This article shows you how to connect to Azure Blob Storage by using the Azure Blob Storage client library for Java. Once connected, use the developer guides to learn how your code can operate on containers, blobs, and features of the Blob Storage service.
If you're looking to start with a complete example, see Quickstart: Azure Blob Storage client library for Java.
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PrerequisitesNote
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.
Open the pom.xml file in your text editor. Install the packages by including the BOM file, or including a direct dependency.
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>
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>
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:
To connect an app 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). For optimal security, Microsoft recommends using Microsoft Entra ID with managed identities to authorize requests against blob data. For more information, see Authorize access to blobs using Microsoft Entra ID.
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 app runs. Use the following table as a guide:
Where the app 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 DefaultAzureCredentialAn 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, and shows how to create container and blob clients, if needed:
// 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(new DefaultAzureCredentialBuilder().build())
.buildClient();
// If needed, you can create a BlobContainerClient object from the BlobServiceClient
BlobContainerClient containerClient = blobServiceClient
.getBlobContainerClient("<container-name>");
// If needed, you can create a BlobClient object from the BlobContainerClient
BlobClient blobClient = containerClient
.getBlobClient("<blob-name>");
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:
Note
For scenarios where shared access signatures (SAS) are used, Microsoft recommends using a user delegation SAS. A user delegation SAS is secured with Microsoft Entra credentials instead of the 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.
The Java Virtual Machine (JVM) caches responses from successful DNS name lookups for a specified period of time, known as time-to-live (TTL). The default TTL value for many JVMs is -1, which means that the JVM caches the response indefinitely, or until the JVM is restarted.
Because Azure resources use DNS name entries that can change, we recommend that you set the JVM TTL value to 10 seconds. This configuration ensures that an updated IP address for a resource is returned with the next DNS query.
To change the TTL value globally for all applications using the JVM, set the networkaddress.cache.ttl property in the java.security file.
networkaddress.cache.ttl=10
For Java 8, the java.security file is located in the $JAVA_HOME/jre/lib/security directory. For Java 11 and higher, the file is located in the $JAVA_HOME/conf/security directory.
As you build apps 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 access data and perform specific actions using the Azure Storage client library for Java:
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