bugfix: Multi Relationships cannot get right conversion type

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

@@ -69,6 +69,11 @@ public final class Constants {
 	public static final String NAME_OF_KNOWN_RELATIONSHIPS_PARAM = "__knownRelationShipIds__";
 	public static final String NAME_OF_ALL_PROPERTIES = "__allProperties__";
 
+	/**
+	 * Optional property for relationship properties' simple class name to keep type info
+	 */
+	public static final String NAME_OF_RELATIONSHIP_TYPE = "__relationshipType__";
+
 	public static final String NAME_OF_SYNTHESIZED_ROOT_NODE = "__sn__";
 	public static final String NAME_OF_SYNTHESIZED_RELATED_NODES = "__srn__";
 	public static final String NAME_OF_SYNTHESIZED_RELATIONS = "__sr__";

src/main/java/org/springframework/data/neo4j/core/mapping/DefaultNeo4jEntityConverter.java

@@ -38,6 +38,7 @@
 import org.neo4j.driver.Record;
 import org.neo4j.driver.Value;
 import org.neo4j.driver.Values;
+import org.neo4j.driver.internal.value.NullValue;
 import org.neo4j.driver.types.MapAccessor;
 import org.neo4j.driver.types.Node;
 import org.neo4j.driver.types.Relationship;
@@ -233,6 +234,10 @@ public void write(Object source, Map<String, Object> parameters) {
 
 		Neo4jPersistentEntity<?> nodeDescription = (Neo4jPersistentEntity<?>) nodeDescriptionStore
 				.getNodeDescription(source.getClass());
+		if (nodeDescription.hasRelationshipPropertyPersistTypeInfoFlag()) {
+			// add type info when write to the database
+			properties.put(Constants.NAME_OF_RELATIONSHIP_TYPE, nodeDescription.getPrimaryLabel());
+		}
 
 		PersistentPropertyAccessor<Object> propertyAccessor = nodeDescription.getPropertyAccessor(source);
 		PropertyHandlerSupport.of(nodeDescription).doWithProperties((Neo4jPersistentProperty p) -> {
@@ -427,6 +432,8 @@ private Neo4jPersistentEntity<?> getMostConcreteTargetNodeDescription(
 
 	/**
 	 * Returns the list of labels for the entity to be created from the "main" node returned.
+	 * In case of a relationship that maps to a relationship properties definition,
+	 * return the optional persisted type.
 	 *
 	 * @param queryResult The complete query result
 	 * @return The list of labels defined by the query variable {@link Constants#NAME_OF_LABELS}.
@@ -440,6 +447,13 @@ private List<String> getLabels(MapAccessor queryResult, @Nullable NodeDescriptio
 		} else if (queryResult instanceof Node) {
 			Node nodeRepresentation = (Node) queryResult;
 			nodeRepresentation.labels().forEach(labels::add);
+		} else if (queryResult instanceof Relationship) {
+			Value value = queryResult.get(Constants.NAME_OF_RELATIONSHIP_TYPE);
+			if (value instanceof NullValue) {
+				labels.addAll(nodeDescription.getStaticLabels());
+			} else {
+				labels.add(value.asString());
+			}
 		} else if (containsOnePlainNode(queryResult)) {
 			for (Value value : queryResult.values()) {
 				if (value.hasType(nodeType)) {

src/main/java/org/springframework/data/neo4j/core/mapping/DefaultNeo4jPersistentEntity.java

@@ -185,6 +185,14 @@ public boolean isRelationshipPropertiesEntity() {
 		return this.isRelationshipPropertiesEntity.get();
 	}
 
+	@Override
+	public boolean hasRelationshipPropertyPersistTypeInfoFlag() {
+		if (!isRelationshipPropertiesEntity()) {
+			return false;
+		}
+		return getRequiredAnnotation(RelationshipProperties.class).persistTypeInfo();
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see BasicPersistentEntity#getFallbackIsNewStrategy()

src/main/java/org/springframework/data/neo4j/core/mapping/Neo4jPersistentEntity.java

@@ -56,6 +56,13 @@ public interface Neo4jPersistentEntity<T>
 	 */
 	boolean isRelationshipPropertiesEntity();
 
+	/**
+	 * Determines if the entity is annotated with {@link org.springframework.data.neo4j.core.schema.RelationshipProperties}
+	 * and has the flag {@link org.springframework.data.neo4j.core.schema.RelationshipProperties#persistTypeInfo()} set to true.
+	 * @return true if this is a relationship properties class and the type info should be persisted, otherwise false.
+	 */
+	boolean hasRelationshipPropertyPersistTypeInfoFlag();
+
 	/**
 	 * @return True if the underlying domain classes uses {@code id()} to compute internally generated ids.
 	 */

src/main/java/org/springframework/data/neo4j/core/schema/RelationshipProperties.java

@@ -52,4 +52,12 @@
 @Inherited
 @API(status = API.Status.STABLE, since = "6.0")
 public @interface RelationshipProperties {
+	/**
+	 * Set to true will persist {@link org.springframework.data.neo4j.core.mapping.Constants#NAME_OF_RELATIONSHIP_TYPE} to {@link Class#getSimpleName()}
+	 * as a property in relationships. This property will be used to determine the type of the relationship
+	 * when mapping back to the domain model.
+	 *
+	 * @return whether to persist type information for the annotated class.
+	 */
+	boolean persistTypeInfo() default false;
 }

src/test/java/org/springframework/data/neo4j/integration/issues/IssuesIT.java

@@ -189,6 +189,13 @@
 import org.springframework.data.neo4j.integration.issues.gh2918.ConditionRepository;
 import org.springframework.data.neo4j.integration.issues.gh2963.MyModel;
 import org.springframework.data.neo4j.integration.issues.gh2963.MyRepository;
+import org.springframework.data.neo4j.integration.issues.gh2973.BaseNode;
+import org.springframework.data.neo4j.integration.issues.gh2973.BaseRelationship;
+import org.springframework.data.neo4j.integration.issues.gh2973.Gh2973Repository;
+import org.springframework.data.neo4j.integration.issues.gh2973.RelationshipA;
+import org.springframework.data.neo4j.integration.issues.gh2973.RelationshipB;
+import org.springframework.data.neo4j.integration.issues.gh2973.RelationshipC;
+import org.springframework.data.neo4j.integration.issues.gh2973.RelationshipD;
 import org.springframework.data.neo4j.integration.issues.qbe.A;
 import org.springframework.data.neo4j.integration.issues.qbe.ARepository;
 import org.springframework.data.neo4j.integration.issues.qbe.B;
@@ -1698,6 +1705,68 @@ void customQueriesShouldKeepWorkingWithoutSpecifyingTheRelDirectionInTheirQuerie
 		assertThat(rootModelFromDbCustom).map(MyModel::getMyNestedModel).isPresent();
 	}
 
+	@Tag("GH-2973")
+	@Test
+	void testTypeMapping(@Autowired Gh2973Repository gh2973Repository) {
+		var node = new BaseNode();
+		var nodeFail = new BaseNode();
+		RelationshipA a1 = new RelationshipA();
+		RelationshipA a2 = new RelationshipA();
+		RelationshipA a3 = new RelationshipA();
+		RelationshipB b1 = new RelationshipB();
+		RelationshipB b2 = new RelationshipB();
+		RelationshipC c1 = new RelationshipC();
+		RelationshipD d1 = new RelationshipD();
+
+		a1.setTargetNode(new BaseNode());
+		a1.setA("a1");
+		a2.setTargetNode(new BaseNode());
+		a2.setA("a2");
+		a3.setTargetNode(new BaseNode());
+		a3.setA("a3");
+
+		b1.setTargetNode(new BaseNode());
+		b1.setB("b1");
+		b2.setTargetNode(new BaseNode());
+		b2.setB("b2");
+
+		c1.setTargetNode(new BaseNode());
+		c1.setC("c1");
+
+		d1.setTargetNode(new BaseNode());
+		d1.setD("d1");
+
+		node.setRelationships(Map.of(
+				"a", List.of(
+						a1, a2, b2
+				),
+				"b", List.of(
+						b1, a3
+				)
+		));
+		nodeFail.setRelationships(Map.of(
+				"c", List.of(
+						c1, d1
+				)
+		));
+		var persistedNode = gh2973Repository.save(node);
+		var persistedNodeFail = gh2973Repository.save(nodeFail);
+
+		// with type info, the relationships are of the correct type
+		var loadedNode = gh2973Repository.findById(persistedNode.getId()).get();
+		List<BaseRelationship> relationshipsA = loadedNode.getRelationships().get("a");
+		List<BaseRelationship> relationshipsB = loadedNode.getRelationships().get("b");
+		assertThat(relationshipsA).hasExactlyElementsOfTypes(RelationshipA.class, RelationshipA.class, RelationshipB.class);
+		assertThat(relationshipsB).hasExactlyElementsOfTypes(RelationshipB.class, RelationshipA.class);
+
+		// without type info, the relationships are all same type and not the base class BaseRelationship
+		var loadedNodeFail = gh2973Repository.findById(persistedNodeFail.getId()).get();
+		List<BaseRelationship> relationshipsCFail = loadedNodeFail.getRelationships().get("c");
+		assertThat(relationshipsCFail.get(0)).isNotExactlyInstanceOf(BaseRelationship.class);
+		var type = relationshipsCFail.get(0).getClass();
+		assertThat(relationshipsCFail).hasExactlyElementsOfTypes(type, type);
+	}
+
 	@Configuration
 	@EnableTransactionManagement
 	@EnableNeo4jRepositories(namedQueriesLocation = "more-custom-queries.properties")
@@ -1855,4 +1924,6 @@ private static EntitiesAndProjections.GH2533Entity createData(GH2533Repository r
 
 		return repository.save(n1);
 	}
+
+
 }

src/test/java/org/springframework/data/neo4j/integration/issues/gh2973/BaseNode.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2011-2025 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.neo4j.integration.issues.gh2973;
+
+import org.springframework.data.neo4j.core.schema.GeneratedValue;
+import org.springframework.data.neo4j.core.schema.Id;
+import org.springframework.data.neo4j.core.schema.Node;
+import org.springframework.data.neo4j.core.schema.Relationship;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+
+
+/**
+ * @author yangyaofei
+ */
+@Node
+public class BaseNode {
+	@Id
+	@GeneratedValue
+	private UUID id;
+	@Relationship(direction = Relationship.Direction.OUTGOING)
+	private Map<String, List<BaseRelationship>> relationships = new HashMap<>();
+
+	public UUID getId() {
+		return id;
+	}
+
+	public void setId(UUID id) {
+		this.id = id;
+	}
+
+	public Map<String, List<BaseRelationship>> getRelationships() {
+		return relationships;
+	}
+
+	public void setRelationships(Map<String, List<BaseRelationship>> relationships) {
+		this.relationships = relationships;
+	}
+}

src/test/java/org/springframework/data/neo4j/integration/issues/gh2973/BaseRelationship.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2011-2025 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.neo4j.integration.issues.gh2973;
+
+import org.springframework.data.neo4j.core.schema.GeneratedValue;
+import org.springframework.data.neo4j.core.schema.RelationshipId;
+import org.springframework.data.neo4j.core.schema.RelationshipProperties;
+import org.springframework.data.neo4j.core.schema.TargetNode;
+
+/**
+ * @author yangyaofei
+ */
+@RelationshipProperties
+public abstract class BaseRelationship {
+	@RelationshipId
+	@GeneratedValue
+	private Long id;
+	@TargetNode
+	private BaseNode targetNode;
+
+	public Long getId() {
+		return id;
+	}
+
+	public void setId(Long id) {
+		this.id = id;
+	}
+
+	public BaseNode getTargetNode() {
+		return targetNode;
+	}
+
+	public void setTargetNode(BaseNode targetNode) {
+		this.targetNode = targetNode;
+	}
+}

src/test/java/org/springframework/data/neo4j/integration/issues/gh2973/Gh2973Repository.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2011-2025 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.neo4j.integration.issues.gh2973;
+
+import org.springframework.data.neo4j.repository.Neo4jRepository;
+
+import java.util.UUID;
+
+/**
+ * Test repository for GH-2973
+ *
+ * @author yangyaofei
+ */
+public interface Gh2973Repository extends Neo4jRepository<BaseNode, UUID> {
+}

src/test/java/org/springframework/data/neo4j/integration/issues/gh2973/RelationshipA.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2011-2025 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.neo4j.integration.issues.gh2973;
+
+import org.springframework.data.neo4j.core.schema.RelationshipProperties;
+
+/**
+ * @author yangyaofei
+ */
+@RelationshipProperties(persistTypeInfo = true)
+public class RelationshipA extends BaseRelationship {
+	String a;
+
+	public String getA() {
+		return a;
+	}
+
+	public void setA(String a) {
+		this.a = a;
+	}
+}

src/test/java/org/springframework/data/neo4j/integration/issues/gh2973/RelationshipB.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2011-2025 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.neo4j.integration.issues.gh2973;
+
+import org.springframework.data.neo4j.core.schema.RelationshipProperties;
+
+/**
+ * @author yangyaofei
+ */
+@RelationshipProperties(persistTypeInfo = true)
+public class RelationshipB extends BaseRelationship {
+	String b;
+
+	public String getB() {
+		return b;
+	}
+
+	public void setB(String b) {
+		this.b = b;
+	}
+}