Scala:从 ProcessBuilder 获取 Scala Stream+Process 实例

Scala: Get Scala Stream+Process instance from ProcessBuilder

我有以下选择:

选项 #1:lineStream(log: ProcessLogger): Stream[String](以及 3 个类似选项)

选项 #2:run(log: ProcessLogger): Process(以及 4 个类似选项)

我怎样才能同时获得,Stream[String] + Process

如果那不可能,当我决定使用第一个选项(Stream[String] 但没有 Process 实例)时,我如何提前销毁系统进程?

Related API Docs Page (ProcessBuilder)

这是我不喜欢 Scala 中的过程 API 的原因之一——您通常可以选择其中之一,但不能同时选择两者。我认为 API 无法满足您的需求。如果您查看 ProcessBuilderImpl.lineStream() 实现,流程引用仅存储在本地并且无法访问它。

这是一个简单的示例,您可以根据 lineStream() 的实际编写方式(参见 ProcessBuilderImplBasicIO)自己实现此类功能。我没有时间完善它(比如 return 比元组更好的东西),但它应该给你一个想法。

  object StreamProcessLogger {
    private val nonzeroException = true // set it to whatever suits you

    def run(processBuilder: ProcessBuilder): (Process, Stream[String]) = {
      val logger = new StreamProcessLogger
      val process = processBuilder.run(logger)
      waitForExitInAnotherThread(process, logger)
      (process, logger.stream)
    }

    private def waitForExitInAnotherThread(process: Process, logger: StreamProcessLogger) = {
      val thread = new Thread() {
        override def run() = { logger.setExitCode(process.exitValue()) }
      }
      thread.start()
    }

  }

  private class StreamProcessLogger extends ProcessLogger {
    val queue = new LinkedBlockingQueue[Either[Int, String]]

    override def buffer[T](f: => T): T = f
    override def out(s: => String): Unit = queue.put(Right(s))
    override def err(s: => String): Unit = queue.put(Right(s))

    def stream = next()
    def setExitCode(exitCode: Int) = queue.put(Left(exitCode))

    private def next(): Stream[String] = queue.take match {
      case Left(0) => Stream.empty
      case Left(code) => if (StreamProcessLogger.nonzeroException) scala.sys.error("Nonzero exit code: " + code) else Stream.empty
      case Right(s) => Stream.cons(s, next())
    }
  }

这是用法:

test("returns stream and process") {
  val (process, stream) = StreamProcessLogger.run(Process("ls"))
  stream.foreach(println)
  println(process.exitValue())
}