java - Java IO异常:从AudioInputStream写入文件时流关闭

Question

因此，我下面的代码片段( concat 方法)主要尝试做两件事:

将多个AudioInputStream(从源文件列表中读取)连接起来，成为一个最终的长流

将该流写入目标WAV文件

public static void concat(ArrayList<String> sourceFiles, String targetFile) {
    AudioInputStream targetBuilder = null;
    String file;
    AudioInputStream nextSource;
    for (int i = 0; i < sourceFiles.size(); i++)
    {
        file = sourceFiles.get(i);
        if(targetBuilder == null)
        {
            targetBuilder = AudioSystem.getAudioInputStream(new File(file));
            continue;
        }
        nextSource = AudioSystem.getAudioInputStream(new File(file));
        AudioInputStream appendedFiles = new AudioInputStream(
                new SequenceInputStream(targetBuilder, nextSource),     
                targetBuilder.getFormat(), 
                targetBuilder.getFrameLength() + nextSource.getFrameLength());
        targetBuilder = appendedFiles;
        nextSource.close();
    }
    AudioSystem.write(targetBuilder, AudioFileFormat.Type.WAVE, new File(targetFile));
    targetBuilder.close();
}

这个想法是从以下线程借来的: Join two WAV files from Java。现在的问题是连续执行了此代码段几次之后，最终它将在AudioSystem.write()行的“stream close”上引发IO Exception。堆栈跟踪如下所示:

java.io.IOException: Stream Closed
at java.io.FileInputStream.readBytes(Native Method)
at java.io.FileInputStream.read(FileInputStream.java:272)
at javax.sound.sampled.AudioInputStream.read(AudioInputStream.java:292)
at java.io.SequenceInputStream.read(SequenceInputStream.java:208)
at java.io.SequenceInputStream.read(SequenceInputStream.java:211)
at javax.sound.sampled.AudioInputStream.read(AudioInputStream.java:292)
at java.io.SequenceInputStream.read(SequenceInputStream.java:208)
at javax.sound.sampled.AudioInputStream.read(AudioInputStream.java:292)
......//with the exact same two lines repeating lots of times
at java.io.SequenceInputStream.read(SequenceInputStream.java:208)
at javax.sound.sampled.AudioInputStream.read(AudioInputStream.java:292)
at com.sun.media.sound.SunFileWriter$NoCloseInputStream.read(SunFileWriter.java:198)
at java.io.SequenceInputStream.read(SequenceInputStream.java:208)
at java.io.InputStream.read(InputStream.java:101)
at com.sun.media.sound.WaveFileWriter.writeWaveFile(WaveFileWriter.java:239)
at com.sun.media.sound.WaveFileWriter.write(WaveFileWriter.java:137)
at javax.sound.sampled.AudioSystem.write(AudioSystem.java:1354)
at com.mycompany.mypackage.AudioUtils.concat(AudioUtils.java:324)
......

因此在我看来，是程序仍然尝试从AudioInputStream读取更多字节到文件时，但有时流( targetBuilder )自身会关闭。这对我来说没有意义，因为我仅在AudioSystem.write()方法之后关闭了此流。

现在，如果我实际上在for循环中对此行发表评论:

//nextSource.close();

这个流关闭异常似乎消失了，取而代之的是“FilesNotFoundException:打开的文件太多”，这对我来说很有意义，因为在循环的每次迭代中，我都创建了一个新的AudioInputStream并将引用分配给nextSource，但是如果我从不关闭最终我用尽了打开的文件描述符。

但是，我不明白的是，关闭此 nextSource 流将如何以任何方式影响 targetBuilder 流的行为？如果我关闭 nextSource 流，为什么此流突然关闭？ (我假设两者之间存在联系，如果我错了，请纠正我)。

谢谢!

Answer 1

SequenceInputStream不会在内存中复制您的流，只是记住链接...这是read方法的代码

public int read() throws IOException
{
  int ch = -1;

  while (in != null && (ch = in.read()) < 0)
    {
      in.close();
      in = getNextStream();
    }

  return ch;
}

因此，如果您要关闭添加到SequenceInputStream的流之一，则会得到异常