Clojure Web Development Reboot

After installing El Capitan last week, I decided it was time for a rethink of my setup for clojure web development. Up until now, I’ve been using the following:

• Leiningen
• Ring
• Compojure
• Component

But there are some new kids on the block that I wanted to take for a spin in a new project I’m working on. And as 2016 is but a few hours away, it’s out with the old and in with the new! ;)

Leiningen -> Boot

Leiningen is THE build and automation tool in the clojurespere, but boot seems to be gaining traction. Check out this article for a great overview of boot and what it can do for you http://www.flyingmachinestudios.com/programming/boot-clj/.

Ring.Core -> Aleph

Aleph has been around for a while now, but was rewritten just over a year ago, so it’s newish :) Aleph is a Ring-spec compliant networking library running on Netty and using Manifold for representing streams.

Compojure -> Bidi

I think most web developers have had a stab at writing a routing library at one time or another. I know I have. Bidi is written for both clojure and clojurescript and avoids the use of macros, instead using data structures for defining your routes.

System -> Mount

Mount is a clojure(script) library for managing application state similar to component but with some differences.

Emacs -> Spacemacs!

One tool that I still use for clojure development is the Emacs/CIDER/nREPL toolchain. If you are already happy with your clojure development environment then skip the next section. If not - here’s my setup (this is a Mac-only guide - sorry!):

1. Install homebrew
2. Install Emacs with brew install emacs-mac --with-spacemacs-icon
3. Install spacemacs following these steps
4. Edit your spacemacs file
   • add clojure to the dotspacemacs-configuration-layers section. This layer provides clojure-mode and Cider, among other things.
   • add (add-to-list 'auto-mode-alist '("\\.boot$" . clojure-mode)) to the dotspacemacs/user-config function. This tells emacs to treat .boot files as clojure files.

Time to create our project :)

Create the following file structure:

$ tree testapp
.
├── build.boot
├── resources
│   └── public
│       └── hello.txt
└── src
    └── clj
        └── testapp
            └── core.clj

Put anything you want into hello.txt. The contents of the other 2 files are as follows:

$ cat build.boot

    (set-env!
      :source-paths #{"src/cljs" "src/clj"}
      :resource-paths #{"resources"}
      :dependencies '[
                       [mount "0.1.7"]
                       [org.clojure/clojure "1.7.0"]
                       [aleph "0.4.1-beta2"]
                       [bidi "1.24.0"]
                       [org.clojure/tools.nrepl "0.2.11"]])

$ cat src/clj/testapp/core.clj

    (ns testapp.core
      (:require
        [aleph.http :as http]
        [mount.core :refer [defstate] :as mount]
        [bidi.ring :refer [make-handler] :as br]))

    (defn index []
      {:status 200
       :headers {"content-type" "text/plain"}
       :body "hello world!"})

    (def routes
      ["" [
            ["/" index]
            ["" (br/resources {:prefix "public"})]]])

    (def handler
      (make-handler routes))

    (defstate http-server
      :start (http/start-server handler {:port 3001})
      :stop (.close http-server))

Let’s jump into an nREPL now to make sure everything is working:

1. Open spacemacs
2. Switch to our testapp directory with C-x d and entering the correct path.
3. Connect to an nrepl using cider with M-x cider-jack-in
4. Once it has connected, you may need to switch to the correct buffer using C-x b
5. Open up our core.clj file in a split next to the repl: C-c 3 and then C-x C-f to find the file.
6. Switch to our testapp.core namespace by pressing C-c M-n while the cursor is in the file.
7. Compile the file using C-c C-k
8. In the cider repl, enter (mount/start) and
   • navigate to localhost:3001
   • navigate to localhost:3001/hello.txt
9. enter (mount/stop). The server should have shut down.

Have a great start to 2016!