SuperAction类中修饰接口引用为什么要使用protected不用private
public class SupperAction extends ActionSupport implements ServletRequestAware,
ServletResponseAware, ServletContextAware {
private static final long serialVersionUID = 1L;
protected ServletContext context;
protected HttpServletResponse respose;
protected HttpServletRequest request;
protected HttpSession session;
正如上面这些代码所示，使用protected修饰HttpServletResponse ，HttpServletRequest，HttpServletRequest， HttpSession 接口引用为受保护属性，把这几个接口类的引用设为private（
private HttpServletResponse ；
private HttpServletRequest；
private HttpServletRequest；
private HttpSession；
）的时候，编译器会显示警告，为什么这里属性不能设为private？
