拦截器实例代码，加上之后必须登录才能访问其他功能接口

package com.itheima.interceptors;

import com.itheima.utils.JwtUtil;
import com.itheima.utils.ThreadLocalUtil;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;

import java.util.Map;

@Component
public class LoginInterceptor implements HandlerInterceptor {
    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        //令牌验证
        String token = request.getHeader("Authorization");
        try {
            //从redis中获取相同的token
            String tk = stringRedisTemplate.opsForValue().get(token);
            if (tk==null){
                //token已经失效了
                throw new RuntimeException();
            }
            Map<String, Object> claims = JwtUtil.parseToken(token);
            //把业务数据存放在ThreadLocal中
            ThreadLocalUtil.set(claims);
            return true;//放行
        } catch (Exception e) {
            //http响应状态码为401
            response.setStatus(401);
            //不放行
            return false;
        }
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        //清空ThreadLocal中的数据
        ThreadLocalUtil.remove();
    }
}

package com.itheima.config;

import com.itheima.interceptors.LoginInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebConfig implements WebMvcConfigurer {
    @Autowired
    private LoginInterceptor loginInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {

        //登录接口和注册接口不拦截
        registry.addInterceptor(loginInterceptor).excludePathPatterns("/user/login","/user/register");
    }
}

过滤器实例代码，和拦截器实现的功能是一样的，加上之后必须登录才能访问其他功能接口

package com.itheima.reggie.filter;

import com.alibaba.fastjson.JSON;
import com.itheima.reggie.common.R;
import lombok.extern.slf4j.Slf4j;
import org.springframework.util.AntPathMatcher;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * 检查用户是否已经完成登录
 */
//参数1：过滤器名称    参数2：拦截路径
@WebFilter(filterName = "loginCheckFilter", urlPatterns = "/*")
@Slf4j
public class LoginCheckFilter implements Filter {
    //路径匹配器，支持通配符
    public static final AntPathMatcher PATH_MATCHER = new AntPathMatcher();

    /**
     * 过滤的方法
     */
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;

        //1、获取本次请求的URI
        String requestURI = request.getRequestURI(); // /backend/index.html

        log.info("拦截到请求：{}", requestURI);

        //下面urls里面的地址不拦截 直接放行
        String[] urls = new String[]{
                "/employee/login",     //登录
                "/employee/logout",   //退出
                "/backend/**",           //静态资源
                "/front/**"
        };

        //2、判断本次请求是否需要处理(检查登录状态)
        boolean check = check(urls, requestURI);

        //3、如果不需要处理，则直接放行
        if (check) {//check为true
            log.info("本次请求{}不需要处理", requestURI);
            filterChain.doFilter(request,response);
            return;
        }

        //4、判断登录状态，如果已登录，则直接放行
        if (request.getSession().getAttribute("employee") != null) {
            log.info("用户已经登录，用户id为{}", request.getSession().getAttribute("employee"));
            filterChain.doFilter(request, response);//放行
            return;
        }
        log.info("用户未登录");
        //5、如果未登录则返回未登录结果,通过输出流方式向客户端响应数据
        response.getWriter().write(JSON.toJSONString(R.error("NOTLOGIN")));
        return;

    }

    /**
     * 路径匹配，检查本次请求是否需要放行
     * @param urls
     * @param requestURI
     * @return
     */
    public boolean check(String[] urls, String requestURI) {
        for (String url : urls) {
            boolean match = PATH_MATCHER.match(url, requestURI);
            if (match) {
                return true;
            }
        }
        return false;
    }
}

 切记要在启动类上面加上ServeltComponentScan注解，这样Springboot才能扫描到servlet相关注解。