Package com.google.gwt.user.client.rpc
Interface AsyncCallback<T>
-
- Type Parameters:
T
- The type of the return value that was declared in the synchronous version of the method. If the return type is a primitive, use the boxed version of that primitive (for example, anint
return type becomes anInteger
type argument, and avoid
return type becomes aVoid
type argument, which is alwaysnull
).
- All Known Implementing Classes:
SimpleRemoteLogHandler.DefaultCallback
public interface AsyncCallback<T>
The primary interface a caller must implement to receive a response from a remote procedure call.If an RPC is successful, then
onSuccess(Object)
is called, otherwiseonFailure(Throwable)
is called.Each callable asynchronous method corresponds to a method in the correlated service interface. The asynchronous method always takes an
AsyncCallback<T>
as its last parameter, whereT
is the return type of the correlated synchronous method.As an example, suppose the service interface defines a method called
getShapes
as follows:Shape[] getShapes(String databaseName) throws ShapeException, DbException;
Its asynchronous counterpart method be declared as:void getShapes(String databaseName, AsyncCallback<Shape[]> callback);
Note thatthrows
declaration is not repeated in the async version.A call with a typical use of
AsyncCallback
might look like this:service.getShapes(dbName, new AsyncCallback
() { public void onSuccess(Shape[] result) { // It's always safe to downcast to the known return type. controller.processShapes(result); } public void onFailure(Throwable caught) { // Convenient way to find out which exception was thrown. try { throw caught; } catch (IncompatibleRemoteServiceException e) { // this client is not compatible with the server; cleanup and refresh the // browser } catch (InvocationException e) { // the call didn't complete cleanly } catch (ShapeException e) { // one of the 'throws' from the original method } catch (DbException e) { // one of the 'throws' from the original method } catch (Throwable e) { // last resort -- a very unexpected exception } } });
-
-
Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description void
onFailure(java.lang.Throwable caught)
Called when an asynchronous call fails to complete normally.void
onSuccess(T result)
Called when an asynchronous call completes successfully.
-
-
-
Method Detail
-
onFailure
void onFailure(java.lang.Throwable caught)
Called when an asynchronous call fails to complete normally.IncompatibleRemoteServiceException
s,InvocationException
s, or checked exceptions thrown by the service method are examples of the type of failures that can be passed to this method.If
caught
is an instance of anIncompatibleRemoteServiceException
the application should try to get into a state where a browser refresh can be safely done.- Parameters:
caught
- failure encountered while executing a remote procedure call
-
onSuccess
void onSuccess(T result)
Called when an asynchronous call completes successfully.- Parameters:
result
- the return value of the remote produced call
-
-