InputStream如何转换为apache.poi工作簿？

Question

我需要Excel文件才能转换为Workbook（apache poi）。 我得到InputStream：

InputStream in = getInputStream(); // from user file.xls
if(in != null){
    HSSFWorkbook hssfWorkbook = new  HSSFWorkbook(in); //exception
}

但是接下来我得到例外：

  

org.apache.poi.poifs.filesystem.NotOLE2FileException：标头无效   签名;读取0x0005060000100809，预期0xE11AB1A1E011CFD0-您的   文件似乎不是有效的OLE2文档

我从文件中获取的InputStream是Apachi Poi构建的

问题NotOLE2FileException: Invalid header signature; read 0x0000000000000000, expected 0xE11AB1A1E011CFD0对我不起作用

我使用Vaadin框架。

MultiFileMemoryBuffer buffer = new MultiFileMemoryBuffer();

Upload upload = new Upload(buffer);
upload.setAcceptedFileTypes("application/vnd.ms-excel");
upload.setMaxFiles(1);
upload.setSizeFull();
upload.addSucceededListener((event) -> {

        name = event.getFileName();

        try (InputStream inputStream = buffer.getInputStream(name) // getInputStream
             ) {
                Workbook workbook = WorkbookFactory.create(inputStream);

            } catch (IOException e) {
                e.printStackTrace();
            }
        });
}