Play Framework JSON and HTTP Request

I am trying to perform a simple method that can handle JSON and HTTP request. Why is this? Because if in some point I decide to create, not only a Webapp also a Mobile APP, I can handle the request with JSON. (I don´t know if this is the best way, if is not please let me know, what would you do?)

My problems is: to handle JSON and HTML in Play, I think that all the request and response need to be intercepted with JavaScript from the HTML side, because need to be parsed as a JSON object. But is there any way to do so , as if it were a simple HTML request?

What is the best way to create a back-end service that will work for a Mobile and WebApp?

Please let me know if you need more info. or something else and your opinion about how I am handling this.

Thanks in advance to all.