单击按钮如何执行处理程序

Question

我必须在单击按钮时调用处理程序，在异常情况下它总是会发生

public void widgetSelected(SelectionEvent e)
                {   
                     IHandlerService handlerService =
                             (IHandlerService) PlatformUI.getWorkbench().getService(
                                 IHandlerService.class);
                         try
                         {
                             handlerService.executeCommand(
                                 DiagnosticsHandler,
                                 null);
                         }
                         catch (Exception e1)
                         {
                             System.out.println(e1.getMessage()+"==getMessage");

                             return;
                         }