ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
try {
    workbook.write(byteArrayOutputStream);
    ByteArrayInputStream byteArrayInputStream = new       ByteArrayInputStream(byteArrayOutputStream.toByteArray());
    //加上设置大小 下载下来的excel文件office在打开前不会提示修复
    response.setHeader("Content-Length",     String.valueOf(byteArrayInputStream.available()));
    //获取响应的流对象
    OutputStream os = response.getOutputStream();

    byte[] b = new byte[1024];
    int length;
    while ((length = byteArrayInputStream.read(b)) > 0) {
        os.write(b, 0, length);
    }
    //关流
    byteArrayOutputStream.close();
    byteArrayInputStream.close();
    //将响应输出流中的数据刷新到浏览器
    os.flush();
    os.close();


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