在.jar导出中使用.mid文件

Question

I'm working on a text-based RPG with some friends using Netbeans. It works all fine and dandy in Netbeans but when I export it to a .jar file I get this error.

Jan 28, 2019 2:27:15 PM Operator.DragonsHead startActionPerformed SEVERE: null java.io.FileNotFoundException: File "src\\Operator\\files\\Opening.mid" does not exist!

This happens when the game starts, as we have a "theme" that plays at boot up. The song plays on Netbeans but not when exported.

I'm relatively new to Java programming, I took a course on it last year.

I've tried looking around the web for people having the same issue, but I can't quite get it to duplicate with my code.

Here's the midi class:

import javax.sound.midi.*;
import java.io.File;
import java.io.IOException;
import java.io.FileNotFoundException;

public class MIDI {

private File file = null;
private Sequencer sequencer = null;

public MIDI (String midiFile) throws FileNotFoundException {
    this.file = new File(midiFile);
    if (!file.isFile()) {
        throw new FileNotFoundException("File \"" + midiFile + "\" does not exist!");
    }
            try{
        sequencer = MidiSystem.getSequencer();
        if (sequencer == null){
            System.err.println("Error: Sequencer not supported");
            return;
        }
        sequencer.open();
        Sequence sequence = MidiSystem.getSequence(file);
        sequencer.setSequence(sequence);
    }
    catch (MidiUnavailableException | InvalidMidiDataException | IOException ex){
    }
}

public void play(){
        sequencer.start();
}

public void stop() {
    sequencer.stop();
}

public void waitAndStop(int millis) {
    Runnable song = () -> {
        try {
            Thread.sleep(millis);
        }
        catch (InterruptedException e) {
            System.err.println("MIDI playback interrupted");
        }
        stop();
    };
    Thread t = new Thread(song);
    t.start();
}

public long songLengthMicroseconds() {
    return sequencer.getMicrosecondLength();
}
public Sequence getSequence(String resource) {
    try {
        return MidiSystem.getSequence(new File(resource));
    }
    catch (InvalidMidiDataException | IOException ex) {
        return null;
    }
}

}

Here's the lines that initialize it and call the song to play:

    MIDI midiTest;
    midiTest = new MIDI("src\\Operator\\files\\Opening.mid");
    midiTest.play();

Answer 1

I'm not sure what the API is of 'MIDI', but unless you want to go through the rigamarole of writing an installer, you cannot use direct file access for resources like icons, pictures, music, and datafiles.

Instead, use the getResource/getResourceAsStream mechanism, which returns URLs/InputStreams. Well written libraries take these just as well as files.

Basic format:

try (InputStream resource = MyClassName.class.getResourceAsStream("Opening.mid")) {
    // do something with resource here.
}

where Opening.mid is in the exact same place that MyClassName.class is (so, if you are shipping as a jar, it's in the jar, in the same folder structure as myClassName.class. If you prefer to have a root dir 'music' in your jar, you can pass for example: /music/Opening.mid , with the leading slash to indicate you're going off of the jar root.

secondary observation, if you don't know what to do with an exception, best solution is to add the exception(s) you cannot handle to your method's 'throws' line. If that is somehow not possible, the proper body for a catch block is:

throw new RuntimeException("unhandled checked exception", e);

because right now if an error occurs, your code will silently just keep going. If that was your intent (because, hey, music is optional I guess), I'd still log it SOMEWHERE , right now if an error occurs, you just won't know about it.