BeanFactory not initialized or already closed - call ‘refresh‘ before accessing beans via the Applic

BeanFactory not initialized or already closed - call ‘refresh’ before accessing beans via the ApplicationContext

我的错误是括号里没写上applicationContext.xml

  public class AccountController {
        public static void main(String[] args) {
            ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");//括号里要写上applicationContext.xml不然运行会报 BeanFactory not initialized or already closed - call 'refresh' before accessing beans via the ApplicationContext的类型错误
            AccountService accountService = app.getBean(AccountService.class);
            accountService.transfer("frank","mark",200);
        } 
        }