GH-2201 - Add test and documentation.

Add another test to verify multi-interface support.
Mention in the documentation not to use interfaces with repositories.

Author: meistermeier

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

@@ -125,6 +125,9 @@ The data structure needed is shown in the following test. The same would be writ
 include::../../../../src/test/java/org/springframework/data/neo4j/integration/imperative/InheritanceMappingIT.java[tag=interface3]
 ----
 
+NOTE: Interfaces cannot define an identifier field.
+As a consequence they are not a valid entity type for repositories.
+
 [[mapping.annotations.node.dynamic.labels]]
 ==== Dynamic or "runtime" managed labels
 

src/test/java/org/springframework/data/neo4j/integration/imperative/InheritanceMappingIT.java

@@ -18,8 +18,10 @@
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.neo4j.driver.Driver;
+import org.neo4j.driver.Record;
 import org.neo4j.driver.Session;
 import org.neo4j.driver.Transaction;
+import org.neo4j.driver.types.Node;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -303,6 +305,25 @@ void mixedImplementationsWrite(@Autowired Neo4jTemplate template) {
 		});
 	}
 
+	@Test // GH-2201
+	void mixedInterfaces(@Autowired Neo4jTemplate template) {
+
+		Inheritance.Mix1AndMix2 mix1AndMix2 = new Inheritance.Mix1AndMix2("a", "b");
+
+		mix1AndMix2 = template.save(mix1AndMix2);
+
+		assertThat(mix1AndMix2.getName()).isEqualTo("a");
+		assertThat(mix1AndMix2.getValue()).isEqualTo("b");
+
+		try (Session session = driver.session()) {
+			List<Record> records = session.run("MATCH (n) RETURN n").list();
+			assertThat(records).hasSize(1);
+			Record record = records.get(0);
+			Node node = record.get("n").asNode();
+			assertThat(node.labels()).containsExactlyInAnyOrder("Mix1", "Mix2", "Mix1AndMix2");
+		}
+	}
+
 	interface PetsRepository extends Neo4jRepository<AbstractPet, Long> {
 
 		@Query("MATCH (n {name: $name}) RETURN n")

src/test/java/org/springframework/data/neo4j/integration/shared/common/Inheritance.java

@@ -279,6 +279,50 @@ public void setRelated2(SomeInterface3 related2) {
 	}
 	// end::interface3[]
 
+	/**
+	 * Interface to get implemented with the one below.
+	 */
+	@Node("Mix1")
+	public interface MixIt1 {
+		String getName();
+	}
+
+	/**
+	 * Interface to get implemented with one above.
+	 */
+	@Node("Mix2")
+	public interface MixIt2 {
+		String getValue();
+	}
+
+	/**
+	 * Implements two interfaces
+	 */
+	@Node
+	public static class Mix1AndMix2 implements MixIt1, MixIt2 {
+
+		@Id
+		@GeneratedValue
+		private Long id;
+
+		private final String name;
+		private final String value;
+
+		public Mix1AndMix2(String name, String value) {
+			this.name = name;
+			this.value = value;
+		}
+
+		@Override
+		public String getName() {
+			return name;
+		}
+
+		@Override
+		public String getValue() {
+			return value;
+		}
+	}
 	/**
 	 * super base class
 	 */