protected List<String> loadDataStoreNameList() {
        final Set<String> nameSet = new HashSet<>();
        final File[] jarFiles = ResourceUtil.getPluginJarFiles(PluginHelper.ArtifactType.DATA_STORE.getId());
        for (final File jarFile : jarFiles) {
            try (FileSystem fs = FileSystems.newFileSystem(jarFile.toPath(), ClassLoader.getSystemClassLoader())) {
                final Path xmlPath = fs.getPath("fess_ds++.xml");

                if (form.jarFile == null) {
                    throwValidationError(messages -> messages.addErrorsPluginFileIsNotFound(GLOBAL, form.id), this::asListHtml);
                }
                if (!form.jarFile.getFileName().endsWith(".jar")) {
                    throwValidationError(messages -> messages.addErrorsFileIsNotSupported(GLOBAL, form.jarFile.getFileName()),
                            this::asListHtml);

        for (final WebResource possibleJar : possibleJars) {
            if (possibleJar.isFile() && possibleJar.getName().endsWith(".jar")) {
                try (final JarFile jarFile = new JarFile(possibleJar.getCanonicalPath())) {
                    final Manifest manifest = jarFile.getManifest();
                    if (manifest != null && manifest.getEntries() != null) {
                        final Attributes attributes = manifest.getMainAttributes();

import org.lastaflute.web.validation.Required;

public class InstallForm {

    @Required
    @Size(max = 400)
    public String id;

    public MultipartFormFile jarFile;

            final List<Artifact> list = new ArrayList<>(jarFiles.length);
            for (final File file : jarFiles) {
                list.add(getArtifactFromFileName(artifactType, file.getName()));
            }
            list.sort(Comparator.comparing(Artifact::getName));
            return list.toArray(new Artifact[list.size()]);
        }

        final File[] jarFiles = ResourceUtil.getPluginJarFiles(artifactType.getId());

    protected void appendJarFile(final String cpSeparator, final StringBuilder buf, final File libDir, final String basePath) {
        final File[] jarFiles = libDir.listFiles((FilenameFilter) (dir, name) -> name.toLowerCase().endsWith(".jar"));
        if (jarFiles != null) {
            for (final File file : jarFiles) {
                buf.append(cpSeparator);
                buf.append(basePath);
                buf.append(file.getName());