Create a Java command-line application that makes requests to the Google Chat API.

Quickstarts explain how to set up and run an app that calls a
Google Workspace API. This quickstart uses a
simplified authentication approach that is appropriate for a testing
environment. For a production environment, we recommend learning about
[authentication and authorization](https://developers.google.com/workspace/guides/auth-overview)
before
[choosing the access credentials](https://developers.google.com/workspace/guides/create-credentials#choose_the_access_credential_that_is_right_for_you)
that are appropriate for your app.

This quickstart uses Google Workspace's recommended API client libraries
to handle some details of the authentication and authorization flow.

## Objectives

- Set up your environment.
- Set up the sample.
- Run the sample.

## Prerequisites

- Java 11 or greater.
- [Gradle 7.0 or greater](https://gradle.org/install/).
- [A Google Cloud project](https://developers.google.com/workspace/guides/create-project).


- A Business or Enterprise [Google Workspace](https://support.google.com/a/answer/6043576) account with access to [Google Chat](https://workspace.google.com/products/chat/).

<br />

## Set up your environment

To complete this quickstart, set up your environment.

### Enable the API

Before using Google APIs, you need to turn them on in a Google Cloud project. You can turn on one or more APIs in a single Google Cloud project.

- In the Google Cloud console, enable the Google Chat API.

  [Enable the API](https://console.cloud.google.com/flows/enableapi?apiid=chat.googleapis.com)

### Configure the OAuth consent screen

If you're using a new Google Cloud project to complete this quickstart, configure
the OAuth consent screen. If you've already
completed this step for your Cloud project, skip to the next section.

1. In the Google API Console, go to Menu \> **Google Auth platform** \> **Branding** .

   [Go to Branding](https://console.developers.google.com/auth/branding)
2. If you have already configured the Google Auth platform, you can configure the following OAuth Consent Screen settings in [Branding](https://console.developers.google.com/auth/branding), [Audience](https://console.developers.google.com/auth/audience), and [Data Access](https://console.developers.google.com/auth/scopes). If you see a message that says **Google Auth platform not configured yet** , click **Get Started**:
   1. Under **App Information** , in **App name**, enter a name for the app.
   2. In **User support email**, choose a support email address where users can contact you if they have questions about their consent.
   3. Click **Next**.
   4. Under **Audience** , select **Internal**.
   5. Click **Next**.
   6. Under **Contact Information** , enter an **Email address** where you can be notified about any changes to your project.
   7. Click **Next**.
   8. Under **Finish** , review the [Google API Services User Data Policy](https://developers.google.com/terms/api-services-user-data-policy) and if you agree, select **I agree to the Google API Services: User Data Policy**.
   9. Click **Continue**.
   10. Click **Create**.
3. For now, you can skip adding scopes. In the future, when you create an app for use outside of your Google Workspace organization, you must change the **User type** to **External** . Then add the authorization scopes that your app requires. To learn more, see the full [Configure OAuth consent](https://developers.google.com/workspace/guides/configure-oauth-consent) guide.

### Authorize credentials for a desktop application

To authenticate end users and access user data in your app, you need to create one or more OAuth 2.0 Client IDs. A client ID is used to identify a single app to Google's OAuth servers. If your app runs on multiple platforms, you must create a separate client ID for each platform.

1. In the Google Cloud Console, go to Menu \> **Google Auth platform** \> **Clients** .

   [Go to Clients](https://console.developers.google.com/auth/clients)
2. Click **Create Client**.
3. Click **Application type** \> **Desktop app**.
4. In the **Name** field, type a name for the credential. This name is only shown in the Google Cloud Console.
5. Optional: If your app is an AI agent that takes actions on behalf of users, select **Use this client for an AI-powered agent**. If your app supports both AI agent workflows and standard user features, create separate OAuth clients for each. You can't change this setting after you create the client.
6. Click **Create** .


   The newly created credential appears under "OAuth 2.0 Client IDs."
7. Save the downloaded JSON file as `credentials.json`, and move the file to your working directory.

### Configure the Google Chat app

> [!NOTE]
> **Note:** To perform read-only API calls with user authentication, such as `GetSpace` or `ListMessages`, you don't need to configure a Google Chat app. You only need to enable the API and create an OAuth client.

To perform create, update, and delete Google Chat API calls, you must configure a
Google Chat app. For any write requests, Google Chat attributes
the Google Chat app in the UI using the following information.

1. In the Google API Console, go to the Chat API **Configuration** page:

   [Go to Chat API Configuration page](https://console.developers.google.com/apis/api/chat.googleapis.com/hangouts-chat)
2. Under **Application info**, enter the following information:

   1. In the **App name** field, enter `Chat API quickstart app`.
   2. In the **Avatar URL** field, enter `https://developers.google.com/chat/images/quickstart-app-avatar.png`.
   3. In the **Description** field, enter `Quickstart for calling the Chat API`.
3. Under **Interactive features** , click the **Enable interactive features**
   toggle to the off position to disable interactive features for the
   Chat app.

4. Click **Save**.

## Prepare the workspace

1. In your working directory, create a new project structure:

       gradle init --type basic
       mkdir -p src/main/java src/main/resources 

2. In the `src/main/resources/` directory, copy the `credentials.json` file
   that you previously downloaded.

3. Open the default `build.gradle` file and replace its contents with the
   following code:


   chat/quickstart/build.gradle [View on GitHub](https://github.com/googleworkspace/java-samples/blob/main/chat/quickstart/build.gradle)

   ```groovy
   apply plugin: 'java'
   apply plugin: 'application'

   mainClassName = 'ChatQuickstart'
   sourceCompatibility = 11
   targetCompatibility = 11
   version = '1.0'

   repositories {
       mavenCentral()
   }

   dependencies {
       implementation 'com.google.auth:google-auth-library-oauth2-http:1.23.0'
       implementation 'com.google.api-client:google-api-client:1.33.0'
       implementation 'com.google.api.grpc:proto-google-cloud-chat-v1:0.8.0'
       implementation 'com.google.api:gax:2.48.1'
       implementation 'com.google.cloud:google-cloud-chat:0.1.0'
       implementation 'com.google.oauth-client:google-oauth-client-jetty:1.34.1'
   }
   ```

   <br />

   <br />

## Set up the sample

1. In the `src/main/java/` directory, create a new Java file with a name that
   matches the `mainClassName` value in your `build.gradle` file.

2. Include the following code in your new Java file:


   chat/quickstart/src/main/java/ChatQuickstart.java [View on GitHub](https://github.com/googleworkspace/java-samples/blob/main/chat/quickstart/src/main/java/ChatQuickstart.java)

   ```java
   import com.google.api.client.auth.oauth2.Credential;
   import com.google.api.client.extensions.java6.auth.oauth2.AuthorizationCodeInstalledApp;
   import com.google.api.client.extensions.jetty.auth.oauth2.LocalServerReceiver;
   import com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeFlow;
   import com.google.api.client.googleapis.auth.oauth2.GoogleClientSecrets;
   import com.google.api.client.googleapis.javanet.GoogleNetHttpTransport;
   import com.google.api.client.json.JsonFactory;
   import com.google.api.client.json.gson.GsonFactory;
   import com.google.api.client.util.store.FileDataStoreFactory;
   import com.google.api.gax.core.FixedCredentialsProvider;
   import com.google.auth.Credentials;
   import com.google.auth.oauth2.AccessToken;
   import com.google.auth.oauth2.UserCredentials;
   import com.google.chat.v1.ChatServiceClient;
   import com.google.chat.v1.ChatServiceSettings;
   import com.google.chat.v1.ListSpacesRequest;
   import com.google.chat.v1.Space;
   import com.google.protobuf.util.JsonFormat;
   import java.io.File;
   import java.io.FileNotFoundException;
   import java.io.IOException;
   import java.io.InputStream;
   import java.io.InputStreamReader;
   import java.util.Collections;
   import java.util.Date;
   import java.util.List;

   /* class to demonstrate use of Google Chat API spaces list API */
   public class ChatQuickstart {
     /** Directory to store authorization tokens for this application. */
     private static final String TOKENS_DIRECTORY_PATH = "tokens";

     /**
      * Global instance of the scopes required by this quickstart. If modifying these scopes, delete
      * your previously saved tokens/ folder.
      */
     private static final List<String> SCOPES =
         Collections.singletonList("https://www.googleapis.com/auth/chat.spaces.readonly");

     /** Global instance of the JSON factory. */
     private static final JsonFactory JSON_FACTORY = GsonFactory.getDefaultInstance();

     private static final String CREDENTIALS_FILE_PATH = "/credentials.json";

     /**
      * Run the OAuth2 flow for local/installed app.
      *
      * @return An authorized Credential object.
      * @throws IOException If the credentials.json file cannot be found.
      */
     private static Credentials getCredentials() throws Exception {
       // Load client secrets.
       InputStream credentialsFileInputStream =
           ChatQuickstart.class.getResourceAsStream(CREDENTIALS_FILE_PATH);
       if (credentialsFileInputStream == null) {
         throw new FileNotFoundException("Credentials file resource not found.");
       }
       GoogleClientSecrets clientSecrets =
           GoogleClientSecrets.load(JSON_FACTORY, new InputStreamReader(credentialsFileInputStream));

       // Set up authorization code flow.
       GoogleAuthorizationCodeFlow flow =
           new GoogleAuthorizationCodeFlow.Builder(
                   GoogleNetHttpTransport.newTrustedTransport(), JSON_FACTORY, clientSecrets, SCOPES)
               // Set these two options to generate refresh token alongside access token.
               .setDataStoreFactory(new FileDataStoreFactory(new File(TOKENS_DIRECTORY_PATH)))
               .setAccessType("offline")
               .build();

       // Authorize.
       Credential credential =
           new AuthorizationCodeInstalledApp(flow, new LocalServerReceiver()).authorize("user");

       // Build and return an authorized Credential object
       AccessToken accessToken =
           new AccessToken(
               credential.getAccessToken(),
               new Date(
                   // put the actual expiry date of access token here
                   System.currentTimeMillis()));
       return UserCredentials.newBuilder()
           .setAccessToken(accessToken)
           .setRefreshToken(credential.getRefreshToken())
           .setClientId(clientSecrets.getInstalled().getClientId())
           .setClientSecret(clientSecrets.getInstalled().getClientSecret())
           .build();
     }

     public static void main(String... args) throws Exception {
       // Override default service settings to supply user credentials.
       Credentials credentials = getCredentials();

       // Create the ChatServiceSettings with the credentials
       ChatServiceSettings chatServiceSettings =
           ChatServiceSettings.newBuilder()
               .setCredentialsProvider(FixedCredentialsProvider.create(credentials))
               .build();

       try (ChatServiceClient chatServiceClient = ChatServiceClient.create(chatServiceSettings)) {
         ListSpacesRequest request =
             ListSpacesRequest.newBuilder()
                 // Filter spaces by space type (SPACE or GROUP_CHAT or
                 // DIRECT_MESSAGE).
                 .setFilter("spaceType = \"SPACE\"")
                 .build();

         // Iterate over results and resolve additional pages automatically.
         for (Space response : chatServiceClient.listSpaces(request).iterateAll()) {
           System.out.println(JsonFormat.printer().print(response));
         }
       }
     }
   }
   ```

   <br />

## Run the sample

1. Run the sample:

   ```
   gradle run
   ```

<!-- -->

2. The first time you run the sample, it prompts you to authorize access:
   1. If you're not already signed in to your Google Account, sign in when prompted. If you're signed in to multiple accounts, select one account to use for authorization.
   2. Click **Accept**.


   Your Java application runs and calls the Google Chat API.


   Authorization information is stored in the file system, so the next time you run the sample
   code, you aren't prompted for authorization.

## Next steps

- [Try the Google Workspace APIs in the APIs explorer](https://developers.google.com/workspace/explore)
- [Google Chat API Javadoc documentation](https://cloud.google.com/java/docs/reference/google-cloud-chat/latest/overview)

<br />