How do I set Accept header on my URL in autocomplete plugin

How do I set Accept header on my URL in autocomplete plugin

I'm trying to develop an autocomplete list box using JQuery autocomplete.  My autocomplete script needs to access a url which runs a Spring MVC RESTFUL controller and obtains data from Solr.  Unfortunately, the Spring JSON view only returns JSON if the URL has a .json extension (which it won't have for REST interace) or has the Accept header of the request set to "application/json".

Unfortunately, I can't seem to see how, or get the syntax right, for the setting the request header on my autocomplete url.  Any examples would be appreciated.

Thanks
Shaun