Ring

Ring is a Clojure web applications library inspired by Python's WSGI and Ruby's Rack. By abstracting the details of HTTP into a simple, unified API, Ring allows web applications to be constructed of modular components that can be shared among a variety of applications, web servers, and web frameworks.

The SPEC file at the root of this distribution for provides a complete description of the Ring interface.

Synopsis

"Hello World" in Ring:

(use 'ring.adapter.jetty)

(defn app [req]
  {:status  200
   :headers {"Content-Type" "text/html"}
   :body    "Hello World from Ring"})

(run-jetty app {:port 8080})

Adding simple middleware:

(defn wrap-upcase [app]
  (fn [req]
    (let [orig-resp (app req)]
      (assoc orig-resp :body (.toUpperCase (:body orig-resp))))))

(def upcase-app (wrap-upcase app))

(run-jetty upcase-app {:port 8080})

Quick Start

To see some working examples, first pull in Ring's dependencies using Leiningen:

$ lein deps

To see a live "Hello World" Ring app, run:

$ java -cp "lib/*" clojure.main example/hello_world.clj

Now visit http://localhost:8080/ in your browser; the Ring app will respond to your request with a simple HTML page indicating the time of day.

To see a more sophisticated Ring app, run:

$ java -cp "lib/*" clojure.main example/wrapping.clj

If you request http://localhost:8080/ in your browser the ring.handler.dump handler will respond with an HTML page representing the request map that it received (see the SPEC for details on the request map).
If you request http://localhost:8080/clojure.png, the ring.middleware.file middleware will detect that there is a clojure.png file in the app's public directory and return that image as a response.
If you request http://localhost:8080/error, the app will produce an error that will be caught by the ring.middleware.stacktrace middleware, which will in turn return a readable stacktrace as the HTML response.

Documentation

Ring namespace and function docs

Available Libraries

ring-core

ring.middleware.file: Serve static files out of a public directory.
ring.middleware.static: Serve static files with specified prefixes out of a public directory.
ring.middleware.file-info: Augment response headers with info about File responses.
ring.middleware.params: Parse query and form params.
ring.middleware.multipart-params: Parse multipart params.
'ring.middleware.keyword-params`: Convert string param keys to keywords.
ring.middleware.cookies: Manage browser cookies.
ring.middleware.session: Manage user sessions. Memory and cookie session stores are available by default.
ring.util.response: Generate Ring responses.

ring-devel

ring.handler.dump: Dumps request maps as HTML responses for debugging.
ring.middleware.lint: Lint requests and responses to ensure compliance with the Ring spec.
ring.middleware.reload: Automatically reload selected libs before each request.
ring.middleware.stacktrace: Catch exceptions and displays readable stacktraces for debugging.

ring-servlet

ring.util.servlet: Utilities for interfacing with Java Servlets.

ring-jetty-adapter

ring.adapter.jetty: Adapter for the Jetty webserver.

ring-httpcore-adapter

ring.adapter.httpcore: Adapter for the Apache HttpCore webserver.

Leiningen Usage

To include one of the above libraries in your Leiningen project, for example ring-core, add the following to your :dependences:

[ring/ring-core "0.2.0-RC2"]

To include all of them, add:

[ring/ring "0.2.0-RC2"]

Development

Ring is being actively developed; you can track its progress and contribute at the project's GitHub page and Google Group.

To run the Ring unit tests, first navigate to the appropriate project and then:

$ lein deps
$ lein test

Thanks

This project borrows heavily from Ruby's Rack and Python's WSGI; thanks to those communities for their work.

License

Clojure logo by Tom Hickey.

ugglan/ring