播放 [Scala]:如何展平 JSON 对象 [英] Play [Scala]: How to flatten a JSON object

问题描述

给定以下 JSON...

Given the following JSON...

{
  "metadata": {
    "id": "1234",
    "type": "file",
    "length": 395
  }
}

...我如何将其转换为

... how do I convert it to

{
  "metadata.id": "1234",
  "metadata.type": "file",
  "metadata.length": 395
}

发送.

推荐答案

这绝对不是微不足道的，但可以通过尝试递归地将其展平.我还没有彻底测试过，但它适用于您的示例以及我使用数组提出的其他一些基本示例:

This is definitely not trivial, but possible by trying to flatten it recursively. I haven't tested this thoroughly, but it works with your example and some other basic one's I've come up with using arrays:

object JsFlattener {

    def apply(js: JsValue): JsValue = flatten(js).foldLeft(JsObject(Nil))(_++_.as[JsObject])

    def flatten(js: JsValue, prefix: String = ""): Seq[JsValue] = {
        js.as[JsObject].fieldSet.toSeq.flatMap{ case (key, values) =>
            values match {
                case JsBoolean(x) => Seq(Json.obj(concat(prefix, key) -> x))
                case JsNumber(x) => Seq(Json.obj(concat(prefix, key) -> x))
                case JsString(x) => Seq(Json.obj(concat(prefix, key) -> x))
                case JsArray(seq) => seq.zipWithIndex.flatMap{ case (x, i) => flatten(x, concat(prefix, key + s"[$i]")) }  
                case x: JsObject => flatten(x, concat(prefix, key))
                case _ => Seq(Json.obj(concat(prefix, key) -> JsNull))
            }
        }
    }

    def concat(prefix: String, key: String): String = if(prefix.nonEmpty) s"$prefix.$key" else key

}

JsObject 有 fieldSet 方法，它返回一个 Set[(String, JsValue)]，我映射了它，与 JsValue 子类，并从那里继续递归消费.

JsObject has the fieldSet method that returns a Set[(String, JsValue)], which I mapped, matched against the JsValue subclass, and continued consuming recursively from there.

您可以通过将 JsValue 传递给 apply 来使用此示例:

You can use this example by passing a JsValue to apply:

val json = Json.parse("""
    {
      "metadata": {
        "id": "1234",
        "type": "file",
        "length": 395
      }
    }
"""
JsFlattener(json)

我们将把它留给读者作为练习，以使代码看起来更漂亮.

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