@RequestMapping("/aa")
public ModelAndView aa(Model model,ModelAndView mav){
System.out.println("进入从controller方法");
String s = "xxxxxxxxxxxx";
// mav.setViewName("index");//返回页面
// mav.addObject("s", s);//传递值
return new ModelAndView("index","s",s);//参数1：返回页面。参数2和参数3:传递的值
}
