Problem with Rails page caching and automatic extensions - ruby-on-rails

Question

I have a JSON and XML based API that needs to be page cached. I have setup my routes on the api to include the format as part of the URL, such that URL's like this work:
http://example.com/foo/1/bar/2/xml
http://example.com/foo/1/bar/2/json
The problem I am seeing is that in the server's public folder, the files are being saved as xml.xml and json.json, and this causes cache misses the next time the URL is accessed.
Is there a way to either:
Turn off the auto extension generation so that they are saved without an extension at all? (EX: RAILS_ROOT/public/foo/1/bar/2/json)
Force all the extensions to be .html for every call. (EX: RAILS_ROOT/public/foo/1/bar/2/json.html)
Either of these would cause my server to return the cached file instead of a miss. How can I do this?
EDIT:
Somebody asked for the relevant route:
scope '(foo/:foo_id)', :foo_id => /\d+/ do
get '/bar/:bar_id/:format' => 'bars#show', :bar_id => /\d+/, :format => /json|xml|html/
end
SOLUTION:
While I was looking for an official way to make this happen using the built in page caching support, I ended up just using an after filter and my own page cache method, as suggested by Anton
# application_controller.rb
def cache_api_page
if REDACTEDServer::Application.config.action_controller.perform_caching
self.class.cache_page(response.body, request.path, '')
puts "CACHED PATH: #{request.path}"
end
end
# bar_controller.rb
after_filter :cache_api_page, :only => [ :show, :index ]

Answer 1

You can do that like this:
class FooController < ApplicationController
after_filter(:only => :show, :if => Proc.new { |c| c.request.format.json? }) do |controller|
controller.class.cache_page(controller.response.body, controller.request.path, '.html')
end
end
When http://example.com/foo/1/bar/2/json is accessed, it will write page to cache (RAILS_ROOT/public/foo/1/bar/2/json.html)
And if you get http://example.com/foo/1/bar/2/json again, you receive RAILS_ROOT/public/foo/1/bar/2/json.html, but your http server(Apache?) should know about content type of this files.
Otherwise content type will set to 'text/html'
UPDATE
To you .htaccess
<FilesMatch "\/json$">
<IfModule mod_headers.c>
Header set Content-Type "text/json"
</IfModule>
</FilesMatch>
<FilesMatch "\/xml$">
<IfModule mod_headers.c>
Header set Content-Type "text/xml"
</IfModule>
</FilesMatch>

Answer 2

In your application.rb configuration block try adding:
config.action_controller.page_cache_extension = '.html'
It should ignore the extension calculated from the request, and always use this.
You could also try using this with an empty string instead.
EDIT: actually this won't work because this only sets a default. If the request has an extension (in your case, concluded from :format) it will be used.
I suggest changing :format in your routes to something else, that rails will not give special meaning to, like :fmt. Then rails should not add the extension and default to '.html'.
EDIT2: If you have to use :format you can monkeypatch Rails:
ActionController::Caching::Pages::ClassMethods
private
def page_cache_file(path)
name = (path.empty? || path == "/") ? "/index" : URI.unescape(path.chomp('/'))
name << page_cache_extension #unless (name.split('/').last || name).include? '.'
return name
end
end
Notice the comment sign I've added before 'unless'. This is the part that overrides the default from my first answer.