private void createContextMenu(TableViewer viewer) {
        // Create menu manager.
     MenuManager menuMgr = new MenuManager();
        menuMgr.setRemoveAllWhenShown(true);

        // Optionally register a listener to fill the menu
        menuMgr.addMenuListener(new IMenuListener() {
                public void menuAboutToShow(IMenuManager mgr) {
                        fillContextMenu(mgr);
                }
        });
        
        // Create menu.
     Menu menu = menuMgr.createContextMenu(viewer.getControl());
        viewer.getControl().setMenu(menu);
        
        // Here you register the menu for menu extensions.
     getSite().registerContextMenu(menuMgr, viewer);

 <command
                  commandId="editMarketingOperations"
                  icon="icons/marketingOperation/marketingOperation_edit.gif"
                  id="editMarketingOperations"
                  label="%editMarketingOperations">
               <visibleWhen>
                  <with
                        variable="activeMenuSelection">
                     <iterate
                           ifEmpty="false"
                           operator="and">
                        <adapt
                              type="common.popup.IMarketingOperation">
                           <and>
                              <with
                                    variable="activeMenuSelection">
                                 <count
                                       value="1">
                                 </count>
                              </with>
                           </and>
                        </adapt>
                     </iterate>
                  </with>
               </visibleWhen>
            </command>

IHandlerService handlerService = (IHandlerService) getSite()
    .getService(IHandlerService.class);
IHandler handler = new AbstractHandler() {
  public Object execute(ExecutionEvent event)
          throws ExecutionException {
    System.out.println("Eat that Taco");
    return null;
  }
};
handlerService
    .activateHandler("z.ex.view.keybindings.eatTaco", handler);