Scala自定义传参

最近在写Spark导数程序的时候，为了实现程序的多元化，即使用同一套程序，实现不同场景的需求，而参考Spark的org.apache.spark.deploy.master.MasterArguments解析main()方法参数写法

@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              读HDFS文件路径 (必选。)\n" +
        "  -e execSQL, --execSQL execSQL     对读数据执行的SQL (可选。default: select * from temp)\n" +
        "  -s outputSchema, --outputSchema outputSchema        写数据的格式 (可选。default: csv)\n" +
        "  -h headLine, --headLine headLine           是否打印头标题。(可选。default: true)\n" +
        "  -m writeMode, --writeMode writeMode     写入数据模式。 (可选。default: append)\n" +
        "  -o outputPath, --outputPath outputPath     写到本地路径 (必选。)\n" +
        "  -n numPartitions, --numPartitions numPartitions     设置写入本地的分区数 (可选。default 1)\n"
    )
    // scalastyle:on println
    System.exit(exitCode)
  }

届时main()方法内部只要调用这个方法旧可以实现程序更具不同场景，做出不同的导出样式。

def main(args: Array[String]): Unit = {
    val argsList: List[String] = args.toList
    println("\n 执行参数匹配：")
    parameterMatching(argsList)
}

如果有些参数不想传，也可以使用默认值，这样也不会影响该程序的正常使用

object Hdfs2LocalPath { 
    // 加载变量 
    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

}