If your question is only about mapping objects from the back-end to the JavaScript front-end, then I suggest using a JAX-RS implementation (RESTEasy, Restlet, Apache CXF, ...) in combination with Jackson (JSON provider).
This combination allows you to publish a REST API with your domain objects converted to JSON, so you can easily access these objects through JavaScript by using AJAX requests.
But of course this leaves a lot of communication handling open to the developer, if you want to have a more complete package, frameworks like Google Web Toolkit are probably a better solution.