对象元信息是对象的属性描述，包括 HTTP 标准属性（HTTP Header）和用户自定义元数据（User Meta）两种。
以下代码展示如何通过 setObjectMeta 接口设置对象的 Content-Type，以及设置对象的自定义元数据，用于标识对象的用途或属性等。
import android.os.Bundle; import android.util.Log; import androidx.appcompat.app.AppCompatActivity; import com.volcengine.tos.TOSV2; import com.volcengine.tos.TOSV2ClientBuilder; import com.volcengine.tos.TosException; import com.volcengine.tos.comm.common.ACLType; import com.volcengine.tos.comm.common.StorageClassType; import com.volcengine.tos.model.object.ObjectMetaRequestOptions; import com.volcengine.tos.model.object.SetObjectMetaInput; import com.volcengine.tos.model.object.SetObjectMetaOutput; import java.io.ByteArrayInputStream; import java.util.HashMap; import java.util.Map; public class SetObjectMetaExample extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { String endpoint = "your endpoint"; String region = "your region"; String accessKey = "your access key"; String secretKey = "your secret key"; String securityToken = "your security token"; String bucketName = "your bucket name"; String objectKey = "your object key"; super.onCreate(savedInstanceState); setContentView(R.layout.activity_display_message); TOSV2 tos = new TOSV2ClientBuilder().build(region, endpoint, accessKey, secretKey, securityToken); Thread tosThread = new Thread(new Runnable() { @Override public void run() { try{ String data = "1234567890abcdefghijklmnopqrstuvwxyz~!@#$%^&*()_+<>?,./ :'1234567890abcdefghijklmnopqrstuvwxyz~!@#$%^&*()_+<>?,./ :'"; ByteArrayInputStream stream = new ByteArrayInputStream(data.getBytes()); ObjectMetaRequestOptions options = new ObjectMetaRequestOptions(); // 设置对象访问权限，此处为私有权限 options.setAclType(ACLType.ACL_PRIVATE); // 设置对象存储类型 options.setStorageClass(StorageClassType.STORAGE_CLASS_STANDARD); // SDK 默认会根据 objectKey 后缀识别 Content-Type，也可以自定义设置 options.setContentType("application/json"); // 设置对象内容语言 options.setContentLanguage("en"); // 设置对象被下载时的名称 options.setContentDisposition("attachment;filename=download.txt"); // 设置对象的网页缓存行为 options.setCacheControl("max-age=600"); // 设置对象MD5，用于服务端校验数据是否与客户端传输的一致 options.setContentMD5("yjtlyPoGKxvDj+QOPocqjg=="); // 设置对象的服务端加密方式，当前只支持 AES256 options.setServerSideEncryption("AES256"); // 自定义对象的元数据，对于自定义的元数据，SDK 会自动对 key 添加 // "X-Tos-Meta-" 的前缀，并存储在服务端。 Map<String, String> custom = new HashMap<>(); custom.put("name", "volc_user"); // 在 TOS 服务端存储的元数据为："X-Tos-Meta-name: volc_user" options.setCustomMetadata(custom); SetObjectMetaInput input = new SetObjectMetaInput().setBucket(bucketName).setKey(objectKey) .setOptions(options); SetObjectMetaOutput output = tos.setObjectMeta(input); Log.i("setObjectMeta", "setObjectMeta succeed, request info is " + output); } catch (TosException e) { Log.e("TosException", "setObjectMeta failed"); e.printStackTrace(); } } }); tosThread.start(); } }
通过 headObject 接口可以获取对象信息，判断对象是否存在，以及获取对象的元数据。以下代码展示如何获取对象的元数据。
import android.os.Bundle; import android.util.Log; import androidx.appcompat.app.AppCompatActivity; import com.volcengine.tos.TOSV2; import com.volcengine.tos.TOSV2ClientBuilder; import com.volcengine.tos.TosException; import com.volcengine.tos.model.object.HeadObjectV2Input; import com.volcengine.tos.model.object.HeadObjectV2Output; public class HeadObjectExample extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { String endpoint = "your endpoint"; String region = "your region"; String accessKey = "your access key"; String secretKey = "your secret key"; String securityToken = "your security token"; String bucketName = "your bucket name"; String objectKey = "your object key"; super.onCreate(savedInstanceState); setContentView(R.layout.activity_display_message); TOSV2 tos = new TOSV2ClientBuilder().build(region, endpoint, accessKey, secretKey, securityToken); Thread tosThread = new Thread(new Runnable() { @Override public void run() { try{ HeadObjectV2Input input = new HeadObjectV2Input().setBucket(bucketName).setKey(objectKey); HeadObjectV2Output output = tos.headObject(input); Log.i("headObject", "headObject succeed, object's metadata is " + output.getHeadObjectBasicOutput()); } catch (TosException e) { if (e.getStatusCode() == 404) { // 下载不存在的对象会返回404 Log.e("TosException", "the object you want to head is not found"); } else { Log.e("TosException", "headObject failed"); } e.printStackTrace(); } } }); tosThread.start(); } }
关于设置对象元数据的 API 文档，请参见 SetObjectMeta。