| The primary interface a caller must implement to receive a response from a
remote procedure call.
If an RPC is successful, then
AsyncCallback.onSuccess(Object) is called, otherwise
AsyncCallback.onFailure(Throwable) is called.
Each callable asynchronous method corresponds to a method in the correlated
service interface. The asynchronous method always takes an
AsyncCallback as its last parameter.
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 callback);
Note that throws 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(Object result) {
// It's always safe to downcast to the known return type.
Shape[] shapes = (Shape[]) result;
controller.processShapes(shapes);
}
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
}
}
});
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Parameters:
T - > |