often your places are "parameterized", think of a detail/edit screen for example that needs the model's id. The token is a generic way to provide additional information (via the URL) to the place (i.e. the activity/-ies), i.e. "#editFoo:42". You can of course re-use one place to dispatch to several activities based on the token. See the (currently not used) for ProxyPlace and ProxyListPlace in the Expenses sample for an example.

PlaceHistoryHandler has been split into a concrete PlaceHistoryHandler and the PlaceHistoryMapper interface, which you're free to implement yourself or use as before, giving your sub-interface to GWT.create() so that it generates the implementation from the @WithTokenizers annotation (and/or factory if you're using PlaceHistoryMapperWithFactory); this approach is similar to the ActivityManager vs. ActivityMapper, with the added generator for the mapper based on PlaceTokenizers and @Prefix.

Activity.Display now is com.google.gwt.user.client.ui.AcceptsOneWidget, which is implemented by SimplePanel (showActivityWidget is thus renamed as setWidget). IsWidget has been moved to com.google.gwt.user.client.ui and is now implemented by Widget (which returns itself); this means that if your view classes extends Widget (most views extend it through Composite) you no longer have to implement the asWidget method. In addition, all widgets now accept IsWidget as argument where they already accepted Widget.

Views A key concept of MVP development is that a view is defined by an interface. This allows multiple view implementations based on client characteristics (such as mobile vs. desktop) and also facilitates lightweight unit testing by avoiding the time-consuming GWTTestCase. There is no View interface or class in GWT which views must implement or extend; however, GWT 2.1 introduces an IsWidget interface that is implemented by most Widgets as well as Composite. It is useful for views to extend IsWidget if they do in fact provide a Widget. Here is a simple view from our sample app. public interface GoodbyeView extends IsWidget {    void setName(String goodbyeName);} The corresponding implementation extends Composite, which keeps dependencies on a particular Widget from leaking out. public class GoodbyeViewImpl extends Composite implements GoodbyeView {    SimplePanel viewPanel = new SimplePanel();    Element nameSpan = DOM.createSpan();    public GoodbyeViewImpl() {        viewPanel.getElement().appendChild(nameSpan);        initWidget(viewPanel);    }    @Override    public void setName(String name) {        nameSpan.setInnerText("Good-bye, " + name);    }}

A place in GWT 2.1 is a Java object representing a particular state of the UI. A Place can be converted to and from a URL history token (see GWT's History object) by defining a PlaceTokenizer for each Place, and the PlaceHistoryHandler automatically updates the browser URL corresponding to each Place in your app.

Place

Entity proxies simply extend the EntityProxy interface and use the @ProxyFor annotation to reference the server-side entity being represented. It is not necessary to represent every property and method from the server-side entity in the EntityProxy, only getters and setters for properties that should be exposed to the client. Note that while getId() is shown in this example, most client code will want to refer to EntityProxy.stableId() instead, as the EntityProxyId returned by this method is used throughout RequestFactory-related classes. Also note that the getSupervisor() method returns another proxy class (EmployeeProxy). All client-side code must reference EntityProxy subclasses. RequestFactory automatically converts proxy types to their corresponding entity types on the server.

There is no public API for checking the status of tasks.  A task is   really nothing more than a normal http request which is monitored by   GAE to retry it if it fails.  The real brains is in the task queue   which is simply a queue of URL's that app engine will fire off at a   given rate and retry failed requests. The only public method to check tasks (http requests) in this queue is   the console webpage.  Its up to you to monitor your tasks yourself by   storing some kind of status data in memcache or the datastore.