GWT RPC
The GWT RPC framework makes it easy for the client and server components of your web application to exchange Java objects over HTTP. The server-side code that gets invoked from the client is often referred to as a service. The implementation of a GWT RPC service is based on the well-known Java servlet architecture. Within the client code, you'll use an automatically-generated proxy class to make calls to the service. GWT will handle serialization of the Java objects passing back and forth—the arguments in the method calls and the return value.
GWT RPC services are not the same as web services based on SOAP or REST. They are simply as a lightweight method for transferring data between your server and the GWT application on the client. To compare single and multi-tier deployment options for integrating GWT RPC services into your application, see the Developer's Guide, Architectural Perspectives.
A fundamental difference between AJAX applications and traditional HTML web applications is that AJAX applications do not need to fetch new HTML pages while they execute. Because AJAX pages actually run more like applications within the browser, there is no need to request new HTML from the server to make user interface updates. However, like all client/server applications, AJAX applications usually do need to fetch data from the server as they execute. The mechanism for interacting with a server across a network is called making a remote procedure call (RPC), also sometimes referred to as a server call. GWT RPC makes it easy for the client and server to pass Java objects back and forth over HTTP. When used properly, RPCs give you the opportunity to move all of your UI logic to the client, resulting in greatly improved performance, reduced bandwidth, reduced web server load, and a pleasantly fluid user experience.
The server-side code that gets invoked from the client is often referred to as a service, so the act of making a remote procedure call is sometimes referred to as invoking a service. To be clear, though, the term service in this context is not the same as the more general "web service" concept. In particular, GWT services are not related to the Simple Object Access Protocol (SOAP).
