The Cascading Bridge Design Pattern

public class AppStore { public static AppStore current() {return current;} public static void install(AppStore as) {current=as;} private static AppStore current; abstract public void commit(Application app); abstract Application retrieve(int id); }public void commit(Application app); abstract Application retrieve(int id); } It has methods for maintaining the current handler (current, install), as well as abstract methods provided for the benefit of the domain model. A simple implementation of AppStore stores Applications in memory: public class AppMemStore extends AppStore { private Hashtable apps = new Hashtable(); public void commit(Application app) { apps.put(new Integer(app.getId()),app); } Application retrieve(int id) { return (Application)apps.get(new Integer(id)); } } A simple application would use an AppMemStore directly: public class Client { static void init() { AppStore.install(new AppMemStore()); } static void test() { Application a1 = new Application(1,"barnie"); a1.commit(); Application a2 = Application.retrieve(1); ... // compare a1 and a2 } public static final void main(String[] argv) { init(); test(); } } If instead a remote connection is desired, the Client.init routine simply installs an appropriate subclass of AppStore: public class Client { static void init() { AppStore.install(new AppRMI()); } ... // same as before } AppRMI communicates to the server using RMI. Here we assume class AppRemote has been defined and had a client stub generated with standard RMI development tools. AppRMI then forwards requests to an AppRemote instance (potentially having to deal with network failures which are ignored here): public class AppRMI extends AppStore {