azure-storage-blob-java – Coding skill for AI agents

Azure Storage Blob SDK for Java

Build blob storage applications using the Azure Storage Blob SDK for Java.

Installation

<dependency>
    <groupId>com.azure</groupId>
    <artifactId>azure-storage-blob</artifactId>
    <version>12.33.0</version>
</dependency>

Client Creation

BlobServiceClient

import com.azure.storage.blob.BlobServiceClient;
import com.azure.storage.blob.BlobServiceClientBuilder;

// With SAS token
BlobServiceClient serviceClient = new BlobServiceClientBuilder()
    .endpoint("<storage-account-url>")
    .sasToken("<sas-token>")
    .buildClient();

// With connection string
BlobServiceClient serviceClient = new BlobServiceClientBuilder()
    .connectionString("<connection-string>")
    .buildClient();

With DefaultAzureCredential

import com.azure.identity.DefaultAzureCredentialBuilder;

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

BlobContainerClient

import com.azure.storage.blob.BlobContainerClient;

// From service client
BlobContainerClient containerClient = serviceClient.getBlobContainerClient("mycontainer");

// Direct construction
BlobContainerClient containerClient = new BlobContainerClientBuilder()
    .connectionString("<connection-string>")
    .containerName("mycontainer")
    .buildClient();

BlobClient

import com.azure.storage.blob.BlobClient;

// From container client
BlobClient blobClient = containerClient.getBlobClient("myblob.txt");

// With directory structure
BlobClient blobClient = containerClient.getBlobClient("folder/subfolder/myblob.txt");

// Direct construction
BlobClient blobClient = new BlobClientBuilder()
    .connectionString("<connection-string>")
    .containerName("mycontainer")
    .blobName("myblob.txt")
    .buildClient();

Storage and bearer-token scope

Verify the account/container/key and current SDK signatures before adapting these independent snippets. Overwrite, snapshot deletion, metadata/header replacement and cross-account copies require exact-target authority and concurrency conditions where needed. Bound in-memory downloads; prefer streaming for large blobs. A SAS is a bearer credential: authorize the object and caller, minimize permission/expiry, use HTTPS, avoid logs and prefer user-delegation SAS where applicable. generateSas needs the appropriate signing credential; DefaultAzureCredential alone does not make that method account-key signing. Check copy completion status and failures rather than assuming waiting guarantees success.

Core Patterns

Create Container

// Create container
serviceClient.createBlobContainer("mycontainer");

// Create if not exists
BlobContainerClient container = serviceClient.createBlobContainerIfNotExists("mycontainer");

// From container client
containerClient.create();
containerClient.createIfNotExists();

Upload Data

import com.azure.core.util.BinaryData;

// Upload string
String data = "Hello, Azure Blob Storage!";
blobClient.upload(BinaryData.fromString(data));

// Upload with overwrite
blobClient.upload(BinaryData.fromString(data), true);

Upload from File

blobClient.uploadFromFile("local-file.txt");

// With overwrite
blobClient.uploadFromFile("local-file.txt", true);

Upload from Stream

import com.azure.storage.blob.specialized.BlockBlobClient;

BlockBlobClient blockBlobClient = blobClient.getBlockBlobClient();

byte[] utf8 = data.getBytes(java.nio.charset.StandardCharsets.UTF_8);
try (ByteArrayInputStream dataStream = new ByteArrayInputStream(utf8)) {
    blockBlobClient.upload(dataStream, utf8.length);
}

Upload with Options

import com.azure.storage.blob.models.BlobHttpHeaders;
import com.azure.storage.blob.options.BlobParallelUploadOptions;

BlobHttpHeaders headers = new BlobHttpHeaders()
    .setContentType("text/plain")
    .setCacheControl("max-age=3600");

Map<String, String> metadata = Map.of("author", "john", "version", "1.0");

try (InputStream stream = new FileInputStream("large-file.bin")) {
    BlobParallelUploadOptions options = new BlobParallelUploadOptions(stream)
        .setHeaders(headers)
        .setMetadata(metadata);
    
    blobClient.uploadWithResponse(options, null, Context.NONE);
}

Upload if Not Exists

import com.azure.storage.blob.models.BlobRequestConditions;

BlobParallelUploadOptions options = new BlobParallelUploadOptions(inputStream, length)
    .setRequestConditions(new BlobRequestConditions().setIfNoneMatch("*"));

blobClient.uploadWithResponse(options, null, Context.NONE);

Download Data

// Download to BinaryData
BinaryData content = blobClient.downloadContent();
String text = content.toString();

// Download to file
blobClient.downloadToFile("downloaded-file.txt");

Download to Stream

try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {
    blobClient.downloadStream(outputStream);
    byte[] data = outputStream.toByteArray();
}

Download with InputStream

import com.azure.storage.blob.specialized.BlobInputStream;

try (BlobInputStream blobIS = blobClient.openInputStream()) {
    byte[] buffer = new byte[1024];
    int bytesRead;
    while ((bytesRead = blobIS.read(buffer)) != -1) {
        // Process buffer
    }
}

Upload via OutputStream

import com.azure.storage.blob.specialized.BlobOutputStream;

try (BlobOutputStream blobOS = blobClient.getBlockBlobClient().getBlobOutputStream()) {
    blobOS.write("Data to upload".getBytes());
}

List Blobs

import com.azure.storage.blob.models.BlobItem;

// List all blobs
for (BlobItem blobItem : containerClient.listBlobs()) {
    System.out.println("Blob: " + blobItem.getName());
}

// List with prefix (virtual directory)
import com.azure.storage.blob.models.ListBlobsOptions;

ListBlobsOptions options = new ListBlobsOptions().setPrefix("folder/");
for (BlobItem blobItem : containerClient.listBlobs(options, null)) {
    System.out.println("Blob: " + blobItem.getName());
}

List Blobs by Hierarchy

import com.azure.storage.blob.models.BlobListDetails;

String delimiter = "/";
ListBlobsOptions options = new ListBlobsOptions()
    .setPrefix("data/")
    .setDetails(new BlobListDetails().setRetrieveMetadata(true));

for (BlobItem item : containerClient.listBlobsByHierarchy(delimiter, options, null)) {
    if (item.isPrefix()) {
        System.out.println("Directory: " + item.getName());
    } else {
        System.out.println("Blob: " + item.getName());
    }
}

Delete Blob

blobClient.delete();

// Delete if exists
blobClient.deleteIfExists();

// Delete with snapshots
import com.azure.storage.blob.models.DeleteSnapshotsOptionType;
blobClient.deleteWithResponse(DeleteSnapshotsOptionType.INCLUDE, null, null, Context.NONE);

Copy Blob

import com.azure.storage.blob.models.BlobCopyInfo;
import com.azure.core.util.polling.SyncPoller;

// Async copy (for large blobs or cross-account)
SyncPoller<BlobCopyInfo, Void> poller = blobClient.beginCopy("<source-blob-url>", Duration.ofSeconds(1));
poller.waitForCompletion();

// Sync copy from URL (for same account)
blobClient.copyFromUrl("<source-blob-url>");

Generate SAS Token

import com.azure.storage.blob.sas.*;
import java.time.OffsetDateTime;

// Blob-level SAS
BlobSasPermission permissions = new BlobSasPermission().setReadPermission(true);
OffsetDateTime expiry = OffsetDateTime.now().plusDays(1);

BlobServiceSasSignatureValues sasValues = new BlobServiceSasSignatureValues(expiry, permissions);
String sasToken = blobClient.generateSas(sasValues);

// Container-level SAS
BlobContainerSasPermission containerPermissions = new BlobContainerSasPermission()
    .setReadPermission(true)
    .setListPermission(true);
    
BlobServiceSasSignatureValues containerSasValues = new BlobServiceSasSignatureValues(expiry, containerPermissions);
String containerSas = containerClient.generateSas(containerSasValues);

Blob Properties and Metadata

import com.azure.storage.blob.models.BlobProperties;

// Get properties
BlobProperties properties = blobClient.getProperties();
System.out.println("Size: " + properties.getBlobSize());
System.out.println("Content-Type: " + properties.getContentType());
System.out.println("Last Modified: " + properties.getLastModified());

// Set metadata
Map<String, String> metadata = Map.of("key1", "value1", "key2", "value2");
blobClient.setMetadata(metadata);

// Set HTTP headers
BlobHttpHeaders headers = new BlobHttpHeaders()
    .setContentType("application/json")
    .setCacheControl("max-age=86400");
blobClient.setHttpHeaders(headers);

Lease Blob

import com.azure.storage.blob.specialized.BlobLeaseClient;
import com.azure.storage.blob.specialized.BlobLeaseClientBuilder;

… (full content is in the download package)