我尝试将我的网络应用程序从Play 2.0.4迁移到Play 2.1-RC2。
我的JSON数据包含未知密钥列表(key1
,key2
),如下所示:
{description: "Blah",
tags: [
key1: ["value1", "value2"],
key2: ["value3"]
]
}
我想将来自JSON的数据存储在元标记列表中。在Play 2.0.4中,我使用了类似这样的内容来阅读tags
- 列表:
def readMetatags(meta: JsObject): List[Metatag] =
meta.keys.toList.map(x => Metatag(x, (meta \ x).as[List[String]])
现在我想使用新的Play 2.1-JSON-API(原型):
import play.api.libs.json._
import play.api.libs.functional.syntax._
object Metatags {
implicit val metatagsRead: Read[Metatags] = (
(JsPath \ "description").read[String] and
(JsPath \ "tags").read[List[Metatag]]
)(Metatags.apply _, unlift(Metatags.unapply _))
implicit val metatagRead: Read[Metatag] = (
JsPath().key. ?? read[String] and // ?!? read key
JsPath().values. ?? read[List[String]] // ?!? read value list
)(Metatag.apply _, unlift(Metatag.unapply _))
}
case class Metatags(description: String, tags: List[Metatag])
case class Metatag(key: String, data: List[String])
如何从JSON中读取密钥?
答案 0 :(得分:5)
这是一个针对MetaTag
类的自定义阅读器的解决方案。阅读只是将JsValue
转换为JsObject
,其中包含有用的fieldSet
方法。
对于MetaTags
,宏启动工作正常
object Application extends Controller {
case class MetaTags(description: String, tags: List[MetaTag])
case class MetaTag(key: String, data: List[String])
implicit val readMetaTag = Reads(js =>
JsSuccess(js.as[JsObject].fieldSet.map(tag =>
MetaTag(tag._1, tag._2.as[List[String]])).toList))
implicit val readMetaTags = Json.reads[MetaTags]
def index = Action {
val json = Json.obj(
"description" -> "Hello world",
"tags" -> Map(
"key1" -> Seq("key1a", "key1b"),
"key2" -> Seq("key2a"),
"key3" -> Seq("Key3a", "key3b", "key3c")))
val meta = json.as[MetaTags]
Ok(meta.tags.map(_.data.mkString(",")).mkString("/"))
// key1a,key1b/key2a/Key3a,key3b,key3c
}
}