Move Sequence to RelationalPersistentProperty.

Sequence details are now maintained on the property level instead of using the entity level. This is a more accurate representation of the underlying model and that properties are annotated and not entities. It also allows future extension of expanding sequence support to general properties.

Extract delegate for sequence generation. Move types to org.springframework.data.jdbc.core.convert to resolve package cycles.

See #2003
Original pull request: #2005

Author: mp911de

Diff for: spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/convert/IdGeneratingEntityCallback.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.jdbc.core.convert;
+
+import org.springframework.data.mapping.PersistentPropertyAccessor;
+import org.springframework.data.mapping.context.MappingContext;
+import org.springframework.data.relational.core.conversion.MutableAggregateChange;
+import org.springframework.data.relational.core.dialect.Dialect;
+import org.springframework.data.relational.core.mapping.RelationalPersistentEntity;
+import org.springframework.data.relational.core.mapping.RelationalPersistentProperty;
+import org.springframework.data.relational.core.mapping.event.BeforeSaveCallback;
+import org.springframework.jdbc.core.namedparam.NamedParameterJdbcOperations;
+import org.springframework.util.Assert;
+
+/**
+ * Callback for generating identifier values through a database sequence.
+ *
+ * @author Mikhail Polivakha
+ * @author Mark Paluch
+ * @since 3.5
+ */
+public class IdGeneratingEntityCallback implements BeforeSaveCallback<Object> {
+
+	private final MappingContext<RelationalPersistentEntity<?>, ? extends RelationalPersistentProperty> context;
+	private final SequenceEntityCallbackDelegate delegate;
+
+	public IdGeneratingEntityCallback(
+			MappingContext<RelationalPersistentEntity<?>, ? extends RelationalPersistentProperty> context, Dialect dialect,
+			NamedParameterJdbcOperations operations) {
+
+		this.context = context;
+		this.delegate = new SequenceEntityCallbackDelegate(dialect, operations);
+	}
+
+	@Override
+	public Object onBeforeSave(Object aggregate, MutableAggregateChange<Object> aggregateChange) {
+
+		Assert.notNull(aggregate, "aggregate must not be null");
+
+		RelationalPersistentEntity<?> entity = context.getRequiredPersistentEntity(aggregate.getClass());
+
+		if (!entity.hasIdProperty()) {
+			return aggregate;
+		}
+
+		RelationalPersistentProperty property = entity.getRequiredIdProperty();
+		PersistentPropertyAccessor<Object> accessor = entity.getPropertyAccessor(aggregate);
+
+		if (!entity.isNew(aggregate) || delegate.hasValue(property, accessor) || !property.hasSequence()) {
+			return aggregate;
+		}
+
+		delegate.generateSequenceValue(property, accessor);
+
+		return accessor.getBean();
+	}
+
+}

Diff for: spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/convert/SequenceEntityCallbackDelegate.java

@@ -0,0 +1,102 @@
+/*
+ * Copyright 2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.jdbc.core.convert;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import org.springframework.data.mapping.PersistentProperty;
+import org.springframework.data.mapping.PersistentPropertyAccessor;
+import org.springframework.data.relational.core.dialect.Dialect;
+import org.springframework.data.relational.core.mapping.RelationalPersistentProperty;
+import org.springframework.data.relational.core.sql.SqlIdentifier;
+import org.springframework.data.util.ReflectionUtils;
+import org.springframework.jdbc.core.namedparam.MapSqlParameterSource;
+import org.springframework.jdbc.core.namedparam.NamedParameterJdbcOperations;
+import org.springframework.lang.Nullable;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.NumberUtils;
+
+/**
+ * Support class for generating identifier values through a database sequence.
+ *
+ * @author Mikhail Polivakha
+ * @author Mark Paluch
+ * @since 3.5
+ * @see org.springframework.data.relational.core.mapping.Sequence
+ */
+class SequenceEntityCallbackDelegate {
+
+	private static final Log LOG = LogFactory.getLog(SequenceEntityCallbackDelegate.class);
+	private final static MapSqlParameterSource EMPTY_PARAMETERS = new MapSqlParameterSource();
+
+	private final Dialect dialect;
+	private final NamedParameterJdbcOperations operations;
+
+	public SequenceEntityCallbackDelegate(Dialect dialect, NamedParameterJdbcOperations operations) {
+		this.dialect = dialect;
+		this.operations = operations;
+	}
+
+	@SuppressWarnings("unchecked")
+	protected void generateSequenceValue(RelationalPersistentProperty property,
+			PersistentPropertyAccessor<Object> accessor) {
+
+		Object sequenceValue = getSequenceValue(property);
+
+		if (sequenceValue == null) {
+			return;
+		}
+
+		Class<?> targetType = ClassUtils.resolvePrimitiveIfNecessary(property.getType());
+		if (sequenceValue instanceof Number && Number.class.isAssignableFrom(targetType)) {
+			sequenceValue = NumberUtils.convertNumberToTargetClass((Number) sequenceValue,
+					(Class<? extends Number>) targetType);
+		}
+
+		accessor.setProperty(property, sequenceValue);
+	}
+
+	protected boolean hasValue(PersistentProperty<?> property, PersistentPropertyAccessor<Object> propertyAccessor) {
+
+		Object identifier = propertyAccessor.getProperty(property);
+
+		if (property.getType().isPrimitive()) {
+
+			Object primitiveDefault = ReflectionUtils.getPrimitiveDefault(property.getType());
+			return !primitiveDefault.equals(identifier);
+		}
+
+		return identifier != null;
+	}
+
+	private @Nullable Object getSequenceValue(RelationalPersistentProperty property) {
+
+		SqlIdentifier sequence = property.getSequence();
+
+		if (sequence != null && !dialect.getIdGeneration().sequencesSupported()) {
+			LOG.warn("""
+					Aggregate type '%s' is marked for sequence usage but configured dialect '%s'
+					does not support sequences. Falling back to identity columns.
+					""".formatted(property.getOwner().getType(), ClassUtils.getQualifiedName(dialect.getClass())));
+			return null;
+		}
+
+		String sql = dialect.getIdGeneration().createSequenceQuery(sequence);
+		return operations.queryForObject(sql, EMPTY_PARAMETERS, (rs, rowNum) -> rs.getObject(1));
+	}
+
+}

Diff for: spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/mapping/IdGeneratingBeforeSaveCallback.java

@@ -25,6 +25,7 @@
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.context.ApplicationContext;
@@ -38,7 +39,6 @@
 import org.springframework.data.jdbc.core.JdbcAggregateTemplate;
 import org.springframework.data.jdbc.core.convert.*;
 import org.springframework.data.jdbc.core.dialect.JdbcDialect;
-import org.springframework.data.jdbc.core.mapping.IdGeneratingBeforeSaveCallback;
 import org.springframework.data.jdbc.core.mapping.JdbcMappingContext;
 import org.springframework.data.jdbc.core.mapping.JdbcSimpleTypes;
 import org.springframework.data.mapping.model.SimpleTypeHolder;
@@ -121,17 +121,17 @@ public JdbcMappingContext jdbcMappingContext(Optional<NamingStrategy> namingStra
 	}
 
 	/**
-	 * Creates a {@link IdGeneratingBeforeSaveCallback} bean using the configured
+	 * Creates a {@link IdGeneratingEntityCallback} bean using the configured
 	 * {@link #jdbcMappingContext(Optional, JdbcCustomConversions, RelationalManagedTypes)} and
 	 * {@link #jdbcDialect(NamedParameterJdbcOperations)}.
 	 *
 	 * @return must not be {@literal null}.
 	 * @since 3.5
 	 */
 	@Bean
-	public IdGeneratingBeforeSaveCallback idGeneratingBeforeSaveCallback(JdbcMappingContext mappingContext,
+	public IdGeneratingEntityCallback idGeneratingBeforeSaveCallback(JdbcMappingContext mappingContext,
 			NamedParameterJdbcOperations operations, Dialect dialect) {
-		return new IdGeneratingBeforeSaveCallback(mappingContext, dialect, operations);
+		return new IdGeneratingEntityCallback(mappingContext, dialect, operations);
 	}
 
 	/**