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Getting Started

Last updated: 2022-05-23 11:57:16

    Download and Installation

    • Download the COS XML Java SDK source code here.
    • Download the XML Java SDK here.
    • Download the demo here.
    • For all the code samples, see here.
    • For the SDK changelog, see Changelog.
    • For SDK FAQs, see Java SDK.
    Note:

    • If you are using COS for the first time, or your data volume is small, in order to avoid the problems of unnecessary and cumbersome code troubleshooting and program positioning, we recommend you use the more user-friendly GUI-based console, COSBrowser, or COSCLI.
    • If you encounter errors such as non-existent functions or methods when using the XML version of the SDK, update the SDK to the latest version and try again.

    Environmental dependencies

    • The SDK supports JDK v1.7, v1.8, and later.
    • For the JDK installation, see Java.
    Note:

    • For the definitions of terms such as SecretId, SecretKey, and bucket, see Introduction.
    • 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 SDK

    You can install the Java SDK using Maven or 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>5.6.54</version>
      </dependency>
      
    • Using source code
      Download the source code from GitHub or here, and import it using Maven. For example, to import it into Eclipse, select File > Import > Maven > Existing Maven Projects.

    Uninstalling SDK

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

    Getting Started

    Before use, don't rush to write the code first. We recommend you spend two minutes conducting the following test to ensure that sent requests can arrive at the COS service. This helps you determine whether you will encounter any of the problems that most Java SDK users have encountered.
    The following test assumes that you are accessing the COS service in the Guangzhou region.

    Using ping to test

    [root@VM_centos /data/home/]# ping cos.ap-guangzhou.myqcloud.com
    PING cos.ap-guangzhou.myqcloud.com (9.*.*.*) xx(xx) bytes of data.
    64 bytes from 9.*.*.* (9.*.*.*): icmp_seq=1 ttl=xx time=0.xxx ms
    64 bytes from 9.*.*.* (9.*.*.*): icmp_seq=2 ttl=xx time=0.xxx ms
    64 bytes from 9.*.*.* (9.*.*.*): icmp_seq=3 ttl=xx time=0.xxx ms
    64 bytes from 9.*.*.* (9.*.*.*): icmp_seq=4 ttl=xx time=0.xxx ms
    64 bytes from 9.*.*.* (9.*.*.*): icmp_seq=5 ttl=xx time=0.xxx ms
    64 bytes from 9.*.*.* (9.*.*.*): icmp_seq=6 ttl=xx time=0.xxx ms
    64 bytes from 9.*.*.* (9.*.*.*): icmp_seq=7 ttl=xx time=0.xxx ms
    ^C
    --- cos.ap-guangzhou.myqcloud.com ping statistics ---
    x packets transmitted, x received, 0% packet loss, time xxxms
    rtt min/avg/max/mdev = 0.xxx/0.xxx/0.xxx/0.xxx ms 
    

    If a result similar to the above is displayed, the basic network connectivity and name service are normal. If an abnormal result is returned, troubleshoot local network problems or contact your local network admin first. After confirming that everything is normal, proceed to the next step.
    On Windows, you can also click Start (or press Win+R) > Run (type cmd) > OK (or press Enter), type the ping cos.ap-guangzhou.myqcloud.com command, and press Enter to test.

    Using curl to test

    For access over HTTP:

    [root@VM_centos /data/home/]# curl http://cos.ap-guangzhou.myqcloud.com -v
    * About to connect() to cos.ap-guangzhou.myqcloud.com port 80 (#0)
    *   Trying 9.*.*.*...
    * Connected to cos.ap-guangzhou.myqcloud.com (9.*.*.*) port 80 (#0)
    > GET / HTTP/1.1
    > User-Agent: curl/*.*.0
    > Host: cos.ap-guangzhou.myqcloud.com
    > Accept: */*
    > 
    < HTTP/1.1 403 Forbidden
    < Content-Type: application/xml
    < Content-Length: XXX
    < Connection: keep-alive
    < Date: XXX XXX GMT
    < Server: tencent-cos
    < x-cos-request-id: NWE2MWQ5MjZfMTBhYzM1MGFfMTA5ODVfMTVj****
    < 
    <?xml version='1.0' encoding='utf-8' ?>
    <Error>
           <Code>AccessDenied</Code>
           <Message>Check auth failure because signture empty.</Message>
           <ServerTime>XXX XXX</ServerTime>
           <Resource>cos.ap-guangzhou.myqcloud.com/</Resource>
           <RequestId>NWE2MWQ5MjZfMTBhYzM1MGFfMTA5ODVfMTVj****==</RequestId>    
    </Error>
    * Connection #0 to host cos.ap-guangzhou.myqcloud.com left intact
    

    For access over HTTPS:

    [root@VM_centos /data/home/]# curl https://cos.ap-guangzhou.myqcloud.com -vk
    * About to connect() to cos.ap-guangzhou.myqcloud.com port 443 (#0)
    *   Trying 9.*.*.*...
    * Connected to cos.ap-guangzhou.myqcloud.com (9.*.*.*) port 443 (#0)
    * Initializing NSS with certpath: XXXX
    * skipping SSL peer certificate verification
    * SSL connection using ******
    * Server certificate:
    *       subject: CN=*.*.*.
    *       start date: XXX XXX GMT
    *       expire date: XXX XXX GMT
    *       common name: *.cos.ap-guangzhou.myqcloud.com
    *       issuer: XXX
    > GET / HTTP/1.1
    > User-Agent: curl/*.*.0
    > Host: cos.ap-guangzhou.myqcloud.com
    > Accept: */*
    > 
    < HTTP/1.1 403 Forbidden
    < Content-Type: application/xml
    < Content-Length: XXX
    < Connection: keep-alive
    < Date: XXX XXX GMT
    < Server: tencent-cos
    < x-cos-request-id: NWE2MWQ5MjZfMTBhYzM1MGFfMTA5ODVfMTVj****
    < 
    <?xml version='1.0' encoding='utf-8' ?>
    <Error>
           <Code>AccessDenied</Code>
           <Message>Check auth failure because signture empty.</Message>
           <ServerTime>XXX XXX</ServerTime>
           <Resource>cos.ap-guangzhou.myqcloud.com/</Resource>
           <RequestId>NWE2MWQ5MjZfMTBhYzM1MGFfMTA5ODVfMTVj****</RequestId>        
    </Error>
    * Connection #0 to host cos.ap-guangzhou.myqcloud.com left intact
    

    If a result similar to the above is displayed, the port connectivity is normal. If an abnormal result is returned, troubleshoot local network problems or contact your local network admin first. After confirming that everything is normal, proceed to the next step.
    On certain versions of Windows, you may need to install the Curl tool before you can run the test.

    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 samples, you can click the class name in your IDE to view details about all 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 executing any requests related to the COS service, you need to generate a COSClient class object to call 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. Make sure that there is only one instance in the program lifecycle, and call the shutdown method to shut down the instance when it is no longer needed. If you need to create a new instance, shut down the previous one first.

    If you use a permanent key to initialize a COSClient, you can get the APPId, SecretId, and SecretKey on the API Key page in the CAM console. A permanent key is suitable for most application scenarios. Below is a sample:

    // 1. Initialize the user credentials (`secretId` and `secretKey`).
    // Log in to the [CAM console](https://console.intl.cloud.tencent.com/cam/capi) to view and manage the `SecretId` and `SecretKey` of your project.
    String secretId = "SECRETID";
    String secretKey = "SECRETKEY";
    COSCredentials cred = new BasicCOSCredentials(secretId, secretKey);
    // 2. Set the bucket region. For the abbreviations for COS regions, visit https://intl.cloud.tencent.com/document/product/436/6224.
    // `clientConfig` contains the set methods to set the region, HTTPS (HTTP by default), timeout, and proxy. For detailed usage, see the source code or the FAQs about the Java SDK.
    Region region = new Region("COS_REGION");
    ClientConfig clientConfig = new ClientConfig(region);
    // The HTTPS protocol is recommended.
    // Starting from v5.6.54, HTTPS is used by default.
    clientConfig.setHttpProtocol(HttpProtocol.https);
    // 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. Below is a sample:

    // 1. Pass in the obtained temporary key (`tmpSecretId`, `tmpSecretKey`, and `sessionToken`).
    String tmpSecretId = "SECRETID";
    String tmpSecretKey = "SECRETKEY";
    String sessionToken = "TOKEN";
    BasicSessionCredentials cred = new BasicSessionCredentials(tmpSecretId, tmpSecretKey, sessionToken);
    // 2. Set the bucket region. For the abbreviations for COS regions, visit https://intl.cloud.tencent.com/document/product/436/6224.
    // `clientConfig` contains the set methods to set the region, HTTPS (HTTP by default), timeout, and proxy. For detailed usage, see the source code or the FAQs about the Java SDK.
    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:

    Member Name Configuration Method Description Type
    region Constructor or set method Bucket region. For the abbreviations for COS regions, see Regions and Access Endpoints. Region
    httpProtocol Set method The protocol used by the request. By default, HTTPS is used to interact with COS. HttpProtocol
    signExpired Set method Validity period (in seconds) of the request signature. Default value: 3600s long
    connectionTimeout Set method Timeout period in milliseconds for connection with COS. Default value: 30000 ms. int
    socketTimeout Set method Timeout period in milliseconds for the client to read data. Default value: 30000 ms. int
    httpProxyIp Set method Proxy server IP. String
    httpProxyPort Set method Proxy server port. int

    Creating bucket

    Create a bucket as shown below:

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

    Querying bucket list

    Query the bucket list as shown below:

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

    Uploading object

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

    Note:

    The classes related to advanced APIs are in the com.qcloud.cos.transfer.* sub-package.

    • 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.
    • To create a directory object, see Java SDK.
    • An object key (Key) is the unique identifier of an object in a bucket. For example, if an object's access endpoint is examplebucket-1250000000.cos.ap-guangzhou.myqcloud.com/images/picture.jpg, its key is images/picture.jpg. For more information, see Object Overview.

    Upload a file up to 5 GB as shown below:

    // Specify the file to be uploaded.
    File localFile = new File(localFilePath);
    // Specify a bucket to store the file.
    String bucketName = "examplebucket-1250000000";
    // Specify the COS path (i.e. the object key) to upload the file. For example, if the object key is `folder/picture.jpg`, the `picture.jpg` file will be uploaded to the `folder` directory.
    String key = "exampleobject";
    PutObjectRequest putObjectRequest = new PutObjectRequest(bucketName, key, localFile);
    PutObjectResult putObjectResult = cosClient.putObject(putObjectRequest);
    

    Querying object list

    Query the list of objects in a bucket as shown below:

    // Enter the bucket name in the format of `BucketName-APPID`.
    String bucketName = "examplebucket-1250000000";
    ListObjectsRequest listObjectsRequest = new ListObjectsRequest();
    // Set the bucket name.
    listObjectsRequest.setBucketName(bucketName);
    // The prefix indicates that the key of the object to be listed must start with this value.
    listObjectsRequest.setPrefix("images/");
    // Set the delimiter to `/` to list objects in the current directory. To list all objects, leave it empty.
    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;
       }
       // `common prefix` indicates the path that ends 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 size
           long fileSize = cosObjectSummary.getSize();
           // File storage class
           String storageClasses = cosObjectSummary.getStorageClass();
       }
        String nextMarker = objectListing.getNextMarker();
       listObjectsRequest.setMarker(nextMarker);
    } while (objectListing.isTruncated());
    

    Download object

    Once an object is uploaded, you can download it by calling the GetObject API with the same key, or by generating a pre-signed URL (specify GET as the download method) to share it 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.
    Download a file to a specified local path as shown below:

    // Enter the bucket name in the format of `BucketName-APPID`.
    String bucketName = "examplebucket-1250000000";
    // Specify the COS path (i.e. the object key) of the file to be downloaded. For example, if the object key is `folder/picture.jpg`, the `picture.jpg` file in the `folder` directory will be downloaded.
    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 to a local directory, e.g. a directory in D drive.
    String outputFilePath = "exampleobject";
    File downFile = new File(outputFilePath);
    getObjectRequest = new GetObjectRequest(bucketName, key);
    ObjectMetadata downObjectMeta = cosClient.getObject(getObjectRequest, downFile);
    

    Deleting object

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

    // Enter the bucket name in the format of `BucketName-APPID`.
    String bucketName = "examplebucket-1250000000";
    // Specify the COS path (i.e. the object key) of the file to be deleted. For example, if the object key is `folder/picture.jpg`, the `picture.jpg` file in the `folder` directory will be deleted.
    String key = "exampleobject";
    cosClient.deleteObject(bucketName, key);
    

    Default retry policy

    By default, if a request initiated by the COSClient generated via the SDK returns an error response, it will be retried. The retry policy is as follows:

    • Number of retries: 3 by default. You can set it using clientConfig.setMaxErrorRetry.
      If it is set to 0, no retries will be performed on requests returning any type of error.
    • Error types for retry: All client-side IOException errors, as well as server-side errors with the status codes 500, 502, 503, and 504.

    You can also configure a retry policy as needed by running the following code:

    Setting the number of retries:

    Region region = new Region("COS_REGION");
    ClientConfig clientConfig = new ClientConfig(region);
    // Set the maximum number of retries to `4`.
    clientConfig.setMaxErrorRetry = 4;
    

    Setting the retry policy:

    // Customize a retry policy.
    public class OnlyIOExceptionRetryPolicy extends RetryPolicy {
       @Override
       public <X extends CosServiceRequest> boolean shouldRetry(CosHttpRequest<X> request,
               HttpResponse response,
               Exception exception,
               int retryIndex) {
           // Retry only for client-side `IOException`.
           if (exception.getCause() instanceof IOException) {
               return true;
           }
           return false;
       }
    }
    Region region = new Region("COS_REGION");
    ClientConfig clientConfig = new ClientConfig(region);
    RetryPolicy myRetryPolicy = new OnlyIOExceptionRetryPolicy();
    // Configure the custom retry policy.
    clientConfig.setRetryPolicy(myRetryPolicy);
    

    Shutting down the client

    Shut down the COSClient and release the server threads connected over HTTP by running the following code:

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

    FAQs

    If you have any questions about the Java SDK, see Java SDK.

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