/**
 * Upload-Field that supports to open the filechooser-dialog when clicking onto the path-field.
 */
public class RwtScoutFileUploadField2 extends RwtScoutFileUploadField implements IRwtScoutFileUploadField {

  @Override
  protected void initializeUi(Composite parent) {
    super.initializeUi(parent);

    Text textField = getUiField();
    FileUpload browseButton = getUiBrowseButton();

    // Register ClientSide Scripting when clicking on the textfield.
    textField.addListener(SWT.MouseDown, FileChooserClientListener.getInstance());

    // To access the filechooser from within the JavaScript, you simply provide a reference to that field.
    WidgetDataUtil.registerDataKeys("widget_filechooser");
    textField.setData("widget_filechooser", WidgetUtil.getId(browseButton));
  }

  private static final class FileChooserClientListener extends ClientListener {

    private static final long serialVersionUID = 1L;

    private static final String JS = "" +
        "var handleEvent = function(event) {" +
        "  var filechooserRef = event.widget.getData('widget_filechooser');" + // get the reference to the browse-button.
        "  var filechooserWrapper = rwt.remote.ObjectRegistry.getEntry(filechooserRef);" +
        "  var filechooserDOM = filechooserWrapper.object._inputElement;" + // get the DOM of the browse-button.
        "  filechooserDOM.click();" + // invoke 'click' on the DOM to open the filechooser.
        "};";

    public static FileChooserClientListener getInstance() {
      return SingletonUtil.getSessionInstance(FileChooserClientListener.class);
    }

    private FileChooserClientListener() {
      super(JS);
    }
  }
}

   <extension
         point="org.eclipse.scout.rt.ui.rap.formfields">
      <formField
            active="true"
            modelClass="org.eclipse.scout.rt.client.ui.form.fields.filechooserfield.IFileChooserField"
            name="File chooser field"
            scope="local">
         <uiClass
               class="org.yourapp.ui.rap.RwtScoutFileUploadField2">
         </uiClass>
      </formField>
   </extension>