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--- title: "Quickstart: Azure Blob Storage library - Java" description: In this quickstart, you learn how to use the Azure Blob Storage client library for Java to create a container and a blob in Blob (object) storage. Next, you learn how to download the blob to your local computer, and how to list all of the blobs in a container. author: stevenmatthew ms.author: shaas ms.date: 09/13/2024 ms.service: azure-blob-storage ms.topic: quickstart ms.devlang: java zone_pivot_groups: azure-blob-storage-quickstart-options ms.custom: - devx-track-java - mode-api - passwordless-java - devx-track-extended-java - devx-track-extended-azdevcli - sfi-image-nochange - sfi-ropc-nochange # Customer intent: As a Java developer, I want to implement a Blob Storage application using the Azure Blob Storage client library, so that I can manage blobs and containers effectively for my projects. --- # Quickstart: Azure Blob Storage client library for Java SE ::: zone pivot="blob-storage-quickstart-scratch" > [!NOTE] > The **Build from scratch** option walks you step by step through the process of creating a new project, installing packages, writing the code, and running a basic console app. This approach is recommended if you want to understand all the details involved in creating an app that connects to Azure Blob Storage. If you prefer to automate deployment tasks and start with a completed project, choose [Start with a template](storage-quickstart-blobs-java.md?pivots=blob-storage-quickstart-template). ::: zone-end ::: zone pivot="blob-storage-quickstart-template" > [!NOTE] > The **Start with a template** option uses the Azure Developer CLI to automate deployment tasks and starts you off with a completed project. This approach is recommended if you want to explore the code as quickly as possible without going through the setup tasks. If you prefer step by step instructions to build the app, choose [Build from scratch](storage-quickstart-blobs-java.md?pivots=blob-storage-quickstart-scratch). ::: zone-end Get started with the Azure Blob Storage client library for Java to manage blobs and containers. ::: zone pivot="blob-storage-quickstart-scratch" In this article, you follow steps to install the package and try out example code for basic tasks. ::: zone-end ::: zone pivot="blob-storage-quickstart-template" In this article, you use the [Azure Developer CLI](/azure/developer/azure-developer-cli/overview) to deploy Azure resources and run a completed console app with just a few commands. ::: zone-end > [!TIP] > If you're working with Azure Storage resources in a Spring application, we recommend that you consider [Spring Cloud Azure](/azure/developer/java/spring-framework/) as an alternative. Spring Cloud Azure is an open-source project that provides seamless Spring integration with Azure services. To learn more about Spring Cloud Azure, and to see an example using Blob Storage, see [Upload a file to an Azure Storage Blob](/azure/developer/java/spring-framework/configure-spring-boot-starter-java-app-with-azure-storage). [API reference documentation](/java/api/overview/azure/storage-blob-readme) | [Library source code](https://github.com/Azure/azure-sdk-for-java/tree/master/sdk/storage/azure-storage-blob) | [Package (Maven)](https://mvnrepository.com/artifact/com.azure/azure-storage-blob) | [Samples](../common/storage-samples-java.md?toc=/azure/storage/blobs/toc.json#blob-samples) ## Prerequisites ::: zone pivot="blob-storage-quickstart-scratch" - Azure account with an active subscription - [create an account for free](https://azure.microsoft.com/pricing/purchase-options/azure-account?cid=msft_learn) - Azure Storage account - [create a storage account](../common/storage-account-create.md). - [Java Development Kit (JDK)](/java/azure/jdk/) version 1.8_101 or above - [Apache Maven](https://maven.apache.org/download.cgi) ::: zone-end ::: zone pivot="blob-storage-quickstart-template" - Azure subscription - [create one for free](https://azure.microsoft.com/pricing/purchase-options/azure-account?cid=msft_learn) - [Java Development Kit (JDK)](/java/azure/jdk/) version 1.8_101 or above - [Apache Maven](https://maven.apache.org/download.cgi) - [Azure Developer CLI](/azure/developer/azure-developer-cli/install-azd) ::: zone-end ## Setting up ::: zone pivot="blob-storage-quickstart-scratch" This section walks you through preparing a project to work with the Azure Blob Storage client library for Java. ### Create the project Create a Java application named *blob-quickstart*. 1. In a console window (such as PowerShell or Bash), use Maven to create a new console app with the name *blob-quickstart*. Type the following **mvn** command to create a "Hello world!" Java project. # [PowerShell](#tab/powershell) ```powershell mvn archetype:generate ` --define interactiveMode=n ` --define groupId=com.blobs.quickstart ` --define artifactId=blob-quickstart ` --define archetypeArtifactId=maven-archetype-quickstart ` --define archetypeVersion=1.4 ``` # [Bash](#tab/bash) ```bash mvn archetype:generate \ --define interactiveMode=n \ --define groupId=com.blobs.quickstart \ --define artifactId=blob-quickstart \ --define archetypeArtifactId=maven-archetype-quickstart \ --define archetypeVersion=1.4 ``` --- 1. The output from generating the project should look something like this: ```console [INFO] Scanning for projects... [INFO] [INFO] ------------------< org.apache.maven:standalone-pom >------------------- [INFO] Building Maven Stub Project (No POM) 1 [INFO] --------------------------------[ pom ]--------------------------------- [INFO] [INFO] >>> maven-archetype-plugin:3.1.2:generate (default-cli) > generate-sources @ standalone-pom >>> [INFO] [INFO] <<< maven-archetype-plugin:3.1.2:generate (default-cli) < generate-sources @ standalone-pom <<< [INFO] [INFO] [INFO] --- maven-archetype-plugin:3.1.2:generate (default-cli) @ standalone-pom --- [INFO] Generating project in Batch mode [INFO] ---------------------------------------------------------------------------- [INFO] Using following parameters for creating project from Archetype: maven-archetype-quickstart:1.4 [INFO] ---------------------------------------------------------------------------- [INFO] Parameter: groupId, Value: com.blobs.quickstart [INFO] Parameter: artifactId, Value: blob-quickstart [INFO] Parameter: version, Value: 1.0-SNAPSHOT [INFO] Parameter: package, Value: com.blobs.quickstart [INFO] Parameter: packageInPathFormat, Value: com/blobs/quickstart [INFO] Parameter: version, Value: 1.0-SNAPSHOT [INFO] Parameter: package, Value: com.blobs.quickstart [INFO] Parameter: groupId, Value: com.blobs.quickstart [INFO] Parameter: artifactId, Value: blob-quickstart [INFO] Project created from Archetype in dir: C:\QuickStarts\blob-quickstart [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 7.056 s [INFO] Finished at: 2019-10-23T11:09:21-07:00 [INFO] ------------------------------------------------------------------------ ``` 1. Switch to the newly created *blob-quickstart* folder. ```console cd blob-quickstart ``` 1. In side the *blob-quickstart* directory, create another directory called *data*. This folder is where the blob data files will be created and stored. ```console mkdir data ``` ### Install the packages Open the `pom.xml` file in your text editor. 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](https://github.com/Azure/azure-sdk-for-java/blob/main/sdk/boms/azure-sdk-bom/README.md). ```xml <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> ``` Then add the following dependency elements to the group of dependencies. The **azure-identity** dependency is needed for passwordless connections to Azure services. ```xml <dependency> <groupId>com.azure</groupId> <artifactId>azure-storage-blob</artifactId> </dependency> <dependency> <groupId>com.azure</groupId> <artifactId>azure-identity</artifactId> </dependency> ``` ### Set up the app framework From the project directory, follow steps to create the basic structure of the app: 1. Navigate to the */src/main/java/com/blobs/quickstart* directory 1. Open the `App.java` file in your editor 1. Delete the line `System.out.println("Hello world!");` 1. Add the necessary `import` directives The code should resemble this framework: ```java package com.blobs.quickstart; /** * Azure Blob Storage quickstart */ import com.azure.identity.*; import com.azure.storage.blob.*; import com.azure.storage.blob.models.*; import java.io.*; public class App { public static void main(String[] args) throws IOException { // Quickstart code goes here } } ``` ::: zone-end ::: zone pivot="blob-storage-quickstart-template" With [Azure Developer CLI](/azure/developer/azure-developer-cli/install-azd) installed, you can create a storage account and run the sample code with just a few commands. You can run the project in your local development environment, or in a [DevContainer](https://code.visualstudio.com/docs/devcontainers/containers). ### Initialize the Azure Developer CLI template and deploy resources From an empty directory, follow these steps to initialize the `azd` template, provision Azure resources, and get started with the code: - Clone the quickstart repository assets from GitHub and initialize the template locally: ```console azd init --template blob-storage-quickstart-java ``` You'll be prompted for the following information: - **Environment name**: This value is used as a prefix for all Azure resources created by Azure Developer CLI. The name must be unique across all Azure subscriptions and must be between 3 and 24 characters long. The name can contain numbers and lowercase letters only. - Log in to Azure: ```console azd auth login ``` - Provision and deploy the resources to Azure: ```console azd up ``` You'll be prompted for the following information: - **Subscription**: The Azure subscription that your resources are deployed to. - **Location**: The Azure region where your resources are deployed. The deployment might take a few minutes to complete. The output from the `azd up` command includes the name of the newly created storage account, which you'll need later to run the code. ## Run the sample code At this point, the resources are deployed to Azure and the code is almost ready to run. Follow these steps to update the name of the storage account in the code, and run the sample console app: - **Update the storage account name**: 1. In the local directory, navigate to the *blob-quickstart/src/main/java/com/blobs/quickstart* directory. 1. Open the file named **App.java** in your editor. Find the `<storage-account-name>` placeholder and replace it with the actual name of the storage account created by the `azd up` command. 1. Save the changes. - **Run the project**: 1. Navigate to the *blob-quickstart* directory containing the `pom.xml` file. Compile the project by using the following `mvn` command: ```console mvn compile ``` 1. Package the compiled code in its distributable format: ```console mvn package ``` 1. Run the following `mvn` command to execute the app: ```console mvn exec:java ``` - **Observe the output**: This app creates a test file in your local *data* folder and uploads it to a container in the storage account. The example then lists the blobs in the container and downloads the file with a new name so that you can compare the old and new files. To learn more about how the sample code works, see [Code examples](#code-examples). When you're finished testing the code, see the [Clean up resources](#clean-up-resources) section to delete the resources created by the `azd up` command. ::: zone-end ## Object model Azure Blob Storage is optimized for storing massive amounts of unstructured data. Unstructured data doesn't adhere to a particular data model or definition, such as text or binary data. Blob storage offers three types of resources: - The storage account - A container in the storage account - A blob in the container The following diagram shows the relationship between these resources.  Use the following Java classes to interact with these resources: - [BlobServiceClient](/java/api/com.azure.storage.blob.blobserviceclient): The `BlobServiceClient` class allows you to manipulate Azure Storage resources and blob containers. The storage account provides the top-level namespace for the Blob service. - [BlobServiceClientBuilder](/java/api/com.azure.storage.blob.blobserviceclientbuilder): The `BlobServiceClientBuilder` class provides a fluent builder API to help aid the configuration and instantiation of `BlobServiceClient` objects. - [BlobContainerClient](/java/api/com.azure.storage.blob.blobcontainerclient): The `BlobContainerClient` class allows you to manipulate Azure Storage containers and their blobs. - [BlobClient](/java/api/com.azure.storage.blob.blobclient): The `BlobClient` class allows you to manipulate Azure Storage blobs. - [BlobItem](/java/api/com.azure.storage.blob.models.blobitem): The `BlobItem` class represents individual blobs returned from a call to [listBlobs](/java/api/com.azure.storage.blob.blobcontainerclient.listblobs). ## Code examples These example code snippets show you how to perform the following actions with the Azure Blob Storage client library for Java: - [Authenticate to Azure and authorize access to blob data](#authenticate-to-azure-and-authorize-access-to-blob-data) - [Create a container](#create-a-container) - [Upload blobs to a container](#upload-blobs-to-a-container) - [List the blobs in a container](#list-the-blobs-in-a-container) - [Download blobs](#download-blobs) - [Delete a container](#delete-a-container) ::: zone pivot="blob-storage-quickstart-scratch" > [!IMPORTANT] > Make sure you have the correct dependencies in pom.xml and the necessary directives for the code samples to work, as described in the [setting up](#setting-up) section. ::: zone-end ::: zone pivot="blob-storage-quickstart-template" > [!NOTE] > The Azure Developer CLI template includes a file with sample code already in place. The following examples provide detail for each part of the sample code. The template implements the recommended passwordless authentication method, as described in the [Authenticate to Azure](#authenticate-to-azure-and-authorize-access-to-blob-data) section. The connection string method is shown as an alternative, but isn't used in the template and isn't recommended for production code. ::: zone-end ### Authenticate to Azure and authorize access to blob data [!INCLUDE [storage-quickstart-passwordless-auth-intro](../../../includes/storage-quickstart-passwordless-auth-intro.md)] ### [Passwordless (Recommended)](#tab/managed-identity) `DefaultAzureCredential` is a class provided by the Azure Identity client library for Java. `DefaultAzureCredential` supports multiple authentication methods and determines which method should be used at runtime. This approach enables your app to use different authentication methods in different environments (local vs. production) without implementing environment-specific code. The order and locations in which `DefaultAzureCredential` looks for credentials can be found in the [Azure Identity library overview](/java/api/overview/azure/identity-readme#defaultazurecredential). For example, your app can authenticate using your Visual Studio Code sign-in credentials with when developing locally. Your app can then use a [managed identity](../../active-directory/managed-identities-azure-resources/overview.md) once it has been deployed to Azure. No code changes are required for this transition. <a name='assign-roles-to-your-azure-ad-user-account'></a> #### Assign roles to your Microsoft Entra user account [!INCLUDE [assign-roles](../../../includes/assign-roles.md)] #### Sign-in and connect your app code to Azure using DefaultAzureCredential You can authorize access to data in your storage account using the following steps: 1. Make sure you're authenticated with the same Microsoft Entra account you assigned the role to on your storage account. You can authenticate via the Azure CLI, Visual Studio Code, or Azure PowerShell. #### [Azure CLI](#tab/sign-in-azure-cli) Sign-in to Azure through the Azure CLI using the following command: ```azurecli az login ``` #### [Visual Studio Code](#tab/sign-in-visual-studio-code) You'll need to [install the Azure CLI](/cli/azure/install-azure-cli) to work with `DefaultAzureCredential` through Visual Studio Code. On the main menu of Visual Studio Code, navigate to **Terminal > New Terminal**. Sign-in to Azure through the Azure CLI using the following command: ```azurecli az login ``` #### [PowerShell](#tab/sign-in-powershell) Sign-in to Azure using PowerShell via the following command: ```azurepowershell Connect-AzAccount ``` 2. To use `DefaultAzureCredential`, make sure that the **azure-identity** dependency is added in `pom.xml`: ```xml <dependency> <groupId>com.azure</groupId> <artifactId>azure-identity</artifactId> </dependency> ``` 3. Add this code to the `Main` method. When the code runs on your local workstation, it will use the developer credentials of the prioritized tool you're logged into to authenticate to Azure, such as the Azure CLI or Visual Studio Code. :::code language="java" source="~/azure-storage-snippets/blobs/quickstarts/Java/blob-quickstart/src/main/java/com/blobs/quickstart/App.java" id="Snippet_CreateServiceClientDAC"::: 4. Make sure to update the storage account name in the URI of your `BlobServiceClient`. The storage account name can be found on the overview page of the Azure portal. :::image type="content" source="./media/storage-quickstart-blobs-java/storage-account-name.png" alt-text="A screenshot showing how to find the storage account name."::: > [!NOTE] > When deployed to Azure, this same code can be used to authorize requests to Azure Storage from an application running in Azure. However, you'll need to enable managed identity on your app in Azure. Then configure your storage account to allow that managed identity to connect. For detailed instructions on configuring this connection between Azure services, see the [Auth from Azure-hosted apps](/azure/developer/java/sdk/identity-azure-hosted-auth) tutorial. ### [Connection String](#tab/connection-string) A connection string includes the storage account access key and uses it to authorize requests. Always be careful to never expose the keys in an unsecure location. > [!NOTE] > To authorize data access with the storage account access key, you'll need permissions for the following Azure RBAC action: [Microsoft.Storage/storageAccounts/listkeys/action](../../role-based-access-control/resource-provider-operations.md#microsoftstorage). The least privileged built-in role with permissions for this action is [Reader and Data Access](../../role-based-access-control/built-in-roles.md#reader-and-data-access), but any role which includes this action will work. [!INCLUDE [retrieve credentials](../../../includes/retrieve-credentials.md)] #### Configure your storage connection string After you copy the connection string, write it to a new environment variable on the local machine running the application. To set the environment variable, open a console window, and follow the instructions for your operating system. Replace `<yourconnectionstring>` with your actual connection string. **Windows**: ```cmd setx AZURE_STORAGE_CONNECTION_STRING "<yourconnectionstring>" ``` After you add the environment variable in Windows, you must start a new instance of the command window. **Linux**: ```bash export AZURE_STORAGE_CONNECTION_STRING="<yourconnectionstring>" ``` The code below retrieves the connection string for the storage account from the environment variable created earlier, and uses the connection string to construct a service client object. ::: zone pivot="blob-storage-quickstart-scratch" Add this code to the end of the `Main` method: ::: zone-end ```java // Retrieve the connection string for use with the application. String connectStr = System.getenv("AZURE_STORAGE_CONNECTION_STRING"); // Create a BlobServiceClient object using a connection string BlobServiceClient blobServiceClient = new BlobServiceClientBuilder() .connectionString(connectStr) .buildClient(); ``` > [!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. --- ### Create a container Create a new container in your storage account by calling the [createBlobContainer](/java/api/com.azure.storage.blob.blobserviceclient#method-details) method on the `blobServiceClient` object. In this example, the code appends a GUID value to the container name to ensure that it's unique. ::: zone pivot="blob-storage-quickstart-scratch" Add this code to the end of the `Main` method: ::: zone-end :::code language="java" source="~/azure-storage-snippets/blobs/quickstarts/Java/blob-quickstart/src/main/java/com/blobs/quickstart/App.java" id="Snippet_CreateContainer"::: To learn more about creating a container, and to explore more code samples, see [Create a blob container with Java](storage-blob-container-create-java.md). > [!IMPORTANT] > Container names must be lowercase. For more information about naming containers and blobs, see [Naming and Referencing Containers, Blobs, and Metadata](/rest/api/storageservices/naming-and-referencing-containers--blobs--and-metadata). ### Upload blobs to a container Upload a blob to a container by calling the [uploadFromFile](/java/api/com.azure.storage.blob.blobclient.uploadfromfile) method. The example code creates a text file in the local *data* directory to upload to the container. ::: zone pivot="blob-storage-quickstart-scratch" Add this code to the end of the `Main` method: ::: zone-end :::code language="java" source="~/azure-storage-snippets/blobs/quickstarts/Java/blob-quickstart/src/main/java/com/blobs/quickstart/App.java" id="Snippet_UploadBlobFromFile"::: To learn more about uploading blobs, and to explore more code samples, see [Upload a blob with Java](storage-blob-upload-java.md). ### List the blobs in a container List the blobs in the container by calling the [listBlobs](/java/api/com.azure.storage.blob.blobcontainerclient.listblobs) method. In this case, only one blob has been added to the container, so the listing operation returns just that one blob. ::: zone pivot="blob-storage-quickstart-scratch" Add this code to the end of the `Main` method: ::: zone-end :::code language="java" source="~/azure-storage-snippets/blobs/quickstarts/Java/blob-quickstart/src/main/java/com/blobs/quickstart/App.java" id="Snippet_ListBlobs"::: To learn more about listing blobs, and to explore more code samples, see [List blobs with Java](storage-blobs-list-java.md). ### Download blobs Download the previously created blob by calling the [downloadToFile](/java/api/com.azure.storage.blob.specialized.blobclientbase.downloadtofile) method. The example code adds a suffix of "DOWNLOAD" to the file name so that you can see both files in local file system. ::: zone pivot="blob-storage-quickstart-scratch" Add this code to the end of the `Main` method: ::: zone-end :::code language="java" source="~/azure-storage-snippets/blobs/quickstarts/Java/blob-quickstart/src/main/java/com/blobs/quickstart/App.java" id="Snippet_DownloadBlob"::: To learn more about downloading blobs, and to explore more code samples, see [Download a blob with Java](storage-blob-download-java.md). ### Delete a container The following code cleans up the resources the app created by removing the entire container using the [delete](/java/api/com.azure.storage.blob.blobcontainerclient.delete) method. It also deletes the local files created by the app. The app pauses for user input by calling `System.console().readLine()` before it deletes the blob, container, and local files. This is a good chance to verify that the resources were created correctly, before they're deleted. ::: zone pivot="blob-storage-quickstart-scratch" Add this code to the end of the `Main` method: ::: zone-end :::code language="java" source="~/azure-storage-snippets/blobs/quickstarts/Java/blob-quickstart/src/main/java/com/blobs/quickstart/App.java" id="Snippet_DeleteContainer"::: To learn more about deleting a container, and to explore more code samples, see [Delete and restore a blob container with Java](storage-blob-container-delete-java.md). ::: zone pivot="blob-storage-quickstart-scratch" ## Run the code This app creates a test file in your local folder and uploads it to Blob storage. The example then lists the blobs in the container and downloads the file with a new name so that you can compare the old and new files. Follow steps to compile, package, and run the code 1. Navigate to the directory containing the `pom.xml` file and compile the project by using the following `mvn` command: ```console mvn compile ``` 1. Package the compiled code in its distributable format: ```console mvn package ``` 1. Run the following `mvn` command to execute the app: ```console mvn exec:java -D exec.mainClass=com.blobs.quickstart.App -D exec.cleanupDaemonThreads=false ``` To simplify the run step, you can add `exec-maven-plugin` to `pom.xml` and configure as shown below: ```xml <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>exec-maven-plugin</artifactId> <version>1.4.0</version> <configuration> <mainClass>com.blobs.quickstart.App</mainClass> <cleanupDaemonThreads>false</cleanupDaemonThreads> </configuration> </plugin> ``` With this configuration, you can execute the app with the following command: ```console mvn exec:java ``` The output of the app is similar to the following example (UUID values omitted for readability): ```output Azure Blob Storage - Java quickstart sample Uploading to Blob storage as blob: https://mystorageacct.blob.core.windows.net/quickstartblobsUUID/quickstartUUID.txt Listing blobs... quickstartUUID.txt Downloading blob to ./data/quickstartUUIDDOWNLOAD.txt Press the Enter key to begin clean up Deleting blob container... Deleting the local source and downloaded files... Done ``` Before you begin the cleanup process, check your *data* folder for the two files. You can compare them and observe that they're identical. ::: zone-end ## Clean up resources ::: zone pivot="blob-storage-quickstart-scratch" After you've verified the files and finished testing, press the **Enter** key to delete the test files along with the container you created in the storage account. You can also use [Azure CLI](storage-quickstart-blobs-cli.md#clean-up-resources) to delete resources. ::: zone-end ::: zone pivot="blob-storage-quickstart-template" When you're done with the quickstart, you can clean up the resources you created by running the following command: ```console azd down ``` You'll be prompted to confirm the deletion of the resources. Enter `y` to confirm. ::: zone-end ## Next step > [!div class="nextstepaction"] > [Azure Storage samples and developer guides for Java](../common/storage-samples-java.md?toc=/azure/storage/blobs/toc.json) > [Azure Storage samples and developer guides for Java](../common/storage-samples-java.md?toc=/azure/storage/blobs/toc.json) > [Quickstart: Quarkus extension for Azure Blob Storage](storage-quickstart-blobs-java-quarkus.md) > [Use Spring Boot to upload a file to Azure Blob Storage](/azure/developer/java/spring-framework/configure-spring-boot-starter-java-app-with-azure-storage?toc=/azure/storage/blobs/toc.json)