exceptions.rb

class Exceptions < Application
  skip_before :parse_supplied_sscj1
  skip_before :ensure_authenticated

  provides :sscj1

  # ...

  # handle RecordInvalid exceptions (406)
  def record_invalid
    @errors = request.exceptions.first.errors
    rename_error_fields!
    render 
  end

  # handle client errors
  def client_error
    # Re-Raise so we get the pretty merb error document instead.
    raise request.exceptions.first if content_type == :html

    @exceptions = request.exceptions
    @show_details = Merb::Config[:exception_details]

    # Leave the :standard_error part, so that the other actions that call
    # this know what template to render
    render :client_error
  end

  # Everything else (500)
  def standard_error
    # Re-Raise so we get the pretty merb error document instead.
    raise request.exceptions.first if content_type == :html

    @exceptions = request.exceptions
    @show_details = Merb::Config[:exception_details]

    # Leave the :standard_error part, so that the other actions that call
    # this know what template to render
    render :standard_error 
  end

  # We want some of the error fields to show up
  # under the service attribute names, rather than
  # the database column names, so here's what to
  # rename them to
  ERROR_FIELDS_TO_RENAME = {
    :template_path => :template_href
  }

  def rename_error_fields!
    ERROR_FIELDS_TO_RENAME.each do |from, to|
      v = @errors.delete(from)
      @errors[to] = v
    end
  end
end

record_invalid.sscj1.erb

<%= j( {
  :_type        => "ResourceInvalid",
  :request_uri  => request.env['REQUEST_URI'],
  :parameters   => JSON.parse(request.raw_post),
  :errors       => @errors.to_hash.map { |f,msg| {:field => f, :messages => msg} }
} ) %>