Büyük nesnelerle çalışırken veya verileri kademeli olarak işlerken, nesnenin tamamını tek seferde belleğe yüklememek için OSS'ten nesne içeriğini parçalar halinde okumak üzere akışlı indirmeyi kullanabilirsiniz. Bu yöntem verimliliği ve performansı artırır. Bellek sınırlarını aşan nesnelerin indirilmesi, bellek kullanımını azaltmak için verilerin gerçek zamanlı işlenmesi ve ağ üzerinden verilerin adım adım alındığı senaryolar için bu yaklaşım uygundur.
Kullanım notları
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Bu konuda China (Hangzhou) bölgesinin genel uç noktası kullanılmıştır. Aynı bölgedeki diğer Alibaba Cloud hizmetlerinden OSS'e erişmek için dahili uç nokta kullanın. Desteklenen bölgeler ve uç noktalar hakkında daha fazla bilgi için bkz. Bölgeler ve uç noktalar.
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Bu konuda erişim kimlik bilgileri ortam değişkenlerinden alınmaktadır. Daha fazla bilgi için bkz. Erişim kimlik bilgilerini yapılandırma.
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Bu konu, bir OSS uç noktası kullanarak bir OSSClient örneği oluşturmayı gösterir. Özel etki alanı kullanımı veya Security Token Service (STS) kimlik bilgileriyle kimlik doğrulama gibi alternatif yapılandırmalar için bkz. İstemci yapılandırması.
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Akışlı indirmeyi kullanmak için
oss:GetObjectiznine sahip olmanız gerekir. Daha fazla bilgi için bkz. Özel ilke atama.
Örnek kod
Aşağıdaki kod, OSS'ten nesne içeriğini parçalar halinde okuyup bir byte dizisinde saklamaya yönelik bir örnek sunar.
import com.aliyun.oss.ClientBuilderConfiguration;
import com.aliyun.oss.OSS;
import com.aliyun.oss.common.auth.*;
import com.aliyun.oss.OSSClientBuilder;
import com.aliyun.oss.OSSException;
import com.aliyun.oss.common.comm.SignVersion;
import com.aliyun.oss.model.*;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
public class Stream {
public static void main(String[] args) throws Exception {
// In this example, the endpoint of the China (Hangzhou) region is used. Specify your actual endpoint. For more information about the endpoints of other regions, see Regions and endpoints.
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. Example: exampledir/exampleobject.txt. Do not include the bucket name in the full path.
String objectName = "exampledir/exampleobject.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 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 {
// ossObject includes the bucket name, object name, object metadata, and an input stream.
OSSObject ossObject = ossClient.getObject(bucketName, objectName);
InputStream inputStream = ossObject.getObjectContent();
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
// Read the object content and store it in a byte array.
byte[] readBuffer = new byte[1024];
int bytesRead;
while ((bytesRead = inputStream.read(readBuffer)) != -1) {
byteArrayOutputStream.write(readBuffer, 0, bytesRead);
}
// Obtain the final result.
byte[] fileBytes = byteArrayOutputStream.toByteArray();
// Display the length of the byte array.
System.out.println("Downloaded file size: " + fileBytes.length + " bytes");
// You must close the obtained stream after the object is read. Otherwise, connection leaks may occur. Consequently, no connections are available and an exception occurs.
inputStream.close();
byteArrayOutputStream.close();
// If you do not close the ossObject object after it is used, connection leaks may occur. Consequently, no connections are available and an exception occurs.
ossObject.close();
} 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 (Throwable 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();
}
}
}
}Aşağıda, D:\localpath dizinindeki examplefile.txt adlı bir dosyaya akış olarak exampleobject.txt adlı bir nesnenin verilerini indirmeye yönelik örnek kod verilmiştir:
import com.aliyun.oss.ClientBuilderConfiguration;
import com.aliyun.oss.OSS;
import com.aliyun.oss.common.auth.*;
import com.aliyun.oss.OSSClientBuilder;
import com.aliyun.oss.OSSException;
import com.aliyun.oss.common.comm.SignVersion;
import com.aliyun.oss.model.OSSObject;
import java.io.*;
public class GetObjectStreamtoLocalFile {
public static void main(String[] args) throws Exception {
// In this example, the endpoint of the China (Hangzhou) region is used. Specify your actual endpoint. For more information about the endpoints of other regions, see Regions and endpoints.
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. Example: exampledir/exampleobject.txt. Do not include the bucket name in the full path.
String objectName = "exampledir/exampleobject.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";
// Specify the local path in which you want to store the files.
String localFilePath = "D:\\localpath\\examplefile.txt"; // Specify the path of the local file.
// Create an OSSClient instance.
// Call the shutdown method to release 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 {
// Retrieve the object's input stream.
OSSObject ossObject = ossClient.getObject(bucketName, objectName);
InputStream inputStream = ossObject.getObjectContent();
// Create an output stream to the local file.
try (FileOutputStream fileOutputStream = new FileOutputStream(localFilePath)) {
byte[] buffer = new byte[1024];
int bytesRead;
// Read the content in chunks and write it to a local file.
while ((bytesRead = inputStream.read(buffer)) != -1) {
fileOutputStream.write(buffer, 0, bytesRead);
}
System.out.println("Downloaded file saved to: " + localFilePath);
}
// Close the input stream.
inputStream.close();
// Close ossObject.
ossObject.close();
} 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 (Throwable 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();
}
}
}
}