public class MyContributionItem extends ContributionItem {

    @Override
    public void fill(final Menu menu, final int index) {

        final MenuItem myItem = new MenuItem( menu, SWT.CASCADE, index );
        myItem.setText( "Test" );

        final Menu myMenu = new Menu( myItem );
        myItem.setMenu( myMenu );

        final MenuItem mySubItem1 = new MenuItem( myMenu, SWT.PUSH );
        mySubItem1.setText( "Send" );
    }

    @Override
    public boolean isDynamic() {
        return true;
    }
}

// somewhere in the ViewPart, e.g. createPartControl(Composite)
MenuManager mgr = new MenuManager();
getSite().registerContextMenu("myMenu", mgr, null);

public class MyMenuConfiguration extends AbstractUiBindingConfiguration {

    private final Menu menu;

    public MyMenuConfiguration(final NatTable natTable, final MenuManager mgr) {
        menu = new PopupMenuBuilder( natTable, mgr ).build();
    }

    @Override
    public void configureUiBindings(final UiBindingRegistry uiBindingRegistry) {
        uiBindingRegistry.registerMouseDownBinding(
                MouseEventMatcher.bodyRightClick( SWT.NONE ), new PopupMenuAction( menu ) );
    }
}

// somewhere in plugin.xml
<extension
         point="org.eclipse.ui.menus">
      <menuContribution
            allPopups="false"
            locationURI="popup:myMenu">
         <dynamic
               class="com.test.ui.MyContributionItem"
               id="MyContributionItem ">
         </dynamic>
      </menuContribution>
  </extension>