Scala Morphia中的错误映射字段

当我试图用Morphia中的save方法保存活动实例时。映射字段异常时出错。我怎样才能修好它

Error mapping field:Campaign.adgroups

@Entity(value = "campaign", noClassnameStored = true)
class Campaign {
  @Id
  var id = new ObjectId
  var name = ""
  var uid = new ObjectId
  var adgroups = new ListBuffer[AdGroup]
  var created_at = ""
  var comment = ""
}

@Entity(value = "ad", noClassnameStored = true)
class Ad{
  @Id
  var id = new ObjectId
  var name = ""
  var uid = new ObjectId
  var ads = new ListBuffer[Ad]
  var created_at = ""
  var comment = ""
}

---

Morphia不知道Scala的ListBuffer是什么。您需要为该类型提供一个转换器。完成后，你就这样告诉morphia：

morphia.getMapper().getConverters().addConverter(ListBufferConverter.class);

---

谢谢，如何编写ListBufferConverter？邮件列表中有一个示例。我对Scala/ListBuffer不太了解，无法给出一个粗略的例子。不过，转换器API非常简单。