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README.md

conf-er

A ridiculously simple application configuration library.

I found myself duplicating this code in almost every project and so decided to break it out into a library. Thanks to @jaley for the original gist.

I hope you find this as useful as I have.

Usage

Add to your leiningen dependencies

{:dependencies [[conf-er "1.0.1"]]}

The idea is to have a single configuration file which consists of a keyworded map, you then look up individual properties with nested keywords, for example:

;; my-config.conf
{:username "joe.bloggs"
 :password "letmein"
 :database {:host "127.0.0.1"
            :port 1234}

 :my.library/number 42}

And then look up the configuration from anywhere within your program! Simply include the conf-er namespace and then either the strict (config) function (which throws if nothing is configured) or (opt-config) which will simply return nil if unconfigured.

(use 'conf-er)

(config :username) => "joe.bloggs"
(configured? :database) => true
(config :database) => {:host "127.0.0.1" :port 1234}
(config :database :port) => 1234

;; Trying to retrieve unconfigured options
(config :database :connections) => (Exception "Couldn't find :database :connections in configuration file")
(opt-config :database :connections) => nil

Tell your program where to find the configuration file from your leiningen project.clj, or if you want to set it when you've packaged up and distributed a jar, simply set it as an option on the java command

...
:jvm-opts ["-Dconfig=my-config.conf"]
...

If you're changing your config on the go, you can reload the config file from your REPL:

=> (reload-config-file)

If you use this from within a library, you must namespace your configuration in case the application using your library also wishes to use conf-er. You can do this like so:

(ns my.library
  (:require [conf-er :refer [config]]))

(config ::number) => 42

Here :number will expand out to the namespaced keyword :my.library/number, which we put in our configuration file earlier.

Testing

If you want to write tests which use this code, it's useful to know that conf-er stores all the settings in conf-er/config-map and so you can with-redefs this for tests. See conf-er's own tests for an example usage.

Issues

Hopefully this project is simplistic enough that nothing much will come up, but please report any issues through the github issue tracker.

License

Copyright © 2013 TouchType Ltd.

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