Spring (Boot) application.properties and Variables
Define an environment variable in environment
export my_config=1337
To make a default value if the environment variable is not defined.
Consume the variable somewhere in the application.
Careful with the naming, it happened several times that I defined the default configuration with dot-notation and then the application did not work. Maybe use rather completely different names for the default value and the Spring property. You will keep staring at such piece of code wondering what is wrong