How can I get and set session in Springmvc?

Question

@Controller
public class MainControll {

    @Autowired
    UserRepository userRepository;

    @RequestMapping("/")
    public String index() {
        return "index";
    }

    @RequestMapping(value = "/index/judement", method = RequestMethod.POST)
    @ResponseBody
    public Map<String,String> hasuser(@RequestBody UserinfoEntity a) {
        if (userRepository.findAccount(a.getNumber())==null || !a.getPassword().equals(userRepository.findAccount(a.getNumber()))) {
            Map<String,String> map = new HashMap<>();
            map.put("message","passwordError");
            return map;
        }

        Map<String,String> map_1 = new HashMap<>();
        map_1.put("message","true");
        return map_1;
    }
}

this is my code, When the user clicks the login button, it will enter the method hasuser, and then I will check the database and compare the password, if true, I want to generate the session and send back the cookie, how can i do? I try one method, but why it can not import ?