获取微信小程序码，并上传到阿里云

先获取小程序码二进制流 

    /**
     * 获取小程序码
     */
    public static InputStream getWxacodeUnlimit(String accessToken, String path, int width) {
        String url = String.format(WXACODE_UNLIMIT_URL, accessToken);

        String[] str = path.split("[?]");
        String pagePath = str[0];
        String scene = str[1];

        // 接收参数json列表
        JSONObject jsonParam = new JSONObject();
        jsonParam.put("scene", scene);
        jsonParam.put("page", pagePath);
        jsonParam.put("width", width);
        jsonParam.put("auto_color", false);
        Map line_color = new HashMap<>();
        line_color.put("r", 0);
        line_color.put("g", 0);
        line_color.put("b", 0);
        jsonParam.put("line_color", line_color);
        jsonParam.put("is_hyaline", false);
        InputStream inputStream = HttpClientUtils.post(url, jsonParam);
        if (inputStream == null) {
            throw new UserWebException("获取二维码失败！");
        }
        return inputStream;
    }

上传阿里云

    // 单例，只需要建立一次链接
    private static OSSClient client = null;

    // 配置参数
    static ClientConfiguration config() {
        ClientConfiguration conf = new ClientConfiguration();
        conf.setMaxConnections(100);
        conf.setConnectionTimeout(5000);
        conf.setMaxErrorRetry(3);
        conf.setSocketTimeout(2000);
        return conf;
    }

    // 客户端单例
    public static OSSClient client() {
        if (client == null) {
            ClientConfiguration conf = config();
            client = new OSSClient(endpoint, accessKeyId, accessKeySecret, conf);
            makeBucket(client, bucketName);
        }
        return client;
    }

    // 创建Bucket
    private static void makeBucket(OSSClient client, String bucketName) {
        boolean exist = client.doesBucketExist(bucketName);
        if (exist) {
            return;
        }
        client.createBucket(bucketName);
    }

    // 上传文件流
    private static String uploadInputStream(InputStream is, String key) {
        try {
            OSSClient client = client();
            ObjectMetadata objectMetadata = new ObjectMetadata();
            objectMetadata.setContentType("image/jpg");
            PutObjectRequest putObjectRequest = new PutObjectRequest(
                    OssUtil.bucketName, key, is, objectMetadata);
            client.putObject(putObjectRequest);

            // 设置这个文件地址的有效时间
            Date expiration = new Date(System.currentTimeMillis() + 3600L * 1000 * 24 * 365 * 10);
            return client.generatePresignedUrl(bucketName, key, expiration).toString();
        } finally {
            IOUtils.closeQuietly(is);
        }
    }

post工具类

    /**
     * post请求
     */
    public static InputStream post(String url, JSONObject jsonParam) {
        InputStream inputStream = null;
        RestTemplate rest = new RestTemplate();
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        org.springframework.http.HttpEntity requestEntity = new org.springframework.http.HttpEntity
                (jsonParam.toJSONString(), headers);
        ResponseEntity entity = rest.exchange(url, HttpMethod.POST,
                requestEntity, byte[].class, new Object[0]);
        byte[] result = entity.getBody();
        if (entity.getHeaders().getContentType().includes(MediaType.APPLICATION_JSON)) {
            log.info(" - post 返回值 - [{}]", new String(result));
            return null;
        }
        inputStream = new ByteArrayInputStream(result);
        return inputStream;
    }

1，如果获取小程序码返回的是错误信息（json）而不是图片流，怎么判断出来呢？

 判断小程序返回的是错误信息还是图片流，通过header的content-type，如果是"application/json"，说明返回的就是错误信息。

2，小程序码返回的InputStream对象是EofSensorInputStream，这个上传到阿里云不能识别

3，图片上传到阿里云后，打开链接提示下载，解决方法：
 objectMetadata.setContentType("image/jpg");

以上三个问题在上面代码都有体现。