The approach in the Java world for many years have been to implement Services (or Repository if it doesn't need a complex operations) and wrap them via facade pattern by utilizing:

- JAX-RS (RESTful)

- JAX-WS (WebService)

- MVC (view-based web-app)

And in contrast to what people believe, you don't need to write tons of code and still get full re-usability from the Services/Repositories layer.

On the front-end, you have a choice of:

- GWT for thick-client via RPC (return serialized Java object) or AJAX (return JSON)

- JSP, JSF, any templating available

- Mobile, Desktop, anything