GeolocationManager.java

public class GeolocationManager {
    private final DatabaseProvider provider;
    public GeolocationManager(LobbyBalancer plugin) throws Exception {
        File dir = new File(plugin.getDataFolder(), "data");
        if (!dir.exists()) {
            dir.mkdir();
        }

        File reader = new File(dir, "geoip2-2.8.0");
        if (!reader.exists()) {
            plugin.getLogger().info("Downloading reader...");
            File packed = new File(dir, "geoip2-2.8.0.zip");
            URL url = new URL("https://github.com/maxmind/GeoIP2-java/releases/download/v2.8.0/geoip2-2.8.0-with-dependencies.zip?raw=true");
            try (ReadableByteChannel rbc = Channels.newChannel(url.openStream())) {
                try (FileOutputStream fos = new FileOutputStream(packed)) {
                    fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
                }
            }

            plugin.getLogger().info("Unpacking reader...");
            ZipFile zipFile = new ZipFile(packed);
            zipFile.extractAll(dir.getAbsolutePath());

            plugin.getLogger().info("Deleting packed archive, success: " + (packed.delete() ? "yes" : "no"));
        }

        plugin.getLogger().info("Loading libraries...");
        if (reader.exists()) {
            File libs = new File(reader, "lib");
            if (libs.exists()) {
                for (File file : libs.listFiles()) {
                    URL url = file.toURI().toURL();
                    URLClassLoader classLoader = (URLClassLoader) ClassLoader.getSystemClassLoader();
                    Method method = URLClassLoader.class.getDeclaredMethod("addURL", URL.class);
                    method.setAccessible(true);
                    method.invoke(classLoader, url);
                }
            }
        }

        File database = new File(dir, "GeoLite2-Country.mmdb");
        if (!database.exists()) {
            plugin.getLogger().info("Downloading database...");
            File packed = new File(dir, "GeoLite2-Country.mmdb.gz");
            URL url = new URL("http://geolite.maxmind.com/download/geoip/database/GeoLite2-Country.mmdb.gz");
            try (ReadableByteChannel rbc = Channels.newChannel(url.openStream())) {
                try (FileOutputStream fos = new FileOutputStream(packed)) {
                    fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
                }
            }

            plugin.getLogger().info("Unpacking database...");
            byte[] buffer = new byte[1024];
            try (GZIPInputStream in = new GZIPInputStream(new FileInputStream(packed))) {
                try (FileOutputStream out = new FileOutputStream(database)) {
                    int len;
                    while ((len = in.read(buffer)) > 0) {
                        out.write(buffer, 0, len);
                    }
                }
            }

            plugin.getLogger().info("Deleting packed archive, success: " + (packed.delete() ? "yes" : "no"));
        } else {
            plugin.getLogger().info("Database exists, no need to download again");
        }

        plugin.getLogger().info("Initializing database...");
        provider = new DatabaseProvider(database);
    }

    public static class DatabaseProvider {
        private final DatabaseReader reader;

        public DatabaseProvider(File file) throws Exception {
            reader = new DatabaseReader.Builder(file).withCache(new CHMCache()).build();
        }

        public DatabaseReader getReader() {
            return reader;
        }
    }

    public DatabaseProvider getProvider() {
        return provider;
    }
}