GH-2225 - Naive imperative solution.

Author: meistermeier

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

@@ -524,7 +524,8 @@ private <T> T processNestedRelations(Neo4jPersistentEntity<?> sourceEntity, Obje
 				Long relatedInternalId;
 				// No need to save values if processed
 				if (stateMachine.hasProcessedValue(relatedValueToStore)) {
-					relatedInternalId = queryRelatedNode(relatedNode, targetEntity, inDatabase);
+					Object thing = stateMachine.getProcessedAs(relatedNode);
+					relatedInternalId = queryRelatedNode(thing, targetEntity, inDatabase);
 				} else {
 					relatedInternalId = saveRelatedNode(relatedNode, targetEntity, inDatabase);
 				}
@@ -560,6 +561,7 @@ private <T> T processNestedRelations(Neo4jPersistentEntity<?> sourceEntity, Obje
 				// if an internal id is used this must get set to link this entity in the next iteration
 				if (targetEntity.isUsingInternalIds()) {
 					targetPropertyAccessor.setProperty(targetEntity.getRequiredIdProperty(), relatedInternalId);
+					stateMachine.markValueAsProcessedAs(relatedNode, targetPropertyAccessor.getBean());
 				}
 				if (processState != ProcessState.PROCESSED_ALL_VALUES) {
 					processNestedRelations(targetEntity, targetPropertyAccessor.getBean(), isEntityNew, inDatabase, stateMachine);

src/main/java/org/springframework/data/neo4j/core/mapping/NestedRelationshipProcessingStateMachine.java

@@ -16,7 +16,9 @@
 package org.springframework.data.neo4j.core.mapping;
 
 import java.util.Collection;
+import java.util.HashMap;
 import java.util.HashSet;
+import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.locks.Lock;
@@ -35,6 +37,24 @@
 @API(status = API.Status.INTERNAL, since = "6.0")
 public final class NestedRelationshipProcessingStateMachine {
 
+	public void markValueAsProcessedAs(Object relatedValueToStore, Object bean) {
+		try {
+			write.lock();
+			processedObjectsAlias.put(relatedValueToStore, bean);
+		} finally {
+			write.unlock();
+		}
+	}
+
+	public Object getProcessedAs(Object entity) {
+		try {
+			read.lock();
+			return processedObjectsAlias.getOrDefault(entity, entity);
+		} finally {
+			read.unlock();
+		}
+	}
+
 	/**
 	 * Valid processing states.
 	 */
@@ -55,6 +75,7 @@ public enum ProcessState {
 	 * The set of already processed related objects.
 	 */
 	private final Set<Object> processedObjects = new HashSet<>();
+	private final Map<Object, Object> processedObjectsAlias = new HashMap<>();
 
 	public NestedRelationshipProcessingStateMachine(Object initialObject) {
 		processedObjects.add(initialObject);