根据类获取bean

• ContextHolder:
  public class ContextHolder {
      /**
       * 可使用{@link org.springframework.context.ApplicationContextAware}接口
       */
      private static ApplicationContext context;
  
      public static ApplicationContext getContext() {
          return context;
      }
  
      public static void setContext(ApplicationContext context) {
          ContextHolder.context = context;
      }
  }

• 获取bean

private UserService userService;

if (userService == null) {
    userService = (UserService) ContextHolder.getContext().getBean(UserService.class);
}