"The client is not always right." (Enzo Ferrari)
Integrating clients with a back-end server may pose some challenges as it involve a mix between asynchronous and synchronous behaviour and data exchange.
The 'communication related APIs' of Java EE 7 APIs have all some asynchronous capabilities, e.g. JAX-RS 2.0, WebSocket 1.0 , JMS 2.0, Servlet 3.1, JAX-WS 2.2.
In his 'JavaFX Integration Strategies' article, Adam Bien explain some strategies to easily integrate JavaFX clients with a back-end using some of the asynchronous capabilities of Java EE 7. The article also illustrate how to push information from the server to the client using WebSocket.
The article uses JavaFX as the client side UI framework but the patterns and strategies described are not necessarily JavaFX specific and are easily applicable to almost any types of client. As Adam says "REST and JSON become the new, least common denominator for communication with HTML5 clients, Java applications, and even low-level devices.". Finally, the article also illustrate how Java SE 8 Lambda leads to a cleaner code.