• Object Storage Service

obs
  1. Help Center
  2. Object Storage Service
  3. Developer Guide (Java SDK)
  4. Object Upload
  5. Setting Object Properties

Setting Object Properties

You can set properties for an object when uploading it. Object properties include the object length, MIME type, MD5 value (for verification), storage class, and customized metadata. You can set properties for an object that is being uploaded in streaming, file-based, and multipart mode when copying the object.

The following table describes object properties.

Property Name

Description

Default Value

Content-Length

Indicates the object length. If the object length exceeds the flow or file length, the object will be truncated.

Actual length of the stream or file

Content-Type

Indicates the MIME type of the object, which defines the type and network code of the object as well as in which mode and coding will the browser read the object.

application/octet-stream

Content-MD5

Indicates the base64-encoded digest of the object data. It is provided to the OBS server to verify data integrity.

None

Storage Class

Indicates the storage class of the object. Different storage classes meet different needs for storage performance and costs. The value defaults to be the same as the object's residing bucket and can be changed.

None

Customized metadata

Indicates the user-defined description of properties of the object uploaded to the bucket. It is used to facilitate the customized management on the object.

None

Setting the Length for an Object

You can call ObjectMetadata.setContentLength to set the length for an object. Sample code is as follows:

String endPoint = "yourdomainname";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";
// Create an instance of ObsClient.
ObsClient obsClient = new ObsClient(ak, sk, endPoint);

ObjectMetadata metadata = new ObjectMetadata();
metadata.setContentLength(1024 * 1024L);// 1MB
obsClient.putObject("bucketname", "objectkey", new File("localfile"), metadata);

// Close obsClient.
obsClient.close();

Setting the MIME Type for an Object

You can call ObjectMetadata.setContentType to set the MIME type for an object. Sample code is as follows:

String endPoint = "yourdomainname";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";
// Create an instance of ObsClient.
ObsClient obsClient = new ObsClient(ak, sk, endPoint);

// Upload an image.
ObjectMetadata metadata = new ObjectMetadata();
metadata.setContentType("image/jpeg");
obsClient.putObject("bucketname", "objectkey.jpg", new File("localimage.jpg"), metadata);

// Close obsClient.
obsClient.close();
NOTE:
  • If this property is not specified, the SDK will automatically identify the MIME type according to the name suffix of the uploaded object. For example, if the name suffix of an object is .xml (.html), the object will be identified as an application/xml (text/html) file.

Setting the MD5 Value for an Object

You can call ObjectMetadata.setContentMd5 to set the MD5 value for an object. Sample code is as follows:

String endPoint = "yourdomainname";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";
// Create an instance of ObsClient.
ObsClient obsClient = new ObsClient(ak, sk, endPoint);
// Upload an image.
ObjectMetadata metadata = new ObjectMetadata();
metadata.setContentMd5("your md5 which should be encoded by base64");
obsClient.putObject("bucketname", "objectkey", new File("localimage.jpg"), metadata);
// Close obsClient.
obsClient.close();
NOTE:
  • The MD5 value of an object must be a base64-encoded digest.
  • The OBS server will compare this MD5 value with the MD5 value obtained by object data calculation. If the two values are not the same, the upload fails with HTTP status code 400 returned.
  • If the MD5 value is not specified, the OBS server will skip MD5 value verification.

Setting the Storage Class for an Object

You can call ObjectMetadata.setObjectStorageClass to set the storage class for an object. Sample code is as follows:

String endPoint = "yourdomainname";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";

// Create an instance of ObsClient.
ObsClient obsClient = new ObsClient(ak, sk, endPoint);

ObjectMetadata metadata = new ObjectMetadata();
// Set the storage class to OBS Cold.
metadata.setObjectStorageClass(StorageClassEnum.WARM);
obsClient.putObject("bucketname", "objectkey", new File("localfile"), metadata);

// Close obsClient.
obsClient.close();
NOTE:
  • If you have not set the storage class for an object, the storage class of the object will be the same as that of its residing bucket.
  • OBS provides objects with three storage classes which are consistent with the storage classes provided for buckets.
  • Before downloading a Cold object, you must restore it.

Customizing Metadata for an Object

You can call ObjectMetadata.addUserMetadata to customize metadata for an object. Sample code is as follows:

String endPoint = "yourdomainname";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";
// Create an instance of ObsClient.
ObsClient obsClient = new ObsClient(ak, sk, endPoint);

ObjectMetadata metadata = new ObjectMetadata();
metadata.addUserMetadata("property1", "property-value1");
metadata.getMetadata().put("property2", "property-value2");
obsClient.putObject("bucketname", "objectkey", new File("localfile"), metadata);

// Close obsClient.
obsClient.close();
NOTE:
  • In the preceding code, two pieces of metadata named property1 and property2 are customized and their respective values are set to property-value1 and property-value2.
  • An object can have multiple pieces of metadata. The total metadata size cannot exceed 8 KB.
  • The customized object metadata can be obtained by using ObsClient.getObjectMetadata. For details, see Obtaining Object Metadata.
  • When you call ObsClient.getObject to download an object, its customized metadata will also be downloaded.