Rails 2.x provide meaningful error message with http basic authentication

I'm using basic http authentication in my rails app via the following code:

class ApplicationController < ActionController::Base
  helper :all # include all helpers, all the time
  before_filter :authenticate

private
  def authenticate
    authenticate_or_request_with_http_basic do |username, password|
      if username.nil? || password.nil?
        render :inline => %(xml.instruct! :xml, :version => "1.0", :encoding => "UTF-8"
                            xml.errors do
                              xml.error('Could not authenticate you.')
                            end), :type => :builder, :status => 401
      end
    end
  end
end

The problem is, if you do a curl http://127.0.0.1:3000/foo/1.xml without providing the -u username:password flag, you get a dead beat response like this:

HTTP/1.1 401 Unauthorized 
Cache-Control: no-cache
WWW-Authenticate: Basic realm="Foo"
X-Runtime: 1
Content-Type: text/html; charset=utf-8
Content-Length: 27
Server: WEBrick/1.3.1 (Ruby/1.9.1/2010-01-10)
Date: Thu, 03 Jun 2010 03:09:18 GMT
Connection: Keep-Alive

HTTP Basic: Access denied.

Is it possible at all to render the inline XML I have above in the event a username and password is not provided by t开发者_如何学Pythonhe user?

This might not be the safest way to go about this, but you can give it a shot.

First, go ahead and build a custom error:

#construct a custom error class
class AuthenticationError < StandardError
  # error code goes here
end

Now in your code block raise that error:

xml.errors do
  raise AuthenticationError
end

You can use ActionController's rescue_from method to handle your custom error message now:

class ApplicationController < ActionController::Base
  rescue_from AuthenticationError { |e| xml_status_error(:unauthorized, e) }

  def xml_status_error(status,exception)
    respond_to do |format|
      format.xml { #here you go! }
      format.any { head status } #just return the status code
    end
  end
end