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.

Quick Start

First clone the Ring source and download Ring’s dependencies:

  
git clone git://github.com/mmcgrana/ring.git
cd ring  
ant deps

To see a live “Hello World” Ring app, run:

java -Djava.ext.dirs=deps clojure.main src/ring/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 -Djava.ext.dirs=deps clojure.main src/ring/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.

Included Libs

• ring.adapter.jetty: Adapter for the Jetty webserver.
• ring.adapter.httpcore: Adapter for the Apache HttpCore webserver.
• ring.middleware.file: Middleware that serves static files out of a public directory.
• ring.middleware.file-info: Middleware that augments response headers with info about File responses.
• ring.middleware.lint: Linter for the Ring interface, ensures compliance with the Ring spec.
• ring.middleware.reload: Middleware to automatically reload selected libs before each requests, minimizing server restarts.
• ring.middleware.stacktrace: Middleware that catches exceptions and displays readable stacktraces for debugging.
• ring.middleware.static: Middleware that serves static files with specified prefixes out of a public directory.
• ring.handler.dump: Handler that dumps request maps as HTML responses for debugging.
• ring.util.servlet: Utilities for interfacing with Java Servlets.
• ring.example.*: Various example Ring apps.

Development

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

To run all the Ring unit tests:

java -Djava.ext.dirs=deps clojure.main test/ring/run.clj

You can learn more about Ring’s dependencies at the following sites:

• clojure.jar, clojure-contrib.jar: clojure.org
• jetty-6.1.14.jar, jetty-util-6.1.14.jar, servlet-api-2.5-6.1.14.jar: mortbay.org/jetty
• httpcore-4.0.jar, httpcore-nio-4.0.jar: hc.apache.org
• commons-io-1.4.jar: commons.apache.org/io
• clj-html.jar, clj-html-helpers.jar, clj-stacktrace.jar, clj-unit: github.com/mmcgrana

Thanks

This project borrows heavily from Ruby’s Rack and Python’s WSGI, and I thank the communities developing and supporting those projects.

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Copyright © 2009 Mark McGranaghan and released under an MIT license.
Clojure logo by Tom Hickey.