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Alex Rupérez

Published: 31 Jan 09:23
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Java/Kotlin library for Actions on Google
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Actions on Google Java/Kotlin Client Library

The Java/Kotlin library makes it easy to create Actions for the Google Assistant and supports Dialogflow and Actions SDK fulfillment. It does so by handling most of the request processing logic letting you focus on your Action’s business logic.


  • IDE: You can create a project using any IDE of your choice. However we recommend IntelliJ IDEA by JetBrains.
  • Java: The Actions on Google Java fulfillment library requires Java 8 or higher. You can download the JDK from here.
  • Kotlin: This library is written in Kotlin. Kotlin is bundled with IntelliJ IDEA version 15+.
  • Google Cloud SDK (if deploying to Google Cloud App Engine): You can initialize and deploy your project to App Engine using the Google Cloud SDK (provides the gcloud CLI). You can download the Google Cloud SDK here.

Setup Instructions

The Actions on Google Java/Kotlin library is hosted on Maven central. To use the library in your project, add the following to the dependencies section of your project’s build.gradle.

repositories {

dependencies {
   compile group: '', name: 'actions-on-google', version: '1.8.0'

If using maven, add the following to your pom.xml file.



We recommend that you start your project from the library boilerplate. The boilerplate is a self-contained project that sets up all the build dependencies using Gradle and allows you to import it easily into IntelliJ or other IDE of choice. It also includes artifacts that make it easy to deploy your project on Google Cloud Platform or AWS.

git clone

Instructions for IntelliJ

  • Start IntelliJ IDEA
  • Click Import Project
  • Select the build.gradle file located in the root directory of the project to import the gradle project.
  • On the Import Project from Gradle dialog box, select Use gradle ‘wrapper’ task configuration, and click OK.

The project should now be setup.

Use the Java/Kotlin library

The Java/Kotlin library makes it easy to implement a fulfillment webhook for your Action. You implement your Action’s logic in intent handlers as explained below.

Intent handler

An intent is a goal or action that the user wants to do, such as listening to a song or ordering coffee. Actions on Google represents the intent as a unique identifier. Your Action webhook provides handlers for intents it wants to handle dynamically. In the Java library, this is implemented as a Java class that extends either DialogflowApp or ActionsSdkApp.

Intent handlers are public methods in this class that are marked with a special annotation - @ForIntent as shown below. Intent handlers accept an ActionRequest as a parameter and return an ActionResponse.

public class MyActionsApp extends DialogflowApp {

 @ForIntent("Default Welcome Intent")
 public ActionResponse welcome(ActionRequest request) {
   // Intent handler implementation.

Assemble a response

Intent handlers return a relevant fulfillment response that is sent back to the Google Assistant, which ultimately conveys it to the user as voice and/or visual response. In the simplest form, a response is text spoken back to the user. Actions on Google also supports many other response formats, which include immersive cards with images, carousels, lists, media, and SSML.

Your Action may also respond with one of the helper intents supported by the Assistant. Examples include requesting confirmation from the user or getting permission from the user to get their location.

The ResponseBuilder class provides a variety of helper methods to assemble a response. In the simplest case, your Action responds back with text:

@ForIntent("Default Welcome Intent")
 public ActionResponse welcome(ActionRequest request) {
   ResponseBuilder responseBuilder = getResponseBuilder(request);
   responseBuilder.add("Welcome to my app");

Here is a response that uses BasicCard to render a visual response:

           .add("This is the first simple response for a basic card.")
           .add(new BasicCard()
                   .setTitle("Title: This is a title")
                   .setSubtitle("This is a subtitle")
                   .setImage(new Image()
                           .setAccessibilityText("Image alt text"))

The library generates a JSON response from the ActionResponse returned from the intent handler (see below). The JSON is eventually handled by the Google Assistant to render an audio/visual response to the end user.

The following response uses a helper intent to request the Assistant to get the relevant information from the user:

 Public ActionResponse askForPermission(ActionRequest request) {
   ResponseBuilder responseBuilder = getResponseBuilder(request);
           .add("Placeholder for permissions text")
           .add(new Permission()
                   .setPermissions(new String[]{
                   .setContext("To provide a better experience"));


You can explore more helper methods in ResponseBuilder.

As you can see from the above examples, the Java library provides an intuitive API to assemble responses from your Action. It provides an idiomatic abstraction over the JSON protocol to make it very easy to assemble all supported responses from your Action.

Core API classes

The Java/Kotlin library includes the following core API classes:

  • App: Top level interface to handle the JSON request and return a JSON response. It defines a single method — handleRequest() — to do this.
  • DefaultApp: Subclass of App, implements the request processing logic.
  • DialogflowApp and ActionsSdkApp: These sub-classes of DefaultApp provide specific implementations to handle requests from Dialogflow or directly from Google Assistant (Actions SDK).
  • ActionRequest: ActionRequest parses and encapsulates the JSON request body.
  • ActionResponse: Encapsulates the webhook response.
  • ResponseBuilder: Provides many helper methods to assemble a response.

You can read more about the classes in the library reference.


This section describes how to test and debug your Java/Kotlin webhook during active development and implement end-end/integration tests.

Unit tests

The boilerplate provides a starting point to unit test your intent handler. Depending on your use case, you can choose one of the following approaches:

  • Create an ActionRequest by reading JSON from a file.
  • Use MockRequestBuilder to build an ActionRequest instance to test your intent handler.

Local debugging

During active development, you may start a local server to run your Action as a RESTful web service. You can send valid POST requests to this server (using tools such as Postman) to debug your intent handlers. Both Dialogflow and the Actions Simulator provide tools to visualize and copy JSON requests between Google Assistant and your webhook.

Integration Tests

You can use the Actions on Google testing library to test your Action end to end. Note that the testing library requires tests to be written in Node.js. The webhook fulfillment can be in Node.js/Java/Kotlin or any other language.

References & Issues

Make Contributions

Please read and follow the steps in the




Your use of this sample is subject to, and by using or downloading the sample files you agree to comply with, the Google APIs Terms of Service.