Ring middleware that augments :params according to the specified Accept request-header field. Helps to indicate which type is acceptable for the response, for example text/html, text/xml or application/json. When no format can be deduced, a default value is set (text/html).

Augments :params with an entry identified by the key :accept and the detected value. You can now render the response in your routes given the desired format, a la Grails.

With Leiningen:

[ring-accept-param "0.1.1"]

With Maven:

<dependency>
  <groupId>ring-accept-param</groupId>
  <artifactId>ring-accept-param</artifactId>
  <version>0.1.1</version>
</dependency>

To configure and use this middleware:

(ns my-app.handler
  (:use [compojure.core :only [defroutes GET]]
        [ring.middleware.accept-param :only [wrap-accept-param]]
        [cheshire.core :only [generate-string]])
  (:require [compojure.handler :as handler]
            [compojure.route :as route]))

(defn do-json-hello []
  {:status 200
   :headers {"Content-Type" "application/json; charset=utf-8"}
   :body (generate-string {:response "Hello World"})})

(defroutes app-routes
  (GET "/" {params :params}
    (do (println params)
    (case (:accept params)
      "json" (do-json-hello)
      "html" "Hello World")))
  (route/not-found "Not Found"))

(def app
  (-> app-routes
    wrap-accept-param
    (handler/site)))

You can test this with curl:

$ curl -i http://127.0.01:3000
HTTP/1.1 200 OK
Date: Wed, 22 Aug 2012 20:49:14 GMT
Content-Type: text/html;charset=UTF-8
Content-Length: 11
Server: Jetty(7.6.1.v20120215)

Hello World

And with a specified Accept: application/json header:

$ curl -i http://127.0.01:3000 -H "Accept: application/json"
HTTP/1.1 200 OK
Date: Wed, 22 Aug 2012 20:49:18 GMT
Content-Type: application/json;charset=utf-8
Content-Length: 26
Server: Jetty(7.6.1.v20120215)

{"response":"Hello World"}

Bunch of planned features:

• Add more types like plain text or YAML.
• Consider vendor-specific types in a non-strict mode.
• Allow middleware configuration (default type, strict mode, etc.).
• Implement Accept request-header field specs.

You can also try:

• https://github.com/ngrunwald/ring-middleware-format

Copyright (C) 2012 Gaylord Mazelier

Distributed under the Eclipse Public License, the same as Clojure.