Drupal create a page that outputs JSON

I would like to ask can one create a page that outputs JSON data as a response to Jquery Ajax request?

In a non-drupal way, I would just create a php file, for example mypage.php and then I would use http://example.com/mypage.php?foo=bar as the URL for my AJAX request. This page will then output JSON data using json_encode().

How can I do it the Drupal way?