Get started with Azure Blob Storage and Java

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

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:

Authorize access and connect to Blob Storage

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 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, 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>");

Configure the JVM TTL for DNS name lookups

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.

Build your app

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:

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