Weavejester/Environ Library Demo

Overview

This Clojure demo project shows how to configure and use the weavejester/environ library.

Running in "test" mode

To use this project, we assume you have already installed Java, Clojure, and Leiningen, installed.

Verify you have Java, Clojure, and Leiningen set up correctly

Try the following commands, and make sure you get similar output:

> java --version
java 13 2019-09-17
Java(TM) SE Runtime Environment (build 13+33)
Java HotSpot(TM) 64-Bit Server VM (build 13+33, mixed mode, sharing)

> lein --version
Leiningen 2.9.1 on Java 13 Java HotSpot(TM) 64-Bit Server VM

Description of `project.clj` and `profiles.clj`

We don’t want to check sensitive information like passords into SCM. Also, we will typically have different credentials for different phases of a project (e.g. database connections for dev, test, prod, etc). For this demo, we place DB connection strings for dev and test into profiles.clj. This file is normally never checked into SCM, but we have included a dummy version in this demo project for illustrative purposes. It looks like this:

{:profiles/dev  {:env {:database-url "jdbc:postgresql://localhost/dev"}}
 :profiles/test {:env {:database-url "jdbc:postgresql://localhost/test"}}}

Running Unit Tests

> lein clean ; lein test

lein test _bootstrap

-----------------------------------
   Clojure 1.10.3    Java 15.0.2
-----------------------------------

lein test tst.demo.core

Ran 2 tests containing 1 assertions.
0 failures, 0 errors.
( lein do clean, test; )  34.44s user 1.90s system 408% cpu 8.906 total

The file test/clj/tst/demo/core.clj verifies that the "test" DB URL is found.

Running `-main` in "dev" mode

> lein clean ; lein run

The file src/clj/tst/demo/core.clj will print out the "dev" DB URL.

Running in demo.core/-main

(environ/env :database-url) => "jdbc:postgresql://localhost/dev"

( lein do clean, run; )  31.89s user 1.80s system 392% cpu 8.576 total

Running `-main` in "prod" mode

Run the code using an environment variable to override profiles.clj:

> DATABASE_URL=jdbc:postgresql://localhost/prod   lein run

Warning: environ value jdbc:postgresql://localhost/dev for key :database-url has been overwritten with jdbc:postgresql://localhost/prod

Running in demo.core/-main
(environ/env :database-url) => "jdbc:postgresql://localhost/prod"

The file src/clj/tst/demo/core.clj will print out the "prod" DB URL from the env var DATABASE_URL. It will also work if you run from a JAR file via java -jar myproj.jar instead of lein run

Keeping Dependency Versions Up-To-Date

This project includes the lein-ancient plugin, which will tell you if any of your dependency libraries are out of date. I have an alias:

alias laca="lein ancient check :all"

which will give you a list of version updates you should make, or just

all artifacts are up-to-date.

if you are already up-to-date on everything.

License

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

io-tupelo-demo/environ