1.创建一个拦截器类，实现HandlerInterceptor接口，并实现preHandle方法：

import com.atguigu.common.constant.AuthServerConstant;
import com.atguigu.common.vo.MemberRespVo;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;/*** @author: * @Desc:* @create: 2024-11-24 19:52**/
@Component
public class LoginUserInterceptor implements HandlerInterceptor {//使用线程池管理登录用户信息，方便全局共享public static ThreadLocal<MemberRespVo>localUser=new ThreadLocal<>();@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {MemberRespVo attribute = (MemberRespVo) request.getSession().getAttribute(AuthServerConstant.LOGIN_USER);if(attribute!=null){localUser.set(attribute);return true;}else {//没登录就拦截重定向到登录页request.getSession().setAttribute("msg","请先登录");response.sendRedirect("http://auth.gulimall.com/login.html");return false;}}
}

2.创建一个OrderWebConfiguration，实现WebMvcConfigurer接口，将上面定义的拦截器，注册到webmvc当中，并指定要拦截的请求地址：

import com.atguigu.gulimall.order.interceptor.LoginUserInterceptor;
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;/*** @author: * @Desc:* @create: 2024-11-24 19:55**/
@Configuration
public class OrderWebConfiguration implements WebMvcConfigurer {@Autowiredprivate LoginUserInterceptor loginUserInterceptor;@Overridepublic void addInterceptors(InterceptorRegistry registry) {//添加拦截器和拦截地址registry.addInterceptor(loginUserInterceptor).addPathPatterns("/**");}
}

如此就实现添加一个拦截器，当系统检测到未登录，就拦截重定向到登录页面。