configuration - specific config by environment in Scala

Question

What is a good way to set up a project in Scala which uses different configuration depending on environments.

I need to specifically have different databases for development, test and production environment (similar to what is done in Rails)

Answer 1

Another strategy I'm using consists of using includes. I usually store my DEV settings in the default application.conf file then I create a new conf file for other environments and include the default one.

Let's say my DEV conf application.conf looks like this:

myapp {
    server-address = "localhost"
    server-port = 9000

    some-other-setting = "cool !"
}

Then for the PROD, I could have another file called prod.conf:

include "application"

# override default (DEV) settings
myapp {
    server-address = ${PROD_SERVER_HOSTNAME}
    server-port = ${PROD_SERVER_PORT}
}

Note that I override only the settings that change in the PROD environment (some-other-setting is thus the same as in DEV).

The config bootstrap code doesn't test anything

...
val conf = ConfigFactory.load()
...

To switch from the DEV to the PROD conf, simply pass a system property with the name of the config file to load:

java -Dconfig.resource=prod.conf ...

In DEV, no need to pass it since application.conf will be loaded by default.

So here we're using Typesafe Config's default loading mechanism to achieve this.

I've created a simple project to demonstrate this technique. Feel free to clone and experiment.