DATAMONGO-1086 - Mapping fails for collection with two embbeded types that extend a generic abstract.

We now use the type information of the raw property type to check if we need to include _class.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/MappingMongoConverter.java

@@ -503,7 +503,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		Object existingValue = accessor.get(prop);
 		BasicDBObject propDbObj = existingValue instanceof BasicDBObject ? (BasicDBObject) existingValue
 				: new BasicDBObject();
-		addCustomTypeKeyIfNecessary(type, obj, propDbObj);
+		addCustomTypeKeyIfNecessary(ClassTypeInformation.from(prop.getRawType()), obj, propDbObj);
 
 		MongoPersistentEntity<?> entity = isSubtype(prop.getType(), obj.getClass()) ? mappingContext
 				.getPersistentEntity(obj.getClass()) : mappingContext.getPersistentEntity(type);
@@ -700,7 +700,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	/**
 	 * Adds custom type information to the given {@link DBObject} if necessary. That is if the value is not the same as
 	 * the one given. This is usually the case if you store a subtype of the actual declared type of the property.
-	 * 
+	 *
 	 * @param type
 	 * @param value must not be {@literal null}.
 	 * @param dbObject must not be {@literal null}.

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/MappingMongoConverterUnitTests.java

@@ -1945,6 +1945,31 @@ public class MappingMongoConverterUnitTests {
 		assertThat(withAnnotatedIdField.key, is("A"));
 	}
 
+	/**
+	 * @see DATAMONGO-1086
+	 */
+	@Test
+	public void shouldIncludeClassIdentifierForGenericAbstractTypesInCollections() {
+
+		ConcreteRoot root = new ConcreteRoot();
+		ConcreteSub sub = new ConcreteSub();
+		sub.abstractType = new Concrete();
+		sub.abstractType.content = "foo";
+		root.listOfGenericSub = Collections.singletonList(sub);
+
+		DBObject dbo = new BasicDBObject();
+		converter.write(root, dbo);
+
+		BasicDBList genericSubType = DBObjectTestUtils.getAsDBList(dbo, "listOfGenericSub");
+		assertThat((String) dbo.get("_class"), is(ConcreteRoot.class.getName()));
+
+		DBObject item0 = DBObjectTestUtils.getAsDBObject(genericSubType, 0);
+		assertThat(item0.get("_class"), nullValue());
+
+		DBObject abstractType = DBObjectTestUtils.getAsDBObject(item0, "abstractType");
+		assertThat((String) abstractType.get("_class"), is(Concrete.class.getName()));
+	}
+
 	static class GenericType<T> {
 		T content;
 	}
@@ -2232,4 +2257,28 @@ public class MappingMongoConverterUnitTests {
 
 		@Id String key;
 	}
+
+	static abstract class AbstractGenericRoot<T extends GenericSub<?>> {
+		List<T> listOfGenericSub;
+	}
+
+	static class ConcreteRoot extends AbstractGenericRoot<ConcreteSub> {
+
+	}
+
+	static abstract class GenericSub<T extends AbstractRoot> {
+		T abstractType;
+	}
+
+	static class ConcreteSub extends GenericSub<Concrete> {
+
+	}
+
+	static abstract class AbstractRoot {
+
+	}
+
+	static class Concrete extends AbstractRoot {
+		String content;
+	}
 }