ネットワークが切断されたことをアラームで知らせるツール.java

NetworkAvailableChecker.java

import java.awt.AWTException;
import java.awt.Image;
import java.awt.MenuItem;
import java.awt.PopupMenu;
import java.awt.SystemTray;
import java.awt.TrayIcon;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Arrays;
import java.util.Date;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.Clip;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.UnsupportedAudioFileException;
import javax.swing.ImageIcon;
import javax.swing.JOptionPane;
import javax.swing.SwingUtilities;

public final class NetworkAvailableChecker {

    static final String title = "ネットワーク死活監視";
    static final String urlString = "..."; // TODO ファイルのURLを設定
    static final byte[] expectedFileContent = "argius".getBytes(); // TODO ファイルの内容を設定
    static final int expectedFileLength = expectedFileContent.length;

    final AtomicBoolean suspend = new AtomicBoolean(false);

    NetworkAvailableChecker() {
        if (!SystemTray.isSupported()) {
            throw new UnsupportedOperationException("プラットフォームがシステムトレイに対応していません");
        }
        SystemTray tray = SystemTray.getSystemTray();
        Image image1 = new ImageIcon(getClass().getResource("icon.png")).getImage();
        Image image2 = new ImageIcon(getClass().getResource("icon2.png")).getImage();
        TrayIcon icon = new TrayIcon(image1, title);
        icon.setPopupMenu(buildPopupMenu(icon, image1, image2));
        try {
            tray.add(icon);
        } catch (AWTException e) {
            throw new IllegalStateException("タスクトレイにアイコンが追加できませんでした", e);
        }
    }

    PopupMenu buildPopupMenu(final TrayIcon icon, Image image1, Image image2) {
        PopupMenu popup = new PopupMenu();
        final MenuItem suspendItem = new MenuItem("保留");
        suspendItem.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String oldLabel = suspendItem.getLabel();
                boolean state = suspend.get();
                String newLabel = state
                    ? "保留"
                    : "再開";
                String tooltip = state
                    ? title
                    : title + "[保留]";
                Image image = state
                    ? image1
                    : image2;
                suspend.compareAndSet(state, !state);
                suspendItem.setLabel(newLabel);
                icon.setToolTip(tooltip);
                icon.setImage(image);
                System.out.printf("%s: [%s]が実行された%n", new Date(), oldLabel);
            }
        });
        MenuItem exitItem = new MenuItem("終了");
        exitItem.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.printf("%s: 終了が実行された%n", new Date());
                exitApp();
            }
        });
        popup.add(suspendItem);
        popup.add(exitItem);
        return popup;
    }

    void exitApp() {
        System.exit(0);
    }

    void runChecker() {
        /*
         * このメソッドはイベントディスパッチスレッドで実行しないこと
         */

        // システムプロパティーを読み込む
        final int intervalSeconds = Integer.getInteger("NetworkAvailableChecker.interval", 15);
        System.out.println("intervalSeconds: " + intervalSeconds);
        Runnable task = new Runnable() {
            @Override
            public void run() {
                if (suspend.get()) {
                    return; // 保留中なら何もしないで抜ける
                }
                try {
                    boolean ok = tryToAccessInternetFile();
                    System.out.printf("%s: check = %s%n", new Date(), ok);
                    if (!ok) {
                        soundAlarm();
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                    exitApp();
                }
            }
        };
        ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
        ScheduledFuture<?> future = scheduler.scheduleAtFixedRate(task, 0, intervalSeconds, TimeUnit.SECONDS);
        try {
            future.get();
        } catch (InterruptedException | ExecutionException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * インターネット上の所定のファイルにアクセスを試みる。
     * @return 正常にアクセスできた場合は <code>true</code>、そうでなければ <code>false</code>
     */
    static boolean tryToAccessInternetFile() {
        try {
            URL url = new URL(urlString); // throws MalformedURLException
            HttpURLConnection conn = (HttpURLConnection)url.openConnection();
            int status = conn.getResponseCode();
            if (status == 200) {
                try (InputStream is = conn.getInputStream()) {
                    byte[] bytes = new byte[expectedFileLength];
                    if (is.read(bytes) == expectedFileLength && Arrays.equals(bytes, expectedFileContent)) {
                        return true; // 正常
                    }
                    else {
                        // 異常(想定外)
                        System.err.println("file content mismatch");
                    }
                }
            }
            else {
                // 異常(想定外)
                System.err.println("unexpected response status: " + status);
            }
        } catch (IOException e) {
            // 異常(おそらくネットワーク切断)
            e.printStackTrace();
        }
        return false;
    }

    /**
     * アラームを鳴らす。
     * @throws Exception 例外
     */
    static void soundAlarm() throws Exception {
        File file = new File("./alarm.wav");
        AudioInputStream ais;
        try {
            ais = AudioSystem.getAudioInputStream(file);
        } catch (UnsupportedAudioFileException e) {
            throw e;
        } catch (IOException e) {
            throw e;
        }
        AudioFormat format = ais.getFormat();
        DataLine.Info info = new DataLine.Info(Clip.class, format);
        try (Clip line = (Clip)AudioSystem.getLine(info)) {
            line.open(ais);
            ais.close();
            line.start();
            while (!line.isRunning()) {
                Thread.sleep(100L); // throws InterruptedException
            }
            while (line.isRunning()) {
                Thread.sleep(100L); // throws InterruptedException
            }
            line.drain();
        } catch (LineUnavailableException e) {
            throw e;
        } catch (IOException e) {
            throw e;
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                try {
                    final NetworkAvailableChecker o = new NetworkAvailableChecker();
                    Executors.newSingleThreadExecutor().execute(new Runnable() {
                        @Override
                        public void run() {
                            o.runChecker();
                        }
                    });
                } catch (Exception e) {
                    e.printStackTrace();
                    JOptionPane.showMessageDialog(null, e.getMessage());
                }
            }
        });
    }

}