最近在寫Spark導數程序的時候，為了實現程序的多元化，即使用同一套程序，實現不同場景的需求，而參考Spark的org.apache.spark.deploy.master.MasterArguments解析main()方法參數寫法

@tailrec
  def parameterMatching(args: List[String]): Unit={
    val argsList: List[String] = args.toList
    argsList match {
      case ("--inputPath" | "-i") :: value :: tail =>
        hdfsPath = value
        parameterMatching(tail)

      case ("--execSQL" | "-e") :: value :: tail =>
        execSQL = value
        parameterMatching(tail)

      case ("--outputSchema" | "-s") :: value :: tail =>
        outputSchema = value
        parameterMatching(tail)

      case ("--headLine" | "-h") :: value :: tail =>
        headLine = value
        parameterMatching(tail)

      case ("--writeMode" | "-m") :: value :: tail =>
        writeMode = value
        parameterMatching(tail)

      case ("--outputPath" | "-o") :: value :: tail =>
        outputPath = value
        parameterMatching(tail)

      case ("--numPartitions" | "-n") :: value :: tail =>
        numPartitions = value.toInt
        parameterMatching(tail)

      case ("--help") :: tail =>
        printUsageAndExit(0)

      case Nil => // No-op

      case _ =>
        printUsageAndExit(1)
    }
  }
  def printUsageAndExit(exitCode: Int): Unit ={
    System.err.println(
      "Usage: Hdfs2MppAbsolutePath [options]\n" +
        "\n" +
        "Options:\n" +
        "  -i hdfsPath, --inputPath hdfsPath              讀HDFS文件路徑 (必選。)\n" +
        "  -e execSQL, --execSQL execSQL     對讀數據執行的SQL (可選。default: select * from temp)\n" +
        "  -s outputSchema, --outputSchema outputSchema        寫數據的格式 (可選。default: csv)\n" +
        "  -h headLine, --headLine headLine           是否打印頭標題。(可選。default: true)\n" +
        "  -m writeMode, --writeMode writeMode     寫入數據模式。 (可選。default: append)\n" +
        "  -o outputPath, --outputPath outputPath     寫到本地路徑 (必選。)\n" +
        "  -n numPartitions, --numPartitions numPartitions     設置寫入本地的分區數 (可選。default 1)\n"
    )
    // scalastyle:on println
    System.exit(exitCode)
  }

屆時main()方法內部只要調用這個方法舊可以實現程序更具不同場景，做出不同的導出樣式。

def main(args: Array[String]): Unit = {
    val argsList: List[String] = args.toList
    println("\n 執行參數匹配：")
    parameterMatching(argsList)
}

如果有些參數不想傳，也可以使用默認值，這樣也不會影響該程序的正常使用

object Hdfs2LocalPath { 
    // 加載變量 
    private var hdfsPath: String = _  
    private var execSQL: String = "select * from temp"  
    private var outputSchema: String = "csv"  
    private var headLine: String = "true"  
    private var writeMode: String = "append"  
    private var outputPath: String = _  
    private var numPartitions: Int = 1

}