REST - HTTP headers - XML Error Handling -ActiveResource

Rails
#1

Hi,

I’m putting together a RESTful API that I would like to play nice with
ActiveResource. I’ve got things mostly working, but I’m beginning to
stumble around error handling and I’m seeking some thoughtful input.

Here’s some context:

(For a detailed look at the issue I’m contemplating see:
http://www.oreillynet.com/onlamp/blog/2003/12/restful_error_handling.html)

Let’s say that I have a REST controller containing code that looks like
this:

def create
@book = @book(params[:book])
respond_to do |format|
if false @book.save
format.xml { head :created, :location => book_url(@book) }
else
format.xml { head 400, :xml=> ErrorCode.new(20, “Save
failed.”).to_xml }
end
end
end

(note, I’m deliberately forcing a failure response with ‘if false’ )
When I execute this method via CURL, I get following (correct, I
believe) response:

#—
t$ curl -i -X POST http://0.0.0.0:3001/books.xml
HTTP/1.1 400 Bad Request
Connection: close
Date: Wed, 11 Apr 2007 19:46:11 GMT
Set-Cookie: _adiserver_session_id=dbe7f61d877a041c3d5d49c29d0086e5;
path=/
Status: 400 Bad Request
Xml: <?xml version="1.0" encoding="UTF-8"?>

20
Could not save book
save failed.

#—

This response looks correct me because it has:

  1. an HTTP Status code
  2. some descriptive XML

Seeing this, I expect that ActiveResource should be happy…

but, alas, when doing a @book.save over ActiveResource (console), I get:

@book.save

ActiveResource::ResourceNotFound: Failed with 404
from/script/…/config/…/config/…/vendor/rails/
activeresource/lib/active_resource/connection.rb:92:in `handle_response’

etc…

Now I would expect to get ‘false’ and/or the the XML containing the
error information that I’ve constructed.

–OR–

My questions are these:

  1. What does ActiveResource expect in the case of failed operation?
  2. In the event of a failed request, how does AR get access to the
    supplemental XML that is sent? Is this possible?
  3. Are some of my assumptions incorrect?

Perhaps “ActiveResource::ResourceNotFound” is an exception that I need
to handle in the following manner:

begin
@book.save
rescue
[…could not save code here …]
end

I look forward to your thoughtful guidance.