Azure Storage Blob client library for Java - version 12.28.1

Artikel
10/09/2024

Azure Blob Storage is Microsoft's object storage solution for the cloud. Blob Storage is optimized for storing massive amounts of unstructured data. Unstructured data is data that does not adhere to a particular data model or definition, such as text or binary data.

Source code | API reference documentation | REST API documentation | Product documentation | Samples

Getting started

Prerequisites

Java Development Kit (JDK) with version 8 or above
- Here are details about Java 8 client compatibility with Azure Certificate Authority.
Azure Subscription
Create Storage Account

Include the package

Include the BOM file

Please include the azure-sdk-bom to your project to take dependency on GA version of the library. In the following snippet, replace the {bom_version_to_target} placeholder with the version number. To learn more about the BOM, see the AZURE SDK BOM README.

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>com.azure</groupId>
            <artifactId>azure-sdk-bom</artifactId>
            <version>{bom_version_to_target}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

and then include the direct dependency in the dependencies section without the version tag.

<dependencies>
  <dependency>
    <groupId>com.azure</groupId>
    <artifactId>azure-storage-blob</artifactId>
  </dependency>
</dependencies>

Include direct dependency

If you want to take dependency on a particular version of the library that is not present in the BOM, add the direct dependency to your project as follows.

<dependency>
    <groupId>com.azure</groupId>
    <artifactId>azure-storage-blob</artifactId>
    <version>12.28.1</version>
</dependency>

Create a Storage Account

To create a Storage Account you can use the Azure Portal or Azure CLI.

az storage account create \
    --resource-group <resource-group-name> \
    --name <storage-account-name> \
    --location <location>

Your storage account URL, subsequently identified as <your-storage-account-url>, would be formatted as follows: http(s)://<storage-account-name>.blob.core.windows.net

Authenticate the client

In order to interact with the Storage Service (Blob, Queue, Message, MessageId, File), you'll need to create an instance of the Service Client class. To make this possible you'll need the Account SAS (shared access signature) string of the Storage Account. Learn more at SAS Token.

Get credentials

SAS Token

a. Use the Azure CLI snippet below to get the SAS token from the Storage Account.

az storage blob generate-sas \
    --account-name {Storage Account name} \
    --container-name {container name} \
    --name {blob name} \
    --permissions {permissions to grant} \
    --expiry {datetime to expire the SAS token} \
    --services {storage services the SAS allows} \
    --resource-types {resource types the SAS allows}

Example:

CONNECTION_STRING=<connection-string>

az storage blob generate-sas \
    --account-name MyStorageAccount \
    --container-name MyContainer \
    --name MyBlob \
    --permissions racdw \
    --expiry 2020-06-15

b. Alternatively, get the Account SAS token from the Azure Portal.

Go to your Storage Account
Select Shared access signature from the menu on the left
Click on Generate SAS and connection string (after setup)

Shared Key Credential

a. Use Account name and Account key. Account name is your Storage Account name.

Go to your Storage Account
Select Access keys from the menu on the left
Under key1/key2 copy the contents of the Key field

b. Use the connection string.

Go to your Storage Account
Select Access keys from the menu on the left
Under key1/key2 copy the contents of the Connection string field

Key concepts

Blob Storage is designed for:

Serving images or documents directly to a browser
Storing files for distributed access
Streaming video and audio
Writing to log files
Storing data for backup and restore, disaster recovery, and archiving
Storing data for analysis by an on-premises or Azure-hosted service

URL format

Blobs are addressable using the following URL format: The following URL addresses a blob:

https://myaccount.blob.core.windows.net/mycontainer/myblob

Resource URI Syntax

For the storage account, the base URI for blob operations includes the name of the account only:

https://myaccount.blob.core.windows.net

For a container, the base URI includes the name of the account and the name of the container:

https://myaccount.blob.core.windows.net/mycontainer

For a blob, the base URI includes the name of the account, the name of the container and the name of the blob:

https://myaccount.blob.core.windows.net/mycontainer/myblob

Note that the above URIs may not hold for more advanced scenarios such as custom domain names.

Examples

The following sections provide several code snippets covering some of the most common Azure Storage Blob tasks, including:

Create a BlobServiceClient
Create a BlobContainerClient
Create a BlobClient
Create a container
Upload data to a blob
Upload a blob from a stream
Upload a blob from local path
Upload a blob if one does not already exist
Upload a blob and overwrite if one already exists
Upload a blob via an OutputStream
Download data from a blob
Download a blob to a stream
Download a blob to local path
Read a blob via an InputStream
Enumerate blobs
Copy a blob
Generate a SAS token
Authenticate with Azure Identity
Set a proxy when building a client

Create a `BlobServiceClient`

Create a BlobServiceClient using the sasToken generated above.

BlobServiceClient blobServiceClient = new BlobServiceClientBuilder()
    .endpoint("<your-storage-account-url>")
    .sasToken("<your-sasToken>")
    .buildClient();

// Only one "?" is needed here. If the SAS token starts with "?", please removing one "?".
BlobServiceClient blobServiceClient = new BlobServiceClientBuilder()
    .endpoint("<your-storage-account-url>" + "?" + "<your-sasToken>")
    .buildClient();

Create a `BlobContainerClient`

Create a BlobContainerClient using a BlobServiceClient.

BlobContainerClient blobContainerClient = blobServiceClient.getBlobContainerClient("mycontainer");

Create a BlobContainerClient from the builder sasToken generated above.

BlobContainerClient blobContainerClient = new BlobContainerClientBuilder()
    .endpoint("<your-storage-account-url>")
    .sasToken("<your-sasToken>")
    .containerName("mycontainer")
    .buildClient();

// Only one "?" is needed here. If the SAS token starts with "?", please removing one "?".
BlobContainerClient blobContainerClient = new BlobContainerClientBuilder()
    .endpoint("<your-storage-account-url>" + "/" + "mycontainer" + "?" + "<your-sasToken>")
    .buildClient();

Create a `BlobClient`

Create a BlobClient using a BlobContainerClient.

BlobClient blobClient = blobContainerClient.getBlobClient("myblob");

Create a BlobClient from the builder sasToken generated above.

BlobClient blobClient = new BlobClientBuilder()
    .endpoint("<your-storage-account-url>")
    .sasToken("<your-sasToken>")
    .containerName("mycontainer")
    .blobName("myblob")
    .buildClient();

// Only one "?" is needed here. If the SAS token starts with "?", please removing one "?".
BlobClient blobClient = new BlobClientBuilder()
    .endpoint("<your-storage-account-url>" + "/" + "mycontainer" + "/" + "myblob" + "?" + "<your-sasToken>")
    .buildClient();

Create a container

Create a container using a BlobServiceClient.

blobServiceClient.createBlobContainer("mycontainer");

Create a container using a BlobContainerClient.

blobContainerClient.create();

Upload data to a blob

Upload BinaryData to a blob using a BlobClient generated from a BlobContainerClient.

BlobClient blobClient = blobContainerClient.getBlobClient("myblockblob");
String dataSample = "samples";
blobClient.upload(BinaryData.fromString(dataSample));

Upload a blob from a stream

Upload from an InputStream to a blob using a BlockBlobClient generated from a BlobContainerClient.

BlockBlobClient blockBlobClient = blobContainerClient.getBlobClient("myblockblob").getBlockBlobClient();
String dataSample = "samples";
try (ByteArrayInputStream dataStream = new ByteArrayInputStream(dataSample.getBytes())) {
    blockBlobClient.upload(dataStream, dataSample.length());
} catch (IOException e) {
    e.printStackTrace();
}

Upload a blob from local path

Upload a file to a blob using a BlobClient generated from a BlobContainerClient.

BlobClient blobClient = blobContainerClient.getBlobClient("myblockblob");
blobClient.uploadFromFile("local-file.jpg");

Upload a blob if one does not already exist

Upload data to a blob and fail if one already exists.

/*
 * Rather than use an if block conditioned on an exists call, there are three ways to upload-if-not-exists using
 * one network call instead of two. Equivalent options are present on all upload methods.
 */
// 1. The minimal upload method defaults to no overwriting
String dataSample = "samples";
try (ByteArrayInputStream dataStream = new ByteArrayInputStream(dataSample.getBytes())) {
    blobClient.upload(dataStream, dataSample.length());
} catch (IOException e) {
    e.printStackTrace();
}

// 2. The overwrite flag can explicitly be set to false to make intention clear
try (ByteArrayInputStream dataStream = new ByteArrayInputStream(dataSample.getBytes())) {
    blobClient.upload(dataStream, dataSample.length(), false /* overwrite */);
} catch (IOException e) {
    e.printStackTrace();
}

// 3. If the max overload is needed, access conditions must be used to prevent overwriting
try (ByteArrayInputStream dataStream = new ByteArrayInputStream(dataSample.getBytes())) {
    BlobParallelUploadOptions options =
        new BlobParallelUploadOptions(dataStream, dataSample.length());
    // Setting IfNoneMatch="*" ensures the upload will fail if there is already a blob at the destination.
    options.setRequestConditions(new BlobRequestConditions().setIfNoneMatch("*"));
    blobClient.uploadWithResponse(options, null, Context.NONE);
} catch (IOException e) {
    e.printStackTrace();
}

Upload a blob and overwrite if one already exists

Upload data to a blob and overwrite any existing data at the destination.

/*
 * Rather than use an if block conditioned on an exists call, there are three ways to upload-if-exists in one
 * network call instead of two. Equivalent options are present on all upload methods.
 */
String dataSample = "samples";

// 1. The overwrite flag can explicitly be set to true. This will succeed as a create and overwrite.
try (ByteArrayInputStream dataStream = new ByteArrayInputStream(dataSample.getBytes())) {
    blobClient.upload(dataStream, dataSample.length(), true /* overwrite */);
} catch (IOException e) {
    e.printStackTrace();
}

/*
 * 2. If the max overload is needed and no access conditions are passed, the upload will succeed as both a
 * create and overwrite.
 */
try (ByteArrayInputStream dataStream = new ByteArrayInputStream(dataSample.getBytes())) {
    BlobParallelUploadOptions options =
        new BlobParallelUploadOptions(dataStream, dataSample.length());
    blobClient.uploadWithResponse(options, null, Context.NONE);
} catch (IOException e) {
    e.printStackTrace();
}

/*
 * 3. If the max overload is needed, access conditions may be used to assert that the upload is an overwrite and
 * not simply a create.
 */
try (ByteArrayInputStream dataStream = new ByteArrayInputStream(dataSample.getBytes())) {
    BlobParallelUploadOptions options =
        new BlobParallelUploadOptions(dataStream, dataSample.length());
    // Setting IfMatch="*" ensures the upload will succeed only if there is already a blob at the destination.
    options.setRequestConditions(new BlobRequestConditions().setIfMatch("*"));
    blobClient.uploadWithResponse(options, null, Context.NONE);
} catch (IOException e) {
    e.printStackTrace();
}

Upload a blob via an `OutputStream`

Upload a blob by opening a BlobOutputStream and writing to it through standard stream APIs.

/*
 * Opening a blob input stream allows you to write to a blob through a normal stream interface. It will not be
 * committed until the stream is closed.
 * This option is convenient when the length of the data is unknown.
 * This can only be done for block blobs. If the target blob already exists as another type of blob, it will
 * fail.
 */
try (BlobOutputStream blobOS = blobClient.getBlockBlobClient().getBlobOutputStream()) {
    blobOS.write(new byte[0]);
} catch (IOException e) {
    e.printStackTrace();
}

Download data from a blob

Download a blob to an OutputStream using a BlobClient.

BinaryData content = blobClient.downloadContent();

Download a blob to a stream

Download a blob to an OutputStream using a BlobClient.

try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {
    blobClient.downloadStream(outputStream);
} catch (IOException e) {
    e.printStackTrace();
}

Download a blob to local path

Download blob to a local file using a BlobClient.

blobClient.downloadToFile("downloaded-file.jpg");

Read a blob via an `InputStream`

Download a blob by opening a BlobInputStream and reading from it through standard stream APIs.

/*
 * Opening a blob input stream allows you to read from a blob through a normal stream interface. It is also
 * mark-able.
*/
try (BlobInputStream blobIS = blobClient.openInputStream()) {
    blobIS.read();
} catch (IOException e) {
    e.printStackTrace();
}

Enumerate blobs

Enumerating all blobs using a BlobContainerClient.

for (BlobItem blobItem : blobContainerClient.listBlobs()) {
    System.out.println("This is the blob name: " + blobItem.getName());
}

Enumerate all blobs and create new clients pointing to the items.

for (BlobItem blobItem : blobContainerClient.listBlobs()) {
    BlobClient blobClient;
    if (blobItem.getSnapshot() != null) {
        blobClient = blobContainerClient.getBlobClient(blobItem.getName(), blobItem.getSnapshot());
    } else {
        blobClient = blobContainerClient.getBlobClient(blobItem.getName());
    }
    System.out.println("This is the new blob uri: " + blobClient.getBlobUrl());
}

Copy a blob

Copying a blob. Please refer to the javadocs on each of these methods for more information around requirements on the copy source and its authentication.

SyncPoller<BlobCopyInfo, Void> poller = blobClient.beginCopy("<url-to-blob>", Duration.ofSeconds(1));
poller.waitForCompletion();

blobClient.copyFromUrl("url-to-blob");

Generate a SAS token

Use an instance of a client to generate a new SAS token.

/*
 * Generate an account sas. Other samples in this file will demonstrate how to create a client with the sas
 * token.
 */
// Configure the sas parameters. This is the minimal set.
OffsetDateTime expiryTime = OffsetDateTime.now().plusDays(1);
AccountSasPermission accountSasPermission = new AccountSasPermission().setReadPermission(true);
AccountSasService services = new AccountSasService().setBlobAccess(true);
AccountSasResourceType resourceTypes = new AccountSasResourceType().setObject(true);

// Generate the account sas.
AccountSasSignatureValues accountSasValues =
    new AccountSasSignatureValues(expiryTime, accountSasPermission, services, resourceTypes);
String sasToken = blobServiceClient.generateAccountSas(accountSasValues);

// Generate a sas using a container client
BlobContainerSasPermission containerSasPermission = new BlobContainerSasPermission().setCreatePermission(true);
BlobServiceSasSignatureValues serviceSasValues =
    new BlobServiceSasSignatureValues(expiryTime, containerSasPermission);
blobContainerClient.generateSas(serviceSasValues);

// Generate a sas using a blob client
BlobSasPermission blobSasPermission = new BlobSasPermission().setReadPermission(true);
serviceSasValues = new BlobServiceSasSignatureValues(expiryTime, blobSasPermission);
blobClient.generateSas(serviceSasValues);

Authenticate with Azure Identity

The Azure Identity library provides Azure Active Directory support for authenticating with Azure Storage.

BlobServiceClient blobStorageClient = new BlobServiceClientBuilder()
    .endpoint("<your-storage-account-url>")
    .credential(new DefaultAzureCredentialBuilder().build())
    .buildClient();

Set a proxy when building a client

ProxyOptions options = new ProxyOptions(ProxyOptions.Type.HTTP, new InetSocketAddress("localhost", 888));
BlobServiceClient client = new BlobServiceClientBuilder()
    .endpoint("<ENDPOINT>")
    .sasToken("<SAS_TOKEN>")
    .httpClient(new NettyAsyncHttpClientBuilder().proxy(options).build())
    .buildClient();

Allow the client builder to determine the HttpClient type to be used but construct it with passed configurations.

HttpClientOptions clientOptions = new HttpClientOptions()
    .setProxyOptions(new ProxyOptions(ProxyOptions.Type.HTTP, new InetSocketAddress("localhost", 888)));
BlobServiceClient client = new BlobServiceClientBuilder()
    .endpoint("<ENDPOINT>")
    .sasToken("<SAS_TOKEN>")
    .clientOptions(clientOptions)
    .buildClient();

Troubleshooting

When interacting with blobs using this Java client library, errors returned by the service correspond to the same HTTP status codes returned for REST API requests. For example, if you try to retrieve a container or blob that doesn't exist in your Storage Account, a 404 error is returned, indicating Not Found.

Default HTTP Client

All client libraries by default use the Netty HTTP client. Adding the above dependency will automatically configure the client library to use the Netty HTTP client. Configuring or changing the HTTP client is detailed in the HTTP clients wiki.

Default SSL library

All client libraries, by default, use the Tomcat-native Boring SSL library to enable native-level performance for SSL operations. The Boring SSL library is an uber jar containing native libraries for Linux / macOS / Windows, and provides better performance compared to the default SSL implementation within the JDK. For more information, including how to reduce the dependency size, refer to the performance tuning section of the wiki.

Next steps

Several Storage blob Java SDK samples are available to you in the SDK's GitHub repository. These samples provide example code for additional scenarios commonly encountered while working with Key Vault:

Next steps Samples

Samples are explained in detail here.

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution.

When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.

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