java后台简单从腾讯云下载文件通知前端以附件的形式保存

腾讯云对象存储和阿里云差不多

这是我的配置

 /**
     *  腾讯云client
     * @return COSClient
     */
    public static COSClient getCOSClient() {
 long appId = 00000;
        String secretId = "";
        String secretKey = "";
        // 1 初始化身份信息
        COSCredentials cred = new BasicCOSCredentials(appId , secretId, secretKey);
        // 2 设置 Bucket 的区域, XML的区域详细信息请参见 可用地域(https://www.qcloud.com/document/product/436/6224) 文档
        ClientConfig clientConfig = new ClientConfig(new Region("cos.na-toronto"));
        // 3 生成 cos 客户端
        return new COSClient(cred, clientConfig);
    }

下载代码

@Autowired
    private COSClient cosClient;

    @Override
    public MessageVo getDownLoadFile(String fileName, String cosKey, HttpServletResponse response, HttpServletRequest request) {
        MessageVo messageVo = MessageVoUtil.getMessageVo();
        try {

            // 从腾讯云下载文件
            GetObjectRequest getObjectRequest = new GetObjectRequest(ManageStaticParam.COSCLIENT_BUCKET_TEST, "/yu/"+cosKey);//bucketName需要自己设置
            COSObject cosObject = cosClient.getObject(getObjectRequest);
            // 已缓冲的方式从字符输入流中读取文本，缓冲各个字符，从而提供字符、数组和行的高效读取
            BufferedReader reader = new BufferedReader(new InputStreamReader(cosObject .getObjectContent()));
            COSObjectInputStream cosObjectInput = cosObject.getObjectContent();
            // 缓冲文件输出流
            BufferedOutputStream outputStream = new BufferedOutputStream(response.getOutputStream());
            // 通知浏览器以附件形式下载
//            response.setHeader("Content-Disposition","attachment;filename="+ URLEncoder.encode(fileName,"UTF-8"));

            response.setContentType("application/doc");
            final String userAgent = request.getHeader("USER-AGENT");
            if(StringUtils.contains(userAgent, "MSIE")){//IE浏览器
                fileName = URLEncoder.encode(fileName,"UTF-8");
            }else if(StringUtils.contains(userAgent, "Mozilla")){//google,火狐浏览器
                fileName = new String(fileName.getBytes(), "ISO8859-1");
            }else{
                fileName = URLEncoder.encode(fileName,"UTF-8");//其他浏览器
            }
            response.addHeader("Content-Disposition", "attachment;filename=" +fileName);//这里设置一下让浏览器弹出下载提示框，而不是直接在浏览器中打开

            // 进行解码
            BASE64Decoder base64Decoder = new BASE64Decoder();
            byte[] car= new byte[];
            while (true) {
                String line = reader.readLine();
                if (line == null) break;
                car =  base64Decoder.decodeBuffer(line);
                outputStream.write(car);
               }
                reader.close();

//                byte[] car = new byte[1024];
//                int L;
//
//                while((L = cosObjectInput.read(car)) != -1){
//                    System.out.println(car+"=========="+car.length);
//                    if (car.length!=0){
//                        outputStream.write(car, 0,L);
//                    }
//                }
                outputStream.flush();
                outputStream.close();
                messageVo.setCode(ReturnCodeEnum.处理成功.getStatenum());
            return  messageVo;
        } catch (IOException e) {
            e.printStackTrace();
            messageVo.setCode(ReturnCodeEnum.请求实体不存在.getStatenum());
            messageVo.setData(" Backend file write error ！！！");
            return messageVo;
        } catch (CosServiceException e){
            messageVo.setCode(ReturnCodeEnum.请求实体不存在.getStatenum());
            messageVo.setData(" The request entity does not exist  ！！！");
            return messageVo;
        }
    }

注意：在实际使用该方法下载的过程中，可能遇到服务器不报错，但就是下载不下来文件的问题，这样有可能是前端页面发出下载请求的方式有误，不能使用AJAX的get方式访问该方法，因为Ajax能够返回的数据格式只能为html,script,json,xml，不接受流的形式。笔者使用的方式是用window.location.href访问，或者使用from表单提交方式（GET/POST）。

腾讯开放平台文档

https://cloud.tencent.com/document/product/436/10199#.E7.AE.80.E5.8D.95.E6.96.87.E4.BB.B6.E4.B8.8A.E4.BC.A0

阿里云下载链接

http://blog.csdn.net/qq_35498405/article/details/77942817