如何将spark dataframe列名和行数据转换为json数据？

import org.apache.spark.sql.{DataFrame, Row}
import org.apache.spark.sql.functions._
import org.apache.spark.sql.types._

def rowToJson(row: Row): String = {
  val fieldNames = row.schema.fieldNames
  val values = row.toSeq
  val jsonPairs = fieldNames.zip(values).map { case (name, value) =>
    s""""$name": "$value""""
  }
  s"{${jsonPairs.mkString(", ")}}"
}

def dataframeToJson(df: DataFrame): String = {
  val rows = df.collect()
  val jsonRows = rows.map(rowToJson)
  s"[${jsonRows.mkString(", ")}]"
}

val json = dataframeToJson(df)