HHH-18815 Generator fixes and tests

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

@@ -48,12 +48,25 @@
  *     {@link GeneratedColumn} annotation, so that Hibernate automatically
  *     generates the correct DDL.
  * </ul>
+ * <p>
+ * A {@code @Generated} field may be generated on
+ * {@linkplain EventType#INSERT inserts}, on
+ * {@linkplain EventType#UPDATE updates}, or on both inserts and updates,
+ * as specified by the {@link #event} member.
+ * By default, {@code @Generated} fields are not immutable, and so a field
+ * which is generated on insert may later be explicitly assigned a new value
+ * by the application program, resulting in its value being updated in the
+ * database. If this is not desired, the {@link Immutable @Immutable}
+ * annotation may be used in conjunction with {@code @Generated} to specify
+ * that the field may never be updated after initial generation of its value.
  *
  * @author Emmanuel Bernard
  *
  * @see jakarta.persistence.GeneratedValue
  * @see ColumnDefault
  * @see GeneratedColumn
+ * @see Formula
+ * @see Immutable
  */
 @ValueGenerationType( generatedBy = GeneratedGeneration.class )
 @IdGeneratorType( GeneratedGeneration.class )
@@ -84,8 +97,12 @@
 	/**
 	 * Determines if the value currently assigned to the annotated property
 	 * is included in SQL {@code insert} and {@code update} statements. This
-	 * is useful if the generated value is obtained by transforming the
-	 * assigned property value as it is being written.
+	 * is useful if:
+	 * <ul>
+	 * <li>the generated value is obtained by transforming the assigned
+	 *     property value as it is being written, or
+	 * <li>assigning a value disables generation of a value.
+	 * </ul>
 	 * <p>
 	 * Often used in combination with {@link SQLInsert}, {@link SQLUpdate},
 	 * or {@link ColumnTransformer#write()}.

hibernate-core/src/main/java/org/hibernate/boot/spi/SessionFactoryOptions.java

@@ -131,6 +131,11 @@ default boolean isAllowRefreshDetachedEntity() {
 
 	BaselineSessionEventsListenerBuilder getBaselineSessionEventsListenerBuilder();
 
+	/**
+	 * Should generated identifiers be reset after entity removal?
+	 *
+	 * @see org.hibernate.cfg.AvailableSettings#USE_IDENTIFIER_ROLLBACK
+	 */
 	boolean isIdentifierRollbackEnabled();
 
 	boolean isCheckNullability();

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

@@ -170,6 +170,7 @@ public interface AvailableSettings
 	/**
 	 * When enabled, specifies that the generated identifier of an entity is unset
 	 * when the entity is {@linkplain org.hibernate.Session#remove(Object) deleted}.
+	 * If the entity is versioned, the version is also reset to its default value.
 	 *
 	 * @settingDefault {@code false} - generated identifiers are not unset
 	 *

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

@@ -80,8 +80,8 @@ public Boolean isUnsaved(@Nullable Object version) throws MappingException {
 			if ( version == null ) {
 				return Boolean.TRUE;
 			}
-			if ( version instanceof Number ) {
-				return ((Number) version).longValue() < 0L;
+			if ( version instanceof Number number ) {
+				return number.longValue() < 0L;
 			}
 			throw new MappingException( "unsaved-value NEGATIVE may only be used with short, int and long types" );
 		}

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

@@ -103,6 +103,7 @@ protected Object saveWithGeneratedId(
 		final EntityPersister persister = source.getEntityPersister( entityName, entity );
 		final Generator generator = persister.getGenerator();
 		final boolean generatedOnExecution = generator.generatedOnExecution( entity, source );
+		final boolean generatedBeforeExecution = generator.generatedBeforeExecution( entity, source );
 		final Object generatedId;
 		if ( generatedOnExecution ) {
 			// the id gets generated by the database
@@ -114,7 +115,7 @@ else if ( !generator.generatesOnInsert() ) {
 			// the @PrePersist callback to happen first
 			generatedId = null;
 		}
-		else {
+		else if ( generatedBeforeExecution ) {
 			// go ahead and generate id, and then set it to
 			// the entity instance, so it will be available
 			// to the entity in the @PrePersist callback
@@ -124,6 +125,11 @@ else if ( !generator.generatesOnInsert() ) {
 			}
 			persister.setIdentifier( entity, generatedId, source );
 		}
+		else {
+			// the generator is refusing to generate anything
+			// so use the identifier currently assigned
+			generatedId = persister.getIdentifier( entity, source );
+		}
 		final boolean delayIdentityInserts =
 				!source.isTransactionInProgress()
 						&& !requiresImmediateIdAccess

hibernate-core/src/main/java/org/hibernate/generator/Assigned.java

@@ -5,6 +5,7 @@
 package org.hibernate.generator;
 
 import org.hibernate.Internal;
+import org.hibernate.engine.spi.SharedSessionContractImplementor;
 
 import java.util.EnumSet;
 
@@ -29,11 +30,26 @@ public boolean generatedOnExecution() {
 		return false;
 	}
 
+	@Override
+	public boolean generatedOnExecution(Object entity, SharedSessionContractImplementor session) {
+		return false;
+	}
+
+	@Override
+	public boolean generatedBeforeExecution(Object entity, SharedSessionContractImplementor session) {
+		return false;
+	}
+
 	@Override
 	public boolean allowAssignedIdentifiers() {
 		return true;
 	}
 
+	@Override
+	public boolean allowMutation() {
+		return true;
+	}
+
 	@Override
 	public EnumSet<EventType> getEventTypes() {
 		return EventTypeSets.NONE;

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

@@ -32,9 +32,10 @@
  *	   SQL {@code select}, though in certain cases this additional round trip may be avoided.
  *	   An important example is id generation using an identity column.
  * </ul>
- * A Generator may implement both interfaces and determine the timing of ID generation at runtime.
- * Furthermore, this condition can be based on the state of the owner entity, see
- * {@link #generatedOnExecution(Object, SharedSessionContractImplementor) generatedOnExecution}.
+ * A {@code Generator} may implement both interfaces and determine the timing of identifier
+ * generation at runtime. Furthermore, this condition can be based on the state of the owner entity,
+ * see {@link #generatedOnExecution(Object, SharedSessionContractImplementor) generatedOnExecution} and
+ * {@link #generatedBeforeExecution(Object, SharedSessionContractImplementor) generatedBeforeExecution}.
  * <p>
  * Generically, a generator may be integrated with the program using the meta-annotation
  * {@link org.hibernate.annotations.ValueGenerationType}, which associates the generator with
@@ -95,30 +96,51 @@ public interface Generator extends Serializable {
 	boolean generatedOnExecution();
 
 	/**
-	 * Determines if the property value is generated when a row is written to the database,
-	 * or in Java code that executes before the row is written.
+	 * Determines if the property value is generated when a row is written to the database.
 	 * <p>
-	 * Defaults to {@link #generatedOnExecution()}, but can be overloaded allowing conditional
-	 * value generation timing (on/before execution) based on the current state of the owner entity.
-	 * Note that a generator <b>must</b> implement both {@link BeforeExecutionGenerator} and
-	 * {@link OnExecutionGenerator} to achieve this behavior.
+	 * Defaults to {@link #generatedOnExecution()}, but may be overridden to allow conditional
+	 * on-execution value generation based on the current state of the owner entity.
 	 *
 	 * @param entity The instance of the entity owning the attribute for which we are generating a value.
 	 * @param session The session from which the request originates.
 	 *
 	 * @return {@code true} if the value is generated by the database as a side effect of
-	 * the execution of an {@code insert} or {@code update} statement, or false if
-	 * it is generated in Java code before the statement is executed via JDBC.
+	 *         the execution of an {@code insert} or {@code update} statement.
 	 *
 	 * @see #generatedOnExecution()
 	 * @see BeforeExecutionGenerator
 	 * @see OnExecutionGenerator
+	 *
 	 * @since 6.4
 	 */
 	default boolean generatedOnExecution(Object entity, SharedSessionContractImplementor session) {
 		return generatedOnExecution();
 	}
 
+	/**
+	 * Determines if the property value is generated before in Java code that executes before
+	 * the row is written.
+	 * <p>
+	 * Defaults to {@link #generatedOnExecution() !generatedOnExecution()}, but may be overridden
+	 * to allow conditional before-execution value generation based on the current state of the
+	 * owner entity.
+	 *
+	 * @param entity The instance of the entity owning the attribute for which we are generating a value.
+	 * @param session The session from which the request originates.
+	 *
+	 * @return {@code true} if the value is generated in Java code before the statement is
+	 *         executed via JDBC.
+	 *
+	 * @see #generatedOnExecution()
+	 * @see BeforeExecutionGenerator
+	 * @see OnExecutionGenerator
+	 *
+	 * @since 7.0
+	 */
+	default boolean generatedBeforeExecution(Object entity, SharedSessionContractImplementor session) {
+		return !generatedOnExecution();
+	}
+
 	/**
 	 * The {@linkplain EventType event types} for which this generator should be called
 	 * to produce a new value.
@@ -143,6 +165,19 @@ default boolean allowAssignedIdentifiers() {
 		return false;
 	}
 
+	/**
+	 * Determine if this generator allows generated fields to be manually assigned a value on
+	 * {@linkplain #getEventTypes events} which do <em>not</em> trigger value generation.
+	 *
+	 * @return {@code true} if this generator allows manually assigned values,
+	 *         {@code false} otherwise (default).
+	 *
+	 * @since 7.0
+	 */
+	default boolean allowMutation() {
+		return false;
+	}
+
 	default boolean generatesSometimes() {
 		return !getEventTypes().isEmpty();
 	}

hibernate-core/src/main/java/org/hibernate/generator/internal/GeneratedGeneration.java

@@ -4,10 +4,10 @@
  */
 package org.hibernate.generator.internal;
 
+import org.hibernate.AnnotationException;
 import org.hibernate.annotations.Generated;
 import org.hibernate.dialect.Dialect;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
-import org.hibernate.generator.BeforeExecutionGenerator;
 import org.hibernate.generator.EventType;
 import org.hibernate.generator.OnExecutionGenerator;
 import org.hibernate.persister.entity.EntityPersister;
@@ -26,7 +26,7 @@
  * @author Steve Ebersole
  * @author Gunnar Morling
  */
-public class GeneratedGeneration implements OnExecutionGenerator, BeforeExecutionGenerator {
+public class GeneratedGeneration implements OnExecutionGenerator {
 
 	private final EnumSet<EventType> eventTypes;
 	private final boolean writable;
@@ -41,7 +41,10 @@ public GeneratedGeneration(EnumSet<EventType> eventTypes) {
 	public GeneratedGeneration(Generated annotation) {
 		eventTypes = fromArray( annotation.event() );
 		sql = isEmpty( annotation.sql() ) ? null : new String[] { annotation.sql() };
-		writable = annotation.writable() || sql != null;
+		writable = annotation.writable();
+		if ( sql != null && writable ) {
+			throw new AnnotationException( "A field marked '@Generated(writable=true)' may not specify explicit 'sql'" );
+		}
 	}
 
 	@Override
@@ -51,7 +54,9 @@ public EnumSet<EventType> getEventTypes() {
 
 	@Override
 	public boolean referenceColumnsInSql(Dialect dialect) {
-		return writable;
+		// include the column in when the field is writable,
+		// or when there is an explicit SQL expression
+		return writable || sql != null;
 	}
 
 	@Override
@@ -61,34 +66,32 @@ public String[] getReferencedColumnValues(Dialect dialect) {
 
 	@Override
 	public boolean writePropertyValue() {
-		return writable && sql==null;
-	}
-
-	@Override
-	public boolean generatedOnExecution() {
-		return true;
+		// include a ? parameter when the field is writable,
+		// but there is no explicit SQL expression
+		return writable;
 	}
 
 	@Override
 	public boolean generatedOnExecution(Object entity, SharedSessionContractImplementor session) {
-		if ( !writable ) {
+		if ( writable ) {
+			// When this is the identifier generator and writable is true, allow pre-assigned identifiers
+			final EntityPersister entityPersister = session.getEntityPersister( null, entity );
+			return entityPersister.getGenerator() != this
+				|| entityPersister.getIdentifier( entity, session ) == null;
+		}
+		else {
 			return true;
 		}
-
-		// When this is the identifier generator and writable is true, allow pre-assigned identifiers
-		final EntityPersister entityPersister = session.getEntityPersister( null, entity );
-		return entityPersister.getGenerator() != this || entityPersister.getIdentifier( entity, session ) == null;
 	}
 
 	@Override
-	public Object generate(SharedSessionContractImplementor session, Object owner, Object currentValue, EventType eventType) {
-		final EntityPersister entityPersister = session.getEntityPersister( null, owner );
-		assert entityPersister.getGenerator() == this;
-		return entityPersister.getIdentifier( owner, session );
+	public boolean allowAssignedIdentifiers() {
+		return writable;
 	}
 
 	@Override
-	public boolean allowAssignedIdentifiers() {
-		return writable;
+	public boolean allowMutation() {
+		// the user may specify @Immutable if mutation should be disallowed
+		return true;
 	}
 }

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

@@ -146,32 +146,47 @@ public Object insert(String entityName, Object entity) {
 			}
 		}
 		final Generator generator = persister.getGenerator();
-		if ( !generator.generatedOnExecution( entity, this ) ) {
-			if ( generator.generatesOnInsert() ) {
-				id = ( (BeforeExecutionGenerator) generator).generate( this, entity, null, INSERT );
-			}
-			else {
-				id = persister.getIdentifier( entity, this );
-				if ( id == null ) {
-					throw new IdentifierGenerationException( "Identifier of entity '" + persister.getEntityName() + "' must be manually assigned before calling 'insert()'" );
-				}
+		if ( generator.generatedBeforeExecution( entity, this ) ) {
+			if ( !generator.generatesOnInsert() ) {
+				throw new IdentifierGenerationException( "Identifier generator must generate on insert" );
 			}
+			id = ( (BeforeExecutionGenerator) generator).generate( this, entity, null, INSERT );
 			if ( firePreInsert(entity, id, state, persister) ) {
 				return id;
 			}
-			getInterceptor().onInsert( entity, id, state, persister.getPropertyNames(), persister.getPropertyTypes() );
-			persister.getInsertCoordinator().insert( entity, id, state, this );
+			else {
+				getInterceptor().onInsert( entity, id, state, persister.getPropertyNames(), persister.getPropertyTypes() );
+				persister.getInsertCoordinator().insert( entity, id, state, this );
+				persister.setIdentifier( entity, id, this );
+			}
 		}
-		else {
+		else if ( generator.generatedOnExecution( entity, this ) ) {
+			if ( !generator.generatesOnInsert() ) {
+				throw new IdentifierGenerationException( "Identifier generator must generate on insert" );
+			}
 			if ( firePreInsert(entity, null, state, persister) ) {
 				return null;
 			}
-			getInterceptor()
-					.onInsert( entity, null, state, persister.getPropertyNames(), persister.getPropertyTypes() );
-			final GeneratedValues generatedValues = persister.getInsertCoordinator().insert( entity, state, this );
-			id = castNonNull( generatedValues ).getGeneratedValue( persister.getIdentifierMapping() );
+			else {
+				getInterceptor().onInsert( entity, null, state, persister.getPropertyNames(), persister.getPropertyTypes() );
+				final GeneratedValues generatedValues = persister.getInsertCoordinator().insert( entity, state, this );
+				id = castNonNull( generatedValues ).getGeneratedValue( persister.getIdentifierMapping() );
+				persister.setIdentifier( entity, id, this );
+			}
+		}
+		else { // assigned identifier
+			id = persister.getIdentifier( entity, this );
+			if ( id == null ) {
+				throw new IdentifierGenerationException( "Identifier of entity '" + persister.getEntityName() + "' must be manually assigned before calling 'insert()'" );
+			}
+			if ( firePreInsert(entity, id, state, persister) ) {
+				return id;
+			}
+			else {
+				getInterceptor().onInsert( entity, id, state, persister.getPropertyNames(), persister.getPropertyTypes() );
+				persister.getInsertCoordinator().insert( entity, id, state, this );
+			}
 		}
-		persister.setIdentifier( entity, id, this );
 		forEachOwnedCollection( entity, id, persister,
 				(descriptor, collection) -> {
 					descriptor.recreate( collection, id, this);

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

@@ -776,7 +776,7 @@ public int getPropertyIndex() {
 
 		@Override
 		public Object execute(SharedSessionContractImplementor session, Object incomingObject) {
-			if ( !generator.generatedOnExecution( incomingObject, session ) ) {
+			if ( generator.generatedBeforeExecution( incomingObject, session ) ) {
 				return generator.generate( session, incomingObject, null, INSERT );
 			}
 			else {