Object Storage Service:Progress bar (OSS SDK for Java 1.0)

Prerequisites

Before you begin, ensure that you have:

• An OSS bucket with at least one object to download

• Access credentials configured as environment variables (OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET)

• The OSS Java SDK V1 dependency added to your project

Usage notes

• The example uses the public endpoint of the China (Hangzhou) region. To access OSS from other Alibaba Cloud services in the same region, use an internal endpoint. For a full list of regions and endpoints, see OSS regions and endpoints.

• Access credentials are read from environment variables. For configuration details, see Configure access credentials.

• The example creates an OSSClient instance using an OSS endpoint. To create one using custom domain names or Security Token Service (STS), see Configuration examples for common scenarios.

Supported methods

The progress bar feature is supported on the following methods. The integration pattern is the same as shown in the example below.

How it works

1. Implement the ProgressListener interface with a progressChanged(ProgressEvent event) method.

2. Attach the listener to your request using withProgressListener(listener).

3. As the transfer runs, OSS fires events that your listener receives and processes.

The progressChanged method receives a ProgressEvent on each callback. Use event.getEventType() to identify the event and event.getBytes() to read the byte count.

Download an object with a progress bar

The following example implements a ProgressListener that tracks download progress and prints it to the console.

import com.aliyun.oss.*;
import com.aliyun.oss.common.auth.*;
import com.aliyun.oss.common.comm.SignVersion;
import com.aliyun.oss.event.ProgressEvent;
import com.aliyun.oss.event.ProgressEventType;
import com.aliyun.oss.event.ProgressListener;
import com.aliyun.oss.model.GetObjectRequest;
import java.io.File;

public class GetObjectProgressListener implements ProgressListener {
    private long bytesRead = 0;
    private long totalBytes = -1;
    private boolean succeed = false;

    public static void main(String[] args) throws Exception {
        // Replace with your actual endpoint. This example uses China (Hangzhou).
        String endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
        // Read credentials from environment variables OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET.
        EnvironmentVariableCredentialsProvider credentialsProvider =
                CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider();
        // Replace with your bucket name, object path, and local destination path.
        String bucketName = "examplebucket";
        String objectName = "testfolder/exampleobject.txt";
        String pathName = "D:\\localpath\\examplefile.txt";
        String region = "cn-hangzhou";

        // Build the OSSClient with signature version V4.
        // Call ossClient.shutdown() when done to release resources.
        ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration();
        clientBuilderConfiguration.setSignatureVersion(SignVersion.V4);
        OSS ossClient = OSSClientBuilder.create()
                .endpoint(endpoint)
                .credentialsProvider(credentialsProvider)
                .clientConfiguration(clientBuilderConfiguration)
                .region(region)
                .build();

        try {
            // Attach the progress listener to the download request.
            ossClient.getObject(
                    new GetObjectRequest(bucketName, objectName)
                            .<GetObjectRequest>withProgressListener(new GetObjectProgressListener()),
                    new File(pathName));
        } 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();
            }
        }
    }

    @Override
    public void progressChanged(ProgressEvent progressEvent) {
        long bytes = progressEvent.getBytes();
        ProgressEventType eventType = progressEvent.getEventType();
        switch (eventType) {
            case TRANSFER_STARTED_EVENT:
                System.out.println("Start to download......");
                break;
            case RESPONSE_CONTENT_LENGTH_EVENT:
                this.totalBytes = bytes;
                System.out.println(this.totalBytes + " bytes in total will be downloaded to a local file");
                break;
            case RESPONSE_BYTE_TRANSFER_EVENT:
                this.bytesRead += bytes;
                if (this.totalBytes != -1) {
                    int percent = (int)(this.bytesRead * 100.0 / this.totalBytes);
                    System.out.println(bytes + " bytes have been read at this time, download progress: "
                            + percent + "%(" + this.bytesRead + "/" + this.totalBytes + ")");
                } else {
                    System.out.println(bytes + " bytes have been read at this time, download ratio: unknown"
                            + "(" + this.bytesRead + "/...)");
                }
                break;
            case TRANSFER_COMPLETED_EVENT:
                this.succeed = true;
                System.out.println("Succeed to download, " + this.bytesRead + " bytes have been transferred in total");
                break;
            case TRANSFER_FAILED_EVENT:
                System.out.println("Failed to download, " + this.bytesRead + " bytes have been transferred");
                break;
            default:
                break;
        }
    }

    public boolean isSucceed() {
        return succeed;
    }
}

When the download runs, the console output looks similar to:

Start to download......
10485760 bytes in total will be downloaded to a local file
65536 bytes have been read at this time, download progress: 0%(65536/10485760)
131072 bytes have been read at this time, download progress: 1%(131072/10485760)
...
Succeed to download, 10485760 bytes have been transferred in total

References

For the complete sample code, see GetProgressSample.java on GitHub.