1. If you haven't already, set up a Java Development Environment (including google-cloud-sdk and maven utilities) by following the java setup guide and create a project.

2. Create a 2nd Gen Cloud SQL Instance by following these instructions. Note the connection string, database user, and database password that you create.

3. Create a database for your application by following these instructions. Note the database name.

4. Create a service account with the 'Cloud SQL Client' permissions by following these instructions. Download a JSON key to use to authenticate your connection.

5. Use the information noted in the previous steps:

export GOOGLE_APPLICATION_CREDENTIALS=/path/to/service/account/key.json
export CLOUD_SQL_CONNECTION_NAME='<MY-PROJECT>:<INSTANCE-REGION>:<MY-DATABASE>'
export DB_USER='my-db-user'
export DB_PASS='my-db-pass'
export DB_NAME='my_db'

Note: Saving credentials in environment variables is convenient, but not secure - consider a more secure solution such as Cloud KMS to help keep secrets safe.

To run this application locally, run the following command inside the project folder:

mvn jetty:run

Navigate towards http://127.0.0.1:8080 to verify your application is running correctly.

To run on GAE-Standard, create an AppEngine project by following the setup for these instructions and verify that appengine-maven-plugin has been added in your build section as a plugin.

The following command will run the application locally in the the GAE-development server:

mvn appengine:run

First, update src/main/webapp/WEB-INF/appengine-web.xml with the correct values to pass the environment variables into the runtime.

Next, the following command will deploy the application to your Google Cloud project:

mvn appengine:deploy