Using Runnable Interface in Applet program?

Question

Hi,

i am on developing Sound Recording applet.Here is the code

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.io.IOException;
import java.io.File;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.TargetDataLine;
import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.AudioFileFormat;

/*<applet code="PlaySoundApplet.class" height=400 width=400></applet> */
public class PlaySoundApplet extends Applet implements ActionListener,Runnable
{
    private volatile Thread PlaySound = null;
     TargetDataLine  m_line;
     AudioFileFormat.Type m_targetType;
     AudioInputStream m_audioInputStream;
     File   m_outputFile; 
    Button play,stop,Record;
    AudioClip audioClip;
    PlaySoundApplet recorder;
     Runnable r;

    public PlaySoundApplet(TargetDataLine line,AudioFileFormat.Type targetType,File file)
    {
     m_line=line;
     m_targetType = targetType;
     m_outputFile = file;
     m_audioInputStream = new AudioInputStream(line);
    }
    public PlaySoundApplet()
    {

    }


  public void init()
  {
    recorder = null;
    play = new Button("  Play in Loop  ");
    add(play);
    play.addActionListener(this);
    stop = new Button("  Stop  ");
    add(stop);
    stop.addActionListener(this);
    Record = new Button("Record");
    add(Record);
    Record.addActionListener(this);
    audioClip = getAudioClip(getCodeBase(), "sample.wav");
  }

  public void actionPerformed(ActionEvent ae)
  {
    Button source = (Button)ae.getSource();
    if (source.getLabel() == "  Play in Loop  ")
    {
      audioClip.play();
    }
    else if(source.getLabel() == "  Stop  ")
    {
      audioClip.stop();
    }
    else if(source.getLabel() == "Record")
    {
        System.out.println("debug 1");
        String strFilename = "D:\\krishna\\sample.wav";
     File outputFile = new File(strFilename);
     System.out.println("debug 2");
     AudioFormat audioFormat = new AudioFormat(AudioFormat.Encoding.PCM_SIGNED,44100.0F, 16, 2, 4, 44100.0F, false);
     DataLine.Info info = new DataLine.Info(TargetDataLine.class, audioFormat);
     TargetDataLine targetDataLine = null;
     try
     {
      targetDataLine = (TargetDataLine) AudioSystem.getLine(info);
      targetDataLine.open(audioFormat);
     }
     catch (LineUnavailableException e)
     {
      System.out.println("unable to get a recording line");
      e.printStackTrace();
      System.exit(1);
     }
     AudioFileFormat.Type targetType = AudioFileFormat.Type.WAVE;
     System.out.println("debug 3");
     PlaySoundApplet another = new PlaySoundApplet(targetDataLine,targetType,outputFile);
     new Thread(another).start();
      }
  }
  public void run()
  {
    try
       {
       System.out.println("debug 5");
      AudioSystem.write(m_audioInputStream,m_targetType,m_outputFile);
      }
       catch(Exception e)
       {
        System.out.println(e.getMessage());
       }
    }
  }

this program works fine for play back. But while recording it should simultaneously write into the sample.wav file. where am i doing wrong?

thanks

krishna

Answer 1

Trying to write to a file from an applet - it's sandboxed.

Answer 2

You need to wrap the file code in a privileged block of code, By default your in a sandbox to get file i.o. permissions you need to invoke the call through the accesscontroller.

Here is an example.

 final String location = "D:\\krishna\\sample.wav"
 File f = (File) AccessController.doPrivileged(new PrivilegedAction()
 {
  public Object run()
  {
   File outputFile = new File(location);
   return outputFile;
  }
 });