springboot拦截器拦截器响应返回json数据给客户端

　　拦截器：package com.xmj.interceptor;  import com.xmj.enums.BizCodeEnum; import com.xmj.model.LoginUser; import com.xmj.utils.CommonUtil; import com.xmj.utils.JWTUtil; import com.xmj.utils.JsonData; import io.jsonwebtoken.Claims; import lombok.extern.slf4j.Slf4j; import org.apache.commons.lang3.StringUtils; import org.springframework.web.servlet.HandlerInterceptor; import org.springframework.web.servlet.ModelAndView;  import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;  @Slf4j public class LoginInterceptor implements HandlerInterceptor {      /**      * 进入方法之前      * @param request      * @param response      * @param handler      * @return      * @throws Exception      */     @Override     public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {         // 头部获取         String accessToken = request.getHeader(＂token＂);         //头部获取不到就url中获取         if (accessToken == null) {             accessToken = request.getParameter(＂token＂);         }         //不为空则解密         if (StringUtils.isNotBlank(accessToken)) {             Claims claims = JWTUtil.checkJWT(accessToken);             if (claims == null) {                 //未登录,返回未登录的json数据给前端                 CommonUtil.sendJsonMessage(response, JsonData.buildResult(BizCodeEnum.ACCOUNT_UNLOGIN));                 return false;             }             Long userId = Long.valueOf(claims.get(＂id＂).toString());             String headImg = (String)claims.get(＂head_img＂);             String name = (String)claims.get(＂name＂);             String mail = (String)claims.get(＂mail＂);              LoginUser loginUser = new LoginUser();             loginUser.setHeadImg(headImg);             loginUser.setId(userId);             loginUser.setMail(mail);             loginUser.setName(name);             return true;         }         CommonUtil.sendJsonMessage(response, JsonData.buildResult(BizCodeEnum.ACCOUNT_UNLOGIN));         return false;     }      @Override     public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {      }      @Override     public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {      } }
　　工具类：
　　CommonUtil/**  * 响应json数据给前端  *  * @param response  * @param obj  */ public static void sendJsonMessage(HttpServletResponse response, Object obj) {     //Spring boot 默认/*    ObjectMapper objectMapper = new ObjectMapper();     // response的头信息     response.setContentType(＂application/json;charset=utf-8＂);     try (PrintWriter writer = response.getWriter();){         writer.print(objectMapper.writeValueAsString(obj));         response.flushBuffer();     } catch (IOException e) {         log.warn(＂响应json数据给前端异常:{}＂,e);      } }