Java Quickstart for App Engine Flexible Environment

This quickstart shows you how to create a small App Engine app that displays a short message.

Before you begin

Before running and deploying this sample, complete the following steps:

  1. Use the GCP Console to create a new GCP project, create an App Engine app, and enable billing:
    Go to App Engine

    When prompted, select the region where you want your App Engine app located and then enable billing.

  2. Install the following prerequisites :
    1. Download and install Git.
    2. Download and install the Cloud SDK. Follow the instructions in the Cloud SDK page to initialize and set your GCP project ID in the gcloud command-line tool:
      Download the Cloud SDK
    3. This quickstart uses Apache Maven to build, run, and deploy the sample app. For details about installing Maven, see Using Apache Maven and the App Engine Plugin.

App Engine locations

App Engine is regional, which means the infrastructure that runs your apps is located in a specific region and is managed by Google to be redundantly available across all the zones within that region.

Meeting your latency, availability, or durability requirements are primary factors for selecting the region where your apps are run. You can generally select the region nearest to your app's users but you should consider the location of the other GCP products and services that are used by your app. Using services across multiple locations can affect your app's latency as well as pricing.

App Engine is available in the following regions:

  • northamerica-northeast1 (Montréal)
  • us-central (Iowa)
  • us-west2 (Los Angeles)
  • us-east1 (South Carolina)
  • us-east4 (Northern Virginia)
  • southamerica-east1 (São Paulo) *
  • europe-west (Belgium)
  • europe-west2 (London)
  • europe-west3 (Frankfurt)
  • asia-northeast1 (Tokyo)
  • asia-east2 (Hong Kong)
  • asia-south1 (Mumbai)
  • australia-southeast1 (Sydney)

* For customers using the São Paulo region, all regional product SLAs remain in force. However, multi-region and cross-region functionality that span across North America and South America might temporarily have reduced availability or performance.

You cannot change an app's region after you set it.

If you already created an App Engine application, you can view the region by running the gcloud app describe command or opening the App Engine Dashboard in the GCP Console. The region of your App Engine application is listed under http://[YOUR_PROJECT_ID]

This quickstart assumes that you have installed Java Development Kit 8

Download the Hello World app

We've created a simple Hello World app for Java so you can quickly get a feel for deploying an app to the App Engine flexible environment. Follow these steps from a command line to download Hello World to your local machine.

  1. Clone the Hello World sample app repository to your local machine.

    git clone

    Alternatively, you can download the sample as a zip file and extract it.

  2. Change to the directory that contains the sample code.

    cd getting-started-java/helloworld-servlet

Run Hello World on your local machine

  1. Start the local Jetty web server using the Jetty Maven plugin.

    mvn jetty:run-exploded
  2. In your web browser, enter the following address:


You can see the Hello World message from the sample app displayed in the page.

In your terminal window, press Ctrl+C to exit the web server.

Deploy and run Hello World on App Engine

To deploy your app to the App Engine flexible environment:

  1. Deploy the Hello World app by running the following commands from the helloworld directory:

    gcloud config set project YOUR_PROJECT_ID
    mvn appengine:deploy
  2. Launch your browser and view the app at

    gcloud app browse

This time, the page that displays the Hello World message is delivered by a web server running on an App Engine instance.

Congratulations! You've deployed your first Java app to App Engine flexible environment!

See the following sections for information about cleaning up as well as links to possible next steps that you can take.

Clean up

To avoid incurring charges, you can delete your GCP project to stop billing for all the resources used within that project.

  1. In the GCP Console, go to the Projects page.

    Go to the Projects page

  2. In the project list, select the project you want to delete and click Delete.
  3. In the dialog, type the project ID, and then click Shut down to delete the project.

What's next

Now that you've completed the Hello World quickstart, you can start exploring your next sample app: the Bookshelf app. The Bookshelf app is a more complete, yet still basic Java web app that uses multiple GCP features, such as data storage, authentication, logging, pub/sub, and more.

Start the Bookshelf app tutorial

For more information about the App Engine flexible environment, see An Overview Of App Engine.

Hello World code review

Hello World is the simplest possible App Engine app, as it contains only one service, has only one version, and all of the code is located within the app's root directory. This section describes each of the app files in detail.

The file specifies a URL pattern that describes where the app will listen for requests, and responds to any requests with the 'Hello World' message.

@WebServlet(name = "helloworld", value = "/")
public class HelloServlet extends HttpServlet {

  public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    PrintWriter out = resp.getWriter();
    out.println("Hello, world - Flex Servlet");


The app.yaml file describes an application's deployment configuration:

runtime: java
env: flex

- url: /.*
  script: this field is required, but ignored

runtime_config:  # Optional
  jdk: openjdk8
  server: jetty9

  instances: 1

Here, app.yaml specifies the runtime used by the app, and sets env: flex, specifying that the app uses the flexible environment.


Hello World also includes a pom.xml file, which contains information about the project, such as its dependencies and the build target.

<project>                               <!-- REQUIRED -->

  <modelVersion>4.0.0</modelVersion>    <!-- REQUIRED -->
  <packaging>war</packaging>            <!-- REQUIRED -->

  <artifactId>helloworld-servlet</artifactId> <!-- Name of your project -->
  <version>1.0-SNAPSHOT</version>       <!-- xx.xx.xx -SNAPSHOT means development -->

    <maven.compiler.source>1.8</maven.compiler.source> <!-- REQUIRED -->
    <>1.8</> <!-- REQUIRED -->

    <failOnMissingWebXml>false</failOnMissingWebXml> <!-- REQUIRED -->

  <parent>                              <!-- Get parameters and allow bulk testing -->

    <dependency>                        <!-- REQUIRED -->
      <groupId>javax.servlet</groupId>  <!-- Java Servlet API -->
      <scope>provided</scope>           <!-- Provided by the Jetty Servlet Container -->

    <!-- For hot reload of the web application when using an IDE Eclipse / IDEA -->


      <plugin>                          <!-- Used for local debugging -->

          <!-- deploy configuration -->
          <deploy.promote>true</deploy.promote>                           <!~~ DEFAULT value ~~>
          <deploy.stopPreviousVersion>true</deploy.stopPreviousVersion>   <!~~ DEFAULT value ~~>

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