Egregious is a rails based exception handling gem for well defined http exception handling for json, xml and html.

If you have a json or xml api into your rails application, you probably have added your own exception handling to map
exceptions to a http status and formatting your json and xml output.  We did to. We were tired of doing it over and
over. We decided to create egregious. One of the major goals is to start providing a more consistent api error
experience for all rails applications. As of the creation of egregious the behavior of rails was to return html when an
exception is thrown with the status code of 500.  With egregious proper json and html of the error will be returned
with a good default mapping of exceptions to http status codes.  This allows api developers to respond to the status
code properly, instead of scratching their head with 500's coming back all the time. If the problem was yours then the
result codes are in the 300 range. If the problem was the server then the status codes are in the 500's.  With the
message and exception type providing more context information.

 What egregious can do:

 * Defines default exception handling for most common ruby, rails, warden and cancan exceptions.
   (warden and cancan are optional)
 * Catches defined exceptions using a rescue_with returning the status code defined for each exception
   and well structured json, xml
 * For html production requests attempts to load the html error pages for the mapped status code,
   falling back to the 500.html page.
 * Defines exceptions for all http status codes allowing you to throw these exceptions anywhere in your code.
 * Allows you to change the exception mapping to fit your needs, adding exceptions and changing status mapping.


REQUIRES:
  Rails 3.x

USAGE:
1) Add to your Gemfile:
gem 'egregious'

2) In your ApplicationController add:
include Egregious

Optionally, to configure create an initializer and add:

Egregious.exception_codes.merge!({NameError => :bad_request})

This will either add a new mapping or replace the existing mapping to a new status code.
You can pass the status code as a symbol, integer or string.

In your code if you want to send an error back just throw an exception. For example:

raise Egregious::BadRequest.new("You can not created an order without a customer.") unless customer_id

All the http status codes have exception classes named after them in the Egregious module. You can throw any exception,
or define your own exceptions. You can find a list in the Rack::Utils::HTTP_STATUS_CODES class.