DATAJDBC-417 - Fixed saving an entity containing a null embeddable with a reference to a further entity.

Constructing the DbActions assumed that the parent of a path exists (i.e. is not null) and created parent nodes.

Original pull request: #169.

spring-data-relational/src/main/java/org/springframework/data/relational/core/conversion/WritingContext.java

@@ -202,7 +202,8 @@ class WritingContext {
 
 		} else {
 
-			List<PathNode> pathNodes = nodesCache.get(path.getParentPath());
+			List<PathNode> pathNodes = nodesCache.getOrDefault(path.getParentPath(), Collections.emptyList());
+
 			pathNodes.forEach(parentNode -> {
 
 				// todo: this should go into pathnode
@@ -238,7 +239,17 @@ class WritingContext {
 
 	@Nullable
 	private Object getFromRootValue(PersistentPropertyPath<RelationalPersistentProperty> path) {
-		return path.getBaseProperty().getOwner().getPropertyAccessor(entity).getProperty(path);
+
+		if (path.getLength() == 0)
+			return entity;
+
+		Object parent = getFromRootValue(path.getParentPath());
+		if (parent == null) {
+			return null;
+		}
+
+		return context.getRequiredPersistentEntity(parent.getClass()).getPropertyAccessor(parent)
+				.getProperty(path.getRequiredLeafProperty());
 	}
 
 	private List<PathNode> createNodes(PersistentPropertyPath<RelationalPersistentProperty> path,

spring-data-relational/src/test/java/org/springframework/data/relational/core/conversion/RelationalEntityWriterUnitTests.java

@@ -29,7 +29,6 @@ import java.util.Set;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.junit.MockitoJUnitRunner;
-
 import org.springframework.data.annotation.Id;
 import org.springframework.data.mapping.PersistentPropertyPath;
 import org.springframework.data.mapping.PersistentPropertyPaths;
@@ -118,6 +117,7 @@ public class RelationalEntityWriterUnitTests {
 				);
 	}
 
+
 	@Test // DATAJDBC-112
 	public void newEntityWithReferenceGetsConvertedToTwoInserts() {
 
@@ -530,6 +530,51 @@ public class RelationalEntityWriterUnitTests {
 				);
 	}
 
+	@Test // DATAJDBC-417
+	public void savingANullEmbeddedWithEntity() {
+
+		EmbeddedReferenceChainEntity entity = new EmbeddedReferenceChainEntity(null);
+		// the embedded is null !!!
+
+		AggregateChange<EmbeddedReferenceChainEntity> aggregateChange = //
+				new AggregateChange<>(Kind.SAVE, EmbeddedReferenceChainEntity.class, entity);
+
+		converter.write(entity, aggregateChange);
+
+		assertThat(aggregateChange.getActions()) //
+				.extracting(DbAction::getClass, //
+						DbAction::getEntityType, //
+						DbActionTestSupport::extractPath, //
+						DbActionTestSupport::actualEntityType, //
+						DbActionTestSupport::isWithDependsOn) //
+				.containsExactly( //
+						tuple(InsertRoot.class, EmbeddedReferenceChainEntity.class, "", EmbeddedReferenceChainEntity.class, false) //
+				);
+	}
+	@Test // DATAJDBC-417
+	public void savingInnerNullEmbeddedWithEntity() {
+
+		RootWithEmbeddedReferenceChainEntity root = new RootWithEmbeddedReferenceChainEntity(null);
+		root.other = new EmbeddedReferenceChainEntity(null);
+		// the embedded is null !!!
+
+		AggregateChange<RootWithEmbeddedReferenceChainEntity> aggregateChange = //
+				new AggregateChange<>(Kind.SAVE, RootWithEmbeddedReferenceChainEntity.class, root);
+
+		converter.write(root, aggregateChange);
+
+		assertThat(aggregateChange.getActions()) //
+				.extracting(DbAction::getClass, //
+						DbAction::getEntityType, //
+						DbActionTestSupport::extractPath, //
+						DbActionTestSupport::actualEntityType, //
+						DbActionTestSupport::isWithDependsOn) //
+				.containsExactly( //
+						tuple(InsertRoot.class, RootWithEmbeddedReferenceChainEntity.class, "", RootWithEmbeddedReferenceChainEntity.class, false), //
+						tuple(Insert.class, EmbeddedReferenceChainEntity.class, "other", EmbeddedReferenceChainEntity.class, true) //
+				);
+	}
+
 	private CascadingReferenceMiddleElement createMiddleElement(Element first, Element second) {
 
 		CascadingReferenceMiddleElement middleElement1 = new CascadingReferenceMiddleElement(null);
@@ -585,6 +630,19 @@ public class RelationalEntityWriterUnitTests {
 		@Embedded(onEmpty = OnEmpty.USE_NULL, prefix = "prefix_") Element other;
 	}
 
+	@RequiredArgsConstructor
+	static class EmbeddedReferenceChainEntity {
+
+		@Id final Long id;
+		@Embedded(onEmpty = OnEmpty.USE_NULL, prefix = "prefix_") ElementReference other;
+	}
+	@RequiredArgsConstructor
+	static class RootWithEmbeddedReferenceChainEntity {
+
+		@Id final Long id;
+		EmbeddedReferenceChainEntity other;
+	}
+
 	@RequiredArgsConstructor
 	static class ReferenceWoIdEntity {
 
@@ -641,6 +699,11 @@ public class RelationalEntityWriterUnitTests {
 		@Id final Long id;
 	}
 
+	@RequiredArgsConstructor
+	private static class ElementReference {
+		final Element element;
+	}
+
 	@RequiredArgsConstructor
 	private static class NoIdListMapContainer {