gistfile1.txt

import org.fusesource.restygwt.client.Method;
import org.fusesource.restygwt.client.MethodCallback;

import com.google.gwt.user.client.Window;

public abstract class MethodCallbackImpl<T> implements MethodCallback<T> {
    @Override
    public void onSuccess(Method method, T result) {
        onSuccess(result);
    }

    @Override
    public void onFailure(Method method, Throwable throwable) {
        String errorFromServer = method.getResponse().getText();

        showErrorMessage(errorFromServer);
    }

    protected void showErrorMessage(String serverError) {
        Window.alert(serverError);
    }

    protected abstract void onSuccess(T result);
}

This way, the client

• can (but is not required to) override onFailure
• can (but is not required to) override showServerError
• must implement onSuccess(T result)