问case class 类中有Map怎么转json？

import scala.beans.BeanProperty
import com.alibaba.fastjson.JSON
import com.alibaba.fastjson.serializer.SerializerFeature
import scala.collection.mutable

case class EventLog(
@BeanProperty var guid: Long,
@BeanProperty var sessionId: String,
@BeanProperty var eventId: String,
@BeanProperty var timeStamp: Long,
@BeanProperty var eventInfo: Map[String, String] )

val events: List[String] = List("appLaunch","pageLoad","adShow","adClick","itemShare","itemCollect","putBack","wakeUp","appClose")
val eventInfoMap: mutable.HashMap[String, String] = new mutable.HashMap()

val eventLog = EventLog(
        RandomUtils.nextLong(1, 1000),
        RandomStringUtils.randomAlphabetic(12).toUpperCase(),
        events(RandomUtils.nextInt(0, events.length)),
        System.currentTimeMillis(),
        eventInfoMap.toMap
      )

val j = JSON.toJSONString(eventLog, SerializerFeature.QuoteFieldNames)

// {"eventId":"wakeUp","eventInfo":{"empty":false,"traversableAgain":true},"guid":100,"sessionId":"NGTPNWELLDYK","timeStamp":1661333145132}