当结果文档缺少一个字段时，Elastic4s搜索案例类示例会出错

Question

我一直在使用Elastic4s手册中的这个例子。直到它试图检索没有在case类中指定字段的文档时，它才正常工作。

在本手册的示例中，假设一个结果只有name，并且缺少location字段。它将产生如下错误:

java.util。NoSuchElementException: key not found: location

我正在寻找一个好的方法来处理有不同字段的搜索结果。

代码示例:

case class Character(name: String, location: String)
implicit object CharacterHitAs extends HitAs[Character] {
  override def as(hit: RichSearchHit): Character = {
Character(hit.sourceAsMap("name").toString, hit.sourceAsMap("location").toString) }}
val resp = client.execute {
search in "gameofthrones" / "characters" query "kings landing"
}.await
val characters :Seq[Character] = resp.as[Character]

Answer 1

当开发具有可选参数的case class时，使用Option:

case class Character(name: String, location: Option[String])
Character("Tyrion Lannister", None)

然后你所要做的就是修改你的数据提取器传递一个None选项，如果它没有找到数据:

val tyrion = Map("location" -> "King's Landing", "name" -> "Cersei Lannister")
val cersei = Map("father" -> "Tywin Lannister?", "name" -> "Cersei Lannister")
val jaime = Map("father" -> "Tywin Lannister", "location" -> "Tower of the Hand")
val characters = List(tyrion, cersei, jaime)
case class Character(name: String, location: Option[String])
characters.map(x => Character(x.getOrElse("name", "A CHARACTER HAS NO NAME"), x.get("location")))

characters.map(...)的结果是:

res0: List[Character] = List(
        Character(Cersei Lannister,Some(King's Landing)), 
        Character(Cersei Lannister,None), 
        Character(A CHARACTER HAS NO NAME NAME,Some(Tower of the Hand)))

从RichSearchHit的源代码来看，sourceAsMap应该返回Map对象:

def sourceAsMap: Map[String, AnyRef] = if (java.sourceAsMap == null) Map.empty else java.sourceAsMap.asScala.toMap

如果您使用的是Map简写，您应该能够将代码转换为:

case class Character(name: String, location: Option[String])
implicit object CharacterHitAs extends HitAs[Character] {
  override def as(hit: RichSearchHit): Character = {
Character(hit.sourceAsMap.getOrElse("name", "A CHARACTER HAS NO NAME"), hit.sourceAsMap.get("location")) }}