Can I set environment variables at runtime with App Engine Standard using Java 8 runtime

Question

As for the official documentation ( https://cloud.google.com/appengine/docs/standard/java/config/appref ), a Java application using App Engine Standard for Java 8 runtime should describe it's env in an appengine-web.xml located under WEB-INF folder.

The chances are high those variables vary from env to env, and I refuse to build env dedicated artifacts.

Can I set those env vars in an external file? If yes how?

Answer 1

In order to set Env Variables for App Engine in Java runtime, you can also set them in the app.yaml file using the env_variables key

for example:

env_variables:
   MY_VAR_COLOR: 'blue'

You can see the recommended documentation in here

Answer 2

You can't include external file for environment variables definition.

For this, I duplicate the appengine-web.xml and I store it in separate subfolders WEB-INF/dev/ , WEB-INF/uat/ , WEB-INF/prod/

Then, I use Maven to copy the appengine-web.xml from the right subfolder according with the profile passed to the build -P param

Not very maintainable because you have to replicate the modification in all the appengine-web.xml files, but I don't find a better trade off for having separate value per environment.