Help Center/ Object Storage Service/ SDK Reference/ Java/ Object APIs (SDK for Java)/ Verifying File Consistency (SDK for Java)/ Using MD5 to Verify File Consistency During Uploads (SDK for Java)
Updated on 2026-08-14 GMT+08:00
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Using MD5 to Verify File Consistency During Uploads (SDK for Java)

You can use MD5 to verify file consistency during uploads through the following APIs:

Sample Code 1: Uploading an Object - File-Based

This example uploads local file localimage.jpg to bucket examplebucket as object objectname and calls ObsClient.base64Md5 to calculate the Content-MD5 header.

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import com.obs.services.ObsClient;
import com.obs.services.exception.ObsException;
import com.obs.services.model.ObjectMetadata;
import java.io.File;
import java.nio.file.Files;
import java.nio.file.Paths;
public class PutObject009 {
    public static void main(String[] args) {
        // Obtain an AK/SK pair using environment variables or import the AK/SK pair in other ways. Using hard coding may result in leakage.
        // Obtain an AK/SK pair on the management console.
        String ak = System.getenv("ACCESS_KEY_ID");
        String sk = System.getenv("SECRET_ACCESS_KEY_ID");
        // (Optional) If you are using a temporary AK/SK pair and a security token to access OBS, you are advised not to use hard coding, which may result in information leakage.
        // Obtain an AK/SK pair and a security token using environment variables or import them in other ways.
        // String securityToken = System.getenv("SECURITY_TOKEN");
        // Enter the endpoint corresponding to the bucket. CN-Hong Kong is used here as an example. Replace it with the one currently in use.
        String endPoint = "https://obs.ap-southeast-1.myhuaweicloud.com";
        // Obtain an endpoint using environment variables or import it in other ways.
        //String endPoint = System.getenv("ENDPOINT");
        
        // Create an ObsClient instance.
        // Use a permanent AK/SK pair to initialize the client.
        ObsClient obsClient = new ObsClient(ak, sk, endPoint);
        // Use a temporary AK/SK pair and security token to initialize the client.
        // ObsClient obsClient = new ObsClient(ak, sk, securityToken, endPoint);

        try {
            // Set the MD5 value for an object.
            // Upload an image.
            ObjectMetadata metadata = new ObjectMetadata();
            // Your file's Base64-encoded MD5
            String base64Md5 = obsClient.base64Md5(Files.newInputStream(Paths.get("localimage.jpg")));
            metadata.setContentMd5(base64Md5);
            obsClient.putObject("examplebucket", "objectname", new File("localimage.jpg"), metadata);
            System.out.println("putObject successfully");
        } catch (ObsException e) {
            System.out.println("putObject failed");
            // Request failed. Print the HTTP status code.
            System.out.println("HTTP Code:" + e.getResponseCode());
            // Request failed. Print the server-side error code.
            System.out.println("Error Code:" + e.getErrorCode());
            // Request failed. Print the error details.
            System.out.println("Error Message:" + e.getErrorMessage());
            // Request failed. Print the request ID.
            System.out.println("Request ID:" + e.getErrorRequestId());
            System.out.println("Host ID:" + e.getErrorHostId());
            e.printStackTrace();
        } catch (Exception e) {
            System.out.println("putObject failed");
            // Print other error information.
            e.printStackTrace();
        }
    }
}

Sample Code 2: Uploading an Object - Append

The following code shows how to use MD5 to verify data consistency during an append upload:

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import com.obs.services.ObsClient;
import com.obs.services.exception.ObsException;
import com.obs.services.model.AppendObjectRequest;
import com.obs.services.model.AppendObjectResult;
import com.obs.services.model.ObjectMetadata;

import java.io.ByteArrayInputStream;

public class AppendObjectWithMD5{
    public static void main(String[] args) {
        // Obtain an AK/SK pair using environment variables or import the AK/SK pair in other ways. Using hard coding may result in leakage.
        // Obtain an AK/SK pair on the management console.
        String ak = System.getenv("ACCESS_KEY_ID");
        String sk = System.getenv("SECRET_ACCESS_KEY_ID");
        // (Optional) If you are using a temporary AK/SK pair and a security token to access OBS, you are advised not to use hard coding, which may result in information leakage.
        // Obtain an AK/SK pair and a security token using environment variables or import them in other ways.
        // String securityToken = System.getenv("SECURITY_TOKEN");
        // Enter the endpoint corresponding to the bucket. CN-Hong Kong is used here as an example. Replace it with the one currently in use.
        String endPoint = "https://obs.ap-southeast-1.myhuaweicloud.com";
        // Obtain an endpoint using environment variables or import it in other ways.
        //String endPoint = System.getenv("ENDPOINT");
        
        // Create an ObsClient instance.
        // Use a permanent AK/SK pair to initialize the client.
        ObsClient obsClient = new ObsClient(ak, sk, endPoint);
        // Use a temporary AK/SK pair and security token to initialize the client.
        // ObsClient obsClient = new ObsClient(ak, sk, securityToken, endPoint);

        try {
            String content = "Hello OBS";
            // Use the MD5 algorithm provided by the OBS client.
            String contentMD5 = obsClient.base64Md5(new ByteArrayInputStream(content.getBytes()));
            System.out.println("Content MD5 calculated: " + contentMD5);
            AppendObjectRequest request = new AppendObjectRequest();
            request.setBucketName("ztw-test11");
            request.setObjectKey("objectname1111");
            request.setPosition(0);
            // Send the MD5 value to the server for verification.
            ObjectMetadata metadata = new ObjectMetadata();
            metadata.setContentMd5(contentMD5);
            request.setMetadata(metadata);
            request.setInput(new ByteArrayInputStream("Hello OBS".getBytes()));
            // Append data to an object.
            obsClient.appendObject(request);
            System.out.println("AppendObject successfully");
        } catch (ObsException e) {
            System.out.println("AppendObject failed");
            // Request failed. Print the HTTP status code.
            System.out.println("HTTP Code:" + e.getResponseCode());
            // Request failed. Print the server-side error code.
            System.out.println("Error Code:" + e.getErrorCode());
            // Request failed. Print the error details.
            System.out.println("Error Message:" + e.getErrorMessage());
            // Request failed. Print the request ID.
            System.out.println("Request ID:" + e.getErrorRequestId());
            System.out.println("Host ID:" + e.getErrorHostId());
            // In an abnormal scenario, print all headers, which may contain error information.
            Map<String, String> headers = e.getResponseHeaders();
            if (headers != null) {
                for (Map.Entry<String, String> header : headers.entrySet()) {
                    System.out.println(header.getKey() + ":" + header.getValue());
                }
            }
            e.printStackTrace();
        } catch (Exception e) {
            System.out.println("AppendObject failed");
            // Print other error information.
            e.printStackTrace();
        }
    }
}

Sample Code 3: Uploading a Part

The following code shows how to use MD5 to verify data consistency during a part upload: 
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import com.obs.services.ObsClient;
import com.obs.services.exception.ObsException;
import com.obs.services.internal.utils.CRC64;
import com.obs.services.model.InitiateMultipartUploadRequest;
import com.obs.services.model.InitiateMultipartUploadResult;
import com.obs.services.model.UploadPartRequest;
import com.obs.services.model.UploadPartResult;
import java.io.File;
import java.util.Map;
import static com.obs.services.internal.Constants.CommonHeaders.HASH_CRC64ECMA;

public class UploadPartWithMD5{
    public static void main(String[] args) {
        // Obtain an AK/SK pair using environment variables or import the AK/SK pair in other ways. Using hard coding may result in leakage.
        // Obtain an AK/SK pair on the management console.
        String ak = System.getenv("ACCESS_KEY_ID");
        String sk = System.getenv("SECRET_ACCESS_KEY_ID");
        // (Optional) If you are using a temporary AK/SK pair and a security token to access OBS, you are advised not to use hard coding, which may result in information leakage.
        // Obtain an AK/SK pair and a security token using environment variables or import them in other ways.
        // String securityToken = System.getenv("SECURITY_TOKEN");
        // Enter the endpoint corresponding to the bucket. CN-Hong Kong is used here as an example. Replace it with the one currently in use.
        String endPoint = "https://obs.ap-southeast-1.myhuaweicloud.com";
        // Obtain an endpoint using environment variables or import it in other ways.
        //String endPoint = System.getenv("ENDPOINT");
        
        // Create an ObsClient instance.
        // Use a permanent AK/SK pair to initialize the client.
        ObsClient obsClient = new ObsClient(ak, sk, endPoint);
        // Use a temporary AK/SK pair and security token to initialize the client.
        // ObsClient obsClient = new ObsClient(ak, sk, securityToken, endPoint);

        try {
            // Upload a part.
            String exampleBucket = "examplebucket";
            String localFilePath = "localfile";
            String exampleObjectKey = "objectKey";
            File exampleFile = new File(localFilePath);
            InitiateMultipartUploadRequest initiateMultipartUploadRequest =
                    new InitiateMultipartUploadRequest(exampleBucket, exampleObjectKey);
            InitiateMultipartUploadResult initiateMultipartUploadResult =
                    obsClient.initiateMultipartUpload(initiateMultipartUploadRequest);
            String uploadId = initiateMultipartUploadResult.getUploadId();

            UploadPartRequest uploadPartRequest = new UploadPartRequest(exampleBucket,
                    exampleObjectKey,
                    exampleFile);
            uploadPartRequest.setUploadId(uploadId);
            // Enable MD5 verification for the uploaded data.
            uploadPartRequest.setAttachMd5(true);
            uploadPartRequest.setPartNumber(1);
            uploadPartRequest.setPartSize(exampleFile.length());
            obsClient.uploadPart(uploadPartRequest);
            System.out.println("UploadPart successfully");
        } catch (ObsException e) {
            System.out.println("UploadPart failed");
            // Request failed. Print the HTTP status code.
            System.out.println("HTTP Code:" + e.getResponseCode());
            // Request failed. Print the server-side error code.
            System.out.println("Error Code:" + e.getErrorCode());
            // Request failed. Print the error details.
            System.out.println("Error Message:" + e.getErrorMessage());
            // Request failed. Print the request ID.
            System.out.println("Request ID:" + e.getErrorRequestId());
            System.out.println("Host ID:" + e.getErrorHostId());
            // In an abnormal scenario, print all headers, which may contain error information.
            Map<String, String> headers = e.getResponseHeaders();
            if(headers != null){
                for (Map.Entry<String, String> header : headers.entrySet()) {
                    System.out.println(header.getKey()+":"+header.getValue());
                }
            }
            e.printStackTrace();
        } catch (Exception e) {
            System.out.println("UploadPart failed");
            // Print other error information.
            e.printStackTrace();
        }
    }
}