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Create projectλ︎

To create a web service we can use two commonly used libraries in Clojure, ring and compojure.

Ring provides many low-level functions to manage web requests and responses as well as providing an embedded web server (ie. Jetty). Most importantly it abstracts away all the complicated details of HTTP communication. So as a developer of the web app you mostly focus on processing a request map and returning a response map.

Compojure provides a simple way to define routes for your application, eg what function is called when a browser requests a specific url.

Note:: Create a new project using Leiningen and the compojure template, then go into the project created.λ︎

lein new compojure shorturl-service

cd shorturl-service

Open the project.clj file in an editor and take a look at the dependencies added to the project.

(defproject shorturl-service "0.1.0-SNAPSHOT"
  :description "FIXME: write description"
  :url ""
  :min-lein-version "2.0.0"
  :dependencies [[org.clojure/clojure "1.8.0"]
                 [compojure "1.5.1"]
                 [ring/ring-defaults "0.2.1"]]
  :plugins [[lein-ring "0.9.7"]]
  :ring {:handler shorturl-service.handler/app}
  {:dev {:dependencies [[javax.servlet/servlet-api "2.5"]
                        [ring/ring-mock "0.3.0"]]}})

Apart from Clojure itself, the compojure and ring libraries have been added.

The :plugins section adds lein-ring which allows us to run the server using the command lein ring server

The :ring section defines the default function to call when running the project

The :profiles section adds libraries useful for development and testing.