Get started with Azure Blob Storage and Java

• .NET
• Java
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This article shows you how to connect to Azure Blob Storage by using the Azure Blob Storage client library for Java. Once connected, your code can operate on containers, blobs, and features of the Blob Storage service.

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Prerequisites

• Azure subscription - create one for free
• Azure storage account - create a storage account
• Java Development Kit (JDK) version 8 or above
• Apache Maven is used for project management in this example

Set up your project

Note

This article uses the Maven build tool to build and run the sample code. Other build tools, such as Gradle, also work with the Azure SDK for Java.

Use Maven to create a new console app, or open an existing project. Follow these steps to install packages and add the necessary import directives.

Install packages

Open the pom.xml file in your text editor. Install the packages by including the BOM file, or including a direct dependency.

Include the BOM file

Add azure-sdk-bom to take a dependency on the latest version of the library. In the following snippet, replace the {bom_version_to_target} placeholder with the version number. Using azure-sdk-bom keeps you from having to specify the version of each individual dependency. 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>

Add the following dependency elements to the group of dependencies. The azure-identity dependency is needed for passwordless connections to Azure services.

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

Include a direct dependency

To take dependency on a particular version of the library, add the direct dependency to your project:

<dependency>
    <groupId>com.azure</groupId>
    <artifactId>azure-storage-blob</artifactId>
    <version>{package_version_to_target}</version>
</dependency>
<dependency>
      <groupId>com.azure</groupId>
      <artifactId>azure-storage-common</artifactId>
      <version>{package_version_to_target}</version>
</dependency>
<dependency>
    <groupId>com.azure</groupId>
    <artifactId>azure-identity</artifactId>
    <version>{package_version_to_target}</version>
</dependency>

Include import directives

Then open your code file and add the necessary import directives. In this example, we add the following directives in the App.java file:

import com.azure.core.credential.*;
import com.azure.identity.*;
import com.azure.storage.blob.*;
import com.azure.storage.blob.models.*;
import com.azure.storage.blob.specialized.*;
import com.azure.storage.common.*;

Blob client library information:

• com.azure.storage.blob: Contains the primary classes (client objects) that you can use to operate on the service, containers, and blobs.
• com.azure.storage.blob.models: Contains utility classes, structures, and enumeration types.
• com.azure.storage.blob.specialized: Contains classes that you can use to perform operations specific to a blob type (For example: append blobs).

Authorize access and connect to Blob Storage

To connect an application to Blob Storage, create an instance of the BlobServiceClient class. You can also use the BlobServiceAsyncClient class for asynchronous programming. This object is your starting point to interact with data resources at the storage account level. You can use it to operate on the storage account and its containers. You can also use the service client to create container clients or blob clients, depending on the resource you need to work with.

To learn more about creating and managing client objects, see Create and manage client objects that interact with data resources.

You can authorize a BlobServiceClient object by using a Microsoft Entra authorization token, an account access key, or a shared access signature (SAS).

Microsoft Entra ID (Recommended)

To authorize with Microsoft Entra ID, you'll need to use a security principal. Which type of security principal you need depends on where your application runs. Use the following table as a guide:

Where the application runs	Security principal	Guidance
Local machine (developing and testing)	Service principal	To learn how to register the app, set up a Microsoft Entra group, assign roles, and configure environment variables, see Authorize access using developer service principals.
Local machine (developing and testing)	User identity	To learn how to set up a Microsoft Entra group, assign roles, and sign in to Azure, see Authorize access using developer credentials.
Hosted in Azure	Managed identity	To learn how to enable managed identity and assign roles, see Authorize access from Azure-hosted apps using a managed identity.
Hosted outside of Azure (for example, on-premises apps)	Service principal	To learn how to register the app, assign roles, and configure environment variables, see Authorize access from on-premises apps using an application service principal

Authorize access using DefaultAzureCredential

An easy and secure way to authorize access and connect to Blob Storage is to obtain an OAuth token by creating a DefaultAzureCredential instance. You can then use that credential to create a BlobServiceClient object.

Make sure you have the correct dependencies in pom.xml and the necessary import directives, as described in Set up your project.

The following example uses BlobServiceClientBuilder to build a BlobServiceClient object using DefaultAzureCredential:

public static BlobServiceClient GetBlobServiceClientTokenCredential() {
    TokenCredential credential = new DefaultAzureCredentialBuilder().build();

    // Azure SDK client builders accept the credential as a parameter
    // TODO: Replace <storage-account-name> with your actual storage account name
    BlobServiceClient blobServiceClient = new BlobServiceClientBuilder()
            .endpoint("https://<storage-account-name>.blob.core.windows.net/")
            .credential(credential)
            .buildClient();

    return blobServiceClient;
}

SAS token

Use BlobServiceClientBuilder to build a BlobServiceClient object using a SAS token:

public static BlobServiceClient GetBlobServiceClientSAS(String sasToken) {
    // TODO: Replace <storage-account-name> with your actual storage account name
    BlobServiceClient blobServiceClient = new BlobServiceClientBuilder()
            .endpoint("https://<storage-account-name>.blob.core.windows.net/")
            .sasToken(sasToken)
            .buildClient();

    return blobServiceClient;
}

To learn more about generating and managing SAS tokens, see the following articles:

• Grant limited access to Azure Storage resources using shared access signatures (SAS)
• Create an account SAS with Java
• Create a service SAS for a container with Java
• Create a service SAS for a blob with Java
• Create a user delegation SAS for a container with Java
• Create a user delegation SAS for a blob with Java

Account key

Create a StorageSharedKeyCredential by using the storage account name and account key. Then use that object to initialize a BlobServiceClient object.

public static BlobServiceClient GetBlobServiceClientAccountKey(String accountName, String accountKey) {
    StorageSharedKeyCredential credential = new StorageSharedKeyCredential(accountName, accountKey);

    // Azure SDK client builders accept the credential as a parameter
    BlobServiceClient blobServiceClient = new BlobServiceClientBuilder()
            .endpoint(String.format("https://%s.blob.core.windows.net/", accountName))
            .credential(credential)
            .buildClient();

    return blobServiceClient;        
}

You can also create a BlobServiceClient object using a connection string.

public static BlobServiceClient GetBlobServiceClientConnectionString(String connectionString) {
    // Azure SDK client builders accept the credential as a parameter
    // TODO: Replace <storage-account-name> with your actual storage account name
    BlobServiceClient blobServiceClient = new BlobServiceClientBuilder()
            .endpoint("https://<storage-account-name>.blob.core.windows.net/")
            .connectionString(connectionString)
            .buildClient();

    return blobServiceClient;        
}

For information about how to obtain account keys and best practice guidelines for properly managing and safeguarding your keys, see Manage storage account access keys.

Important

The account access key should be used with caution. If your account access key is lost or accidentally placed in an insecure location, your service may become vulnerable. Anyone who has the access key is able to authorize requests against the storage account, and effectively has access to all the data. DefaultAzureCredential provides enhanced security features and benefits and is the recommended approach for managing authorization to Azure services.

Build your application

As you build applications to work with data resources in Azure Blob Storage, your code primarily interacts with three resource types: storage accounts, containers, and blobs. To learn more about these resource types, how they relate to one another, and how apps interact with resources, see Understand how apps interact with Blob Storage data resources.

The following guides show you how to work with data resources and perform specific actions using the Azure Storage client library for Java:

Guide	Description
Create a container	Create containers.
Delete and restore containers	Delete containers, and if soft-delete is enabled, restore deleted containers.
List containers	List containers in an account and the various options available to customize a listing.
Manage properties and metadata (containers)	Get and set properties and metadata for containers.
Create and manage container leases	Establish and manage a lock on a container.
Create and manage blob leases	Establish and manage a lock on a blob.
Upload blobs	Learn how to upload blobs by using strings, streams, file paths, and other methods.
Download blobs	Download blobs by using strings, streams, and file paths.
Copy blobs	Copy a blob from one location to another.
List blobs	List blobs in different ways.
Delete and restore	Delete blobs, and if soft-delete is enabled, restore deleted blobs.
Find blobs using tags	Set and retrieve tags as well as use tags to find blobs.
Manage properties and metadata (blobs)	Get and set properties and metadata for blobs.
Set or change a blob's access tier	Set or change the access tier for a block blob.