Build API clients for Java with Microsoft identity authentication

Required tools

• Java Development Kit (JDK) 16
• Gradle 7.4

Create a project

Use Gradle to initialize a Java application project.

gradle init --dsl groovy --test-framework junit --type java-application --project-name getuserclient --package getuserclient

Add dependencies

Before you can compile and run the generated API client, you need to make sure the generated source files are part of a project with the required dependencies. Your project must have a reference to the abstraction package. Additionally, you must either use the Kiota default implementations or provide your own custom implementations of the following packages.

• Authentication (Kiota default Azure authentication)
• HTTP (Kiota default OkHttp-based implementation)
• Form serialization (Kiota default)
• JSON serialization (Kiota default)
• Text serialization (Kiota default)
• Multipart serialization (Kiota default)

For this tutorial, use the default implementations.

Edit ./app/build.gradle to add the following dependencies.

implementation 'com.microsoft.kiota:microsoft-kiota-abstractions:1.1.14'
implementation 'com.microsoft.kiota:microsoft-kiota-authentication-azure:1.1.14'
implementation 'com.microsoft.kiota:microsoft-kiota-http-okHttp:1.1.14'
implementation 'com.microsoft.kiota:microsoft-kiota-serialization-json:1.1.14'
implementation 'com.microsoft.kiota:microsoft-kiota-serialization-text:1.1.14'
implementation 'com.microsoft.kiota:microsoft-kiota-serialization-form:1.1.14'
implementation 'com.microsoft.kiota:microsoft-kiota-serialization-multipart:1.1.14'
implementation 'com.azure:azure-identity:1.12.2'

Generate the API client

Kiota generates API clients from OpenAPI documents. Create a file named get-me.yml and add the following.

openapi: 3.0.3
info:
  title: Microsoft Graph get user API
  version: 1.0.0
servers:
  - url: https://graph.microsoft.com/v1.0/
paths:
  /me:
    get:
      responses:
        200:
          description: Success!
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/microsoft.graph.user"
components:
  schemas:
    microsoft.graph.user:
      type: object
      properties:
        id:
          type: string
        displayName:
          type: string

You can then use the Kiota command line tool to generate the SDK classes.

kiota generate -l java -d get-me.yml -c GetUserApiClient -n getuserclient.apiclient -o ./app/src/main/java/getuserclient/apiclient

Register an application

To be able to authenticate with the Microsoft identity platform and get an access token for Microsoft Graph, you need to create an application registration. You can install the Microsoft Graph PowerShell SDK and use it to create the app registration, or register the app manually in the Azure Active Directory admin center.

The following instructions register an app and enable device code flow for authentication.

Connect-MgGraph -Scopes "Application.ReadWrite.All"
$app = New-MgApplication -displayName "Kiota Test Client" -IsFallbackPublicClient

> $app.AppId
1cddd83e-eda6-4c65-bccf-920a86f220ab

Create the client application

The final step is to update the ./app/src/main/java/getuserclient/App.java file that was generated as part of the console application to include the following code. Replace YOUR_CLIENT_ID with the client ID from your app registration.

package getuserclient;

import com.azure.identity.DeviceCodeCredential;
import com.azure.identity.DeviceCodeCredentialBuilder;
import com.microsoft.kiota.authentication.AzureIdentityAuthenticationProvider;
import com.microsoft.kiota.http.OkHttpRequestAdapter;

import getuserclient.apiclient.GetUserApiClient;
import getuserclient.apiclient.models.User;


public class App {

    public static void main(String[] args) {
        final String clientId = "YOUR_CLIENT_ID";

        // The auth provider will only authorize requests to
        // the allowed hosts, in this case Microsoft Graph
        final String[] allowedHosts = new String[] { "graph.microsoft.com" };
        final String[] graphScopes = new String[] { "User.Read" };

        final DeviceCodeCredential credential = new DeviceCodeCredentialBuilder()
            .clientId(clientId)
            .challengeConsumer(challenge -> System.out.println(challenge.getMessage()))
            .build();


        final AzureIdentityAuthenticationProvider authProvider =
            new AzureIdentityAuthenticationProvider(credential, allowedHosts, graphScopes);
        final OkHttpRequestAdapter adapter = new OkHttpRequestAdapter(authProvider);

        final GetUserApiClient client = new GetUserApiClient(adapter);

        try {
            final User me = client.me().get();
            System.out.printf("Hello %s, your ID is %s%n",
                    me.getDisplayName(), me.getId());
        } catch (Exception err) {
            System.out.printf("Error: %s%n", err.getMessage());
        }
    }
}

Run the application

To start the application, run the following command in your project directory.

./gradlew --console plain run

See also

• kiota-samples repository contains the code from this guide.
• ToDoItem Sample API implements a sample OpenAPI in ASP.NET Core and sample clients in multiple languages.