How to play MIDI files using the Java Sound API (specify the MIDI device to use)

Introduction

This is a continuation of the previous article (https://qiita.com/absol_abcX/items/e9c230b808e522154ae5).

Overview

Implement the MIDI synthesizer selection function to be used in the previous MIDI file playback sample. Below is the actual execution screen.

[0] Gervill
[1] LoopBe Internal MIDI
[2] Microsoft MIDI Mapper
[3] CoolSoft MIDIMapper
[4] Microsoft GS Wavetable Synth
[5] VirtualMIDISynth #1
[6] LoopBe Internal MIDI
[7] Real Time Sequencer

Enter the number of the MIDI device to use>> 4
[Microsoft GS Wavetable Synth]Is open...

MIDI file path>> sample.mid
Playing...
Enter an appropriate character string to finish.
>>a
Stop

By the way, The 0th device called "Gervill" is a MIDI synthesizer provided by the Java library. By default, this device is specified.

The "Microsoft GS Wavetable Synth" used this time is a synthesizer that comes standard with Windows.

Sample code

SamplePlayer.java

import java.io.File;
import java.io.IOException;
import java.util.Scanner;

import javax.sound.midi.InvalidMidiDataException;
import javax.sound.midi.MidiDevice;
import javax.sound.midi.MidiSystem;
import javax.sound.midi.MidiUnavailableException;
import javax.sound.midi.Receiver;
import javax.sound.midi.Sequence;
import javax.sound.midi.Sequencer;

public class SamplePlayer {

    public static void main(String[] args) {
        //Hardware to play MIDI data/An instance of a software device.
        Sequencer sequencer = null;

        Scanner scanner = new Scanner(System.in);

        try {
            //Get a Sequencer instance.
            sequencer = MidiSystem.getSequencer(false);

            //Open the device and acquire resources.
            sequencer.open();

            //Get a list of available MIDI devices.
    		MidiDevice.Info[] infos = MidiSystem.getMidiDeviceInfo();
    		for (int i=0; i<infos.length; i++) {
    			String line = String.format("[%s] %s", i, infos[i].getName());
    			System.out.println(line);
    		}
    		System.out.println();

    		int index = 0;
    		while (true) {
    			//Get the index of the MIDI device to use from the console input.
	    		System.out.print("Enter the number of the MIDI device to use>> ");
	    		String str = scanner.next();

	    		try {
	    			index = Integer.parseInt(str);
	    		}
	    		catch (NumberFormatException nfe) {
	    			continue;
	    		}
	    		break;
	    	}

    		//Request a MIDI device with device information that represents the device of interest to the system.
    		MidiDevice device = MidiSystem.getMidiDevice(infos[index]);

    		System.out.println("[" + device.getDeviceInfo().getName() + "]Is open...");

    		//Open a MIDI device.
    		if (device.isOpen() == false) {
    			device.open();
    		}

    		//Connect the MIDI OUT of the sequencer to the MIDI IN of the MIDI device.
			Receiver receiver = device.getReceiver();
			sequencer.getTransmitter().setReceiver(receiver);
        }
        catch (MidiUnavailableException e) {
            e.printStackTrace();
        }
        System.out.println();

        //Get the MIDI file path from the console input.
        System.out.print("MIDI file path>> ");
        String path = scanner.next();

        try {
            //MIDI data from MIDI files(Sequence object)Get.
            File file = new File(path);
            Sequence sequence = MidiSystem.getSequence(file);

            //Set the acquired MIDI data in the sequencer.
            sequencer.setSequence(sequence);
        }
        catch (InvalidMidiDataException e) {
            e.printStackTrace();
        }
        catch (IOException e) {
            e.printStackTrace();
        }

        //Sequencer playback
        sequencer.start();
        System.out.println("Playing...");

        //Waiting for key input
        System.out.println("Enter an appropriate character string to finish.");
        System.out.print(">>");
        scanner.next();
        scanner.close();

        //Sequencer stop
        sequencer.stop();
        System.out.println("Stop");

        //Close the sequencer and release the resources you were using.
        sequencer.close();
    }
}

Commentary

Get a list of available device information

Gets an object array of all available MIDI device information.

//Get a list of available MIDI devices.
MidiDevice.Info[] infos = MidiSystem.getMidiDeviceInfo();

Get device object

You can get the corresponding device by calling getMidiDevice using the obtained device information object. You can operate it by calling open on the acquired device.

//Request a MIDI device with device information that represents the device of interest to the system.
MidiDevice device = MidiSystem.getMidiDevice(infos[index]);

//Open a MIDI device.
if (device.isOpen() == false) {
   device.open();
}

Connect the sequencer and device

There are two interfaces provided by the MIDI device class:

This time, connect the MIDI receiver port (Receiver) of the specified MIDI device to the MIDI transmit port (Transmitter) of the sequencer.

//Connect the MIDI OUT of the sequencer to the MIDI IN of the MIDI device.
Receiver receiver = device.getReceiver();
sequencer.getTransmitter().setReceiver(receiver);

Then, the configuration image will look like this.

This completes the device connection.