Java Sound：在IntelliJ中运行时找到的设备，但在SBT中没有 [英] Java Sound: devices found when run in IntelliJ, but not in SBT

问题描述

我正在尝试在Scala SBT管理的项目中使用Java Sound API。

I'm trying to to use Java Sound API in a Scala SBT-managed project.

这是一个播放笔记的玩具应用程序。

Here is a toy app that plays a note.

import javax.sound.midi._

object MyMain extends App {
  val infos = MidiSystem.getMidiDeviceInfo()
  println( "[DEBUG] midi devices found: " + infos.length )

  val myMsg = new ShortMessage;
  // Start playing the note Middle C (60),
  // moderately loud (velocity = 93).
  myMsg.setMessage(ShortMessage.NOTE_ON, 0, 60, 93);
  val timeStamp = -1;
  val rcvr : Receiver = MidiSystem.getReceiver();
  rcvr.send(myMsg, timeStamp);

  readChar()  // give time to play note
}

当我在SBT中执行运行时，我得到 javax.sound.midi.MidiUnavailableException ，因为 infos.length 返回0.也就是说，当我在IntelliJ中运行应用程序时，找到了两个设备并且笔记播放得很好。

When I execute run in SBT, I get the javax.sound.midi.MidiUnavailableException because infos.length returns 0. That said, when I run the app in IntelliJ, two devices are found and the note plays just fine.

SBT需要知道什么才能让它运行？是否有需要添加到类路径的东西？我注意到IntelliJ将一大堆罐子附加到执行命令（但是，删除来自jdk / jre / lib /的罐子没有效果，而其他罐子与scala相关或与IntelliJ相关）。

What does SBT need to know to make it run? Is there something which needs to be added to the classpath? I noticed that IntelliJ attaches a whole bunch of jars to the execution command (however, removing those of the jars that come from jdk/jre/lib/ had no effect, while the others are scala related or IntelliJ related).

推荐答案

SBT在进程中运行你的应用程序，带有一些类加载器魔法，可能会阻止 MidiSystem 从查找（使用SPI）声音组件。

SBT runs your application in-process, with some classloader magic, which probably prevents MidiSystem from finding (using SPI) the sound components.

您可以尝试使用新的JVM来运行您的应用程序： fork in run：= true 。请参阅文档中的分叉。

You can try forking a new JVM to run your application: fork in run := true. See Forking in the documentation.

请注意：

• 默认情况下，它不会将输入重定向到应用程序。你可以添加：

• by default it does not redirect input to the application. You can add that with:

connectInput in run := true

分叉的JVM可以被任何外部工具杀死而没有问题（使用 kill 或任何类型的任务管理器）

the forked JVM can be killed by any external tool without problem (using kill or any kind of task manager)

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