User-defined update thingy (WIP name)

Signed-off-by: Gerrit Meier <[email protected]>

Author: meistermeier

src/main/java/org/springframework/data/neo4j/core/Neo4jTemplate.java

@@ -87,6 +87,8 @@
 import org.springframework.data.neo4j.core.mapping.SpringDataCypherDsl;
 import org.springframework.data.neo4j.core.mapping.callback.EventSupport;
 import org.springframework.data.neo4j.core.schema.TargetNode;
+import org.springframework.data.neo4j.core.support.UserDefinedChangeEvaluator;
+import org.springframework.data.neo4j.core.support.UserDefinedChangeSupport;
 import org.springframework.data.neo4j.core.transaction.Neo4jTransactionManager;
 import org.springframework.data.neo4j.repository.NoResultException;
 import org.springframework.data.neo4j.repository.query.QueryFragments;
@@ -156,6 +158,7 @@ public boolean isReadOnly() {
 
 	@Nullable
 	private TransactionTemplate transactionTemplateReadOnly;
+	private final Map<Class, UserDefinedChangeEvaluator> userDefinedChangeEvaluators = new HashMap<>();
 
 	public Neo4jTemplate(Neo4jClient neo4jClient) {
 		this(neo4jClient, new Neo4jMappingContext());
@@ -452,7 +455,9 @@ public <T> T save(T instance) {
 	private <T> T saveImpl(T instance, @Nullable Collection<PropertyFilter.ProjectedPath> includedProperties,
 			@Nullable NestedRelationshipProcessingStateMachine stateMachine) {
 
-		if (stateMachine != null && stateMachine.hasProcessedValue(instance)) {
+		if ((stateMachine != null && stateMachine.hasProcessedValue(instance))
+			|| (instance instanceof UserDefinedChangeSupport udcs && !udcs.needsUpdate())
+			|| (this.userDefinedChangeEvaluators.containsKey(instance.getClass()) && !this.userDefinedChangeEvaluators.get(instance.getClass()).needsUpdate(instance))) {
 			return instance;
 		}
 
@@ -977,11 +982,26 @@ private <T> T processNestedRelations(Neo4jPersistentEntity<?> sourceEntity,
 					.identifyAndExtractRelationshipTargetNode(relatedValueToStore);
 				Neo4jPersistentEntity<?> targetEntity = this.neo4jMappingContext
 					.getRequiredPersistentEntity(relatedObjectBeforeCallbacksApplied.getClass());
-				boolean isNewEntity = targetEntity.isNew(relatedObjectBeforeCallbacksApplied);
+				var isNewEntity = targetEntity.isNew(relatedObjectBeforeCallbacksApplied);
+				var skipUpdateOfEntity = false;
+				if (relatedValueToStore instanceof UserDefinedChangeSupport udcs) {
+					skipUpdateOfEntity = !isNewEntity && !udcs.needsUpdate();
+				}
+				if (relatedValueToStore instanceof MappingSupport.RelationshipPropertiesWithEntityHolder rpweh) {
+					var relatedEntity = rpweh.getRelatedEntity();
+					if (relatedEntity instanceof UserDefinedChangeSupport udcs) {
+						skipUpdateOfEntity = !isNewEntity && !udcs.needsUpdate();
+					}
+				}
+				else if (!skipUpdateOfEntity) {
+					skipUpdateOfEntity = this.userDefinedChangeEvaluators.containsKey(relatedValueToStore.getClass());
+				}
 
 				Object newRelatedObject = stateMachine.hasProcessedValue(relatedObjectBeforeCallbacksApplied)
 						? stateMachine.getProcessedAs(relatedObjectBeforeCallbacksApplied)
-						: this.eventSupport.maybeCallBeforeBind(relatedObjectBeforeCallbacksApplied);
+						: skipUpdateOfEntity
+							? relatedObjectBeforeCallbacksApplied
+							: this.eventSupport.maybeCallBeforeBind(relatedObjectBeforeCallbacksApplied);
 
 				Object relatedInternalId;
 				Entity savedEntity = null;
@@ -990,7 +1010,7 @@ private <T> T processNestedRelations(Neo4jPersistentEntity<?> sourceEntity,
 					relatedInternalId = stateMachine.getObjectId(relatedValueToStore);
 				}
 				else {
-					if (isNewEntity || relationshipDescription.cascadeUpdates()) {
+					if ((isNewEntity || relationshipDescription.cascadeUpdates()) && !skipUpdateOfEntity) {
 						savedEntity = saveRelatedNode(newRelatedObject, targetEntity, includeProperty,
 								currentPropertyPath);
 					}
@@ -1101,7 +1121,9 @@ else if (relationshipDescription.hasRelationshipProperties() && fromId != null)
 					else {
 						if (isNewRelationship && idProperty != null) {
 							newRelationshipPropertiesRows.add(properties);
-							newRelationshipPropertiesToStore.add(relatedValueToStore);
+							if (!skipUpdateOfEntity) {
+								newRelationshipPropertiesToStore.add(relatedValueToStore);
+							}
 						}
 						else {
 							this.neo4jMappingContext.getEntityConverter()
@@ -1325,6 +1347,8 @@ public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
 			}
 		}
 		setTransactionManager(transactionManager);
+		this.userDefinedChangeEvaluators.putAll(beanFactory.getBeanProvider(UserDefinedChangeEvaluator.class).stream()
+				.collect(Collectors.toMap(e -> e.getEvaluatingClass(), e -> e)));
 	}
 
 	// only used for the CDI configuration

src/main/java/org/springframework/data/neo4j/core/support/UserDefinedChangeEvaluator.java

@@ -0,0 +1,21 @@
+package org.springframework.data.neo4j.core.support;
+
+/**
+ * Interface to attach to a {@link org.springframework.data.neo4j.core.schema.Node}
+ * to indicate if an entity needs to be processed by built-in update procedures.
+ * @param <T> type to implement the UserDefinedChangeEvaluator for
+ * @author Gerrit Meier
+ */
+public interface UserDefinedChangeEvaluator<T> {
+	/**
+	 * Report if this entity needs to be considered for an update.
+	 * This includes possible relationships.
+	 * @param instance instance of type `T` to check
+	 * @return true, if it should be processed
+	 */
+	default boolean needsUpdate(T instance) {
+		return true;
+	}
+
+	Class<T> getEvaluatingClass();
+}

src/main/java/org/springframework/data/neo4j/core/support/UserDefinedChangeSupport.java

@@ -0,0 +1,15 @@
+package org.springframework.data.neo4j.core.support;
+
+/**
+ * Interface to attach to a {@link org.springframework.data.neo4j.core.schema.Node}
+ * to indicate if an entity needs to be processed by built-in update procedures.
+ * @author Gerrit Meier
+ */
+public interface UserDefinedChangeSupport {
+	/**
+	 * Report if this entity needs to be considered for an update.
+	 * This includes possible relationships.
+	 * @return true, if it should be processed
+	 */
+	boolean needsUpdate();
+}