Manage symbolic links in Java - Object Storage Service - Alibaba Cloud Documentation Center

You can use symbolic links to easily access frequently used objects in a bucket. After you create a symbolic link, you can use it to access the target object. This is similar to a shortcut in Windows.

Usage notes

In this topic, the public endpoint of the China (Hangzhou) region is used. To access OSS from other Alibaba Cloud services in the same region, use an internal endpoint. For details about supported regions and endpoints, see Regions and endpoints.
In this topic, access credentials are obtained from environment variables. For more information about how to configure access credentials, see Configure access credentials.
In this topic, an OSSClient instance is created by using an OSS endpoint. If you want to create an OSSClient instance by using custom domain names or Security Token Service (STS), see Configuration examples for common scenarios.
To create a symbolic link, you must have the oss:PutObject permission. To read a symbolic link, you must have the oss:GetObject permission. For more information, see Attach a custom policy to a RAM user.

Create a symbolic link

The following code shows how to create a symbolic link:

import com.aliyun.oss.*; import com.aliyun.oss.common.auth.*; import com.aliyun.oss.common.comm.SignVersion; import com.aliyun.oss.model.*; public class Demo { public static void main(String[] args) throws Exception { // In this example, the endpoint of the China (Hangzhou) region is used. Specify your actual endpoint. String endpoint = "https://oss-cn-hangzhou.aliyuncs.com"; // Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider(); // Specify the bucket name. Example: examplebucket. String bucketName = "examplebucket"; // Specify the name of the symbolic link. String symLink = "yourSymLink"; // Specify the name of the object to which the symbolic link points. String destinationObjectName = "yourDestinationObjectName"; // Specify the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the region to cn-hangzhou. String region = "cn-hangzhou"; // Create an OSSClient instance. // Call the shutdown method to release resources when the OSSClient instance is no longer in use. ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration(); clientBuilderConfiguration.setSignatureVersion(SignVersion.V4); OSS ossClient = OSSClientBuilder.create() .endpoint(endpoint) .credentialsProvider(credentialsProvider) .clientConfiguration(clientBuilderConfiguration) .region(region) .build(); try { // Create metadata for the file to be uploaded. ObjectMetadata metadata = new ObjectMetadata(); metadata.setContentType("text/plain"); // Set the value of the custom metadata property to property-value. metadata.addUserMetadata("property", "property-value"); // Specify whether to overwrite an object that has the same name when you create the symbolic link. // metadata.setHeader("x-oss-forbid-overwrite", "true"); // Specify the access permissions of the object. // metadata.setHeader(OSSHeaders.OSS_OBJECT_ACL, CannedAccessControlList.Default); // Specify the storage class of the object. // metadata.setHeader(OSSHeaders.OSS_STORAGE_CLASS, StorageClass.Standard); // Create a CreateSymlinkRequest. CreateSymlinkRequest createSymlinkRequest = new CreateSymlinkRequest(bucketName, symLink, destinationObjectName); // Set the metadata. createSymlinkRequest.setMetadata(metadata); // Create the symbolic link. ossClient.createSymlink(createSymlinkRequest); } catch (OSSException oe) { System.out.println("Caught an OSSException, which means your request made it to OSS, " + "but was rejected with an error response for some reason."); System.out.println("Error Message:" + oe.getErrorMessage()); System.out.println("Error Code:" + oe.getErrorCode()); System.out.println("Request ID:" + oe.getRequestId()); System.out.println("Host ID:" + oe.getHostId()); } catch (ClientException ce) { System.out.println("Caught an ClientException, which means the client encountered " + "a serious internal problem while trying to communicate with OSS, " + "such as not being able to access the network."); System.out.println("Error Message:" + ce.getMessage()); } finally { if (ossClient != null) { ossClient.shutdown(); } } } }

Get a symbolic link

The following code shows how to read a symbolic link and retrieve the name of the target object file:

import com.aliyun.oss.*; import com.aliyun.oss.common.auth.*; import com.aliyun.oss.common.comm.SignVersion; import com.aliyun.oss.model.*; public class Demo { public static void main(String[] args) throws Exception { // In this example, the endpoint of the China (Hangzhou) region is used. Specify your actual endpoint. String endpoint = "https://oss-cn-hangzhou.aliyuncs.com"; // Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider(); // Specify the bucket name. Example: examplebucket. String bucketName = "examplebucket"; // Specify the name of the symbolic link. String symLink = "yourSymLink"; // Specify the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the region to cn-hangzhou. String region = "cn-hangzhou"; // Create an OSSClient instance. // Call the shutdown method to release resources when the OSSClient instance is no longer in use. ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration(); clientBuilderConfiguration.setSignatureVersion(SignVersion.V4); OSS ossClient = OSSClientBuilder.create() .endpoint(endpoint) .credentialsProvider(credentialsProvider) .clientConfiguration(clientBuilderConfiguration) .region(region) .build(); try { // Get the symbolic link and the name of the object file to which the symbolic link points. OSSSymlink symbolicLink = ossClient.getSymlink(bucketName, symLink); System.out.println(symbolicLink.getSymlink()); System.out.println(symbolicLink.getTarget()); System.out.println(symbolicLink.getRequestId()); } catch (OSSException oe) { System.out.println("Caught an OSSException, which means your request made it to OSS, " + "but was rejected with an error response for some reason."); System.out.println("Error Message:" + oe.getErrorMessage()); System.out.println("Error Code:" + oe.getErrorCode()); System.out.println("Request ID:" + oe.getRequestId()); System.out.println("Host ID:" + oe.getHostId()); } catch (ClientException ce) { System.out.println("Caught an ClientException, which means the client encountered " + "a serious internal problem while trying to communicate with OSS, " + "such as not being able to access the network."); System.out.println("Error Message:" + ce.getMessage()); } finally { if (ossClient != null) { ossClient.shutdown(); } } } }

References

For more information about the API operation used to create a symbolic link, see PutSymlink.
For more information about the API operation used to read a symbolic link, see GetSymlink.