Node.getId() はどちらを返す？

  <ScrollPane fx:id="fxsource_pane" id="source_pane" fitToHeight="true" fitToWidth="true" prefHeight="511.0" prefWidth="600.0" BorderPane.alignment="CENTER">

     <content>

        <TextArea fx:id="source_text" prefHeight="200.0" prefWidth="200.0">

           <font>

              <Font name="SansSerif Regular" size="12.0" />

           </font>

        </TextArea>

     </content>

  </ScrollPane>

    ScrollPane sp = FXMLLoader.load(getClass().getResource("SimpleTextView.fxml"));

    System.out.println("getId() returned: " + sp.getId());

>getId() returned source_pane