Substituting environment variables in tomcat configuration file

I was looking to run my application running under tomcat in Kubernetes cluster. For that I need to create a container image. I don't want to put username and passwords of database in the image. But at the same time I need it in tomcat configuration. I was looking for a way to  substitute environment variables in tomcat configuration.

In Kubernetes we can populate environment variables from secrets managed by Kubernetes. This way you can keep your secrets and containerize your application also.

You need to add following argument to CATALINA_OPTS

-Dorg.apache.tomcat.util.digester.PROPERTY_SOURCE=org.apache.tomcat.util.digester.EnvironmentPropertySource

 

After passing this argument you can use environment variables same way as system properties. You can use it like this:

${ENV_VARIABE_NAME}