Idiomatic way to reference a bundled data file from Clojure source?

[stu]

Hi,

I'd like to bundle a collection of (JSON) datafiles with a Clojure
project source tree so that Clojure functions can reliably find and
open those datafiles.

What's the idiomatic way of going about this? In the past with other
languages I've used tricks like Ruby's ".dirname(__FILE__)/..."
construct but this kind of approach doesn't seem a good fit for
Clojure or for the JVM facilities it provides.

Can anyone point to a Clojure project that does this well?

Thanks,

Stu

[Dave Ray]

Hey,

I don't have a good example, but the right way to do is with resources
which are basically just files that live on the classpath:

* Put the files in a folder on your classpath. If your using
leiningen, the resources/ directory does this by default.
* Get a URL to the file with clojure.java.io/resource. If your file is
root/resources/my-project/my-resource.txt, you'd use (resource
"my-project/my-resource.txt").
* Read the contents of the file by passing the resource URL to
clojure.java.io/reader or one of its friends.

When you jar up your app the resource files will be included in the
jar and "just work".

Hope this helps.

Dave

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[Stephen C. Gilardi]

> I'd like to bundle a collection of (JSON) datafiles with a Clojure
> project source tree so that Clojure functions can reliably find and
> open those datafiles.
>
> What's the idiomatic way of going about this?

One idiomatic way to do this in Clojure is:

- store the files within a directory named resources at the top level of your project folder,
- arrange for that folder to be in your classpath at runtime,
- obtain a reference to the files at runtime using .getResource with a relative path.

If you use lieningen, the resources folder will be in your class path automatically and the files/directories it contains will be copied to the top level of your jar file if you make one.

Here's an example:

(defn resource [path]
(when path
(-> (Thread/currentThread) .getContextClassLoader (.getResource path))))

(require '[clojure.java.io :as io])
(slurp (io/file (resource "js/boo.js")))

I did this in a leiningen project called scratch. It returned the contents of the file

scratch/resources/js/boo.js

because scratch/resources was on the classpath.

See also http://alexott.net/en/clojure/ClojureLein.html .

--Steve

[stu]

On Jun 29, 12:17 pm, "Stephen C. Gilardi" <squee...@mac.com> wrote:

> > I'd like to bundle a collection of (JSON) datafiles with a Clojure
> > project source tree so that Clojure functions can reliably find and
> > open those datafiles.
>
> > What's the idiomatic way of going about this?

Many thanks to Dave and Stephen for your answers--just what I
needed.

Stu

[Shantanu Kumar]

The idiomatic way may be to include the file(s) in the classpath and
there is already a `resource` function in clojure.java.io that can
load it from the classpath:

$ lein new foo
$ cd foo
$ mkdir resources
$ cat>resources/test.txt
hello
world
foo
bar
^D
$ # edit src/foo/core.clj as follows
(ns foo.core
(:require [clojure.java.io :as jio]))

(println (slurp (jio/resource "test.txt")))

$ lein deps
$ lein repl
user=> (require 'foo.core)
hello
world
foo
bar
user=>

Regards,
Shantanu