Apache Maven is abuild automation tool for Java.

App Engine provides a Maven plugin that you can use to build and deployyour app to App Engine. The plugin does not support EnterpriseApplication Archive (EAR) projects.

Before you start

1. Determine if Maven is installed and which version you have by runningthe following command:

   mvn-v

   If Maven is installed, a long string of information beginning withApache Maven and followed by a version number such as3.9.1 willdisplay.

2. If you don't have Maven 3.9.1 or newer installed:

   1. Download Maven 3.9.1 or newer.
   2. Install Maven 3.9.1 or newer.
   Note: Linux users might need to download Maven instead of usingapt-get install to install Maven 3.9.1 or newer.

3. If you haven't already done so, follow the stepshereto download the gcloud CLI, create your Google Cloud project, andinitialize your App Engine app.

4. Install the gcloud CLIapp-engine-java component:

   gcloudcomponentsinstallapp-engine-java

Adding the App Engine Maven plugin

To use theApp Engine Maven plugin, add the following lines to theplugins section inyour project'spom.xml file:

<plugins><plugin><groupId>com.google.cloud.tools</groupId><artifactId>appengine-maven-plugin</artifactId><version>2.8.1</version></plugin><plugin><groupId>org.eclipse.jetty</groupId><artifactId>jetty-maven-plugin</artifactId><version>9.4.56.v20240826</version></plugin></plugins>

Using the Jetty Maven plugin to test your app locally

During the development phase, you can run and test your app at any time inthe development server by invoking the Jetty Maven plugin.

To run your app in the development server:

1. Build your app if you haven't already done so:

   mvnpackage

2. Change directory to the top level of your project (for example, tomyapp),and run your app by invoking Maven:

   mvnjetty:run

3. Wait for the server to start and use your browser to visithttp://localhost:8080/ to access your app.

4. Shut down the app and the development server by pressingControl+C.

Building and deploying your app

After you add the App Engine Maven plugin to your project'spom.xmlfile, you can use the following command to build deploy your app:

mvn package appengine:deploy -Dapp.deploy.projectId=PROJECT_ID

ReplacePROJECT_ID with the ID of your Google Cloud project. Ifyourpom.xml file alreadyspecifies yourproject ID, you don't need to include the-Dapp.deploy.projectId property in thecommand you run.

Thepackage goal builds and packages your app, and theappengine:deploy goaldoes the following:

1. Generates a unique version ID for the new version of your app.

2. Deploys the new version to App Engine.

3. Routes all traffic to the new version.

Changing the deployment defaults

You can change the default deployment behavior by passing parameters in theappengine:deploy command. For example, the following command deploys theservice defined in yourpom.xml file to a specific Google Cloud project,assigns a custom version ID to the service, and turns off automatic trafficrouting for the new version:

mvnappengine:deploy-Dapp.deploy.projectId=PROJECT_ID-Dapp.deploy.version=VERSION_ID-Dapp.deploy.promote=False

You can also use theappengine:deploy command to deploy configuration files,such ascron.yaml,dispatch.yaml, andindex.yaml.

For more information, see theappengine:deployreference.

What's next

• Review theJDK 21 App Engine Maven plugin sample.
• Explore the plugin code and report issues onGitHub.
• Learn how to specify parameters for tasks by referring toApp Engine Maven Goals and Parameters.