oss获取Object的Meta信息，就是我们在上传照片的时特殊设置

  NSString *endpoint = @"";

    // 明文设置secret的方式建议只在测试时使用，更多鉴权模式请参考后面的`访问控制`章节

  //    NSLog(@"--%@--%@--%@",self.accessKeyId,self.accessKeySecret,self.securityToken);

    id<OSSCredentialProvider> credential = [[OSSStsTokenCredentialProvider alloc] initWithAccessKeyId:self.accessKeyId secretKeyId:self.accessKeySecret securityToken:self.securityToken];

   //设置网络请求的一些参数

    OSSClientConfiguration * conf=[OSSClientConfiguration new];

    

    //最大重试次数

    conf.maxRetryCount=3;

    

    conf.timeoutIntervalForRequest=30;// 网络请求的超时时间

    

    OSSClient* client = [[OSSClient alloc] initWithEndpoint:endpoint credentialProvider:credential];

    OSSHeadObjectRequest * head = [OSSHeadObjectRequest new];

    head.bucketName = @"";

    head.objectKey = @"";

    OSSTask * headTask = [client headObject:head];

   [headTask continueWithBlock:^id(OSSTask *task) {

    if (!task.error) {

        OSSHeadObjectResult * headResult = task.result;

        NSLog(@"all response header: %@", headResult.httpResponseHeaderFields);

        // some object properties include the 'x-oss-meta-*'s

        NSLog(@"head object result: %@", headResult.objectMeta);

    } else {

        NSLog(@"head object error: %@", task.error);

    }

    return nil;

  }];