Environ is a Clojure library for managing environment settings from a number of different sources.

Currently, Environ supports three sources; environment variables, Java system properties and the Leiningen project map using the lein-environ plugin.

Include the following dependency in your project.clj file:

:dependencies [[environ "0.4.0"]]

If you want to be able to draw settings from the Leiningen project map, you'll also need the following plugin:

:plugins [[lein-environ "0.4.0"]]

A good place to put this is in your profiles.clj file.

Let's say you have an application that requires an AWS access key and secret key.

You can use Leiningen's profiles to add this information to your development environment in your ~/.lein/profiles.clj file, as it's likely you'll be using the same AWS account for all development:

{:user {:env {:aws-access-key "XXXXXXXXXXXXXXX"
              :aws-secret-key "YYYYYYYYYYYYYYYYYYYYYY"}}}

In your application, you can access these values through the environ.core/env map:

(use 'environ.core)

(def aws-creds
  {:access-key (env :aws-access-key)
   :secret-key (env :aws-secret-key)})

You'll likely also want to add .lein-env to your .gitignore file (or the equivalent for your version control system).

When you deploy to a production environment, you can use standard environment variables to configure the same settings.

AWS_ACCESS_KEY=XXXXXXXXXXXXXXX
AWS_SECRET_KEY=YYYYYYYYYYYYYYYYYYYYYY

Notice that the equivalent environment variables are uppercase, and the "-" character has been replaced with "_".

You can also use Java system properties:

java -jar app-standalone.jar -Daws.access.key=XX -Daws.secret.key=YY

Note in this case that the "-" character has been replace with ".", since this is the standard separator for system properties.

Copyright © 2013 James Reeves

Distributed under the Eclipse Public License, the same as Clojure.