Prerequisite:

Linux

Install the Appengine SDK.

$ sudo apt-get install google-cloud-sdk-app-engine-java

Mac

Install the Google Cloud SDK.

$ brew install google-cloud-sdk

Use GCloud CLI to install the Java Appengine

$ gcloud components install app-engine-java

How to regenerate the WAR, deploy and run in appengine?

$ mvn appengine:run