Scala +如何从文件中替换Spark Dataframe列中的占位符？

import org.apache.spark.sql.SparkSession
import org.apache.spark.sql.functions.lit

object ReplaceColumnValues {
  def main(args: Array[String]): Unit = {
    val spark = SparkSession.builder()
      .appName("ReplaceColumnValues")
      .getOrCreate()

    // 读取文件内容
    val fileContent = scala.io.Source.fromFile("path/to/file.txt").mkString

    // 替换占位符
    val replacedContent = fileContent.replaceAll("<placeholder>", "replacement")

    // 将替换后的字符串转换为Dataframe列
    val replacedColumn = lit(replacedContent)

    // 读取原始Dataframe
    val originalDataframe = spark.read.format("csv").load("path/to/original.csv")

    // 添加替换后的列到Dataframe
    val newDataframe = originalDataframe.withColumn("replaced_column", replacedColumn)

    newDataframe.show()
  }
}