访问controller返回???

原始controller：

@Controller
public class UserController {

    @RequestMapping(value = "/subLogin",method = RequestMethod.POST)
    @ResponseBody
    public String subLogin(user user){
        Subject subject = SecurityUtils.getSubject();
        UsernamePasswordToken token = new UsernamePasswordToken
                (user.getUsername(),user.getPassword());
        try {
            subject.login(token);
        }catch (AuthenticationException e){
            return  e.getMessage();
        }
        return "登录成功";
    }
}

访问时：

修改后：

@Controller
public class UserController {

    @RequestMapping(value = "/subLogin",method = RequestMethod.POST,
    produces = "application/json;charset=utf-8")
    @ResponseBody
    public String subLogin(user user){
        Subject subject = SecurityUtils.getSubject();
        UsernamePasswordToken token = new UsernamePasswordToken
                (user.getUsername(),user.getPassword());
        try {
            subject.login(token);
        }catch (AuthenticationException e){
            return  e.getMessage();
        }
        return "登录成功";
    }
}

运行结果正常显示：