Object Storage Service (OSS) SDK for Java uses MD5 verification and CRC-64 to ensure data integrity when you upload, download, and copy objects.
Usage notes
In this topic, the public endpoint of the China (Hangzhou) region is used. If you want to access OSS from other Alibaba Cloud services in the same region as OSS, use an internal endpoint. For more information about OSS regions and endpoints, see Regions, endpoints and open ports.
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 Create an OSSClient instance.
MD5 verification
If you configure Content-MD5 in an object upload request, OSS calculates the MD5 hash of the uploaded object. If the calculated MD5 hash is different from the MD5 hash configured in the upload request, InvalidDigest is returned. This allows OSS to ensure data integrity for object uploads. If InvalidDigest is returned, you need to upload the object again.
MD5 verification is also supported for multipart upload. In a multipart upload request, meta specifies the metadata of the object to upload. MD5 verification is performed for each part during multipart upload. The setMd5Digest function is called in an UploadPartRequest request for the client to calculate the MD5 hash.
Note
MD5 verification is supported for PutObject, GetObject, AppendObject, PostObject, Multipart upload, and UploadPart.
The following sample code provides an example on how to configure MD5 verification in a PutObject operation:
import com.aliyun.oss.*; import com.aliyun.oss.common.auth.*; import com.aliyun.oss.common.utils.BinaryUtil; import com.aliyun.oss.model.ObjectMetadata; import java.io.ByteArrayInputStream; public class Demo { public static void main(String[] args) throws Throwable { // 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. String objectName = "exampledir/object"; // 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. ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration(); clientBuilderConfiguration.setSignatureVersion(SignVersion.V4); OSS ossClient = OSSClientBuilder.create() .endpoint(endpoint) .credentialsProvider(credentialsProvider) .clientConfiguration(clientBuilderConfiguration) .region(region) .build(); try { // Upload the string. String content = "Hello OSS"; ObjectMetadata meta = new ObjectMetadata(); // Configure MD5 verification. String md5 = BinaryUtil.toBase64String(BinaryUtil.calculateMd5(content.getBytes())); meta.setContentMD5(md5); ossClient.putObject(bucketName, objectName, new ByteArrayInputStream(content.getBytes()), meta); } 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(); } } } }The following sample code provides an example on how to configure MD5 verification in a multipart upload operation:
import java.io.File; import java.io.FileInputStream; import java.io.InputStream; import java.util.ArrayList; import java.util.List; import com.aliyun.oss.OSS; import com.aliyun.oss.OSSClientBuilder; import com.aliyun.oss.common.auth.CredentialsProviderFactory; import com.aliyun.oss.common.auth.EnvironmentVariableCredentialsProvider; import com.aliyun.oss.common.utils.BinaryUtil; import com.aliyun.oss.model.CompleteMultipartUploadRequest; import com.aliyun.oss.model.CompleteMultipartUploadResult; import com.aliyun.oss.model.InitiateMultipartUploadRequest; import com.aliyun.oss.model.InitiateMultipartUploadResult; import com.aliyun.oss.model.PartETag; import com.aliyun.oss.model.UploadPartRequest; import com.aliyun.oss.model.UploadPartResult; 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 = "http://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. String objectName = "exampledir/object"; // Specify the path of the local file that you want to upload. String localFile = "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. ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration(); clientBuilderConfiguration.setSignatureVersion(SignVersion.V4); OSS ossClient = OSSClientBuilder.create() .endpoint(endpoint) .credentialsProvider(credentialsProvider) .clientConfiguration(clientBuilderConfiguration) .region(region) .build(); // Create an InitiateMultipartUploadRequest object. InitiateMultipartUploadRequest request = new InitiateMultipartUploadRequest(bucketName, objectName); // Optional. Specify the storage class. // ObjectMetadata metadata = new ObjectMetadata(); // metadata.setHeader(OSSHeaders.OSS_STORAGE_CLASS, StorageClass.Standard.toString()); // request.setObjectMetadata(metadata); // Initiate a multipart upload task. InitiateMultipartUploadResult upresult = ossClient.initiateMultipartUpload(request); // Obtain an upload ID. The upload ID uniquely identifies the multipart upload task. You can use the upload ID to initiate related requests such as canceling and querying a multipart upload task. String uploadId = upresult.getUploadId(); // partETags is a set of PartETags. The PartETag of a part consists of the part number and ETag value of the part. List<PartETag> partETags = new ArrayList<PartETag>(); // Calculate the total number of parts to upload. final long partSize = 1 * 1024 * 1024L; // 1MB final File sampleFile = new File(localFile); long fileLength = sampleFile.length(); int partCount = (int) (fileLength / partSize); if (fileLength % partSize != 0) { partCount++; } // Upload all parts. for (int i = 0; i < partCount; i++) { long startPos = i * partSize; long curPartSize = (i + 1 == partCount) ? (fileLength - startPos) : partSize; InputStream instream = new FileInputStream(sampleFile); InputStream instream1 = new FileInputStream(sampleFile); // Skip parts that have been uploaded. instream.skip(startPos); instream1.skip(startPos); String md5; if(i==partCount-1){ // The size of the last part is not necessarily equal to the specified part size. md5 = md5(instream1,fileLength - startPos); }else{ md5 = md5(instream1,partSize); } // instream1.skip(n) UploadPartRequest uploadPartRequest = new UploadPartRequest(); uploadPartRequest.setBucketName(bucketName); uploadPartRequest.setKey(objectName); uploadPartRequest.setUploadId(uploadId); uploadPartRequest.setInputStream(instream); uploadPartRequest.setMd5Digest(md5); // Specify the part size. Each part except the last part must be equal to or greater than 100 KB. uploadPartRequest.setPartSize(curPartSize); // Configure part numbers. Each part is configured with a part number. The value ranges from 1 to 10000. If you configure a number beyond the range, OSS returns an InvalidArgument error code. uploadPartRequest.setPartNumber( i + 1); // Parts are not necessarily uploaded in order and can be uploaded from different OSS clients. OSS sorts the parts based on the part numbers and combines the parts into a complete object. UploadPartResult uploadPartResult = ossClient.uploadPart(uploadPartRequest); // System.out.println("server md5" +uploadPartResult.getETag()); // Each time a part is uploaded, OSS returns a result that contains a PartETag. The PartETag is stored in partETags. partETags.add(uploadPartResult.getPartETag()); } // Create a CompleteMultipartUploadRequest object. // When you call the CompleteMultipartUpload operation, you must provide all valid PartETags. After OSS receives the partETags, OSS verifies all parts one by one. After part verification is successful, OSS combines these parts into a complete object. CompleteMultipartUploadRequest completeMultipartUploadRequest = new CompleteMultipartUploadRequest(bucketName, objectName, uploadId, partETags); // Optional. Set the access control list (ACL) of the object. // completeMultipartUploadRequest.setObjectACL(CannedAccessControlList.PublicRead); // Complete the multipart upload task. CompleteMultipartUploadResult completeMultipartUploadResult = ossClient.completeMultipartUpload(completeMultipartUploadRequest); // Close your OSSClient. ossClient.shutdown(); } public static String md5(InputStream in , long length1) throws Exception{ byte[] bytes = new byte[(int) length1]; long length_tmp = length1; int readSize = in.read(bytes, (int) 0, (int) length_tmp); return BinaryUtil.toBase64String(BinaryUtil.calculateMd5(bytes)); } }
CRC-64 verification
CRC-64 verification is enabled by default in object upload, download, and copy operations to check data integrity.
Note
CRC-64 can be used in the PutObject, GetObject, AppendObject, and UploadPart operations. By default, CRC-64 is enabled when you upload an object. If the CRC-64 checksum calculated on the client is different from the CRC-64 checksum returned by the OSS server, the InconsistentException error is returned.
CRC-64 verification is not supported for range download.
CRC-64 consumes CPU resources and slows down uploads and downloads.
CRC-64 in object download
The following sample code provides an example on how to perform CRC-64 when you download an object:
import com.aliyun.oss.*; import com.aliyun.oss.common.auth.*; import com.aliyun.oss.common.utils.IOUtils; import com.aliyun.oss.internal.OSSHeaders; import com.aliyun.oss.internal.OSSUtils; import com.aliyun.oss.model.GetObjectRequest; import com.aliyun.oss.model.OSSObject; import java.io.BufferedReader; import java.io.InputStreamReader; public class Demo { public static void main(String[] args) throws Throwable { // 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. String objectName = "exampledir/object"; // 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. ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration(); clientBuilderConfiguration.setSignatureVersion(SignVersion.V4); OSS ossClient = OSSClientBuilder.create() .endpoint(endpoint) .credentialsProvider(credentialsProvider) .clientConfiguration(clientBuilderConfiguration) .region(region) .build(); try { // Download the object in streaming mode. GetObjectRequest getObjectRequest = new GetObjectRequest(bucketName, objectName); OSSObject ossObject = ossClient.getObject(bucketName, objectName); // Read the object from the stream to obtain clientCRC. System.out.println("Object content:"); BufferedReader reader = new BufferedReader(new InputStreamReader(ossObject.getObjectContent())); while (true) { String line = reader.readLine(); if (line == null) break; System.out.println("\n" + line); } // 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. reader.close(); // Check whether CRC-64 is enabled on the client. By default, CRC-64 is enabled on the client. Boolean isCrcCheckEnabled = ((OSSClient)ossClient).getClientConfiguration().isCrcCheckEnabled(); // Check whether the download quest is a range download request. CRC-64 verification is not supported for range download. Boolean isRangGetRequest = getObjectRequest.getHeaders().get(OSSHeaders.RANGE) != null; // Check whether the CRC-64 value in the returned result is the same as that of the downloaded object. if (isCrcCheckEnabled && !isRangGetRequest) { Long clientCRC = IOUtils.getCRCValue(ossObject.getObjectContent()); OSSUtils.checkChecksum(clientCRC, ossObject.getServerCRC(), ossObject.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(); } } } }CRC-64 in append upload
The following sample code provides an example on how to perform CRC-64 when you upload an object by using append upload:
import com.aliyun.oss.ClientException; 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.model.*; import java.io.ByteArrayInputStream; 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 name of the bucket. Example: examplebucket. String bucketName = "examplebucket"; // Specify the full path of the object. Example: exampleobject.txt. Do not include the bucket name in the full path. String objectName = "exampleobject.txt"; // Enter the content of the first append upload, such as Hello. String firstAppendContent = "Hello"; // Enter the content of the second append upload, such as World. String secondAppendContent = "World"; // 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. ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration(); clientBuilderConfiguration.setSignatureVersion(SignVersion.V4); OSS ossClient = OSSClientBuilder.create() .endpoint(endpoint) .credentialsProvider(credentialsProvider) .clientConfiguration(clientBuilderConfiguration) .region(region) .build(); try { // Perform the first append operation. AppendObjectRequest appendObjectRequest = new AppendObjectRequest(bucketName, objectName, new ByteArrayInputStream(firstAppendContent.getBytes())); appendObjectRequest.setPosition(0L); // Set the initial CRC-64 value. OSS SDK for Java performs CRC-64 on the uploaded content by default. appendObjectRequest.setInitCRC(0L); AppendObjectResult appendObjectResult = ossClient.appendObject(appendObjectRequest); // Perform the second append upload operation. appendObjectRequest = new AppendObjectRequest(bucketName, objectName, new ByteArrayInputStream(secondAppendContent.getBytes())); appendObjectRequest.setPosition(appendObjectResult.getNextPosition()); // Set the CRC-64 value to that of the uploaded object. OSS SDK for Java performs CRC-64 on the uploaded content by default. appendObjectRequest.setInitCRC(appendObjectResult.getClientCRC()); ossClient.appendObject(appendObjectRequest); } 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 the complete sample code for MD5 verification and CRC-64, visit GitHub.