用apache common io包获得文件扩展名

apache common io包包含了很多非常实用的工具类，比如
连获得文件的扩展名都有了，比如：

import org.apache.commons.io.FilenameUtils;

String extension = FilenameUtils.getExtension(fileName);
      
if (extension.equals("zip") || extension.equals("bar")) {
        ZipInputStream zip = new ZipInputStream(fileInputStream);
        repositoryService.createDeployment().addZipInputStream(zip).deploy();