springMVC初识，后台传给前台页面数据的4种方法

@RequestMapping(value="/test.do",method = RequestMethod.POST)
public String checknameIsExist(@RequestParam("sid") String sid,Model model,HttpServletRequest request,Map map) {
Student stu = studentService.getStudent(sid);
if(stu != null){
System.out.println(stu.getSname());
}
//1.放在model里 建议使用
model.addAttribute("mode", "modeValue");
//2.放在request里
request.setAttribute("request", "requestValue");
//3.放在map里
map.put("map", "mapvalue");

List<String> list = new ArrayList<String>();
list.add("1");
list.add("2");
list.add("3");

map.put("listmap", list);
return "user";
}

@RequestMapping(value="/test2.do",method = RequestMethod.POST)
public ModelAndView checknameIsExist2(@RequestParam("sid") String sid,Model model,HttpServletRequest request) {
ModelAndView mav = new ModelAndView("user");
mav.addObject("ModelAndView", "ModelAndViewValue");
mav.setViewName("user");
return mav;
}