HHH-15789 allow any InMemoryGenerator to generate ids

hibernate-core/src/main/java/org/hibernate/annotations/GenericGenerator.java

@@ -6,7 +6,7 @@
  */
 package org.hibernate.annotations;
 
-import org.hibernate.id.IdentifierGenerator;
+import org.hibernate.tuple.InMemoryGenerator;
 
 import java.lang.annotation.Repeatable;
 import java.lang.annotation.Retention;
@@ -74,12 +74,11 @@ public @interface GenericGenerator {
 	 */
 	String name();
 	/**
-	 * The type of identifier generator, a class implementing
+	 * The type of identifier generator, a class implementing {@link InMemoryGenerator}.
-	 * {@link org.hibernate.id.IdentifierGenerator}.
 	 *
 	 * @since 6.2
 	 */
-	Class<? extends IdentifierGenerator> type() default IdentifierGenerator.class;
+	Class<? extends InMemoryGenerator> type() default InMemoryGenerator.class;
 	/**
 	 * The type of identifier generator, the name of either:
 	 * <ul>

hibernate-core/src/main/java/org/hibernate/annotations/IdGeneratorType.java

@@ -11,6 +11,7 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 import org.hibernate.id.IdentifierGenerator;
+import org.hibernate.tuple.InMemoryGenerator;
 
 import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
 import static java.lang.annotation.RetentionPolicy.RUNTIME;
@@ -63,8 +64,8 @@ import static java.lang.annotation.RetentionPolicy.RUNTIME;
 @Retention(RUNTIME)
 public @interface IdGeneratorType {
 	/**
-	 * A class that implements {@link IdentifierGenerator} and has a
+	 * A class that implements {@link InMemoryGenerator} and has a constructor
-	 * constructor with the signature:
+	 * with the signature:
 	 * <pre>{@code
 	 * public GeneratorType(AnnotationType config, Member idMember,
 	 *                      CustomIdGeneratorCreationContext creationContext)
@@ -73,5 +74,5 @@ public @interface IdGeneratorType {
 	 * {@code IdentifierGenerator}, and {@code AnnotationType} is the
 	 * annotation type to which this annotation was applied.
 	 */
-	Class<? extends IdentifierGenerator> value();
+	Class<? extends InMemoryGenerator> value();
 }

hibernate-core/src/main/java/org/hibernate/boot/internal/InFlightMetadataCollectorImpl.java

@@ -46,6 +46,7 @@ import org.hibernate.boot.model.naming.ImplicitIndexNameSource;
 import org.hibernate.boot.model.naming.ImplicitUniqueKeyNameSource;
 import org.hibernate.boot.model.relational.AuxiliaryDatabaseObject;
 import org.hibernate.boot.model.relational.Database;
+import org.hibernate.boot.model.relational.ExportableProducer;
 import org.hibernate.boot.model.relational.Namespace;
 import org.hibernate.boot.model.relational.QualifiedTableName;
 import org.hibernate.boot.model.source.internal.ImplicitColumnNamingSecondPass;
@@ -102,6 +103,7 @@ import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.metamodel.spi.EmbeddableInstantiator;
 import org.hibernate.query.named.NamedObjectRepository;
 import org.hibernate.query.sqm.function.SqmFunctionDescriptor;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.descriptor.java.JavaType;
 import org.hibernate.type.descriptor.jdbc.JdbcType;
 import org.hibernate.type.spi.TypeConfiguration;
@@ -2314,13 +2316,15 @@ public class InFlightMetadataCollectorImpl implements InFlightMetadataCollector
 		//		It was done this way in the old code too, so no "regression" here; but
 		//		it could be done better
 		try {
-			final IdentifierGenerator ig = identifierValueBinding.createIdentifierGenerator(
+			final InMemoryGenerator generator = identifierValueBinding.createIdentifierGenerator(
 					bootstrapContext.getIdentifierGeneratorFactory(),
 					dialect,
 					entityBinding
 			);
 
-			ig.registerExportables( getDatabase() );
+			if ( generator instanceof ExportableProducer ) {
+				( (ExportableProducer) generator ).registerExportables( getDatabase() );
+			}
 		}
 		catch (MappingException e) {
 			// ignore this for now.  The reasoning being "non-reflective" binding as needed

hibernate-core/src/main/java/org/hibernate/boot/model/IdentifierGeneratorDefinition.java

@@ -7,10 +7,20 @@
 package org.hibernate.boot.model;
 
 import java.io.Serializable;
+import java.lang.annotation.Annotation;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
 
+import jakarta.persistence.GenerationType;
+import jakarta.persistence.Index;
+import jakarta.persistence.SequenceGenerator;
+import jakarta.persistence.TableGenerator;
+import jakarta.persistence.UniqueConstraint;
+import org.hibernate.AssertionFailure;
+import org.hibernate.Internal;
+import org.hibernate.id.IdentifierGenerator;
 import org.hibernate.internal.util.collections.CollectionHelper;
 
 import static java.util.Collections.emptyMap;
@@ -74,6 +84,171 @@ public class IdentifierGeneratorDefinition implements Serializable {
 		return parameters;
 	}
 
+	@Internal
+	public static IdentifierGeneratorDefinition createImplicit(
+			String name,
+			Class<?> idType,
+			String generatorName,
+			IdGeneratorStrategyInterpreter generationInterpreter,
+			GenerationType generationType) {
+		// If we were unable to locate an actual matching named generator assume
+		// a sequence/table of the given name, make one based on GenerationType.
+
+		if ( generationType == null) {
+			return buildSequenceGeneratorDefinition( name, generationInterpreter );
+		}
+
+		final String strategyName;
+		switch ( generationType ) {
+			case SEQUENCE:
+				return buildSequenceGeneratorDefinition( name, generationInterpreter );
+			case TABLE:
+				return buildTableGeneratorDefinition( name, generationInterpreter );
+			// really AUTO and IDENTITY work the same in this respect, aside from the actual strategy name
+			case IDENTITY:
+				strategyName = "identity";
+				break;
+			case AUTO:
+				strategyName = generationInterpreter.determineGeneratorName(
+						generationType,
+						new IdGeneratorStrategyInterpreter.GeneratorNameDeterminationContext() {
+							@Override
+							public Class<?> getIdType() {
+								return idType;
+							}
+							@Override
+							public String getGeneratedValueGeneratorName() {
+								return generatorName;
+							}
+						}
+				);
+				break;
+			default:
+				throw new AssertionFailure( "unknown generator type: " + generationType );
+		}
+
+		return new IdentifierGeneratorDefinition(
+				name,
+				strategyName,
+				Collections.singletonMap( IdentifierGenerator.GENERATOR_NAME, name )
+		);
+	}
+
+	private static IdentifierGeneratorDefinition buildTableGeneratorDefinition(String name, IdGeneratorStrategyInterpreter generationInterpreter) {
+		final Builder builder = new Builder();
+		generationInterpreter.interpretTableGenerator(
+				new TableGenerator() {
+					@Override
+					public String name() {
+						return name;
+					}
+
+					@Override
+					public String table() {
+						return "";
+					}
+
+					@Override
+					public int initialValue() {
+						return 0;
+					}
+
+					@Override
+					public int allocationSize() {
+						return 50;
+					}
+
+					@Override
+					public String catalog() {
+						return "";
+					}
+
+					@Override
+					public String schema() {
+						return "";
+					}
+
+					@Override
+					public String pkColumnName() {
+						return "";
+					}
+
+					@Override
+					public String valueColumnName() {
+						return "";
+					}
+
+					@Override
+					public String pkColumnValue() {
+						return "";
+					}
+
+					@Override
+					public UniqueConstraint[] uniqueConstraints() {
+						return new UniqueConstraint[0];
+					}
+
+					@Override
+					public Index[] indexes() {
+						return new Index[0];
+					}
+
+					@Override
+					public Class<? extends Annotation> annotationType() {
+						return TableGenerator.class;
+					}
+				},
+				builder
+		);
+
+		return builder.build();
+	}
+
+	private static IdentifierGeneratorDefinition buildSequenceGeneratorDefinition(String name, IdGeneratorStrategyInterpreter generationInterpreter) {
+		final Builder builder = new Builder();
+		generationInterpreter.interpretSequenceGenerator(
+				new SequenceGenerator() {
+					@Override
+					public String name() {
+						return name;
+					}
+
+					@Override
+					public String sequenceName() {
+						return "";
+					}
+
+					@Override
+					public String catalog() {
+						return "";
+					}
+
+					@Override
+					public String schema() {
+						return "";
+					}
+
+					@Override
+					public int initialValue() {
+						return 1;
+					}
+
+					@Override
+					public int allocationSize() {
+						return 50;
+					}
+
+					@Override
+					public Class<? extends Annotation> annotationType() {
+						return SequenceGenerator.class;
+					}
+				},
+				builder
+		);
+
+		return builder.build();
+	}
+
 	@Override
 	public boolean equals(Object o) {
 		if ( this == o ) {

hibernate-core/src/main/java/org/hibernate/cfg/AnnotationBinder.java

@@ -53,6 +53,7 @@ import org.hibernate.annotations.ParamDef;
 import org.hibernate.annotations.Parameter;
 import org.hibernate.annotations.Parent;
 import org.hibernate.annotations.TimeZoneStorage;
+import org.hibernate.annotations.ValueGenerationType;
 import org.hibernate.annotations.common.reflection.ReflectionManager;
 import org.hibernate.annotations.common.reflection.XAnnotatedElement;
 import org.hibernate.annotations.common.reflection.XClass;
@@ -91,6 +92,7 @@ import org.hibernate.property.access.internal.PropertyAccessStrategyMixedImpl;
 import org.hibernate.property.access.spi.PropertyAccessStrategy;
 import org.hibernate.resource.beans.spi.ManagedBean;
 import org.hibernate.resource.beans.spi.ManagedBeanRegistry;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.BasicType;
 import org.hibernate.type.CustomType;
 import org.hibernate.type.descriptor.java.BasicJavaType;
@@ -152,6 +154,7 @@ import static org.hibernate.cfg.InheritanceState.getInheritanceStateOfSuperEntit
 import static org.hibernate.cfg.InheritanceState.getSuperclassInheritanceState;
 import static org.hibernate.cfg.PropertyHolderBuilder.buildPropertyHolder;
 import static org.hibernate.cfg.annotations.HCANNHelper.findContainingAnnotation;
+import static org.hibernate.cfg.annotations.PropertyBinder.generatorCreator;
 import static org.hibernate.cfg.annotations.PropertyBinder.identifierGeneratorCreator;
 import static org.hibernate.internal.CoreLogging.messageLogger;
 import static org.hibernate.mapping.Constraint.hashedName;
@@ -477,10 +480,10 @@ public final class AnnotationBinder {
 		else if ( generatorAnnotation instanceof GenericGenerator ) {
 			final GenericGenerator genericGenerator = (GenericGenerator) generatorAnnotation;
 			definitionBuilder.setName( genericGenerator.name() );
-			final String strategy = genericGenerator.type().equals(IdentifierGenerator.class)
+			final String strategy = genericGenerator.type().equals(InMemoryGenerator.class)
 					? genericGenerator.strategy()
 					: genericGenerator.type().getName();
-			definitionBuilder.setStrategy(strategy);
+			definitionBuilder.setStrategy( strategy );
 			for ( Parameter parameter : genericGenerator.parameters() ) {
 				definitionBuilder.addParam( parameter.name(), parameter.value() );
 			}
@@ -1806,9 +1809,14 @@ public final class AnnotationBinder {
 					+ "' belongs to an '@IdClass' and may not be annotated '@Id' or '@EmbeddedId'" );
 		}
 		final XProperty idProperty = inferredData.getProperty();
-		final Annotation generatorAnnotation = findContainingAnnotation( idProperty, IdGeneratorType.class );
+		final Annotation idGeneratorAnnotation = findContainingAnnotation( idProperty, IdGeneratorType.class );
-		if ( generatorAnnotation != null ) {
+		final Annotation generatorAnnotation = findContainingAnnotation( idProperty, ValueGenerationType.class );
-			idValue.setCustomIdGeneratorCreator( identifierGeneratorCreator( idProperty, generatorAnnotation ) );
+		//TODO: validate that we don't have too many generator annotations and throw
+		if ( idGeneratorAnnotation != null ) {
+			idValue.setCustomIdGeneratorCreator( identifierGeneratorCreator( idProperty, idGeneratorAnnotation ) );
+		}
+		else if ( generatorAnnotation != null ) {
+			idValue.setCustomGeneratorCreator( generatorCreator( idProperty, generatorAnnotation ) );
 		}
 		else {
 			final XClass entityClass = inferredData.getClassOrElement();

hibernate-core/src/main/java/org/hibernate/cfg/BinderHelper.java

@@ -11,7 +11,6 @@ import java.lang.annotation.Repeatable;
 import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.EnumSet;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -41,8 +40,6 @@ import org.hibernate.annotations.SqlFragmentAlias;
 import org.hibernate.annotations.common.reflection.XAnnotatedElement;
 import org.hibernate.annotations.common.reflection.XClass;
 import org.hibernate.annotations.common.reflection.XProperty;
-import org.hibernate.boot.model.IdGeneratorStrategyInterpreter;
-import org.hibernate.boot.model.IdGeneratorStrategyInterpreter.GeneratorNameDeterminationContext;
 import org.hibernate.boot.model.IdentifierGeneratorDefinition;
 import org.hibernate.boot.spi.InFlightMetadataCollector;
 import org.hibernate.boot.spi.MetadataBuildingContext;
@@ -74,10 +71,6 @@ import org.jboss.logging.Logger;
 
 import jakarta.persistence.GeneratedValue;
 import jakarta.persistence.GenerationType;
-import jakarta.persistence.Index;
-import jakarta.persistence.SequenceGenerator;
-import jakarta.persistence.TableGenerator;
-import jakarta.persistence.UniqueConstraint;
 
 import static org.hibernate.cfg.AnnotatedColumn.buildColumnOrFormulaFromAnnotation;
 import static org.hibernate.internal.util.StringHelper.isNotEmpty;
@@ -777,7 +770,7 @@ public class BinderHelper {
 
 		if ( !isEmptyAnnotationValue( generatorName ) ) {
 			//we have a named generator
-			final IdentifierGeneratorDefinition definition = getIdentifierGenerator(
+			final IdentifierGeneratorDefinition definition = makeIdentifierGeneratorDefinition(
 					generatorName,
 					property,
 					localGenerators,
@@ -823,7 +816,7 @@ public class BinderHelper {
 		makeIdGenerator( id, idXProperty, generatorType, generatorName, buildingContext, localIdentifiers );
 	}
 
-	private static IdentifierGeneratorDefinition getIdentifierGenerator(
+	private static IdentifierGeneratorDefinition makeIdentifierGeneratorDefinition(
 			String name,
 			XProperty idXProperty,
 			Map<String, IdentifierGeneratorDefinition> localGenerators,
@@ -843,174 +836,21 @@ public class BinderHelper {
 
 		log.debugf( "Could not resolve explicit IdentifierGeneratorDefinition - using implicit interpretation (%s)", name );
 
-		// If we were unable to locate an actual matching named generator assume a sequence/table of the given name.
+		final GeneratedValue generatedValue = idXProperty.getAnnotation( GeneratedValue.class );
-		//		this really needs access to the `jakarta.persistence.GenerationType` to work completely properly
+		if ( generatedValue == null ) {
-		//
-		// 		(the crux of HHH-12122)
-
-		// temporarily, in lieu of having access to GenerationType, assume the EnhancedSequenceGenerator
-		//		for the purpose of testing the feasibility of the approach
-
-		final GeneratedValue generatedValueAnn = idXProperty.getAnnotation( GeneratedValue.class );
-		if ( generatedValueAnn == null ) {
 			// this should really never happen, but it's easy to protect against it...
 			return new IdentifierGeneratorDefinition( "assigned", "assigned" );
 		}
 
-		final IdGeneratorStrategyInterpreter generationInterpreter =
+		return IdentifierGeneratorDefinition.createImplicit(
-				buildingContext.getBuildingOptions().getIdGenerationTypeInterpreter();
-
-		final GenerationType generationType = interpretGenerationType( generatedValueAnn );
-
-		if ( generationType == null || generationType == GenerationType.SEQUENCE ) {
-			// NOTE : `null` will ultimately be interpreted as "hibernate_sequence"
-			log.debugf( "Building implicit sequence-based IdentifierGeneratorDefinition (%s)", name );
-			final IdentifierGeneratorDefinition.Builder builder = new IdentifierGeneratorDefinition.Builder();
-			generationInterpreter.interpretSequenceGenerator(
-					new SequenceGenerator() {
-						@Override
-						public String name() {
-							return name;
-						}
-
-						@Override
-						public String sequenceName() {
-							return "";
-						}
-
-						@Override
-						public String catalog() {
-							return "";
-						}
-
-						@Override
-						public String schema() {
-							return "";
-						}
-
-						@Override
-						public int initialValue() {
-							return 1;
-						}
-
-						@Override
-						public int allocationSize() {
-							return 50;
-						}
-
-						@Override
-						public Class<? extends Annotation> annotationType() {
-							return SequenceGenerator.class;
-						}
-					},
-					builder
-			);
-
-			return builder.build();
-		}
-		else if ( generationType == GenerationType.TABLE ) {
-			// NOTE : `null` will ultimately be interpreted as "hibernate_sequence"
-			log.debugf( "Building implicit table-based IdentifierGeneratorDefinition (%s)", name );
-			final IdentifierGeneratorDefinition.Builder builder = new IdentifierGeneratorDefinition.Builder();
-			generationInterpreter.interpretTableGenerator(
-					new TableGenerator() {
-						@Override
-						public String name() {
-							return name;
-						}
-
-						@Override
-						public String table() {
-							return "";
-						}
-
-						@Override
-						public int initialValue() {
-							return 0;
-						}
-
-						@Override
-						public int allocationSize() {
-							return 50;
-						}
-
-						@Override
-						public String catalog() {
-							return "";
-						}
-
-						@Override
-						public String schema() {
-							return "";
-						}
-
-						@Override
-						public String pkColumnName() {
-							return "";
-						}
-
-						@Override
-						public String valueColumnName() {
-							return "";
-						}
-
-						@Override
-						public String pkColumnValue() {
-							return "";
-						}
-
-						@Override
-						public UniqueConstraint[] uniqueConstraints() {
-							return new UniqueConstraint[0];
-						}
-
-						@Override
-						public Index[] indexes() {
-							return new Index[0];
-						}
-
-						@Override
-						public Class<? extends Annotation> annotationType() {
-							return TableGenerator.class;
-						}
-					},
-					builder
-			);
-
-			return builder.build();
-		}
-
-
-		// really AUTO and IDENTITY work the same in this respect, aside from the actual strategy name
-		final String strategyName;
-		if ( generationType == GenerationType.IDENTITY ) {
-			strategyName = "identity";
-		}
-		else {
-			strategyName = generationInterpreter.determineGeneratorName(
-					generationType,
-					new GeneratorNameDeterminationContext() {
-						@Override
-						public Class<?> getIdType() {
-							return buildingContext
-									.getBootstrapContext()
-									.getReflectionManager()
-									.toClass( idXProperty.getType() );
-						}
-
-						@Override
-						public String getGeneratedValueGeneratorName() {
-							return generatedValueAnn.generator();
-						}
-					}
-			);
-		}
-
-		log.debugf( "Building implicit generic IdentifierGeneratorDefinition (%s) : %s", name, strategyName );
-		return new IdentifierGeneratorDefinition(
 				name,
-				strategyName,
+				buildingContext
-				Collections.singletonMap( IdentifierGenerator.GENERATOR_NAME, name )
+						.getBootstrapContext()
+						.getReflectionManager()
+						.toClass( idXProperty.getType() ),
+				generatedValue.generator(),
+				buildingContext.getBuildingOptions().getIdGenerationTypeInterpreter(),
+				interpretGenerationType( generatedValue )
 		);
 	}
 

hibernate-core/src/main/java/org/hibernate/cfg/annotations/PropertyBinder.java

@@ -21,6 +21,7 @@ import org.hibernate.annotations.OptimisticLock;
 import org.hibernate.annotations.ValueGenerationType;
 import org.hibernate.annotations.common.reflection.XClass;
 import org.hibernate.annotations.common.reflection.XProperty;
+import org.hibernate.boot.model.relational.ExportableProducer;
 import org.hibernate.boot.spi.MetadataBuildingContext;
 import org.hibernate.cfg.AccessType;
 import org.hibernate.cfg.AnnotatedColumns;
@@ -37,6 +38,7 @@ import org.hibernate.mapping.Component;
 import org.hibernate.mapping.GeneratorCreator;
 import org.hibernate.mapping.IdentifierGeneratorCreator;
 import org.hibernate.mapping.KeyValue;
+import org.hibernate.mapping.MappedSuperclass;
 import org.hibernate.mapping.Property;
 import org.hibernate.mapping.RootClass;
 import org.hibernate.mapping.SimpleValue;
@@ -49,6 +51,7 @@ import org.hibernate.tuple.Generator;
 import org.hibernate.tuple.AttributeBinder;
 import org.hibernate.tuple.GeneratorCreationContext;
 import org.hibernate.tuple.GenerationTiming;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.jboss.logging.Logger;
 
 import java.lang.annotation.Annotation;
@@ -168,6 +171,38 @@ public class PropertyBinder {
 		this.declaringClassSet = true;
 	}
 
+	private boolean isToOneValue(Value value) {
+		return value instanceof ToOne;
+	}
+
+	public void setProperty(XProperty property) {
+		this.property = property;
+	}
+
+	public void setReturnedClass(XClass returnedClass) {
+		this.returnedClass = returnedClass;
+	}
+
+	public BasicValueBinder getBasicValueBinder() {
+		return basicValueBinder;
+	}
+
+	public Value getValue() {
+		return value;
+	}
+
+	public void setId(boolean id) {
+		this.isId = id;
+	}
+
+	public boolean isId() {
+		return isId;
+	}
+
+	public void setInheritanceStatePerClass(Map<XClass, InheritanceState> inheritanceStatePerClass) {
+		this.inheritanceStatePerClass = inheritanceStatePerClass;
+	}
+
 	private void validateBind() {
 		if ( property.isAnnotationPresent( Immutable.class ) ) {
 			throw new AnnotationException( "Property '" + qualify( holder.getPath(), name )
@@ -243,7 +278,8 @@ public class PropertyBinder {
 		if ( isId ) {
 			final RootClass rootClass = (RootClass) holder.getPersistentClass();
 			//if an xToMany, it has to be wrapped today.
-			//FIXME this poses a problem as the PK is the class instead of the associated class which is not really compliant with the spec
+			//FIXME this poses a problem as the PK is the class instead of the
+			//      associated class which is not really compliant with the spec
 			if ( isXToMany || entityBinder.wrapIdsInEmbeddedComponents() ) {
 				Component identifier = (Component) rootClass.getIdentifier();
 				if (identifier == null) {
@@ -270,7 +306,7 @@ public class PropertyBinder {
 				}
 				else {
 					rootClass.setIdentifierProperty( prop );
-					final org.hibernate.mapping.MappedSuperclass superclass = getMappedSuperclassOrNull(
+					final MappedSuperclass superclass = getMappedSuperclassOrNull(
 							declaringClass,
 							inheritanceStatePerClass,
 							buildingContext
@@ -343,7 +379,7 @@ public class PropertyBinder {
 	}
 
 	private void handleNaturalId(Property prop) {
-		NaturalId naturalId = property.getAnnotation(NaturalId.class);
+		final NaturalId naturalId = property.getAnnotation(NaturalId.class);
 		if ( naturalId != null ) {
 			if ( !entityBinder.isRootEntity() ) {
 				throw new AnnotationException( "Property '" + qualify( holder.getPath(), name )
@@ -415,13 +451,14 @@ public class PropertyBinder {
 	 * Instantiates the given generator annotation type, initializing it with the given instance of the corresponding
 	 * generator annotation and the property's type.
 	 */
-	private <A extends Annotation> GeneratorCreator generatorCreator(XProperty property, A annotation) {
+	public static GeneratorCreator generatorCreator(XProperty property, Annotation annotation) {
 		final Member member = HCANNHelper.getUnderlyingMember( property );
 		final Class<? extends Annotation> annotationType = annotation.annotationType();
 		final ValueGenerationType generatorAnnotation = annotationType.getAnnotation( ValueGenerationType.class );
 		if ( generatorAnnotation == null ) {
 			return null;
 		}
+		checkGeneratorType( generatorAnnotation.generatedBy() );
 		return creationContext -> {
 			final Generator generator =
 					instantiateGenerator(
@@ -438,13 +475,27 @@ public class PropertyBinder {
 		};
 	}
 
+	private static void checkGeneratorType(Class<? extends Generator> generatorClass) {
+		// we don't yet support the additional "fancy" operations of
+		// IdentifierGenerator with regular generators, though this
+		// would be extremely easy to add if anyone asks for it
+		if ( IdentifierGenerator.class.isAssignableFrom( generatorClass ) ) {
+			throw new AnnotationException("Generator class '" + generatorClass.getName()
+					+ "' implements 'IdentifierGenerator' and may not be used with '@ValueGenerationType'");
+		}
+		if ( ExportableProducer.class.isAssignableFrom( generatorClass ) ) {
+			throw new AnnotationException("Generator class '" + generatorClass.getName()
+					+ "' implements 'ExportableProducer' and may not be used with '@ValueGenerationType'");
+		}
+	}
+
 	public static IdentifierGeneratorCreator identifierGeneratorCreator(XProperty idProperty, Annotation annotation) {
 		final Member member = HCANNHelper.getUnderlyingMember( idProperty );
 		final Class<? extends Annotation> annotationType = annotation.annotationType();
 		final IdGeneratorType idGeneratorType = annotationType.getAnnotation( IdGeneratorType.class );
 		assert idGeneratorType != null;
 		return creationContext -> {
-			final IdentifierGenerator generator =
+			final InMemoryGenerator generator =
 					instantiateGenerator(
 							annotation,
 							member,
@@ -505,11 +556,11 @@ public class PropertyBinder {
 		}
 	}
 
-	private void checkVersionGenerationAlways(XProperty property, Generator generator) {
+	private static void checkVersionGenerationAlways(XProperty property, Generator generator) {
 		if ( property.isAnnotationPresent(Version.class) ) {
 			final GenerationTiming timing = generator.getGenerationTiming();
 			if ( !timing.isAlways() ) {
-				throw new AnnotationException("Property '" + qualify( holder.getPath(), name )
+				throw new AnnotationException("Property '" + property.getName()
 						+ "' is annotated '@Version' but has a value generator with timing " + timing.name()
 						+ " (the value generation timing must be ALWAYS)"
 				);
@@ -517,35 +568,4 @@ public class PropertyBinder {
 		}
 	}
 
-	private boolean isToOneValue(Value value) {
-		return value instanceof ToOne;
-	}
-
-	public void setProperty(XProperty property) {
-		this.property = property;
-	}
-
-	public void setReturnedClass(XClass returnedClass) {
-		this.returnedClass = returnedClass;
-	}
-
-	public BasicValueBinder getBasicValueBinder() {
-		return basicValueBinder;
-	}
-
-	public Value getValue() {
-		return value;
-	}
-
-	public void setId(boolean id) {
-		this.isId = id;
-	}
-
-	public boolean isId() {
-		return isId;
-	}
-
-	public void setInheritanceStatePerClass(Map<XClass, InheritanceState> inheritanceStatePerClass) {
-		this.inheritanceStatePerClass = inheritanceStatePerClass;
-	}
 }

hibernate-core/src/main/java/org/hibernate/collection/spi/PersistentIdentifierBag.java

@@ -368,7 +368,7 @@ public class PersistentIdentifierBag<E> extends AbstractPersistentCollection<E>
 			final Integer loc = i++;
 			if ( !identifiers.containsKey( loc ) ) {
 				//TODO: native ids
-				final Object id = persister.getIdentifierGenerator().generate( getSession(), entry );
+				final Object id = persister.getGenerator().generate( getSession(), entry, null );
 				identifiers.put( loc, id );
 			}
 		}

hibernate-core/src/main/java/org/hibernate/dialect/temptable/TemporaryTable.java

@@ -18,7 +18,6 @@ import org.hibernate.boot.model.relational.QualifiedNameParser;
 import org.hibernate.boot.model.relational.QualifiedTableName;
 import org.hibernate.boot.model.relational.SqlStringGenerationContext;
 import org.hibernate.dialect.Dialect;
-import org.hibernate.id.IdentifierGenerator;
 import org.hibernate.id.OptimizableGenerator;
 import org.hibernate.id.PostInsertIdentifierGenerator;
 import org.hibernate.id.enhanced.Optimizer;
@@ -42,6 +41,7 @@ import org.hibernate.metamodel.mapping.PluralAttributeMapping;
 import org.hibernate.metamodel.spi.RuntimeModelCreationContext;
 import org.hibernate.persister.entity.EntityPersister;
 import org.hibernate.persister.entity.SingleTableEntityPersister;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.BasicType;
 import org.hibernate.type.StandardBasicTypes;
 import org.hibernate.type.spi.TypeConfiguration;
@@ -253,8 +253,7 @@ public class TemporaryTable implements Exportable, Contributable {
 					final PersistentClass entityBinding = runtimeModelCreationContext.getBootModel()
 							.getEntityBinding( entityDescriptor.getEntityName() );
 
-					final IdentifierGenerator identifierGenerator = entityDescriptor.getEntityPersister()
+					final InMemoryGenerator identifierGenerator = entityDescriptor.getEntityPersister().getGenerator();
-							.getIdentifierGenerator();
 					final boolean identityColumn = identifierGenerator instanceof PostInsertIdentifierGenerator;
 					final boolean hasOptimizer;
 					if ( identityColumn ) {

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

@@ -46,6 +46,7 @@ import org.hibernate.query.spi.QueryEngine;
 import org.hibernate.relational.SchemaManager;
 import org.hibernate.service.spi.ServiceRegistryImplementor;
 import org.hibernate.stat.spi.StatisticsImplementor;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.Type;
 import org.hibernate.type.descriptor.WrapperOptions;
 import org.hibernate.type.spi.TypeConfiguration;
@@ -183,6 +184,11 @@ public class SessionFactoryDelegatingImpl implements SessionFactoryImplementor,
 		return delegate.getIdentifierGenerator( rootEntityName );
 	}
 
+	@Override
+	public InMemoryGenerator getGenerator(String rootEntityName) {
+		return delegate.getGenerator( rootEntityName );
+	}
+
 	@Override
 	public Map<String, Object> getProperties() {
 		return delegate.getProperties();

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

@@ -33,6 +33,7 @@ import org.hibernate.query.sqm.spi.SqmCreationContext;
 import org.hibernate.service.spi.ServiceRegistryImplementor;
 import org.hibernate.sql.ast.spi.SqlAstCreationContext;
 import org.hibernate.stat.spi.StatisticsImplementor;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.descriptor.WrapperOptions;
 import org.hibernate.type.spi.TypeConfiguration;
 
@@ -120,9 +121,16 @@ public interface SessionFactoryImplementor
 
 	/**
 	 * Get the identifier generator for the hierarchy
+	 * 
+	 * @deprecated use {@link #getGenerator(String)}
 	 */
+	@Deprecated(since = "6.2")
 	IdentifierGenerator getIdentifierGenerator(String rootEntityName);
 
+	/**
+	 * Get the identifier generator for the hierarchy
+	 */
+	InMemoryGenerator getGenerator(String rootEntityName);
 
 	EntityNotFoundDelegate getEntityNotFoundDelegate();
 

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

@@ -111,7 +111,7 @@ public abstract class AbstractSaveEventListener<C>
 		processIfSelfDirtinessTracker( entity, SelfDirtinessTracker::$$_hibernate_clearDirtyAttributes );
 
 		EntityPersister persister = source.getEntityPersister( entityName, entity );
-		Object generatedId = persister.getIdentifierGenerator().generate( source, entity );
+		Object generatedId = persister.getGenerator().generate( source, entity, null );
 		if ( generatedId == null ) {
 			throw new IdentifierGenerationException( "null id generated for: " + entity.getClass() );
 		}
@@ -127,7 +127,7 @@ public abstract class AbstractSaveEventListener<C>
 				LOG.debugf(
 						"Generated identifier: %s, using strategy: %s",
 						persister.getIdentifierType().toLoggableString( generatedId, source.getFactory() ),
-						persister.getIdentifierGenerator().getClass().getName()
+						persister.getGenerator().getClass().getName()
 				);
 			}
 			return performSave( entity, generatedId, persister, false, context, source, true );

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

@@ -122,7 +122,7 @@ public class DefaultPersistEventListener
 			// NOTE: entityEntry must be null to get here, so we cannot use any of its values
 			final EntityPersister persister = source.getFactory().getMappingMetamodel()
 					.getEntityDescriptor( entityName );
-			if ( persister.getIdentifierGenerator() instanceof ForeignGenerator ) {
+			if ( persister.getGenerator() instanceof ForeignGenerator ) {
 				if ( LOG.isDebugEnabled() && persister.getIdentifier( entity, source ) != null ) {
 					LOG.debug( "Resetting entity id attribute to null for foreign generator" );
 				}

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

@@ -22,18 +22,31 @@ import org.hibernate.type.Type;
 import static org.hibernate.tuple.GenerationTiming.INSERT;
 
 /**
- * The general contract between a class that generates unique
+ * A classic extension point from the very earliest days of Hibernate,
- * identifiers and the {@link org.hibernate.Session}. It is not
+ * this interface is now no longer the only way to generate identifiers.
- * intended that this interface ever be exposed to the application.
+ * Any {@link InMemoryGenerator} may now be used.
- * It <em>is</em> intended that users implement this interface to
- * provide custom identifier generation strategies.
  * <p>
- * Implementors should provide a public default constructor.
+ * This interface extends {@code InMemoryGenerator} with some additional
+ * machinery for {@linkplain #configure configuration}, and for caching
+ * {@link #initialize(SqlStringGenerationContext) generated SQL}.
  * <p>
- * Implementations that accept configuration parameters should also
+ * Any identifier generator, including a generator which directly implements
- * implement {@link Configurable}.
+ * {@code InMemoryGenerator}, may also implement {@link ExportableProducer}.
+ * For the sake of convenience, {@code PersistentIdentifierGenerator} extends
+ * {@code ExportableProducer}, in case the implementation needs to export
+ * objects to the database as part of the process of schema export.
  * <p>
- * Implementors <em>must</em> be thread-safe
+ * The {@link #configure(Type, Properties, ServiceRegistry)} method accepts
+ * a properties object containing named values. These include:
+ * <ul>
+ * <li>several "standard" parameters with keys defined as static members of
+ *     this interface: {@value #ENTITY_NAME}, {@value #JPA_ENTITY_NAME},
+ *     {@value #GENERATOR_NAME}, {@value #CONTRIBUTOR_NAME}, along with
+ * <li>additional parameters supplied by Hibernate to its built-in generators,
+ *     depending on the generator class, and, possibly,
+ * <li>{@linkplain org.hibernate.annotations.Parameter parameters} specified
+ *     using {@link org.hibernate.annotations.GenericGenerator#parameters()}.
+ * </ul>
  *
  * @author Gavin King
  *

hibernate-core/src/main/java/org/hibernate/id/factory/internal/IdentifierGeneratorUtil.java

@@ -0,0 +1,132 @@
+/*
+ * 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.id.factory.internal;
+
+import org.hibernate.cfg.AvailableSettings;
+import org.hibernate.dialect.Dialect;
+import org.hibernate.engine.config.spi.ConfigurationService;
+import org.hibernate.engine.config.spi.StandardConverters;
+import org.hibernate.id.IdentifierGenerator;
+import org.hibernate.id.OptimizableGenerator;
+import org.hibernate.id.PersistentIdentifierGenerator;
+import org.hibernate.id.enhanced.LegacyNamingStrategy;
+import org.hibernate.id.enhanced.SingleNamingStrategy;
+import org.hibernate.id.factory.IdentifierGeneratorFactory;
+import org.hibernate.mapping.Column;
+import org.hibernate.mapping.RootClass;
+import org.hibernate.mapping.SimpleValue;
+import org.hibernate.mapping.Table;
+
+import java.util.Properties;
+
+public class IdentifierGeneratorUtil {
+
+	public static IdentifierGenerator createLegacyIdentifierGenerator(
+			SimpleValue simpleValue,
+			IdentifierGeneratorFactory identifierGeneratorFactory,
+			Dialect dialect,
+			String defaultCatalog,
+			String defaultSchema,
+			RootClass rootClass) {
+		final Properties params = new Properties();
+
+		// This is for backwards compatibility only;
+		// when this method is called by Hibernate ORM, defaultSchema and defaultCatalog are always
+		// null, and defaults are handled later.
+		if ( defaultSchema != null ) {
+			params.setProperty( PersistentIdentifierGenerator.SCHEMA, defaultSchema);
+		}
+
+		if ( defaultCatalog != null ) {
+			params.setProperty( PersistentIdentifierGenerator.CATALOG, defaultCatalog);
+		}
+
+		// default initial value and allocation size per-JPA defaults
+		params.setProperty( OptimizableGenerator.INITIAL_PARAM, String.valueOf( OptimizableGenerator.DEFAULT_INITIAL_VALUE ) );
+		final ConfigurationService cs = simpleValue.getMetadata().getMetadataBuildingOptions().getServiceRegistry()
+				.getService( ConfigurationService.class );
+
+		final String idNamingStrategy = cs.getSetting(
+				AvailableSettings.ID_DB_STRUCTURE_NAMING_STRATEGY,
+				StandardConverters.STRING,
+				null
+		);
+
+		if ( LegacyNamingStrategy.STRATEGY_NAME.equals( idNamingStrategy )
+				|| LegacyNamingStrategy.class.getName().equals( idNamingStrategy )
+				|| SingleNamingStrategy.STRATEGY_NAME.equals( idNamingStrategy )
+				|| SingleNamingStrategy.class.getName().equals( idNamingStrategy ) ) {
+			params.setProperty( OptimizableGenerator.INCREMENT_PARAM, "1" );
+		}
+		else {
+			params.setProperty(
+					OptimizableGenerator.INCREMENT_PARAM,
+					String.valueOf( OptimizableGenerator.DEFAULT_INCREMENT_SIZE )
+			);
+		}
+		//init the table here instead of earlier, so that we can get a quoted table name
+		//TODO: would it be better to simply pass the qualified table name, instead of
+		//	  splitting it up into schema/catalog/table names
+		final String tableName = simpleValue.getTable().getQuotedName(dialect);
+		params.setProperty( PersistentIdentifierGenerator.TABLE, tableName );
+
+		//pass the column name (a generated id almost always has a single column)
+		final String columnName = ( (Column) simpleValue.getSelectables().get(0) ).getQuotedName(dialect);
+		params.setProperty( PersistentIdentifierGenerator.PK, columnName );
+
+		//pass the entity-name, if not a collection-id
+		if ( rootClass != null ) {
+			params.setProperty( IdentifierGenerator.ENTITY_NAME, rootClass.getEntityName() );
+			params.setProperty( IdentifierGenerator.JPA_ENTITY_NAME, rootClass.getJpaEntityName() );
+			// The table name is not really a good default for subselect entities, so use the JPA entity name which is short
+			if ( simpleValue.getTable().isSubselect() ) {
+				params.setProperty( OptimizableGenerator.IMPLICIT_NAME_BASE, rootClass.getJpaEntityName() );
+			}
+			else {
+				params.setProperty( OptimizableGenerator.IMPLICIT_NAME_BASE, simpleValue.getTable().getName() );
+			}
+
+			final StringBuilder tables = new StringBuilder();
+			for ( Table table : rootClass.getIdentityTables() ) {
+				tables.append( table.getQuotedName(dialect) );
+				if ( tables.length()>0 ) {
+					tables.append( ", " );
+				}
+			}
+			params.setProperty( PersistentIdentifierGenerator.TABLES, tables.toString() );
+		}
+		else {
+			params.setProperty( PersistentIdentifierGenerator.TABLES, tableName );
+			params.setProperty( OptimizableGenerator.IMPLICIT_NAME_BASE, tableName );
+		}
+
+		if ( simpleValue.getIdentifierGeneratorParameters() != null ) {
+			params.putAll( simpleValue.getIdentifierGeneratorParameters() );
+		}
+
+		// TODO : we should pass along all settings once "config lifecycle" is hashed out...
+
+		params.put(
+				IdentifierGenerator.CONTRIBUTOR_NAME,
+				simpleValue.getBuildingContext().getCurrentContributorName()
+		);
+
+		if ( cs.getSettings().get( AvailableSettings.PREFERRED_POOLED_OPTIMIZER ) != null ) {
+			params.put(
+					AvailableSettings.PREFERRED_POOLED_OPTIMIZER,
+					cs.getSettings().get( AvailableSettings.PREFERRED_POOLED_OPTIMIZER )
+			);
+		}
+
+		return identifierGeneratorFactory.createIdentifierGenerator(
+				simpleValue.getIdentifierGeneratorStrategy(),
+				simpleValue.getType(),
+				params
+		);
+	}
+
+}

hibernate-core/src/main/java/org/hibernate/id/factory/internal/StandardIdentifierGeneratorFactory.java

@@ -52,7 +52,7 @@ import org.hibernate.type.descriptor.java.JavaType;
 import static org.hibernate.id.factory.IdGenFactoryLogging.ID_GEN_FAC_LOGGER;
 
 /**
- * Basic {@code templated} support for {@link org.hibernate.id.factory.IdentifierGeneratorFactory} implementations.
+ * Basic implementation of {@link org.hibernate.id.factory.IdentifierGeneratorFactory}.
  *
  * @author Steve Ebersole
  */

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

@@ -124,6 +124,7 @@ import org.hibernate.service.spi.SessionFactoryServiceRegistryFactory;
 import org.hibernate.stat.spi.StatisticsImplementor;
 import org.hibernate.tool.schema.spi.DelayedDropAction;
 import org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.Type;
 import org.hibernate.type.descriptor.WrapperOptions;
 import org.hibernate.type.spi.TypeConfiguration;
@@ -183,7 +184,7 @@ public class SessionFactoryImpl implements SessionFactoryImplementor {
 	private volatile DelayedDropAction delayedDropAction;
 
 	// todo : move to MetamodelImpl
-	private final transient Map<String,IdentifierGenerator> identifierGenerators;
+	private final transient Map<String, InMemoryGenerator> identifierGenerators;
 	private final transient Map<String, FilterDefinition> filters;
 	private final transient Map<String, FetchProfile> fetchProfiles;
 
@@ -293,12 +294,14 @@ public class SessionFactoryImpl implements SessionFactoryImplementor {
 			//Generators:
 			this.identifierGenerators = new HashMap<>();
 			bootMetamodel.getEntityBindings().stream().filter( model -> !model.isInherited() ).forEach( model -> {
-				final IdentifierGenerator generator = model.getIdentifier().createIdentifierGenerator(
+				final InMemoryGenerator generator = model.getIdentifier().createGenerator(
 						bootstrapContext.getIdentifierGeneratorFactory(),
 						jdbcServices.getJdbcEnvironment().getDialect(),
 						(RootClass) model
 				);
-				generator.initialize( sqlStringGenerationContext );
+				if ( generator instanceof IdentifierGenerator ) {
+					( (IdentifierGenerator) generator ).initialize( sqlStringGenerationContext );
+				}
 				identifierGenerators.put( model.getEntityName(), generator );
 			} );
 			bootMetamodel.validate();
@@ -985,8 +988,14 @@ public class SessionFactoryImpl implements SessionFactoryImplementor {
 		return unmodifiableSet( fetchProfiles.keySet() );
 	}
 
+	@Deprecated
 	public IdentifierGenerator getIdentifierGenerator(String rootEntityName) {
-		return identifierGenerators.get(rootEntityName);
+		return (IdentifierGenerator) getGenerator( rootEntityName );
+	}
+
+	@Deprecated
+	public InMemoryGenerator getGenerator(String rootEntityName) {
+		return identifierGenerators.get( rootEntityName );
 	}
 
 	private boolean canAccessTransactionManager() {

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

@@ -93,7 +93,7 @@ public class StatelessSessionImpl extends AbstractSharedSessionContract implemen
 	public Object insert(String entityName, Object entity) {
 		checkOpen();
 		EntityPersister persister = getEntityPersister( entityName, entity );
-		Object id = persister.getIdentifierGenerator().generate( this, entity );
+		Object id = persister.getGenerator().generate( this, entity, null );
 		Object[] state = persister.getValues( entity );
 		if ( persister.isVersioned() ) {
 			boolean substitute = Versioning.seedVersion(

hibernate-core/src/main/java/org/hibernate/mapping/Component.java

@@ -18,6 +18,7 @@ import java.util.stream.Collectors;
 import org.hibernate.MappingException;
 import org.hibernate.Remove;
 import org.hibernate.boot.model.relational.Database;
+import org.hibernate.boot.model.relational.ExportableProducer;
 import org.hibernate.boot.model.relational.SqlStringGenerationContext;
 import org.hibernate.boot.model.source.internal.hbm.MappingDocument;
 import org.hibernate.boot.registry.classloading.spi.ClassLoaderService;
@@ -33,6 +34,7 @@ import org.hibernate.internal.util.collections.ArrayHelper;
 import org.hibernate.internal.util.collections.JoinedIterator;
 import org.hibernate.metamodel.spi.EmbeddableInstantiator;
 import org.hibernate.property.access.spi.Setter;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.ComponentType;
 import org.hibernate.type.EmbeddedComponentType;
 import org.hibernate.type.Type;
@@ -70,7 +72,7 @@ public class Component extends SimpleValue implements MetaAttributable, Sortable
 	// lazily computed based on 'properties' field: invalidate by setting to null when properties are modified
 	private transient List<Column> cachedColumns;
 
-	private transient IdentifierGenerator builtIdentifierGenerator;
+	private transient InMemoryGenerator builtIdentifierGenerator;
 
 	public Component(MetadataBuildingContext metadata, PersistentClass owner) throws MappingException {
 		this( metadata, owner.getTable(), owner );
@@ -412,34 +414,30 @@ public class Component extends SimpleValue implements MetaAttributable, Sortable
 	}
 
 	@Override
-	public IdentifierGenerator createIdentifierGenerator(
+	public InMemoryGenerator createGenerator(
 			IdentifierGeneratorFactory identifierGeneratorFactory,
 			Dialect dialect,
-			String defaultCatalog,
-			String defaultSchema,
 			RootClass rootClass) throws MappingException {
 		if ( builtIdentifierGenerator == null ) {
 			builtIdentifierGenerator = buildIdentifierGenerator(
 					identifierGeneratorFactory,
 					dialect,
-					defaultCatalog,
-					defaultSchema,
 					rootClass
 			);
 		}
 		return builtIdentifierGenerator;
 	}
 
-	private IdentifierGenerator buildIdentifierGenerator(
+	private InMemoryGenerator buildIdentifierGenerator(
 			IdentifierGeneratorFactory identifierGeneratorFactory,
 			Dialect dialect,
-			String defaultCatalog,
-			String defaultSchema,
 			RootClass rootClass) throws MappingException {
 		final boolean hasCustomGenerator = ! DEFAULT_ID_GEN_STRATEGY.equals( getIdentifierGeneratorStrategy() );
 		if ( hasCustomGenerator ) {
-			return super.createIdentifierGenerator(
+			return super.createGenerator(
-					identifierGeneratorFactory, dialect, defaultCatalog, defaultSchema, rootClass
+					identifierGeneratorFactory,
+					dialect,
+					rootClass
 			);
 		}
 
@@ -469,25 +467,16 @@ public class Component extends SimpleValue implements MetaAttributable, Sortable
 			if ( property.getValue().isSimpleValue() ) {
 				final SimpleValue value = (SimpleValue) property.getValue();
 
-				if ( DEFAULT_ID_GEN_STRATEGY.equals( value.getIdentifierGeneratorStrategy() ) ) {
+				if ( !DEFAULT_ID_GEN_STRATEGY.equals( value.getIdentifierGeneratorStrategy() ) ) {
 					// skip any 'assigned' generators, they would have been handled by
 					// the StandardGenerationContextLocator
-					continue;
+					generator.addGeneratedValuePlan(
+							new ValueGenerationPlan(
+									value.createGenerator( identifierGeneratorFactory, dialect, rootClass ),
+									injector( property, attributeDeclarer )
+							)
+					);
 				}
-
-				final IdentifierGenerator valueGenerator = value.createIdentifierGenerator(
-						identifierGeneratorFactory,
-						dialect,
-						defaultCatalog,
-						defaultSchema,
-						rootClass
-				);
-				generator.addGeneratedValuePlan(
-						new ValueGenerationPlan(
-								valueGenerator,
-								injector( property, attributeDeclarer )
-						)
-				);
 			}
 		}
 		return generator;
@@ -523,11 +512,11 @@ public class Component extends SimpleValue implements MetaAttributable, Sortable
 	}
 
 	public static class ValueGenerationPlan implements CompositeNestedGeneratedValueGenerator.GenerationPlan {
-		private final IdentifierGenerator subGenerator;
+		private final InMemoryGenerator subGenerator;
 		private final Setter injector;
 
 		public ValueGenerationPlan(
-				IdentifierGenerator subGenerator,
+				InMemoryGenerator subGenerator,
 				Setter injector) {
 			this.subGenerator = subGenerator;
 			this.injector = injector;
@@ -535,18 +524,21 @@ public class Component extends SimpleValue implements MetaAttributable, Sortable
 
 		@Override
 		public void execute(SharedSessionContractImplementor session, Object incomingObject, Object injectionContext) {
-			final Object generatedValue = subGenerator.generate( session, incomingObject );
+			injector.set( injectionContext, subGenerator.generate( session, incomingObject, null ) );
-			injector.set( injectionContext, generatedValue );
 		}
 
 		@Override
 		public void registerExportables(Database database) {
-			subGenerator.registerExportables( database );
+			if ( subGenerator instanceof ExportableProducer ) {
+				( (ExportableProducer) subGenerator ).registerExportables( database );
+			}
 		}
 
 		@Override
 		public void initialize(SqlStringGenerationContext context) {
-			subGenerator.initialize( context );
+			if ( subGenerator instanceof IdentifierGenerator ) {
+				( (IdentifierGenerator) subGenerator ).initialize( context );
+			}
 		}
 	}
 

hibernate-core/src/main/java/org/hibernate/mapping/IdentifierGeneratorCreator.java

@@ -6,10 +6,10 @@
  */
 package org.hibernate.mapping;
 
-import org.hibernate.id.IdentifierGenerator;
 import org.hibernate.id.factory.spi.CustomIdGeneratorCreationContext;
+import org.hibernate.tuple.InMemoryGenerator;
 
 @FunctionalInterface
 public interface IdentifierGeneratorCreator {
-	IdentifierGenerator createGenerator(CustomIdGeneratorCreationContext context);
+	InMemoryGenerator createGenerator(CustomIdGeneratorCreationContext context);
 }

hibernate-core/src/main/java/org/hibernate/mapping/KeyValue.java

@@ -6,10 +6,10 @@
  */
 package org.hibernate.mapping;
 
-import org.hibernate.MappingException;
 import org.hibernate.dialect.Dialect;
 import org.hibernate.id.IdentifierGenerator;
 import org.hibernate.id.factory.IdentifierGeneratorFactory;
+import org.hibernate.tuple.InMemoryGenerator;
 
 /**
  * A mapping model {@link Value} which may be treated as an identifying key of a
@@ -21,23 +21,6 @@ import org.hibernate.id.factory.IdentifierGeneratorFactory;
  */
 public interface KeyValue extends Value {
 
-	/**
-	 * @deprecated Use {@link #createIdentifierGenerator(IdentifierGeneratorFactory, Dialect, RootClass)}
-	 * instead.
-	 */
-	@Deprecated
-	IdentifierGenerator createIdentifierGenerator(
-			IdentifierGeneratorFactory identifierGeneratorFactory,
-			Dialect dialect,
-			String defaultCatalog,
-			String defaultSchema,
-			RootClass rootClass) throws MappingException;
-
-	IdentifierGenerator createIdentifierGenerator(
-			IdentifierGeneratorFactory identifierGeneratorFactory,
-			Dialect dialect,
-			RootClass rootClass) throws MappingException;
-
 	boolean isIdentityColumn(IdentifierGeneratorFactory identifierGeneratorFactory, Dialect dialect);
 	
 	ForeignKey createForeignKeyOfEntity(String entityName);
@@ -47,4 +30,34 @@ public interface KeyValue extends Value {
 	String getNullValue();
 	
 	boolean isUpdateable();
+
+	InMemoryGenerator createGenerator(
+			IdentifierGeneratorFactory identifierGeneratorFactory,
+			Dialect dialect,
+			RootClass rootClass);
+
+	/**
+	 * @deprecated Use {@link #createGenerator(IdentifierGeneratorFactory, Dialect, RootClass)} instead.
+	 */
+	@Deprecated
+	default IdentifierGenerator createIdentifierGenerator(
+			IdentifierGeneratorFactory identifierGeneratorFactory,
+			Dialect dialect,
+			String defaultCatalog,
+			String defaultSchema,
+			RootClass rootClass) {
+		return (IdentifierGenerator) createGenerator( identifierGeneratorFactory, dialect, rootClass );
+	}
+
+	/**
+	 * @deprecated Use {@link #createGenerator(IdentifierGeneratorFactory, Dialect, RootClass)} instead.
+	 */
+	@Deprecated
+	default IdentifierGenerator createIdentifierGenerator(
+			IdentifierGeneratorFactory identifierGeneratorFactory,
+			Dialect dialect,
+			RootClass rootClass) {
+		return (IdentifierGenerator) createGenerator( identifierGeneratorFactory, dialect, rootClass );
+	}
+
 }

hibernate-core/src/main/java/org/hibernate/mapping/SimpleValue.java

@@ -34,17 +34,10 @@ import org.hibernate.boot.registry.classloading.spi.ClassLoadingException;
 import org.hibernate.boot.spi.InFlightMetadataCollector;
 import org.hibernate.boot.spi.MetadataBuildingContext;
 import org.hibernate.boot.spi.MetadataImplementor;
-import org.hibernate.cfg.AvailableSettings;
 import org.hibernate.dialect.Dialect;
-import org.hibernate.engine.config.spi.ConfigurationService;
-import org.hibernate.engine.config.spi.StandardConverters;
 import org.hibernate.engine.spi.Mapping;
 import org.hibernate.id.IdentifierGenerator;
 import org.hibernate.id.IdentityGenerator;
-import org.hibernate.id.OptimizableGenerator;
-import org.hibernate.id.PersistentIdentifierGenerator;
-import org.hibernate.id.enhanced.LegacyNamingStrategy;
-import org.hibernate.id.enhanced.SingleNamingStrategy;
 import org.hibernate.id.factory.IdentifierGeneratorFactory;
 import org.hibernate.id.factory.spi.CustomIdGeneratorCreationContext;
 import org.hibernate.internal.CoreLogging;
@@ -54,6 +47,7 @@ import org.hibernate.internal.util.collections.ArrayHelper;
 import org.hibernate.metamodel.model.convert.spi.JpaAttributeConverter;
 import org.hibernate.resource.beans.spi.ManagedBeanRegistry;
 import org.hibernate.service.ServiceRegistry;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.Type;
 import org.hibernate.type.descriptor.JdbcTypeNameMapper;
 import org.hibernate.type.descriptor.java.JavaType;
@@ -67,6 +61,8 @@ import org.hibernate.usertype.DynamicParameterizedType;
 
 import jakarta.persistence.AttributeConverter;
 
+import static org.hibernate.id.factory.internal.IdentifierGeneratorUtil.createLegacyIdentifierGenerator;
+
 /**
  * A mapping model object that represents any value that maps to columns.
  *
@@ -104,6 +100,10 @@ public abstract class SimpleValue implements KeyValue {
 	private ConverterDescriptor attributeConverterDescriptor;
 	private Type type;
 
+	private IdentifierGeneratorCreator customIdGeneratorCreator;
+	private GeneratorCreator customGeneratorCreator;
+	private InMemoryGenerator generator;
+
 	public SimpleValue(MetadataBuildingContext buildingContext) {
 		this.buildingContext = buildingContext;
 		this.metadata = buildingContext.getMetadataCollector();
@@ -136,7 +136,7 @@ public abstract class SimpleValue implements KeyValue {
 		this.attributeConverterDescriptor = original.attributeConverterDescriptor;
 		this.type = original.type;
 		this.customIdGeneratorCreator = original.customIdGeneratorCreator;
-		this.identifierGenerator = original.identifierGenerator;
+		this.generator = original.generator;
 	}
 
 	public MetadataBuildingContext getBuildingContext() {
@@ -359,9 +359,6 @@ public abstract class SimpleValue implements KeyValue {
 		getTable().createUniqueKey( getConstraintColumns() );
 	}
 
-	private IdentifierGeneratorCreator customIdGeneratorCreator;
-	private IdentifierGenerator identifierGenerator;
-
 	/**
 	 * Returns the cached {@link IdentifierGenerator}, or null if
 	 * {@link #createIdentifierGenerator(IdentifierGeneratorFactory, Dialect, String, String, RootClass)}
@@ -371,7 +368,7 @@ public abstract class SimpleValue implements KeyValue {
 	 */
 	@Deprecated(since = "6.0")
 	public IdentifierGenerator getIdentifierGenerator() {
-		return identifierGenerator;
+		return (IdentifierGenerator) generator;
 	}
 
 	public void setCustomIdGeneratorCreator(IdentifierGeneratorCreator customIdGeneratorCreator) {
@@ -382,171 +379,41 @@ public abstract class SimpleValue implements KeyValue {
 		return customIdGeneratorCreator;
 	}
 
-	@Override
+	public GeneratorCreator getCustomGeneratorCreator() {
-	public IdentifierGenerator createIdentifierGenerator(
+		return customGeneratorCreator;
-			IdentifierGeneratorFactory identifierGeneratorFactory,
+	}
-			Dialect dialect,
+
-			RootClass rootClass) throws MappingException {
+	public void setCustomGeneratorCreator(GeneratorCreator customGeneratorCreator) {
-		return createIdentifierGenerator( identifierGeneratorFactory, dialect, null, null, rootClass );
+		this.customGeneratorCreator = customGeneratorCreator;
 	}
 
 	@Override
-	public IdentifierGenerator createIdentifierGenerator(
+	public InMemoryGenerator createGenerator(
 			IdentifierGeneratorFactory identifierGeneratorFactory,
-			Dialect dialect, 
+			Dialect dialect,
-			String defaultCatalog, 
-			String defaultSchema, 
 			RootClass rootClass) throws MappingException {
-		if ( identifierGenerator != null ) {
+		if ( generator != null ) {
-			return identifierGenerator;
+			return generator;
 		}
 
 		if ( customIdGeneratorCreator != null ) {
-			final CustomIdGeneratorCreationContext creationContext = new CustomIdGeneratorCreationContext() {
+			generator = customIdGeneratorCreator.createGenerator(
-				@Override
+					new IdGeneratorCreationContext( identifierGeneratorFactory, null, null, rootClass )
-				public IdentifierGeneratorFactory getIdentifierGeneratorFactory() {
-					return identifierGeneratorFactory;
-				}
-
-				@Override
-				public Database getDatabase() {
-					return buildingContext.getMetadataCollector().getDatabase();
-				}
-
-				@Override
-				public ServiceRegistry getServiceRegistry() {
-					return buildingContext.getBootstrapContext().getServiceRegistry();
-				}
-
-				@Override
-				public String getDefaultCatalog() {
-					return defaultCatalog;
-				}
-
-				@Override
-				public String getDefaultSchema() {
-					return defaultSchema;
-				}
-
-				@Override
-				public RootClass getRootClass() {
-					return rootClass;
-				}
-
-				@Override
-				public PersistentClass getPersistentClass() {
-					return rootClass;
-				}
-
-				@Override
-				public Property getProperty() {
-					return rootClass.getIdentifierProperty();
-				}
-			};
-
-			identifierGenerator = customIdGeneratorCreator.createGenerator( creationContext );
-			return identifierGenerator;
-		}
-
-		final Properties params = new Properties();
-
-		// This is for backwards compatibility only;
-		// when this method is called by Hibernate ORM, defaultSchema and defaultCatalog are always
-		// null, and defaults are handled later.
-		if ( defaultSchema != null ) {
-			params.setProperty( PersistentIdentifierGenerator.SCHEMA, defaultSchema);
-		}
-
-		if ( defaultCatalog != null ) {
-			params.setProperty( PersistentIdentifierGenerator.CATALOG, defaultCatalog );
-		}
-
-		// default initial value and allocation size per-JPA defaults
-		params.setProperty( OptimizableGenerator.INITIAL_PARAM, String.valueOf( OptimizableGenerator.DEFAULT_INITIAL_VALUE ) );
-		final ConfigurationService cs = metadata.getMetadataBuildingOptions().getServiceRegistry()
-				.getService( ConfigurationService.class );
-
-		final String idNamingStrategy = cs.getSetting(
-				AvailableSettings.ID_DB_STRUCTURE_NAMING_STRATEGY,
-				StandardConverters.STRING,
-				null
-		);
-
-		if ( LegacyNamingStrategy.STRATEGY_NAME.equals( idNamingStrategy )
-				|| LegacyNamingStrategy.class.getName().equals( idNamingStrategy )
-				|| SingleNamingStrategy.STRATEGY_NAME.equals( idNamingStrategy )
-				|| SingleNamingStrategy.class.getName().equals( idNamingStrategy ) ) {
-			params.setProperty( OptimizableGenerator.INCREMENT_PARAM, "1" );
-		}
-		else {
-			params.setProperty(
-					OptimizableGenerator.INCREMENT_PARAM,
-					String.valueOf( OptimizableGenerator.DEFAULT_INCREMENT_SIZE )
 			);
+			return generator;
 		}
-		//init the table here instead of earlier, so that we can get a quoted table name
+		else if ( customGeneratorCreator != null ) {
-		//TODO: would it be better to simply pass the qualified table name, instead of
+			// we may as well allow this, so you don't have to annotate generator
-		//      splitting it up into schema/catalog/table names
+			// annotations twice, with @IdGeneratorType and @ValueGenerationType
-		final String tableName = getTable().getQuotedName( dialect );
+			//TODO: this typecast is ugly ... throw a better exception at least
-		params.setProperty( PersistentIdentifierGenerator.TABLE, tableName );
+			generator = (InMemoryGenerator) customGeneratorCreator.createGenerator(
-
+					new IdGeneratorCreationContext( identifierGeneratorFactory, null, null, rootClass )
-		//pass the column name (a generated id almost always has a single column)
-		final String columnName = ( (Column) getSelectables().get(0) ).getQuotedName( dialect );
-		params.setProperty( PersistentIdentifierGenerator.PK, columnName );
-
-		//pass the entity-name, if not a collection-id
-		if ( rootClass != null ) {
-			params.setProperty( IdentifierGenerator.ENTITY_NAME, rootClass.getEntityName() );
-			params.setProperty( IdentifierGenerator.JPA_ENTITY_NAME, rootClass.getJpaEntityName() );
-			// The table name is not really a good default for subselect entities, so use the JPA entity name which is short
-			if ( getTable().isSubselect() ) {
-				params.setProperty( OptimizableGenerator.IMPLICIT_NAME_BASE, rootClass.getJpaEntityName() );
-			}
-			else {
-				params.setProperty( OptimizableGenerator.IMPLICIT_NAME_BASE, getTable().getName() );
-			}
-
-			final StringBuilder tables = new StringBuilder();
-			final Iterator<Table> itr = rootClass.getIdentityTables().iterator();
-			while ( itr.hasNext() ) {
-				final Table table = itr.next();
-				tables.append( table.getQuotedName( dialect ) );
-				if ( itr.hasNext() ) {
-					tables.append( ", " );
-				}
-			}
-			params.setProperty( PersistentIdentifierGenerator.TABLES, tables.toString() );
-		}
-		else {
-			params.setProperty( PersistentIdentifierGenerator.TABLES, tableName );
-			params.setProperty( OptimizableGenerator.IMPLICIT_NAME_BASE, tableName );
-		}
-
-		if ( identifierGeneratorParameters != null ) {
-			params.putAll(identifierGeneratorParameters);
-		}
-
-		// TODO : we should pass along all settings once "config lifecycle" is hashed out...
-
-		params.put(
-				IdentifierGenerator.CONTRIBUTOR_NAME,
-				buildingContext.getCurrentContributorName()
-		);
-
-		if ( cs.getSettings().get( AvailableSettings.PREFERRED_POOLED_OPTIMIZER ) != null ) {
-			params.put(
-					AvailableSettings.PREFERRED_POOLED_OPTIMIZER,
-					cs.getSettings().get( AvailableSettings.PREFERRED_POOLED_OPTIMIZER )
 			);
+			return generator;
 		}
 
-		identifierGenerator = identifierGeneratorFactory.createIdentifierGenerator(
+		generator = createLegacyIdentifierGenerator(this, identifierGeneratorFactory, dialect, null, null, rootClass );
-				identifierGeneratorStrategy,
+		return generator;
-				getType(),
-				params
-		);
-
-		return identifierGenerator;
 	}
 
 	public boolean isUpdateable() {
@@ -1185,4 +1052,58 @@ public abstract class SimpleValue implements KeyValue {
 			return columnLengths;
 		}
 	}
+
+	private class IdGeneratorCreationContext implements CustomIdGeneratorCreationContext {
+		private final IdentifierGeneratorFactory identifierGeneratorFactory;
+		private final String defaultCatalog;
+		private final String defaultSchema;
+		private final RootClass rootClass;
+
+		public IdGeneratorCreationContext(IdentifierGeneratorFactory identifierGeneratorFactory, String defaultCatalog, String defaultSchema, RootClass rootClass) {
+			this.identifierGeneratorFactory = identifierGeneratorFactory;
+			this.defaultCatalog = defaultCatalog;
+			this.defaultSchema = defaultSchema;
+			this.rootClass = rootClass;
+		}
+
+		@Override
+		public IdentifierGeneratorFactory getIdentifierGeneratorFactory() {
+			return identifierGeneratorFactory;
+		}
+
+		@Override
+		public Database getDatabase() {
+			return buildingContext.getMetadataCollector().getDatabase();
+		}
+
+		@Override
+		public ServiceRegistry getServiceRegistry() {
+			return buildingContext.getBootstrapContext().getServiceRegistry();
+		}
+
+		@Override
+		public String getDefaultCatalog() {
+			return defaultCatalog;
+		}
+
+		@Override
+		public String getDefaultSchema() {
+			return defaultSchema;
+		}
+
+		@Override
+		public RootClass getRootClass() {
+			return rootClass;
+		}
+
+		@Override
+		public PersistentClass getPersistentClass() {
+			return rootClass;
+		}
+
+		@Override
+		public Property getProperty() {
+			return rootClass.getIdentifierProperty();
+		}
+	}
 }

hibernate-core/src/main/java/org/hibernate/persister/collection/AbstractCollectionPersister.java

@@ -128,6 +128,7 @@ import org.hibernate.sql.model.jdbc.JdbcDeleteMutation;
 import org.hibernate.sql.model.jdbc.JdbcMutationOperation;
 import org.hibernate.sql.results.graph.DomainResult;
 import org.hibernate.sql.results.internal.SqlSelectionImpl;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.CollectionType;
 import org.hibernate.type.CompositeType;
 import org.hibernate.type.EntityType;
@@ -225,7 +226,7 @@ public abstract class AbstractCollectionPersister
 	protected final SqlExceptionHelper sqlExceptionHelper;
 	private final SessionFactoryImplementor factory;
 	private final EntityPersister ownerPersister;
-	private final IdentifierGenerator identifierGenerator;
+	private final InMemoryGenerator identifierGenerator;
 	private final PropertyMapping elementPropertyMapping;
 	private final EntityPersister elementPersister;
 	private final CollectionDataAccess cacheAccessStrategy;
@@ -509,12 +510,14 @@ public abstract class AbstractCollectionPersister
 			Column col = idColl.getIdentifier().getColumns().get(0);
 			identifierColumnName = col.getQuotedName( dialect );
 			identifierColumnAlias = col.getAlias( dialect );
-			identifierGenerator = idColl.getIdentifier().createIdentifierGenerator(
+			identifierGenerator = idColl.getIdentifier().createGenerator(
 					creationContext.getBootstrapContext().getIdentifierGeneratorFactory(),
 					factory.getJdbcServices().getDialect(),
 					null
 			);
-			identifierGenerator.initialize( creationContext.getSessionFactory().getSqlStringGenerationContext() );
+			if ( identifierGenerator instanceof IdentifierGenerator ) {
+				( (IdentifierGenerator) identifierGenerator ).initialize( creationContext.getSessionFactory().getSqlStringGenerationContext() );
+			}
 		}
 		else {
 			identifierType = null;
@@ -1139,8 +1142,13 @@ public abstract class AbstractCollectionPersister
 		return ownerPersister;
 	}
 
-	@Override
+	@Override @Deprecated
 	public IdentifierGenerator getIdentifierGenerator() {
+		return (IdentifierGenerator) identifierGenerator;
+	}
+
+	@Override
+	public InMemoryGenerator getGenerator() {
 		return identifierGenerator;
 	}
 

hibernate-core/src/main/java/org/hibernate/persister/collection/CollectionPersister.java

@@ -33,6 +33,7 @@ import org.hibernate.persister.entity.EntityPersister;
 import org.hibernate.sql.ast.spi.SqlAstCreationState;
 import org.hibernate.sql.ast.tree.from.TableGroup;
 import org.hibernate.sql.ast.tree.predicate.Predicate;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.CollectionType;
 import org.hibernate.type.Type;
 
@@ -231,9 +232,19 @@ public interface CollectionPersister extends Restrictable {
 
 	/**
 	 * Get the surrogate key generation strategy (optional operation)
+	 *
+	 * @deprecated use {@link #getGenerator()}
 	 */
+	@Deprecated
 	IdentifierGenerator getIdentifierGenerator();
 
+	/**
+	 * Get the surrogate key generation strategy (optional operation)
+	 */
+	default InMemoryGenerator getGenerator() {
+		return getIdentifierGenerator();
+	}
+
 	/**
 	 * Get the type of the surrogate key
 	 */

hibernate-core/src/main/java/org/hibernate/persister/entity/AbstractEntityPersister.java

@@ -259,6 +259,7 @@ import org.hibernate.stat.spi.StatisticsImplementor;
 import org.hibernate.tuple.Generator;
 import org.hibernate.tuple.InDatabaseGenerator;
 import org.hibernate.tuple.GenerationTiming;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.tuple.NonIdentifierAttribute;
 import org.hibernate.tuple.entity.EntityBasedAssociationAttribute;
 import org.hibernate.tuple.entity.EntityMetamodel;
@@ -3936,11 +3937,16 @@ public abstract class AbstractEntityPersister
 		return entityMetamodel.isLazy() && !entityMetamodel.getBytecodeEnhancementMetadata().isEnhancedForLazyLoading();
 	}
 
-	@Override
+	@Override @Deprecated
 	public IdentifierGenerator getIdentifierGenerator() throws HibernateException {
 		return entityMetamodel.getIdentifierProperty().getIdentifierGenerator();
 	}
 
+	@Override
+	public InMemoryGenerator getGenerator() {
+		return entityMetamodel.getIdentifierProperty().getGenerator();
+	}
+
 	@Override
 	public String getRootEntityName() {
 		return entityMetamodel.getRootName();
@@ -4821,9 +4827,9 @@ public abstract class AbstractEntityPersister
 			sqmMultiTableMutationStrategy = null;
 		}
 
-		if ( !needsMultiTableInsert && getIdentifierGenerator() instanceof BulkInsertionCapableIdentifierGenerator ) {
+		if ( !needsMultiTableInsert && getGenerator() instanceof BulkInsertionCapableIdentifierGenerator ) {
-			if ( getIdentifierGenerator() instanceof OptimizableGenerator ) {
+			if ( getGenerator() instanceof OptimizableGenerator ) {
-				final Optimizer optimizer = ( (OptimizableGenerator) getIdentifierGenerator() ).getOptimizer();
+				final Optimizer optimizer = ( (OptimizableGenerator) getGenerator() ).getOptimizer();
 				needsMultiTableInsert = optimizer != null && optimizer.getIncrementSize() > 1;
 			}
 		}

hibernate-core/src/main/java/org/hibernate/persister/entity/EntityPersister.java

@@ -44,6 +44,7 @@ import org.hibernate.query.sqm.mutation.spi.SqmMultiTableMutationStrategy;
 import org.hibernate.sql.ast.spi.SqlAliasStemHelper;
 import org.hibernate.sql.ast.tree.from.RootTableGroupProducer;
 import org.hibernate.sql.ast.tree.from.TableGroup;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.tuple.entity.EntityMetamodel;
 import org.hibernate.type.BasicType;
 import org.hibernate.type.Type;
@@ -451,9 +452,16 @@ public interface EntityPersister
 	 * Determine which identifier generation strategy is used for this entity.
 	 *
 	 * @return The identifier generation strategy.
+	 *
+	 * @deprecated use {@link #getGenerator()}
 	 */
+	@Deprecated
 	IdentifierGenerator getIdentifierGenerator();
 
+	default InMemoryGenerator getGenerator() {
+		return getIdentifierGenerator();
+	}
+
 	@Override
 	default AttributeMapping getAttributeMapping(int position) {
 		return getAttributeMappings().get( position );

hibernate-core/src/main/java/org/hibernate/persister/entity/UnionSubclassEntityPersister.java

@@ -112,7 +112,7 @@ public class UnionSubclassEntityPersister extends AbstractEntityPersister {
 
 		super( persistentClass, cacheAccessStrategy, naturalIdRegionAccessStrategy, creationContext );
 
-		if ( getIdentifierGenerator() instanceof IdentityGenerator ) {
+		if ( getGenerator() instanceof IdentityGenerator ) {
 			throw new MappingException(
 					"Cannot use identity column key generation with <union-subclass> mapping for: " +
 							getEntityName()

hibernate-core/src/main/java/org/hibernate/query/sqm/internal/QuerySqmImpl.java

@@ -44,7 +44,6 @@ import org.hibernate.graph.RootGraph;
 import org.hibernate.graph.spi.AppliedGraph;
 import org.hibernate.graph.spi.RootGraphImplementor;
 import org.hibernate.id.BulkInsertionCapableIdentifierGenerator;
-import org.hibernate.id.IdentifierGenerator;
 import org.hibernate.id.OptimizableGenerator;
 import org.hibernate.id.enhanced.Optimizer;
 import org.hibernate.internal.CoreLogging;
@@ -108,6 +107,7 @@ import org.hibernate.query.sqm.tree.update.SqmAssignment;
 import org.hibernate.query.sqm.tree.update.SqmUpdateStatement;
 import org.hibernate.sql.results.internal.TupleMetadata;
 import org.hibernate.sql.results.spi.ListResultsConsumer;
+import org.hibernate.tuple.InMemoryGenerator;
 
 import static org.hibernate.jpa.HibernateHints.HINT_CACHEABLE;
 import static org.hibernate.jpa.HibernateHints.HINT_CACHE_MODE;
@@ -838,8 +838,9 @@ public class QuerySqmImpl<R>
 
 		boolean useMultiTableInsert = entityDescriptor.isMultiTable();
 		if ( !useMultiTableInsert && !isSimpleValuesInsert( sqmInsert, entityDescriptor ) ) {
-			final IdentifierGenerator identifierGenerator = entityDescriptor.getIdentifierGenerator();
+			final InMemoryGenerator identifierGenerator = entityDescriptor.getGenerator();
-			if ( identifierGenerator instanceof BulkInsertionCapableIdentifierGenerator && identifierGenerator instanceof OptimizableGenerator ) {
+			if ( identifierGenerator instanceof BulkInsertionCapableIdentifierGenerator
+					&& identifierGenerator instanceof OptimizableGenerator ) {
 				final Optimizer optimizer = ( (OptimizableGenerator) identifierGenerator ).getOptimizer();
 				if ( optimizer != null && optimizer.getIncrementSize() > 1 ) {
 					useMultiTableInsert = !hasIdentifierAssigned( sqmInsert, entityDescriptor );

hibernate-core/src/main/java/org/hibernate/query/sqm/mutation/internal/cte/CteInsertHandler.java

@@ -21,7 +21,6 @@ import org.hibernate.dialect.temptable.TemporaryTable;
 import org.hibernate.engine.jdbc.spi.JdbcServices;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.id.BulkInsertionCapableIdentifierGenerator;
-import org.hibernate.id.IdentifierGenerator;
 import org.hibernate.id.OptimizableGenerator;
 import org.hibernate.id.PostInsertIdentifierGenerator;
 import org.hibernate.id.enhanced.Optimizer;
@@ -95,6 +94,7 @@ import org.hibernate.sql.results.graph.DomainResult;
 import org.hibernate.sql.results.graph.basic.BasicResult;
 import org.hibernate.sql.results.internal.SqlSelectionImpl;
 import org.hibernate.sql.results.spi.ListResultsConsumer;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.spi.TypeConfiguration;
 
 /**
@@ -273,7 +273,7 @@ public class CteInsertHandler implements InsertHandler {
 									rowNumberColumn
 							);
 						}
-						if ( !assignsId && entityDescriptor.getIdentifierGenerator() instanceof PostInsertIdentifierGenerator ) {
+						if ( !assignsId && entityDescriptor.getGenerator() instanceof PostInsertIdentifierGenerator ) {
 							querySpec.getSelectClause().addSqlSelection(
 									new SqlSelectionImpl(
 											1,
@@ -337,7 +337,7 @@ public class CteInsertHandler implements InsertHandler {
 		processingStateStack.push( oldState );
 		sqmConverter.pruneTableGroupJoins();
 
-		if ( !assignsId && entityDescriptor.getIdentifierGenerator() instanceof PostInsertIdentifierGenerator ) {
+		if ( !assignsId && entityDescriptor.getGenerator() instanceof PostInsertIdentifierGenerator ) {
 			// Add the row number to the assignments
 			final CteColumn rowNumberColumn = cteTable.getCteColumns()
 					.get( cteTable.getCteColumns().size() - 1 );
@@ -389,7 +389,7 @@ public class CteInsertHandler implements InsertHandler {
 			);
 			final CteColumn idColumn = fullEntityCteTable.getCteColumns().get( 0 );
 			final BasicValuedMapping idType = (BasicValuedMapping) idColumn.getJdbcMapping();
-			final Optimizer optimizer = ( (OptimizableGenerator) entityDescriptor.getIdentifierGenerator() ).getOptimizer();
+			final Optimizer optimizer = ( (OptimizableGenerator) entityDescriptor.getGenerator() ).getOptimizer();
 			final BasicValuedMapping integerType = (BasicValuedMapping) rowNumberColumn.getJdbcMapping();
 			final Expression rowNumberMinusOneModuloIncrement = new BinaryArithmeticExpression(
 					new BinaryArithmeticExpression(
@@ -428,7 +428,7 @@ public class CteInsertHandler implements InsertHandler {
 								rowNumberColumnReference
 						)
 				);
-				final String fragment = ( (BulkInsertionCapableIdentifierGenerator) entityDescriptor.getIdentifierGenerator() )
+				final String fragment = ( (BulkInsertionCapableIdentifierGenerator) entityDescriptor.getGenerator() )
 						.determineBulkInsertionIdentifierGenerationSelectFragment(
 								sessionFactory.getSqlStringGenerationContext()
 						);
@@ -581,7 +581,7 @@ public class CteInsertHandler implements InsertHandler {
 				statement.addCteStatement( entityCte );
 			}
 		}
-		else if ( !assignsId && entityDescriptor.getIdentifierGenerator() instanceof PostInsertIdentifierGenerator ) {
+		else if ( !assignsId && entityDescriptor.getGenerator() instanceof PostInsertIdentifierGenerator ) {
 			final String baseTableName = "base_" + entityCteTable.getTableExpression();
 			final CteStatement baseEntityCte = new CteStatement(
 					entityCteTable.withName( baseTableName ),
@@ -775,7 +775,7 @@ public class CteInsertHandler implements InsertHandler {
 				true
 		);
 
-		final IdentifierGenerator identifierGenerator = entityDescriptor.getEntityPersister().getIdentifierGenerator();
+		final InMemoryGenerator identifierGenerator = entityDescriptor.getEntityPersister().getGenerator();
 		final List<Map.Entry<List<CteColumn>, Assignment>> tableAssignments = assignmentsByTable.get( rootTableReference );
 		if ( ( tableAssignments == null || tableAssignments.isEmpty() ) && !( identifierGenerator instanceof PostInsertIdentifierGenerator ) ) {
 			throw new IllegalStateException( "There must be at least a single root table assignment" );

hibernate-core/src/main/java/org/hibernate/query/sqm/mutation/internal/temptable/InsertExecutionDelegate.java

@@ -23,7 +23,6 @@ import org.hibernate.engine.jdbc.spi.JdbcServices;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.id.BulkInsertionCapableIdentifierGenerator;
-import org.hibernate.id.IdentifierGenerator;
 import org.hibernate.id.OptimizableGenerator;
 import org.hibernate.id.PostInsertIdentifierGenerator;
 import org.hibernate.id.PostInsertIdentityPersister;
@@ -74,6 +73,7 @@ import org.hibernate.sql.exec.spi.JdbcParameterBindings;
 import org.hibernate.sql.results.graph.basic.BasicFetch;
 import org.hibernate.sql.results.internal.SqlSelectionImpl;
 import org.hibernate.sql.results.spi.ListResultsConsumer;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.descriptor.ValueBinder;
 
 /**
@@ -301,7 +301,7 @@ public class InsertExecutionDelegate implements TableBasedInsertHandler.Executio
 				true
 		);
 
-		final IdentifierGenerator identifierGenerator = entityDescriptor.getEntityPersister().getIdentifierGenerator();
+		final InMemoryGenerator identifierGenerator = entityDescriptor.getEntityPersister().getGenerator();
 		final List<Assignment> assignments = assignmentsByTable.get( updatingTableReference );
 		if ( ( assignments == null || assignments.isEmpty() )
 				&& !( identifierGenerator instanceof PostInsertIdentifierGenerator )
@@ -507,10 +507,7 @@ public class InsertExecutionDelegate implements TableBasedInsertHandler.Executio
 							rootIdentity,
 							new JdbcParameterBindingImpl(
 									identifierMapping.getJdbcMapping(),
-									identifierGenerator.generate(
+									identifierGenerator.generate( executionContext.getSession(), null, null )
-											executionContext.getSession(),
-											null
-									)
 							)
 					);
 					jdbcServices.getJdbcMutationExecutor().execute(
@@ -654,7 +651,7 @@ public class InsertExecutionDelegate implements TableBasedInsertHandler.Executio
 		}
 	}
 
-	private boolean needsIdentifierGeneration(IdentifierGenerator identifierGenerator) {
+	private boolean needsIdentifierGeneration(InMemoryGenerator identifierGenerator) {
 		if ( !( identifierGenerator instanceof OptimizableGenerator ) ) {
 			return false;
 		}
@@ -721,7 +718,7 @@ public class InsertExecutionDelegate implements TableBasedInsertHandler.Executio
 		}
 		final String targetKeyColumnName = keyColumns[0];
 		final AbstractEntityPersister entityPersister = (AbstractEntityPersister) entityDescriptor.getEntityPersister();
-		final IdentifierGenerator identifierGenerator = entityPersister.getIdentifierGenerator();
+		final InMemoryGenerator identifierGenerator = entityPersister.getGenerator();
 		final boolean needsKeyInsert;
 		if ( identifierGenerator instanceof PostInsertIdentifierGenerator ) {
 			needsKeyInsert = true;

hibernate-core/src/main/java/org/hibernate/query/sqm/mutation/internal/temptable/TableBasedInsertHandler.java

@@ -20,7 +20,6 @@ import org.hibernate.dialect.temptable.TemporaryTableColumn;
 import org.hibernate.dialect.temptable.TemporaryTableSessionUidColumn;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
-import org.hibernate.id.IdentifierGenerator;
 import org.hibernate.id.OptimizableGenerator;
 import org.hibernate.id.enhanced.Optimizer;
 import org.hibernate.internal.util.collections.CollectionHelper;
@@ -53,6 +52,7 @@ import org.hibernate.sql.ast.tree.update.Assignment;
 import org.hibernate.sql.exec.internal.JdbcParameterImpl;
 import org.hibernate.sql.exec.spi.ExecutionContext;
 import org.hibernate.sql.results.internal.SqlSelectionImpl;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.BasicType;
 
 import org.jboss.logging.Logger;
@@ -201,8 +201,8 @@ public class TableBasedInsertHandler implements InsertHandler {
 									new Assignment( columnReference, columnReference )
 							);
 						}
-						else if ( entityDescriptor.getIdentifierGenerator() instanceof OptimizableGenerator ) {
+						else if ( entityDescriptor.getGenerator() instanceof OptimizableGenerator ) {
-							final Optimizer optimizer = ( (OptimizableGenerator) entityDescriptor.getIdentifierGenerator() ).getOptimizer();
+							final Optimizer optimizer = ( (OptimizableGenerator) entityDescriptor.getGenerator() ).getOptimizer();
 							if ( optimizer != null && optimizer.getIncrementSize() > 1 ) {
 								if ( !sessionFactory.getJdbcServices().getDialect().supportsWindowFunctions() ) {
 									return;
@@ -254,7 +254,7 @@ public class TableBasedInsertHandler implements InsertHandler {
 		}
 		else {
 			// Add the row number column if there is one
-			final IdentifierGenerator generator = entityDescriptor.getIdentifierGenerator();
+			final InMemoryGenerator generator = entityDescriptor.getGenerator();
 			final BasicType<?> rowNumberType;
 			if ( generator instanceof OptimizableGenerator ) {
 				final Optimizer optimizer = ( (OptimizableGenerator) generator ).getOptimizer();

hibernate-core/src/main/java/org/hibernate/query/sqm/sql/BaseSqmToSqlAstConverter.java

@@ -44,7 +44,6 @@ import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.graph.spi.AppliedGraph;
 import org.hibernate.id.BulkInsertionCapableIdentifierGenerator;
 import org.hibernate.id.CompositeNestedGeneratedValueGenerator;
-import org.hibernate.id.IdentifierGenerator;
 import org.hibernate.id.OptimizableGenerator;
 import org.hibernate.id.PostInsertIdentifierGenerator;
 import org.hibernate.id.enhanced.Optimizer;
@@ -384,6 +383,7 @@ import org.hibernate.sql.results.graph.FetchableContainer;
 import org.hibernate.sql.results.graph.instantiation.internal.DynamicInstantiation;
 import org.hibernate.sql.results.internal.SqlSelectionImpl;
 import org.hibernate.sql.results.internal.StandardEntityGraphTraversalStateImpl;
+import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.BasicType;
 import org.hibernate.type.CustomType;
 import org.hibernate.type.EnumType;
@@ -1225,18 +1225,13 @@ public abstract class BaseSqmToSqlAstConverter<T extends Statement> extends Base
 			EntityPersister entityDescriptor, TableGroup rootTableGroup) {
 		final List<SqmPath<?>> targetPaths = sqmStatement.getInsertionTargetPaths();
 		final EntityDiscriminatorMapping discriminatorMapping = entityDescriptor.getDiscriminatorMapping();
-		IdentifierGenerator identifierGenerator = entityDescriptor.getIdentifierGenerator();
 		Expression versionExpression = null;
 		Expression discriminatorExpression = null;
 		BasicEntityIdentifierMapping identifierMapping = null;
 		// We use the id property name to null the identifier generator variable if the target paths contain the id
 		final String identifierPropertyName;
-		if ( identifierGenerator != null ) {
+		InMemoryGenerator identifierGenerator = entityDescriptor.getGenerator();
-			identifierPropertyName = entityDescriptor.getIdentifierPropertyName();
+		identifierPropertyName = identifierGenerator != null ? entityDescriptor.getIdentifierPropertyName() : null;
-		}
-		else {
-			identifierPropertyName = null;
-		}
 		final String versionAttributeName;
 		boolean needsVersionInsert;
 		if ( entityDescriptor.isVersioned() ) {
@@ -1351,7 +1346,7 @@ public abstract class BaseSqmToSqlAstConverter<T extends Statement> extends Base
 	public static class AdditionalInsertValues {
 		private final Expression versionExpression;
 		private final Expression discriminatorExpression;
-		private final IdentifierGenerator identifierGenerator;
+		private final InMemoryGenerator identifierGenerator;
 		private final BasicEntityIdentifierMapping identifierMapping;
 		private Expression identifierGeneratorParameter;
 		private SqlSelection versionSelection;
@@ -1361,7 +1356,7 @@ public abstract class BaseSqmToSqlAstConverter<T extends Statement> extends Base
 		public AdditionalInsertValues(
 				Expression versionExpression,
 				Expression discriminatorExpression,
-				IdentifierGenerator identifierGenerator,
+				InMemoryGenerator identifierGenerator,
 				BasicEntityIdentifierMapping identifierMapping) {
 			this.versionExpression = versionExpression;
 			this.discriminatorExpression = discriminatorExpression;
@@ -1453,9 +1448,9 @@ public abstract class BaseSqmToSqlAstConverter<T extends Statement> extends Base
 
 	private static class IdGeneratorParameter extends AbstractJdbcParameter {
 
-		private final IdentifierGenerator generator;
+		private final InMemoryGenerator generator;
 
-		public IdGeneratorParameter(BasicEntityIdentifierMapping identifierMapping, IdentifierGenerator generator) {
+		public IdGeneratorParameter(BasicEntityIdentifierMapping identifierMapping, InMemoryGenerator generator) {
 			super( identifierMapping.getJdbcMapping() );
 			this.generator = generator;
 		}
@@ -1468,7 +1463,7 @@ public abstract class BaseSqmToSqlAstConverter<T extends Statement> extends Base
 				ExecutionContext executionContext) throws SQLException {
 			getJdbcMapping().getJdbcValueBinder().bind(
 					statement,
-					generator.generate( executionContext.getSession(), null ),
+					generator.generate( executionContext.getSession(), null, null ),
 					startPosition,
 					executionContext.getSession()
 			);

hibernate-core/src/main/java/org/hibernate/tuple/AnnotationBasedGenerator.java

@@ -11,18 +11,22 @@ import java.lang.reflect.Member;
 
 
 /**
- * A {@link Generator} based on a custom Java generator annotation type.
+ * A {@link Generator} which receives parameters from a custom
- * Every instance must implement either {@link InMemoryGenerator} or
+ * {@linkplain org.hibernate.annotations.ValueGenerationType generator annotation} or
- * {@link InDatabaseGenerator}. Implementing this interface is just a
+ * {@linkplain org.hibernate.annotations.IdGeneratorType id generator annotation}.
- * slightly more typesafe alternative to providing a constructor with
+ * <p>
- * the same signature as the method
+ * Implementing this interface is the same as providing a constructor with the same
- * {@link #initialize(Annotation, Member, GeneratorCreationContext)}.
+ * signature as the {@link #initialize} method. But implementing this interface is
+ * slightly more typesafe.
+ * <p>
+ * Every instance of this class must implement either {@link InMemoryGenerator} or
+ * {@link InDatabaseGenerator}.
  *
  * @param <A> The generator annotation type supported by an implementation
  *
  * @see org.hibernate.annotations.ValueGenerationType
+ * @see org.hibernate.annotations.IdGeneratorType
  *
- * @author Gunnar Morling
  * @author Gavin King
  *
  * @since 6.2
@@ -31,8 +35,9 @@ public interface AnnotationBasedGenerator<A extends Annotation> extends Generato
 	/**
 	 * Initializes this generation strategy for the given annotation instance.
 	 *
-	 * @param annotation an instance of the strategy's annotation type. Typically, implementations will retrieve the
+	 * @param annotation an instance of the strategy's annotation type. Typically,
-	 *                   annotation's attribute values and store them in fields.
+	 *                   implementations will retrieve the annotation's attribute
+	 *                   values and store them in fields.
 	 * @param member the Java member annotated with the generator annotation.
 	 * @param context a {@link GeneratorCreationContext}
 	 * @throws org.hibernate.HibernateException in case an error occurred during initialization, e.g. if

hibernate-core/src/main/java/org/hibernate/tuple/AnnotationValueGeneration.java

@@ -15,23 +15,29 @@ import java.lang.reflect.Method;
 
 
 /**
- * A {@link ValueGeneration} based on a custom Java generator annotation type.
+ * An implementation of {@link ValueGeneration} which receives parameters from a custom
+ * {@linkplain org.hibernate.annotations.ValueGenerationType generator annotation}.
+ * <p>
+ * This is an older API that predates {@link Generator} and {@link AnnotationBasedGenerator}.
+ * It's often cleaner to implement {@code AnnotationBasedGenerator} directly.
  *
  * @param <A> The generator annotation type supported by an implementation
  *
  * @see org.hibernate.annotations.ValueGenerationType
  *
  * @author Gunnar Morling
+ *
+ * @see ValueGeneration
  */
 public interface AnnotationValueGeneration<A extends Annotation>
 		extends ValueGeneration, AnnotationBasedGenerator<A> {
 	/**
 	 * Initializes this generation strategy for the given annotation instance.
 	 *
-	 * @param annotation   an instance of the strategy's annotation type. Typically, implementations will retrieve the
+	 * @param annotation   an instance of the strategy's annotation type. Typically,
-	 *                     annotation's attribute values and store them in fields.
+	 *                     implementations will retrieve the annotation's attribute
-	 * @param propertyType the type of the property annotated with the generator annotation. Implementations may use
+	 *                     values and store them in fields.
-	 *                     the type to determine the right {@link ValueGenerator} to be applied.
+	 * @param propertyType the type of the property annotated with the generator annotation.
 	 * @throws org.hibernate.HibernateException in case an error occurred during initialization, e.g. if
 	 *                                          an implementation can't create a value for the given property type.
 	 */

hibernate-core/src/main/java/org/hibernate/tuple/Generator.java

@@ -6,15 +6,18 @@
  */
 package org.hibernate.tuple;
 
+import org.hibernate.engine.spi.SharedSessionContractImplementor;
+
 import java.io.Serializable;
 
 /**
  * Describes the generation of values of a certain field or property of an entity. A generated
  * value might be generated in Java, or by the database. Every instance must implement either
- * {@link InMemoryGenerator} or {@link InDatabaseGenerator}
+ * {@link InMemoryGenerator} or {@link InDatabaseGenerator} depending on whether values are
- * depending on whether values are generated in Java code, or by the database.
+ * generated in Java code, or by the database.
  * <ul>
- * <li>Java value generation is the responsibility of an associated {@link ValueGenerator}.
+ * <li>Value generation via arbitrary code written in Java is the responsibility of the method
+ *     {@link InMemoryGenerator#generate(SharedSessionContractImplementor, Object, Object)}.
  *	   In this case, the generated value is written to the database just like any other field
  *	   or property value.
  * <li>A value generated by the database might be generated implicitly, by a trigger, or using
@@ -23,11 +26,21 @@ import java.io.Serializable;
  *	   statement. In this case, the generated value is retrieved from the database using a SQL
  *	   {@code select}.
  * </ul>
- * If an implementation of {@code ValueGenerationStrategy} may be associated with an entity
+ * A generator may receive parameters from {@linkplain org.hibernate.annotations.ValueGenerationType
- * via a {@linkplain org.hibernate.annotations.ValueGenerationType custom annotation}, it
+ * an annotation}. The generator may either:
- * should implement {@link AnnotationBasedGenerator}.
+ * <ul>
+ * <li>implement {@link AnnotationBasedGenerator}, and receive the annotation as an argument to
+ *     {@link AnnotationBasedGenerator#initialize},
+ * <li>declare a constructor with the same signature as {@link AnnotationBasedGenerator#initialize},
+ * <li>declare a constructor which accepts just the annotation instance, or
+ * <li>declare a only default constructor, in which case it will not receive parameters.
+ * </ul>
+ * On the other hand, there is some special machinery for configuring the much older interface
+ * {@link org.hibernate.id.IdentifierGenerator}. But this machinery is only available for
+ * identifier generation.
  *
  * @see org.hibernate.annotations.ValueGenerationType
+ * @see org.hibernate.annotations.IdGeneratorType
  * @see org.hibernate.annotations.Generated
  * @see org.hibernate.annotations.GeneratorType
  *

hibernate-core/src/main/java/org/hibernate/tuple/IdentifierAttribute.java

@@ -16,8 +16,11 @@ public interface IdentifierAttribute extends Attribute {
 
 	boolean isEmbedded();
 
+	@Deprecated
 	IdentifierGenerator getIdentifierGenerator();
 
+	InMemoryGenerator getGenerator();
+
 	boolean isIdentifierAssignedByInsert();
 
 	boolean hasIdentifierMapper();

hibernate-core/src/main/java/org/hibernate/tuple/IdentifierProperty.java

@@ -20,7 +20,7 @@ public class IdentifierProperty extends AbstractAttribute implements IdentifierA
 
 	private final boolean virtual;
 	private final boolean embedded;
-	private final IdentifierGenerator identifierGenerator;
+	private final InMemoryGenerator identifierGenerator;
 	private final boolean identifierAssignedByInsert;
 	private final boolean hasIdentifierMapper;
 
@@ -38,7 +38,7 @@ public class IdentifierProperty extends AbstractAttribute implements IdentifierA
 			String name,
 			Type type,
 			boolean embedded,
-			IdentifierGenerator identifierGenerator) {
+			InMemoryGenerator identifierGenerator) {
 		super( name, type );
 		this.virtual = false;
 		this.embedded = embedded;
@@ -59,7 +59,7 @@ public class IdentifierProperty extends AbstractAttribute implements IdentifierA
 			Type type,
 			boolean embedded,
 			boolean hasIdentifierMapper,
-			IdentifierGenerator identifierGenerator) {
+			InMemoryGenerator identifierGenerator) {
 		super( null, type );
 		this.virtual = true;
 		this.embedded = embedded;
@@ -80,6 +80,11 @@ public class IdentifierProperty extends AbstractAttribute implements IdentifierA
 
 	@Override
 	public IdentifierGenerator getIdentifierGenerator() {
+		return (IdentifierGenerator) identifierGenerator;
+	}
+
+	@Override
+	public InMemoryGenerator getGenerator() {
 		return identifierGenerator;
 	}
 

hibernate-core/src/main/java/org/hibernate/tuple/InDatabaseGenerator.java

@@ -14,6 +14,10 @@ import org.hibernate.dialect.Dialect;
  * by a SQL expression occurring explicitly in the SQL {@code insert} or {@code update}
  * statement. In this case, the generated value is retrieved from the database using a SQL
  * {@code select}.
+ * <p>
+ * Implementations should override {@link #referenceColumnsInSql()},
+ * {@link #writePropertyValue()}, and {@link #getReferencedColumnValues(Dialect)} as needed
+ * in order to achieve the desired behavior.
  *
  * @author Steve Ebersole
  *
@@ -22,9 +26,9 @@ import org.hibernate.dialect.Dialect;
 public interface InDatabaseGenerator extends Generator {
 
 	/**
-	 * Determines if the columns whose values are generated are included in the column list of
+	 * Determines if the columns whose values are generated are included in the column list
-	 * the SQL {@code insert} or {@code update} statement, in the case where the value is
+	 * of the SQL {@code insert} or {@code update} statement. For example, this method should
-	 * generated by the database. For example, this method should return:
+	 * return:
 	 * <ul>
 	 * <li>{@code true} if the value is generated by calling a SQL function like
 	 *     {@code current_timestamp}, or
@@ -32,10 +36,6 @@ public interface InDatabaseGenerator extends Generator {
 	 *     by {@link org.hibernate.annotations.GeneratedColumn generated always as}, or
 	 *     using a {@linkplain org.hibernate.annotations.ColumnDefault column default value}.
 	 * </ul>
-	 * If the value is generated in Java, this method is not called, and so for backward
-	 * compatibility with Hibernate 5 it is permitted to return any value. On the other hand,
-	 * when a property value is generated in Java, the column certainly must be included in
-	 * the column list, and so it's most correct for this method to return {@code true}!
 	 *
 	 * @return {@code true} if the column is included in the column list of the SQL statement.
 	 */
@@ -48,18 +48,16 @@ public interface InDatabaseGenerator extends Generator {
 	boolean writePropertyValue();
 
 	/**
-	 * A SQL expression indicating how to calculate the generated values when the property values
+	 * A SQL expression indicating how to calculate the generated values when the mapped columns
-	 * are {@linkplain #generatedByDatabase() generated in the database} and the mapped columns
 	 * are {@linkplain #referenceColumnsInSql() included in the SQL statement}. The SQL expressions
 	 * might be:
 	 * <ul>
 	 * <li>function calls like {@code current_timestamp} or {@code nextval('mysequence')}, or
 	 * <li>syntactic markers like {@code default}.
 	 * </ul>
-	 * When the property values are generated in Java, this method is not called.
 	 *
 	 * @param dialect The {@linkplain Dialect SQL dialect}, allowing generation of an expression
-	 *				in dialect-specific SQL.
+	 *				  in dialect-specific SQL.
 	 * @return The column value to be used in the generated SQL statement.
 	 */
 	String[] getReferencedColumnValues(Dialect dialect);

hibernate-core/src/main/java/org/hibernate/tuple/InMemoryGenerator.java

@@ -9,9 +9,16 @@ package org.hibernate.tuple;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 
 /**
- * Java value generation is the responsibility of an associated {@link ValueGenerator}.
+ * A generator that is called to produce a value just before a row is written to the database.
- * In this case, the generated value is written to the database just like any other field
+ * The {@link #generate} method may execute arbitrary Java code, it may even, in principle,
- * or property value.
+ * access the database via JDBC. But however it is produced, the generated value is sent to the
+ * database via a parameter of a JDBC prepared statement, just like any other field or property
+ * value.
+ * <p>
+ * Any {@link InMemoryGenerator} may be used to produce {@linkplain jakarta.persistence.Id
+ * identifiers}. The built-in identifier generators all implement the older extension point
+ * {@link org.hibernate.id.IdentifierGenerator}, which is a subtype of this interface, but that
+ * is no longer a requirement for custom id generators.
  *
  * @author Steve Ebersole
  *

hibernate-core/src/main/java/org/hibernate/tuple/PropertyFactory.java

@@ -11,7 +11,6 @@ import org.hibernate.boot.spi.MetadataImplementor;
 import org.hibernate.boot.spi.SessionFactoryOptions;
 import org.hibernate.bytecode.enhance.spi.interceptor.EnhancementHelper;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
-import org.hibernate.id.IdentifierGenerator;
 import org.hibernate.mapping.PersistentClass;
 import org.hibernate.mapping.Property;
 import org.hibernate.metamodel.spi.RuntimeModelCreationContext;
@@ -44,7 +43,7 @@ public final class PropertyFactory {
 	 */
 	public static IdentifierProperty buildIdentifierAttribute(
 			PersistentClass mappedEntity,
-			IdentifierGenerator generator) {
+			InMemoryGenerator generator) {
 		Type type = mappedEntity.getIdentifier().getType();
 		Property property = mappedEntity.getIdentifierProperty();
 

hibernate-core/src/main/java/org/hibernate/tuple/ValueGeneration.java

@@ -11,11 +11,15 @@ import org.hibernate.dialect.Dialect;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 
 /**
- * A value generator that can adapt to both Java value generation and database value
+ * A value generator that can adapt to both Java value generation and database value generation.
- * generation.
+ * <p>
+ * This is an older API that predates {@link Generator}. It's often cleaner to implement either
+ * {@link InMemoryGenerator} or {@link InDatabaseGenerator} directly.
  *
  * @author Steve Ebersole
  * @author Gavin King
+ *
+ * @see AnnotationValueGeneration
  */
 public interface ValueGeneration extends InMemoryGenerator, InDatabaseGenerator {
 	/**

hibernate-core/src/main/java/org/hibernate/tuple/entity/EntityMetamodel.java

@@ -158,7 +158,7 @@ public class EntityMetamodel implements Serializable {
 
 		identifierAttribute = PropertyFactory.buildIdentifierAttribute(
 				persistentClass,
-				sessionFactory.getIdentifierGenerator( rootName )
+				sessionFactory.getGenerator( rootName )
 		);
 
 		versioned = persistentClass.isVersioned();

hibernate-core/src/test/java/org/hibernate/orm/test/id/PooledHiLoSequenceIdentifierTest.java

@@ -37,10 +37,8 @@ import org.hibernate.engine.spi.SessionImplementor;
 
 import org.hibernate.testing.TestForIssue;
 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.AfterEach;
 import org.junit.jupiter.api.Test;
 

hibernate-core/src/test/java/org/hibernate/orm/test/idgen/enhanced/forcedtable/BasicForcedTableSequenceTest.java

@@ -36,9 +36,9 @@ public class BasicForcedTableSequenceTest {
         final EntityPersister persister = scope.getSessionFactory()
 				.getMappingMetamodel()
 				.getEntityDescriptor(Entity.class.getName());
-		assertThat( persister.getIdentifierGenerator(), instanceOf( SequenceStyleGenerator.class ) );
+		assertThat( persister.getGenerator(), instanceOf( SequenceStyleGenerator.class ) );
 
-		final SequenceStyleGenerator generator = ( SequenceStyleGenerator ) persister.getIdentifierGenerator();
+		final SequenceStyleGenerator generator = (SequenceStyleGenerator) persister.getGenerator();
 		assertThat( generator.getDatabaseStructure(), instanceOf( TableStructure.class ) );
 		assertThat( generator.getOptimizer(), instanceOf( NoopOptimizer.class ) );
 

hibernate-core/src/test/java/org/hibernate/orm/test/idgen/enhanced/sequence/BasicSequenceTest.java

@@ -40,9 +40,9 @@ public class BasicSequenceTest {
         final EntityPersister persister = scope.getSessionFactory()
 				.getMappingMetamodel()
 				.getEntityDescriptor(Entity.class.getName());
-		assertThat( persister.getIdentifierGenerator(), instanceOf( SequenceStyleGenerator.class ) );
+		assertThat( persister.getGenerator(), instanceOf( SequenceStyleGenerator.class ) );
 
-		final SequenceStyleGenerator generator = (SequenceStyleGenerator) persister.getIdentifierGenerator();
+		final SequenceStyleGenerator generator = (SequenceStyleGenerator) persister.getGenerator();
 
 		final int count = 5;
 
@@ -71,9 +71,9 @@ public class BasicSequenceTest {
         final EntityPersister persister = scope.getSessionFactory()
 				.getMappingMetamodel()
 				.getEntityDescriptor(overriddenEntityName);
-		assertThat( persister.getIdentifierGenerator(), instanceOf( SequenceStyleGenerator.class ) );
+		assertThat( persister.getGenerator(), instanceOf( SequenceStyleGenerator.class ) );
 
-		final SequenceStyleGenerator generator = (SequenceStyleGenerator) persister.getIdentifierGenerator();
+		final SequenceStyleGenerator generator = (SequenceStyleGenerator) persister.getGenerator();
 		assertEquals( "ID_SEQ_BSC_ENTITY" + SequenceStyleGenerator.DEF_SEQUENCE_SUFFIX,
 				generator.getDatabaseStructure().getPhysicalName().render() );
 

hibernate-core/src/test/java/org/hibernate/orm/test/idgen/enhanced/table/BasicTableTest.java

@@ -29,9 +29,9 @@ public class BasicTableTest {
         final EntityPersister persister = scope.getSessionFactory()
 				.getMappingMetamodel()
 				.getEntityDescriptor(Entity.class.getName());
-		assertThat( persister.getIdentifierGenerator(), instanceOf( TableGenerator.class ) );
+		assertThat( persister.getGenerator(), instanceOf( TableGenerator.class ) );
 
-		final TableGenerator generator = ( TableGenerator ) persister.getIdentifierGenerator();
+		final TableGenerator generator = ( TableGenerator ) persister.getGenerator();
 
 		scope.inTransaction(
 				(s) -> {

hibernate-core/src/test/java/org/hibernate/orm/test/idgen/userdefined/UserDefinedGeneratorsTests.java

@@ -39,7 +39,6 @@ import org.hibernate.resource.beans.container.spi.BeanContainer;
 import org.hibernate.resource.beans.container.spi.BeanContainer.LifecycleOptions;
 import org.hibernate.resource.beans.container.spi.ContainedBean;
 import org.hibernate.resource.beans.internal.FallbackBeanInstanceProducer;
-import org.hibernate.service.spi.ServiceRegistryImplementor;
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.orm.junit.BaseUnitTest;