List blob containers with Java

When you list the containers in an Azure Storage account from your code, you can specify several options to manage how results are returned from Azure Storage. This article shows how to list containers using the Azure Storage client library for Java.

• Azure subscription - create one for trial
• Azure storage account - create a storage account
• Java Development Kit (JDK) version 8 or later (we recommend version 17 for the best experience)
• Apache Maven is used for project management in this example

If you don't have an existing project, this section shows you how to set up a project to work with the Azure Blob Storage client library for Java. For more information, see Get started with Azure Blob Storage and Java.

To work with the code examples in this article, follow these steps to set up your project.

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

Add the following import statements:

import com.azure.core.http.rest.*;
import com.azure.storage.blob.*;
import com.azure.storage.blob.models.*;

The authorization mechanism must have the necessary permissions to list blob containers. For authorization with Microsoft Entra ID (recommended), you need Azure RBAC built-in role Storage Blob Data Contributor or higher. To learn more, see the authorization guidance for List Containers (REST API).

To connect an app to Blob Storage, create an instance of BlobServiceClient.

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.chinacloudapi.cn/")
        .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>");

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

When listing containers from your code, you can specify options to manage how results are returned from Azure Storage. You can specify the number of results to return in each set of results, and then retrieve the subsequent sets. You can also filter the results by a prefix, and return container metadata with the results. These options are described in the following sections.

To list containers in a storage account, call the following method:

• listBlobContainers

This method returns an iterable of type BlobContainerItem. Containers are ordered lexicographically by name.

By default, a listing operation returns up to 5000 results at a time. To return a smaller set of results, provide a nonzero value for the size of the page of results to return. You can set this value using the following method:

• ListBlobContainersOptions.setMaxResultsPerPage

The examples presented in this article show you how to return results in pages. To learn more about pagination concepts, see Pagination with the Azure SDK for Java.

To filter the list of containers, specify a string for the prefix parameter. The prefix string can include one or more characters. Azure Storage then returns only the containers whose names start with that prefix. You can set this value using the following method:

• ListBlobContainersOptions.setPrefix

To include container metadata with the results, create a BlobContainerListDetails instance and pass true to the following method:

• BlobContainerListDetails.setRetrieveMetadata

Then pass the BlobContainerListDetails object to the following method:

• ListBlobContainersOptions.setDetails

To include soft-deleted containers with the results, create a BlobContainerListDetails instance and pass true to the following method:

• BlobContainerListDetails.setRetrieveDeleted

Then pass the BlobContainerListDetails object to the following method:

• ListBlobContainersOptions.setDetails

The following example lists containers and filters the results by a specified prefix:

public void listContainers(BlobServiceClient blobServiceClient) {
    // Set a prefix to filter results based on a specified character or string
    ListBlobContainersOptions options = new ListBlobContainersOptions()
            .setPrefix("container-");

    System.out.println("List containers:");
    for (BlobContainerItem blobContainerItem : blobServiceClient.listBlobContainers(options, null)) {
        System.out.printf("Container name: %s%n", blobContainerItem.getName());
    }
}

You can also return a smaller set of results, by specifying the size of the page of results to return:

public void listContainersWithPaging(BlobServiceClient blobServiceClient) {
    // Set a prefix to filter results and specify a page limit
    ListBlobContainersOptions options = new ListBlobContainersOptions()
            .setMaxResultsPerPage(2)  // Low number for demonstration purposes
            .setPrefix("container-");

    int i = 0;
    Iterable<PagedResponse<BlobContainerItem>> blobContainerPages = blobServiceClient
            .listBlobContainers(options, null).iterableByPage();
    for (PagedResponse<BlobContainerItem> page : blobContainerPages) {
        System.out.printf("Page %d%n", ++i);
        page.getElements().forEach(container -> {
            System.out.printf("Name: %s%n", container.getName());
        });
    }
}

To learn more about listing containers using the Azure Blob Storage client library for Java, see the following resources.

• View code samples from this article (GitHub)

The Azure SDK for Java contains libraries that build on top of the Azure REST API, allowing you to interact with REST API operations through familiar Java paradigms. The client library methods for listing containers use the following REST API operation:

• List Containers (REST API)

• Client library reference documentation
• Client library source code
• Package (Maven)

• Enumerating Blob Resources

• This article is part of the Blob Storage developer guide for Java. To learn more, see the full list of developer guide articles at Build your Java app.