scala怎么用 json4s判断key是否存在

最近碰到一个场景，需要在Scala里面判断json里面是否存在某个key。如果用fastjson，判断key是否存在很简单，直接containsKey即可。但是项目用的是json4s这个库，用法稍微有些不同，特此记录一下。代码如下：

package dev.json

import org.json4s.DefaultFormats
import org.json4s.JsonDSL._
import org.json4s.jackson.JsonMethods._

object Course2 {

  implicit val formats = DefaultFormats
  val key = "key-to-remove"
  val s =
    """
      |{"@type":{"version":"1.0.2","name":"application-content","data":[]},"key-to-remove":[{"blah":"more blah"}],"@value":[]}
      |""".stripMargin
  val obj = parse(s)

  def main(args: Array[String]): Unit = {
    containsKey()
  }

  def containsKey(): Unit = {
    if (null != obj) {
      val key2 = "random key"
      println(s"key:[$key] exists" , !obj.findField(_._1.equals(key)).isEmpty)
      println(s"key:[$key2] exists", !obj.findField(_._1.equals(key2)).isEmpty)
    }
  }

  def deleteKey(): Unit = {
    if (null != obj) {
      val obj2 = obj.removeField(_._1.equals(key))
      val out = compact(render(obj2))
      println(out)
    }
  }
}