GH-2214 - Improve documentation for @RelationshipProperties.

This closes #2214.

Author: michael-simons

src/main/asciidoc/object-mapping/mapping.adoc

@@ -164,6 +164,10 @@ You must define a property for the generated, internal ID so that SDN can determ
 can be safely overwritten without losing properties.
 If SDN does not find a field for storing the internal node id, it will fail during startup.
 
+NOTE: The only supported generated ID field on classes annotated with `@RelationshipProperties` is `@GeneratedValue` with
+      using the default ID generator `InternalIdGenerator` as shown above. Other generators will lead to a failure during
+      startup..
+
 .Defining relationship properties for an entity
 [source,java,indent=0]
 ----

src/test/java/org/springframework/data/neo4j/core/mapping/Neo4jMappingContextTest.java

@@ -28,6 +28,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.UUID;
 
 import org.assertj.core.api.Assertions;
 import org.junit.jupiter.api.Nested;
@@ -75,7 +76,7 @@ class Neo4jMappingContextTest {
 	class InvalidRelationshipProperties {
 
 		@Test // GH-2118
-		void startupShouldFail() {
+		void startupWithoutInternallyGeneratedIDShouldFail() {
 
 			Neo4jMappingContext schema = new Neo4jMappingContext();
 			assertThatIllegalStateException().isThrownBy(() -> {
@@ -86,6 +87,18 @@ void startupShouldFail() {
 					}).withMessage("The target class `org.springframework.data.neo4j.core.mapping.Neo4jMappingContextTest$InvalidRelationshipPropertyContainer` for the properties of the relationship `RELATIONSHIP_PROPERTY_CONTAINER` is missing a property for the generated, internal ID (`@Id @GeneratedValue Long id`) which is needed for safely updating properties.");
 		}
 
+		@Test // GH-2214
+		void startupWithWrongKindOfGeneratedIDShouldFail() {
+
+			Neo4jMappingContext schema = new Neo4jMappingContext();
+			assertThatIllegalStateException().isThrownBy(() -> {
+				schema.setInitialEntitySet(new HashSet<>(
+						Arrays.asList(IrrelevantSourceContainer3.class, InvalidRelationshipPropertyContainer2.class,
+								IrrelevantTargetContainer.class)));
+				schema.initialize();
+			}).withMessage("The target class `org.springframework.data.neo4j.core.mapping.Neo4jMappingContextTest$InvalidRelationshipPropertyContainer2` for the properties of the relationship `RELATIONSHIP_PROPERTY_CONTAINER` is missing a property for the generated, internal ID (`@Id @GeneratedValue Long id`) which is needed for safely updating properties.");
+		}
+
 		@Test // GH-2118
 		void noWarningShouldBeLogged(LogbackCapture logbackCapture) {
 
@@ -578,6 +591,25 @@ static class InvalidRelationshipPropertyContainer {
 		private IrrelevantTargetContainer irrelevantTargetContainer;
 	}
 
+	@Node
+	static class IrrelevantSourceContainer3 {
+		@Id @GeneratedValue
+		private Long id;
+
+		@Relationship(type = "RELATIONSHIP_PROPERTY_CONTAINER")
+		InvalidRelationshipPropertyContainer2 relationshipPropertyContainer;
+	}
+
+	@RelationshipProperties
+	static class InvalidRelationshipPropertyContainer2 {
+
+		@Id @GeneratedValue(GeneratedValue.UUIDGenerator.class)
+		private UUID id;
+
+		@TargetNode
+		private IrrelevantTargetContainer irrelevantTargetContainer;
+	}
+
 	@Node
 	static class IrrelevantTargetContainer {
 		@Id @GeneratedValue