This is a repository that contains Java code samples for Google App Engine standard Java 11 environment.

These samples use the Apache Maven build system. Before getting started, be sure to download and install it. When you use Maven as described here, it will automatically download the needed client libraries.

If you haven't already created a project, create one now. Projects enable you to manage all Google Cloud Platform resources for your app, including deployment, access control, billing, and services.

1. Open the Cloud Platform Console.
2. In the drop-down menu at the top, select Create a project.
3. Give your project a name.
4. Make a note of the project ID, which might be different from the project name. The project ID is used in commands and in configurations.

To switch to an Open JDK 11 in a Cloud shell session, you can use:

   sudo update-alternatives --config java
   # And select the usr/lib/jvm/java-11-openjdk-amd64/bin/java version.
   # Also, set the JAVA_HOME variable for Maven to pick the correct JDK:
   export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64

One way to deploy to App Engine Java 11 is directly from source.

• springboot-helloworld: Deploy a spring-boot application from source
• http-server: Deploy an http application from source

Another way is using the Maven App Engine Plugin to deploy an executable Uber JAR. App Engine will automatically configure the entrypoint to run the JAR file. Use this method when your application requires dependencies that are located locally, such as the appengine-simple-jetty-main artifact.

• gaeinfo: Build a JAR using the Maven JAR Plugin

In addition, App Engine allows you to execute the java command directly in the app.yaml entrypoint field, so you can further customize your app's startup.

• custom-entrypoint: Run a simple server
• helloworld-servlet: Run a WAR package servlet

With a custom entrypoint, you can also construct and package your application as a thin JAR (or an exploded JAR). When you deploy your application, the App Engine plugin will only upload the files that changed, rather than the entire Uber JAR package.

For more information on the Java 11 runtime, see Building an App and Migrating your App Engine app from Java 8 to Java 11.

To migrate to the Java 11 runtime, your application must have a Main class that starts a web server. appengine-simple-jetty-main is a shared artifact that provides a Jetty Web Server for the servlet based runtime. Packaged as a jar, the Main Class will load a war file, passed as an argument, as the context root of the web application listening to port 8080. Some samples create a <sample-name>.war which is used as an argument in the App Engine app.yaml entrypoint field.

The App Engine Plugin will stage all the files to upload into App Engine runtime in ${build.directory}/appengine-staging. When deploying an Uber JAR, the JAR is automatically copied into this staging directory and uploaded. It's possible to copy other files into this staging directory (such as additional JVM Agents) and having them available in the deployed App Engine runtime directory.

• To stage the files to be uploaded:

mvn appengine:stage