Is it possible to restrict a route for AJAX only?

Question

I know this question is a bit older but meanwhile a new way to achieve this was introduced in Symfony 2.4.

Matching Expressions

For an ajax restriction it would look like this:

contact:
    path:     /contact
    defaults: { _controller: AcmeDemoBundle:Main:contact }
    condition: "request.isXmlHttpRequest()"

Also possible in Annotation:

/**
 * ContactAction
 *
 * @Route("/contact", name="contact", condition="request.isXmlHttpRequest()")
 */