Download and Installation

Relevant resources

• Download the COS XML Java SDK source code here.
• Download the XML Java SDK here.
• Download the demo here.
• For the complete sample, go to GitHub.

Environmental dependencies

• The SDK supports JDK v1.7, v1.8 or higher.
• For more information on JDK installation, see Java Installation and Configuration.

Note：

• For the definitions of terms such as SecretId, SecretKey, and Bucket, see COS Glossary.
• You can find common classes for the COS Java SDK in the following packages:
• The classes related to client configuration are in the com.qcloud.cos.* package.
• The classes related to permissions are in the com.qcloud.cos.auth.* sub-package.
• The classes related to exceptions are in the com.qcloud.cos.exception.* sub-package.
• The classes related to requests are in the com.qcloud.cos.model.* sub-package.
• The classes related to regions are in the com.qcloud.cos.region.* sub-package.
• The classes related to advanced APIs are in the com.qcloud.cos.transfer.* sub-package.

Installing the SDK

You can install the Java SDK through Maven or via source code:

• Using Maven
  Add required dependencies to the pom.xml file of your Maven project as follows:

  <dependency>
    <groupId>com.qcloud</groupId>
    <artifactId>cos_api</artifactId>
    <version>5.6.24</version>
  </dependency>

• Using source code
  Download the source code here or by downloading the SDK, and import it through Maven. For example, to import it into Eclipse, select File > Import > maven > Existing Maven Projects.

Uninstalling the SDK

Uninstall the SDK by removing the POM dependencies or source code.

Getting Started

The following describes how to use the COS Java SDK to complete basic operations, such as initializing the client, creating a bucket, querying a bucket list, uploading an object, querying an object list, downloading an object, and deleting an object. For the classes in the examples, you can click on the class name in your IDE to view more details on all of its fields and functions.

Importing classes

The COS Java SDK package is named com.qcloud.cos.*. You can import the classes required for running your program through your IDE such as Eclipse and IntelliJ.

Initializing the client

Before making any request for COS services, you need to generate a COSClient class object for calling the COS APIs.

Note：

COSClient is a thread-safe class that allows multi-thread access to the same instance. Because an instance maintains a connection pool internally, creating multiple instances may lead to resource exhaustion. Please ensure there is only one instance in the program lifecycle, and call the shutdown method to turn off the instance when no longer needed. If you need to create a new instance, shut down the previous instance first.

If you use a permanent key to initialize the COSClient, you need to obtain your SecretId and SecretKey from the API Key Management page on the CAM Console. A permanent key can be used for most application scenarios. An example is provided below:

// 1. Initialize the user credentials (secretId, secretKey).
String secretId = "COS_SECRETID";
String secretKey = "COS_SECRETKEY";
COSCredentials cred = new BasicCOSCredentials(secretId, secretKey);
// 2. Set the bucket region. For the abbreviations of COS regions, see https://intl.cloud.tencent.com/document/product/436/6224.
// clientConfig contains set methods to set region, HTTPS (HTTP by default), timeout, proxy, etc. For details, see the source code or the Java SDK FAQs.
Region region = new Region("COS_REGION");
ClientConfig clientConfig = new ClientConfig(region);
// 3. Generate a COS client.
COSClient cosClient = new COSClient(cred, clientConfig);

You can also use a temporary key to initialize the COSClient. For more information on how to generate and use a temporary key, see Generating and Using Temporary Keys. An example is shown below:

// 1. Pass in the obtained temporary key (tmpSecretId, tmpSecretKey, sessionToken)
String tmpSecretId = "COS_SECRETID";
String tmpSecretKey = "COS_SECRETKEY";
String sessionToken = "COS_TOKEN";
BasicSessionCredentials cred = new BasicSessionCredentials(tmpSecretId, tmpSecretKey, sessionToken);
// 2. Set the bucket region. For the abbreviations of COS regions, see https://intl.cloud.tencent.com/document/product/436/6224.
// clientConfig contains set methods to set region, HTTPS (HTTP by default), timeout, and proxy, etc. For details, see the source code or the Java SDK FAQs.
Region region = new Region("COS_REGION");
ClientConfig clientConfig = new ClientConfig(region);
// 3. Generate a COS client.
COSClient cosClient = new COSClient(cred, clientConfig);

The ClientConfig class is a configuration class containing the following main members:

Creating a bucket

The following example creates a bucket for the selected region and bucket:

String bucket = "examplebucket-1250000000"; // Bucket name in the format: `BucketName-APPID`
CreateBucketRequest createBucketRequest = new CreateBucketRequest(bucket);
// Set the bucket permission to Private (private read/write). Other options include public read/private write and public read/write
createBucketRequest.setCannedAcl(CannedAccessControlList.Private);
try{
    Bucket bucketResult = cosClient.createBucket(createBucketRequest);
} catch (CosServiceException serverException) {
    serverException.printStackTrace();
} catch (CosClientException clientException) {
    clientException.printStackTrace();
}

Querying a bucket list

The sample below queries a bucket list:

List<Bucket> buckets = cosClient.listBuckets();
for (Bucket bucketElement : buckets) {
    String bucketName = bucketElement.getName();
    String bucketLocation = bucketElement.getLocation();
}

Uploading an object

Upload a local file or input stream with a known length to COS. It is most suitable for uploading small image files below 20 MB. The maximum file size allowed is 5 GB. For larger files, you need to use multipart upload or the advanced upload API.

• If most of your local files are over 20 MB, we recommend you upload them with the advanced upload API.
• If an object with the same key already exists in COS, it will be overwritten by the newly-uploaded one.
• If you want to create a directory project, see How to create a directory in the SDK?.
• An object key (Key) is the unique identifier of an object in a bucket. For example, in the object endpoint examplebucket-1250000000.cos.ap-guangzhou.myqcloud.com/images/picture.jpg, the object key is images/picture.jpg. For more information, see Object Key.

Below is a example of uploading a file up to 5 GB:

// Specify the file to be uploaded
File localFile = new File(localFilePath);
// Specify the destination bucket
String bucketName = "examplebucket-1250000000";
// Specify the key of the object to be uploaded to COS
String key = "exampleobject";
PutObjectRequest putObjectRequest = new PutObjectRequest(bucketName, key, localFile);
PutObjectResult putObjectResult = cosClient.putObject(putObjectRequest);

Querying an object list

The sample below queries a list of objects in a bucket:

// Enter the bucket name in the format: BucketName-APPID.
String bucketName = "examplebucket-1250000000";
ListObjectsRequest listObjectsRequest = new ListObjectsRequest();
// Set the bucket name
listObjectsRequest.setBucketName(bucketName);
// The prefix indicates to list objects whose key starts with this value
listObjectsRequest.setPrefix("images/");
// Set the delimiter to "/" to list objects in the current directory; and to null to list all objects
listObjectsRequest.setDelimiter("/");
// Set the maximum number of traversed objects (up to 1,000 per listobject request)
listObjectsRequest.setMaxKeys(1000);
ObjectListing objectListing = null;
do {
    try {
        objectListing = cosClient.listObjects(listObjectsRequest);
    } catch (CosServiceException e) {
        e.printStackTrace();
        return;
    } catch (CosClientException e) {
        e.printStackTrace();
        return;
    }
    // A common prefix indicates paths that end with the delimiter. If the delimiter is set to "/", the common prefix indicates the paths of all subdirectories
    List<String> commonPrefixs = objectListing.getCommonPrefixes();

    // The object summary shows all listed objects
    List<COSObjectSummary> cosObjectSummaries = objectListing.getObjectSummaries();
    for (COSObjectSummary cosObjectSummary : cosObjectSummaries) {
        // File path key
        String key = cosObjectSummary.getKey();
        // File Etag
        String etag = cosObjectSummary.getETag();
        // File length
        long fileSize = cosObjectSummary.getSize();
        // File storage class
        String storageClasses = cosObjectSummary.getStorageClass();
    }

    String nextMarker = objectListing.getNextMarker();
    listObjectsRequest.setMarker(nextMarker);
} while (objectListing.isTruncated());

Downloading an object

Once an object is uploaded, you can download it by calling the GET Object API with the same key, or by generating a pre-signed URL (Please specify GET as the download method) to share to another device for download. Note that the pre-signed URL may be valid only for a limited period if your file is set to private-read.
The sample below downloads a file to a specified local path:

// Enter the bucket name in the format: BucketName-APPID.
String bucketName = "examplebucket-1250000000";
String key = "exampleobject";
// Method 1. Get the input stream of the downloaded file
GetObjectRequest getObjectRequest = new GetObjectRequest(bucketName, key);
COSObject cosObject = cosClient.getObject(getObjectRequest);
COSObjectInputStream cosObjectInput = cosObject.getObjectContent();
// Download the CRC64 value of the object
String crc64Ecma = cosObject.getObjectMetadata().getCrc64Ecma();
// Close the input stream
cosObjectInput.close();

// Method 2. Download the file locally
String outputFilePath = "exampleobject";
File downFile = new File(outputFilePath);
getObjectRequest = new GetObjectRequest(bucketName, key);
ObjectMetadata downObjectMeta = cosClient.getObject(getObjectRequest, downFile);

Deleting an object

You can delete an object in a specified path in COS with the following code:

// Enter the bucket name in the format: BucketName-APPID.
String bucketName = "examplebucket-1250000000";
String key = "exampleobject";
cosClient.deleteObject(bucketName, key);

Closing the client

Close the COSClient and release the server threads connected over HTTP with the following code:

// Close the client (release server threads)
cosClient.shutdown();