从阿里云上下载文件

@RequestMapping(value = "downloadDatumInfo", method = {RequestMethod.POST})
public void downloadDatumInfo(@RequestParam(value="parmData") String parmData,HttpServletRequest request, HttpServletResponse response) throws IOException{
    Map<String, Object> map = CommonUtil.jsonToObject(parmData);
    request.setCharacterEncoding("utf-8");
    response.setCharacterEncoding("utf-8");
    String fileName = (String) map.get("fileName");
    String filePath = (String) map.get("filePath");
    response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName,"utf-8"));
    String companyCode = filePath.substring(42, 45);
    String diskName = "yunsuo"+companyCode+"/";
    String key = filePath.substring(filePath.lastIndexOf("/")+1,filePath.length());
    OSSClient ossClient = new OSSClient(aliyunOssConfig.getEndPoint(), aliyunOssConfig.getAccessKeyId(), aliyunOssConfig.getAccessKeySecret());
    InputStream in = OSSUnit.getOSS2InputStream(ossClient, "yunsuo", diskName, key);        
    byte[] buff = new byte[1024];
    BufferedInputStream bis = null;
    OutputStream os = null;
    try {
        os = response.getOutputStream();
        bis =new BufferedInputStream(in);
        int len = 0;
        while ((len = in.read(buff)) != -1) {
            os.write(buff, 0, len);
        }
        os.flush();
        os.close();
        in.close();
    } catch (Exception e) {
        e.printStackTrace();
    }   
}

/**
* 根据key获取OSS服务器上的文件输入流
*
* @param client
* OSS客户端
* @param bucketName
* bucket名称
* @param diskName
* 文件路径
* @param key
* Bucket下的文件的路径名+文件名
*/
public static InputStream getOSS2InputStream(OSSClient client, String bucketName, String diskName, String key) {
OSSObject ossObj = client.getObject(bucketName, diskName + key);
return ossObj.getObjectContent();
}