code: private FormLayout initForm() {
  
          FormLayout form = new FormLayout();
          form.setWidth("100%");
  
          IndexedContainer sites = CmsVaadinUtils.getAvailableSitesContainer(m_context.getCms(), CAPTION_PROPERTY);
          m_siteComboBox = prepareComboBox(sites, org.opencms.workplace.Messages.GUI_LABEL_SITE_0);
          m_siteComboBox.select(m_context.getCms().getRequestContext().getSiteRoot());
          form.addComponent(m_siteComboBox);
          ValueChangeListener changeListener = new ValueChangeListener() {
  
              private static final long serialVersionUID = 1L;
  
              public void valueChange(ValueChangeEvent event) {
  
                  submit();
              }
          };
          m_siteComboBox.addValueChangeListener(changeListener);
          return form;
      }
docs: Initializes the form component.<p>
  
  @return the form component