如何从自定义porltet Liferay -7的documents & media库中选择文件

import com.liferay.document.library.kernel.model.DLFileEntry;
import com.liferay.document.library.kernel.service.DLAppServiceUtil;
import com.liferay.portal.kernel.exception.PortalException;
import com.liferay.portal.kernel.repository.model.FileEntry;
import com.liferay.portal.kernel.theme.ThemeDisplay;
import com.liferay.portal.kernel.util.WebKeys;

// 获取当前主题的上下文
ThemeDisplay themeDisplay = (ThemeDisplay) request.getAttribute(WebKeys.THEME_DISPLAY);

// 获取Documents & Media库中的文件
List<FileEntry> fileEntries = DLAppServiceUtil.getFileEntries(themeDisplay.getScopeGroupId(), folderId);

// 遍历文件列表并处理
for (FileEntry fileEntry : fileEntries) {
    // 获取文件的名称
    String fileName = fileEntry.getTitle();

    // 获取文件的URL
    String fileURL = DLUtil.getPreviewURL(fileEntry, fileEntry.getFileVersion(), themeDisplay, "");

    // 处理文件...
}