Springboot怎么使用校验注解把错误提示返回给前端

package cn.jiyun.controller;

import cn.jiyun.common.DataGridView;
import cn.jiyun.pojo.Emp;
import cn.jiyun.service.EmpService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BindingResult;
import org.springframework.validation.FieldError;
import org.springframework.validation.ObjectError;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.validation.Valid;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.List;

@Controller
public class EmpController {

@Autowired
public EmpService empService;
/*@Autowired
public RestTemplate restTemplate;*/

/* @Aut