如何将OutputStream转为InputStream呢?

实现思路:
    将OutputStream转换为字节数组
	然后再根据字节数组生成inputStream
	采用这种方式,就可实现OutputStream转InputStream

  
XSSFWorkbook wb = null;
try {
    
	wb = buildExcel();
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    wb.write(bos);
    byte[] buffer = bos.toByteArray();
    InputStream inputStream = new ByteArrayInputStream(buffer);

    String fileName = getFileName();
    uploadFile(inputStream, fileName);
} catch (Exception e) {
    e.printStackTrace();
    throw new RuntimeException(e.getMessage());
} finally {
    if (wb != null) {
        try {
            wb.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}