder mappingBinder, File hbmXmlFile, Origin origin) {
 		try ( final FileInputStream fileStream = new FileInputStream( hbmXmlFile ) ) {