1.

response.setCharacterEncoding("UTF-8");
    response.setContentType("application/json");
        PrintWriter out = response.getWriter();
        RespBean bean = RespBean.error("未登录，请登录");
        bean.setCode(401);
        out.write(new ObjectMapper().writeValueAsString(bean));
        out.flush();
        out.close();

2.登陆拦截器中的使用

package com.mszlu.blog.handler;

import com.alibaba.fastjson.JSON;
import com.mszlu.blog.dao.pojo.SysUser;
import com.mszlu.blog.service.LoginService;
import com.mszlu.blog.vo.ErrorCode;
import com.mszlu.blog.vo.Result;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@Component
@Slf4j
public class LoginInterceptor implements HandlerInterceptor {
    @Autowired
    private LoginService loginService;

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
            //在执行controller方法(Handler)之前进行执行
        /**
         * 1. 需要判断 请求的接口路径 是否为 HandlerMethod (controller方法)
         * 2. 判断 token是否为空，如果为空 未登录
         * 3. 如果token 不为空，登录验证 loginService checkToken
         * 4. 如果认证成功 放行即可
         */
        //如果不是我们的方法进行放行
        if (!(handler instanceof HandlerMethod)){
        //handler 可能是 RequestResourceHandler springboot 程序 访问静态资源 默认去classpath下的static目录去查询
            return true;
        }
        String token = request.getHeader("Authorization");
        
        log.info("=================request start===========================");
        String requestURI = request.getRequestURI();
        log.info("request uri:{}",requestURI);
        log.info("request method:{}",request.getMethod());
        log.info("token:{}", token);
        log.info("=================request end===========================");

        if(StringUtils.isBlank(token)){
            Result result = Result.fail(ErrorCode.NO_LOGIN.getCode(), "未登录");
            //设置浏览器识别返回的是json
            response.setContentType("application/json;charset=utf-8");
            //https://www.cnblogs.com/qlqwjy/p/7455706.html response.getWriter().print()
            //SON.toJSONString则是将对象转化为Json字符串
            response.getWriter().print(JSON.toJSONString(result));
            return false;
        }
        SysUser sysUser = loginService.checkToken(token);
        if (sysUser == null){
            Result result = Result.fail(ErrorCode.NO_LOGIN.getCode(), "未登录");
            response.setContentType("application/json;charset=utf-8");
            response.getWriter().print(JSON.toJSONString(result));
            return false;
        }
        //是登录状态，放行
                //登录验证成功，放行
        //我希望在controller中 直接获取用户的信息 怎么获取?

        return true;
    }
}