Valery&Galina :

Let's integrate GWT RPC with Spring PetStore sample application. To keep the domain code separate from the RPC and client-side code, you have to create and maintain copies of domain beans implementing IsSerializable interface (we omitted setters and getters here for brevity).

Google Web Toolkit. Integration with Spring framework. Mapping domain beans to client-side beans

But what about using Dozer ?