Object Storage Service:Prevent objects with the same name from being overwritten (Android SDK)

Prerequisites

Before you begin, ensure that you have:

• An initialized OSSClient instance. For setup instructions, see Initialization

How x-oss-forbid-overwrite works

Set this header on ObjectMetadata before submitting the request:

Simple upload

// Enter the bucket name. Example: examplebucket.
String bucketName = "examplebucket";
// Enter the full path of the object. Do not include the bucket name. Example: exampledir/exampleobject.txt.
String objectKey = "exampledir/exampleobject.txt";
// Enter the full path of the local file to upload.
String localFile = "/storage/emulated/0/oss/examplefile.txt";

PutObjectRequest put = new PutObjectRequest(bucketName, objectKey, localFile);
ObjectMetadata metadata = new ObjectMetadata();

// Specify whether to overwrite an object with the same name.
// If you do not specify x-oss-forbid-overwrite, an object with the same name is overwritten by default.
// If you set x-oss-forbid-overwrite to false, an object with the same name is overwritten.
// If you set x-oss-forbid-overwrite to true, an object with the same name is not overwritten. If an object with the same name exists, the program reports an error.
metadata.setHeader("x-oss-forbid-overwrite", "true");
put.setMetadata(metadata);

OSSAsyncTask task = oss.asyncPutObject(put, new OSSCompletedCallback<PutObjectRequest, PutObjectResult>() {
    @Override
    public void onSuccess(PutObjectRequest request, PutObjectResult result) {
        Log.d("PutObject", "UploadSuccess");
        Log.d("ETag", result.getETag());
        Log.d("RequestId", result.getRequestId());
    }

    @Override
    public void onFailure(PutObjectRequest request, ClientException clientExcepion, ServiceException serviceException) {
        if (clientExcepion != null) {
            // A client exception occurred, such as a network error.
            clientExcepion.printStackTrace();
        }
        if (serviceException != null) {
            // A server-side exception occurred.
            Log.e("ErrorCode", serviceException.getErrorCode());
            Log.e("RequestId", serviceException.getRequestId());
            Log.e("HostId", serviceException.getHostId());
            Log.e("RawMessage", serviceException.getRawMessage());
        }
    }
});

Object copy

// Enter the source bucket name.
String srcBucketName = "srcbucket";
// Enter the full path of the source object.
String srcObjectKey = "dir1/srcobject.txt";
// Enter the destination bucket name.
String destBucketName = "destbucket";
// Enter the full path of the destination object.
String destObjectKey = "dir2/destobject.txt";

CopyObjectRequest copyObjectRequest = new CopyObjectRequest(srcBucketName, srcObjectKey, destBucketName, destObjectKey);
ObjectMetadata metadata = new ObjectMetadata();

// Specify whether to overwrite an object with the same name during the copy.
// If you do not specify x-oss-forbid-overwrite, an object with the same name is overwritten by default.
// If you set x-oss-forbid-overwrite to false, an object with the same name is overwritten.
// If you set x-oss-forbid-overwrite to true, an object with the same name is not overwritten. If an object with the same name exists, the program reports an error.
metadata.setHeader("x-oss-forbid-overwrite", "true");
copyObjectRequest.setNewObjectMetadata(metadata);

OSSAsyncTask copyTask = oss.asyncCopyObject(copyObjectRequest, new OSSCompletedCallback<CopyObjectRequest, CopyObjectResult>() {
    @Override
    public void onSuccess(CopyObjectRequest request, CopyObjectResult result) {
        Log.d("copyObject", "copy success!");
    }

    @Override
    public void onFailure(CopyObjectRequest request, ClientException clientExcepion, ServiceException serviceException) {
        if (clientExcepion != null) {
            // A client exception occurred, such as a network error.
            clientExcepion.printStackTrace();
        }
        if (serviceException != null) {
            // A service exception occurred.
            Log.e("ErrorCode", serviceException.getErrorCode());
            Log.e("RequestId", serviceException.getRequestId());
            Log.e("HostId", serviceException.getHostId());
            Log.e("RawMessage", serviceException.getRawMessage());
        }
    }
});

Multipart upload

A multipart upload involves three API operations: InitiateMultipartUpload, UploadPart, and CompleteMultipartUpload. Set x-oss-forbid-overwrite at both the InitiateMultipartUpload and CompleteMultipartUpload steps.

// Enter the bucket name. Example: examplebucket.
String bucketName = "examplebucket";
// Enter the full path of the object. Do not include the bucket name. Example: exampledir/exampleobject.txt.
String objectKey = "exampledir/exampleobject.txt";
// Enter the full path of the local file to upload.
String localFile = "/storage/emulated/0/oss/examplefile.txt";

// Initialize the multipart upload.
InitiateMultipartUploadRequest init = new InitiateMultipartUploadRequest(bucketName, objectKey);
ObjectMetadata metadata = new ObjectMetadata();
// Specify whether to overwrite an object with the same name during the upload.
// If you do not specify x-oss-forbid-overwrite, an object with the same name is overwritten by default.
// If you set x-oss-forbid-overwrite to false, an object with the same name is overwritten.
// If you set x-oss-forbid-overwrite to true, an object with the same name is not overwritten. If an object with the same name exists, the program reports an error.
metadata.setHeader("x-oss-forbid-overwrite", "true");
init.setMetadata(metadata);

InitiateMultipartUploadResult initResult = oss.initMultipartUpload(init);
// The upload ID uniquely identifies this multipart upload. Use it to upload parts, cancel, or query the upload.
String uploadId = initResult.getUploadId();

// Set the size of each part in bytes. The value must be between 100 KB and 5 GB.
int partCount = 100 * 1024;

// Upload parts.
List<PartETag> partETags = new ArrayList<PartETag>();
for (int i = 1; i < 5; i++) {
    byte[] data = new byte[partCount];

    RandomAccessFile raf = new RandomAccessFile(localFile, "r");
    long skip = (i - 1) * partCount;
    raf.seek(skip);
    raf.readFully(data, 0, partCount);

    UploadPartRequest uploadPart = new UploadPartRequest();
    uploadPart.setBucketName(bucketName);
    uploadPart.setObjectKey(objectKey);
    uploadPart.setUploadId(uploadId);
    // Part numbers start from 1. The value must be between 1 and 10,000.
    uploadPart.setPartNumber(i);
    uploadPart.setPartContent(data);
    try {
        UploadPartResult result = oss.uploadPart(uploadPart);
        PartETag partETag = new PartETag(uploadPart.getPartNumber(), result.getETag());
        partETags.add(partETag);
    } catch (ServiceException serviceException) {
        OSSLog.logError(serviceException.getErrorCode());
    }
}

Collections.sort(partETags, new Comparator<PartETag>() {
    @Override
    public int compare(PartETag lhs, PartETag rhs) {
        if (lhs.getPartNumber() < rhs.getPartNumber()) {
            return -1;
        } else if (lhs.getPartNumber() > rhs.getPartNumber()) {
            return 1;
        } else {
            return 0;
        }
    }
});

// Complete the multipart upload.
CompleteMultipartUploadRequest complete = new CompleteMultipartUploadRequest(bucketName, objectKey, uploadId, partETags);
metadata = new ObjectMetadata();
// Specify whether to overwrite an object with the same name when you complete the upload.
// If you do not specify x-oss-forbid-overwrite, an object with the same name is overwritten by default.
// If you set x-oss-forbid-overwrite to false, an object with the same name is overwritten.
// If you set x-oss-forbid-overwrite to true, an object with the same name is not overwritten. If an object with the same name exists, the program reports an error.
metadata.setHeader("x-oss-forbid-overwrite", "true");
complete.setMetadata(metadata);
CompleteMultipartUploadResult completeResult = oss.completeMultipartUpload(complete);

What's next

• PutObject — API reference for simple upload

• CopyObject — API reference for object copy

• InitiateMultipartUpload — API reference for initiating a multipart upload

• UploadPart — API reference for uploading a part

• CompleteMultipartUpload — API reference for completing a multipart upload

• Initialization — How to initialize an OSSClient instance