Since my last post a lot has happened in Clojure- and Compojure-Land. Managing dependencies and building projects is much easier now that there is Leiningen and more people have played around with Clojure on Google App Engine, some are even deploying live apps (check out TheDeadline).
So I decided to build upon these great contributions and (finally) continue this little tutorial.
From my last post, you can still read the part about Emacs, but you can forget about getting all the dependencies. We'll use Leiningen for that. To install Leiningen, follow the installation instructions. Then create a new project:
lein new compojureongae
This creates the basic directory structure with some skeleton code. Edit the project.clj file to look like this:
(defproject compojureongae "0.1.0-SNAPSHOT"
:description "Example app for deployoing Compojure on Google App Engine"
:dependencies [[compojure "0.4.0-SNAPSHOT"]
[ring/ring-jetty-adapter "0.2.0"]]
:dev-dependencies [[leiningen/lein-swank "1.1.0"]])
I removed the direct dependencies on clojure and clojure-contrib, since depending on compojure automatically pulls these, but you could leave them in (e.g. if you need a specific version). The dev-dependency on lein-swank gives me integration with Emacs while letting Leiningen handle the classpath config.
Running lein deps (in the directory containing project.clj) downloads all required libraries and puts them in the lib directory.
Run lein swank to start a REPL, open Emacs and enter M-x slime-connect to connect to the REPL. Now we can start hacking away in Emacs! Open src/compojureongae/core.clj and enter the following:
(ns compojureongae.core
(:use compojure.core
ring.adapter.jetty)
(:require [compojure.route :as route]))
(defroutes example
(GET "/" [] "<h1>Hello World Wide Web!</h1>")
(route/not-found "Page not found"))
(run-jetty example {:port 8080})
(This is taken directly from Compojure's Getting Started page.) Pressing C-c C-k compiles the file and starts the server - you can see the output in the shell where you ran lein swank. Now browse to http://localhost:8080/ to see your first Compojure app.
Next step: Deploying this to Google App Engine!