Write mp3 file to disk while playing in Java

Question

I have an application playing remote MP3 files over HTTP using the JLayer/BasicPlayer libraries. I want to save the played mp3 files to disk without re-downloading them.

This is the code using the JLayer based BasicPlayer for Playing the MP3 file.

String mp3Url = "http://ia600402.us.archive.org/6/items/Stockfinster.-DeadLinesutemos025/01_Push_Push.mp3";
URL url = new URL(mp3Url);
URLConnection conn = url.openConnection();
InputStream is = conn.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);

BasicPlayer player = new BasicPlayer();
player.open(bis);
player.play();

How would I save the mp3 file to disk?

Answer 1

To avoid having to go through the bytes twice, you need to wrap the input stream from the connection in a filter that writes any data that is read to an output stream, i.e. a kind of a "tee pipe input stream." Such a class is not that difficult to write yourself, but you can save the work by using TeeInputStream from the Apache Commons IO library.

Apache Commons IO: http://commons.apache.org/io/
TeeInputStream javadoc: http://commons.apache.org/io/apidocs/org/apache/commons/io/input/TeeInputStream.html

Edit: Proof-of-concept:

import java.io.*;

public class TeeInputStream extends InputStream {
    private InputStream in;
    private OutputStream out;

    public TeeInputStream(InputStream in, OutputStream branch) {
        this.in=in;
        this.out=branch;
    }
    public int read() throws IOException {
        int read = in.read();
        if (read != -1) out.write(read);
        return read;
    }
    public void close() throws IOException {
        in.close();
        out.close();
    }
}

How to use it:

...
BufferedInputStream bis = new BufferedInputStream(is);
TeeInputStream tis = new TeeInputStream(bis,new FileOutputStream("test.mp3"));

BasicPlayer player = new BasicPlayer();
player.open(tis);
player.play();