Compojure Address Book Part 2

Recap and Restructure

So far we have modified the default Compojure template to include a basic POST route and used Midje and Ring-Mock to write a test to confirm that it works. Before we get started with templates and creating our address book we should provide some additional structure to our application in an effort to keep things organized as the project grows.

Create two new directories

So far all of our application code has lived in src/address_book/core/handler.clj. From here on out handler.clj is going to hold: an initialize function that will run on project start up, our default not found route and most importantly the app definition. The app definition is where we combine all routes from our project and wrap them with any needed middleware. You might be able to guess what we are going to keep in the two new directories. All the logic for the routes in the address book will go in routes and views is going to hold our soon to be introduced hiccup templates.

Let’s restructure src/address_book/core/handler.clj so it only includes the following:

(ns address-book.core.handler
  (:require [compojure.core :refer [defroutes routes]]
            [compojure.route :as route]
            [ring.middleware.defaults :refer [wrap-defaults site-defaults]]
            [address-book.core.routes.address-book-routes :refer [address-book-routes]]))

(defn init []
  (println "Address book application is starting"))

(defroutes app-routes
  (route/not-found "Not Found"))

(def app
  (-> (routes address-book-routes app-routes)
      (wrap-defaults (assoc-in site-defaults [:security :anti-forgery] false))))

Notice that we add an init function. Currently it will just print a string, but eventually we will use this as a hook to ensure that our database exists upon starting the application. We also add the address-book-routes in our app definition. We need to let our app know about the new init method. To achieve this we need to add a line to the :ring map in project.clj.

:ring {:handler address-book.core.handler/app
       :init    address-book.core.handler/init}

Finally, we can move our existing routes into /src/address_book/core/routes/address_book_routes.clj.

(ns address-book.core.routes.address-book-routes
  (:require [compojure.core :refer [defroutes GET POST]]
            [address-book.core.views.address-book-layout :refer [common-layout]]))

(defn example-post [request]
  (let [post-value (get-in request [:params :example-post])]
    (str "You posted: " post-value)))

(defroutes address-book-routes
  (GET  "/"     [] "Example GET")
  (POST "/post" [] example-post))

Hiccup Templates

Hiccup is a library for representing HTML in Clojure. It uses vectors to represent elements and maps to represent an element’s attributes. If you understand HTML then it is intuitive to use and will be well suited for our application.

We start by adding [hiccup "1.0.5"] as a dependency in project.clj. With that done we can populate src/address_book/core/views/address_book_layout.clj with the following:

(ns address-book.core.views.address-book-layout
  (:require [ :refer [html5 include-css]]))

(defn common-layout [& body]
      [:title "Address Book"]
      (include-css "/css/address-book.css")]
      [:h1#content-title "Address Book"]

What we have done here is created a common layout that we will grow into the base for all of the applications views. We can use a common frame and pass in the desired body contents. You will also notice the include-css function. Our lein template came with an empty resources directory that our application can access. We will store our style sheet in here and serve it up with our templates. To get our feet wet with templates let’s extend our basic GET route to use the common-layout. We need to require the common-layout in src/address_book/core/routes/address_book_routes.clj and we will generate the response body for our GET request from a new function named example-get. Update your address_book_routes.clj with the following pieces:

(ns address-book.core.routes.address-book-routes
  (:require [compojure.core :refer :all]
            [address-book.core.views.address-book-layout :refer [common-layout]]))

(defn example-get [request]
    [:p "Example GET"]))

(defroutes address-book-routes
  (GET "/" [] example-get)
  (POST "/post" [] example-post))

Before we test out our new templates, let us also add some content to our style sheet so we can be sure that is being properly included. Create this file resources/public/css/address-book.css and add to it, the following:

body {
  background-color: #BCE5FF

h1 {
  color: #FF6967;

At this point when we visit http://localhost:3000/ we should see the following: Basic GET route

Due to our using a template now we should have a failing test. No longer is the response equal to “Example GET” so we need to change our assertion to

(:body response) => (contains "Example GET")

Wrap Up

At this point we have successfully laid the ground work for the majority of our application. In the next installment we will add the real style sheet and create hiccup templates for our primary views.

You can find all the code for this section in Part 2.

Read Part 3 In The Series