Example Web Application in Clojure

This repo is a simple web application using Integrant, Ring, Reitit, and Selmer connected to a local SQLite database.

For learning purpose, I redid from scratch the very useful Sean Corfield’s usermanager repo and decided to move some libraries to learn them too in the process.

Compojure -> Reitit
Component -> Integrant

A Single Page App version that use Inertia-clojure library can be found here.

Requirements

This example assumes that you have the Clojure CLI installed, and provides a deps.edn file.

Clojure 1.10 (or later) is required. The “model” of this example app uses namespace-qualified keys in hash maps. It uses next.jdbc – the “next generation” JDBC library for Clojure – which produces namespace-qualified hash maps from result sets.

Usage

Run the Application

Clone the repo, cd into it, then follow below to Run the Application or Run the application in REPL. You can launch the application by directly calling the namespace which contains the -main function in an terminal

$ clj -m usermanager.system

or more conveniently, using an alias configured in deps.edn file.

$ clj -A:server

Now acces the app at: http://localhost:3000/.

Run the Application in REPL

$ clj -A:dev

Once REPL starts, run the system:

user=> (go)

Now acces the app at: http://localhost:3000/.

Build an Uberjar

For production deployment, you typically want to build an “uberjar” – a .jar file that contains Clojure itself and all of the code from your application and its dependencies, so that you can run it with the java -jar command.

The build.clj file – mentioned above – contains a ci task that:

cleans up the `target` folder
compiles the application (sometimes called “AOT compilation”)
produces a standalone `.jar` file

clojure -T:build ci

You should see something like this:

Cleaning target...

Skipping pom.xml because :lib and/or :version were omitted...
Copying src, resources...
Compiling system.main...
2022-05-25 18:20:13.069:INFO::main: Logging initialized @3981ms to org.eclipse.jetty.util.log.StdErrLog
Building uberjar target/reitit-example-standalone.jar...

The target folder will be created if it doesn’t exist and it will include a classes folder containing all of the compiled Clojure source code from the usermanager application and all of its dependencies including Clojure itself:

$ ls target/classes/
cheshire  clojure  clout  com  compojure  crypto  instaparse  json_html  layouts  medley  next  public  ring  selmer  usermanager  views

It will also include the standalone .jar file which you can run like this:

java -jar target/example-standalone.jar

This should behave the same as the Run the Application example above.

This JAR file can be deployed to any server that have Java installed and run with no other external dependencies or files.

License & Copyright

Distributed under the Apache Source License 2.0.