看你的代码，貌似实现的是要读取Excel文件吧。代码如下：具体的跟你的POI所支持的EXCEL版本有关系的。
public List<RackVo> importExcel(@File("upload")FileItem fileInput, ErrorContext error) {
List<RackVo> list = null;

    if (null == fileInput) {
        throw new ServiceException(ErrorCode.Params_Lost, "机柜导入文件");
    }
    Workbook wb = null;
    InputStream is = null;
    Sheet sheet = null;
    try {
        is = fileInput.getInputStream();
        wb = new XSSFWorkbook(is);
        sheet = wb.getSheet(sheetName);
    } catch (Exception e) {
        throw new ServiceException(ErrorCode.Upload_File_Error, "上传excel版本文件解析失败");
    } finally {
        if (is != null) {
            try {
                is.close();
            } catch (IOException e) {
            }
        }
    }

    if (sheet != null) {
        // 初始化Excel栏目
        List<CellMapping> mappingList = RackUtil.getModColumns(null);
        try {
            list = ExcelUtils.excel2bean(sheet, RackVo.class, mappingList);
        } catch (Exception e) {
            throw new ServiceException(ErrorCode.Upload_File_Error, "Excel解析失败");
        }
    } else {
        throw new ServiceException(ErrorCode.Upload_File_Error, "未找到模板对应sheet");
    }

    return list;

}