如何获取嵌套结构中字符串类型的spark中的所有列名

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

val spark = SparkSession.builder()
  .appName("Nested Structure Column Names")
  .getOrCreate()

val data = Seq(
  ("John", 25, Map("city" -> "New York", "country" -> "USA")),
  ("Alice", 30, Map("city" -> "London", "country" -> "UK"))
)

val df = spark.createDataFrame(data).toDF("name", "age", "address")

def getNestedColumnNames(df: DataFrame, parent: String = ""): Array[String] = {
  df.schema.fields.flatMap { field =>
    val columnName = if (parent.isEmpty) field.name else s"$parent.${field.name}"
    field.dataType match {
      case structType: org.apache.spark.sql.types.StructType =>
        getNestedColumnNames(df.select(columnName), columnName)
      case _ =>
        if (field.dataType.typeName == "string") Array(columnName) else Array.empty[String]
    }
  }
}

val stringColumns = getNestedColumnNames(df)

stringColumns.foreach(println)