Use uma barra de progresso para acompanhar o andamento do upload ou download de objetos. Este tópico descreve como utilizar esse recurso ao chamar o método ossClient.getObject para baixar um objeto.
Observações de uso
Este exemplo utiliza o endpoint público da região China (Hangzhou). Para acessar o OSS a partir de outros serviços da Alibaba Cloud na mesma região, use um endpoint interno. Para obter detalhes sobre as regiões e endpoints compatíveis, consulte Regiões e endpoints.
Neste tópico, as credenciais de acesso são obtidas por meio de variáveis de ambiente. Para mais informações, consulte Configurar credenciais de acesso.
Este tópico demonstra a criação de uma instância OSSClient com um endpoint do OSS. Para configurações alternativas, como uso de domínio personalizado ou autenticação com credenciais do Security Token Service (STS), consulte Configuração do cliente.
Exemplos
O código de exemplo a seguir mostra como implementar uma barra de progresso durante o download de um objeto com o método ossClient.getObject.
Os seguintes métodos oferecem suporte ao recurso de barra de progresso: ossClient.putObject, ossClient.getObject, ossClient.uploadPart, ossClient.uploadFile e ossClient.downloadFile. O procedimento para aplicar barras de progresso nesses métodos é idêntico ao do método ossClient.putObject.
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 {
// 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 name of the bucket. Example: examplebucket.
String bucketName = "examplebucket";
// Specify the full path of the object. Do not include the bucket name in the full path. Example: testfolder/exampleobject.txt.
String objectName = "testfolder/exampleobject.txt";
// Specify the full path of the local file. Example: D:\\localpath\\examplefile.txt.
String pathName = "D:\\localpath\\examplefile.txt";
// 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 associated resources when the OSSClient 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 {
// Specify progress listening when you download the object.
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;
}
}
Referências
Para acessar o código de exemplo completo sobre como configurar barras de progresso no download de objetos, visite o GitHub.