How to use TextResource in GWT ClientBundle (link)

interface Resources extends ClientBundle {
  Resources INSTANCE = GWT.create(Resources.class);

  @Source("a.txt")
  TextResource synchronous();

  @Source("b.txt")
  ExternalTextResource asynchronous();
}

// Using a TextResource
myTextArea.setInnerText(Resources.INSTANCE.synchronous().getText());

// Using an ExternalTextResource
Resources.INSTANCE.asynchronous().getText(new ResourceCallback<TextResource>() {
  public void onError(ResourceException e) { ... }
  public void onSuccess(TextResource r) {
    myTextArea.setInnerText(r.getText());
  }
});

http://www.gwtproject.org/doc/latest/DevGuideClientBundle.html#TextResource