# 分段相关接口概述(HarmonyOS SDK)
对于较大文件上传，可以切分成段上传。用户可以在如下的应用场景内（但不仅限于此），使用分段上传的模式：
- 上传超过100MB大小的文件。
- 网络条件较差，和OBS服务端之间的链接经常断开。
- 上传前无法确定将要上传文件的大小。
分段上传分为如下3个步骤：
1. [初始化分段上传任务](https://support.huaweicloud.com/sdk-harmony-devg-obs/obs_34_0411.html)。
2. [逐个或并行上传段](https://support.huaweicloud.com/sdk-harmony-devg-obs/obs_34_0412.html)。
3. [合并段](https://support.huaweicloud.com/sdk-harmony-devg-obs/obs_34_0415.html)或[取消分段上传任务](https://support.huaweicloud.com/sdk-harmony-devg-obs/obs_34_0416.html)。
以下代码简单展示了分段上传的各个步骤：
```
// 引入依赖包
import ObsClient, { Part, ICommonMsg } from '@obs/esdk-obs-harmony';
import { process } from '@kit.ArkTS';
import { BusinessError } from '@kit.BasicServicesKit';
import { hilog } from '@kit.PerformanceAnalysisKit';
const processManager = new process.ProcessManager();
// 创建ObsClient实例
const obsClient = new ObsClient({
  // 推荐通过环境变量获取AKSK，这里也可以使用其他外部引入方式传入，如果使用硬编码可能会存在泄露风险
  // 您可以登录访问管理控制台获取访问密钥AK/SK，获取方式请参见https://support.huaweicloud.com/usermanual-ca/ca_01_0003.html
  AccessKeyId: processManager.getEnvironmentVar("ACCESS_KEY_ID"),
  SecretAccessKey: processManager.getEnvironmentVar("SECRET_ACCESS_KEY"),
  // 【可选】如果使用临时AK/SK和SecurityToken访问OBS，同样建议您尽量避免使用硬编码，以降低信息泄露风险。您可以通过环境变量获取访问密钥AK/SK，也可以使用其他外部引入方式传入
  // SecurityToken: processManager.getEnvironmentVar("SECURITY_TOKEN"),
  // Server填写Bucket对应的Endpoint, 这里以华北-北京四为例，其他地区请按实际情况填写
  Server: "https://obs.cn-north-4.myhuaweicloud.com",
});
// 指定存储桶名称
const bucketName = "examplebucket";
// 指定对象，此处以 example/objectname 为例
const objectName = "example/objectname";
async function run() {
  try {
    // 初始化分段上传任务
    const initiateMultipartUploadOutput = await obsClient.initiateMultipartUpload({
      Bucket: bucketName,
      Key: objectName
    });
    if (initiateMultipartUploadOutput.CommonMsg.Status > 300) {
      logErrorMessage(initiateMultipartUploadOutput.CommonMsg);
      return;
    }
    const uploadId = initiateMultipartUploadOutput.InterfaceResult.UploadId;
    const parts: Part[] = [];
    // 上传段
    const uploadPartOutput = await obsClient.uploadPart({
      Bucket: bucketName,
      Key: objectName,
      UploadId: uploadId,
      PartNumber: 1,
      Body: "Hello OBS~"
    });
    if (uploadPartOutput.CommonMsg.Status > 300) {
      logErrorMessage(uploadPartOutput.CommonMsg);
      return;
    }
    parts.push({
      PartNumber: 1,
      ETag: uploadPartOutput.InterfaceResult.ETag,
    });
    // 合并段
    const completeMultipartUploadOutput = await obsClient.completeMultipartUpload({
      Bucket: bucketName,
      Key: objectName,
      UploadId: uploadId,
      Parts: parts
    });
    if (completeMultipartUploadOutput.CommonMsg.Status > 300) {
      logErrorMessage(uploadPartOutput.CommonMsg);
      return;
    }
    hilog.info(0x0001, 'OBS-Harmony', "uploadFile successful!!");
    hilog.info(0x0001, 'OBS-Harmony', "RequestId: %s", completeMultipartUploadOutput.CommonMsg.RequestId);
    hilog.info(0x0001, 'OBS-Harmony', "ETag:%s", completeMultipartUploadOutput.InterfaceResult.ETag);
  } catch(error) {
    hilog.info(0x0001, 'OBS-Harmony', "An Exception was found, which means the client encountered an internal problem when attempting to communicate with OBS, for example, the client was unable to access the network.");
    hilog.info(0x0001, 'OBS-Harmony', error);
  }
}
function logErrorMessage(commonMsg: ICommonMsg) {
  hilog.error(0x0001, 'OBS-Harmony', "An ObsError was found, which means your request sent to OBS was rejected with an error response.");
  hilog.error(0x0001, 'OBS-Harmony', "Status: %d", commonMsg.Status);
  hilog.error(0x0001, 'OBS-Harmony', "Code: %s", commonMsg.Code);
  hilog.error(0x0001, 'OBS-Harmony', "Message: %s", commonMsg.Message);
  hilog.error(0x0001, 'OBS-Harmony', "RequestId: %s", commonMsg.RequestId);
}
```
其他分段操作请参考：
- [分段上传-列举分段上传任务](https://support.huaweicloud.com/sdk-harmony-devg-obs/obs_34_0306.html)
- [分段上传-列举已上传的段](https://support.huaweicloud.com/sdk-harmony-devg-obs/obs_34_0414.html)
- [分段上传-复制段](https://support.huaweicloud.com/sdk-harmony-devg-obs/obs_34_0413.html)