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Announcing ring-clj-params

Feb 15, 2012

What is it?

A Ring middleware that augments :params according to a parsed Clojure data literal request body.

Where is it?



In your :dependencies section add the following:

[ring-clj-params "0.1.0"]


To use this middleware using Ring and Compojure, create a new Leiningen project with a project.clj file of the form:

 (defproject awesomeness "0.0.1"
   :description ""true power awesomeness
   :dependencies [[org.clojure/clojure "1.3.0"]
                  [ring "1.0.2"]
                  [compojure "1.0.1"]
                  [ring-clj-params "0.1.0"]]
   :main awesome-app)

Next, create a file in src called my_awesome_service.clj with the following:

(ns my-awesome-service
  (:use compojure.core)
  (:use ring.middleware.clj-params))

(defn generate-response [data & [status]]
  {:status (or status 200)
   :headers {"Content-Type" "application/clojure"}
   :body (print-str data)})

(defroutes handler
  (GET "/" []
       (generate-response {:hello :cleveland}))

  (PUT "/" [name]
       (generate-response {:hello name})))

(def app
  (-> handler

And finally, create another file in src named awesome_app.clj with the following:

(ns awesome-app
  (:use ring.adapter.jetty)
  (:require [my-awesome-service :as awe]))

(defn -main
  [& args]
  (run-jetty #'awe/app {:port 8080}))


Run this app in your console with lein run and test with curl using the following:

$ curl -X GET http://localhost:8080/

#=> {:hello :cleveland}                               

$ curl -X PUT -H "Content-Type: application/clojure" \ 
  -d '{:name :barnabas}' http://localhost:8080/

#=> {:hello :barnabas}%  

The Clojure *eval-read* functionality is turned off and trying to use it will result in a server-side exception thus resulting in an empty response for the eval form; such as:

$ curl -X PUT -H "Content-Type: application/clojure" \ 
  -d '{:name #=(+ 1 2)}' http://localhost:8080/ 

#=> ...

I’m currently only supporting data literals for Clojure versions 1.3 and below. Support for later versions (including tagged literal support) is planned.


Thanks to Mark McGranaghan for his work on Ring and ring-json-params on which this project was based. Also thanks to Craig Andera for reminding me about *read-eval*. Finally, thanks to Relevance for allowing me the time to work on such projects during work hours.


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