package server.demo.configure;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import server.demo.entity.User;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
@Component
public class MyInterceptor  implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        //获取当前的session
        HttpSession session=request.getSession();
        //从session中寻求cur_user变量
        Object obj=session.getAttribute("cur_user");
        //判断是否存在用户变量
        //不存在则跳转到登录界面
        if(obj==null||!(obj instanceof User)){
          response.sendRedirect("/login");
         }else{
            //存在则再次注入session
            session.setAttribute("cur_user",(User)obj);
            System.out.println(((User) obj).getName()+((User) obj).getPassword());
        }
        return true;// 只有返回true才会继续向下执行，返回false取消当前请求
    }
    @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 {

    }
}

package server.demo.configure;
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.WebMvcConfigurerAdapter;
import java.util.ArrayList;
import java.util.List;
@Configuration
public class MyWebAppConfigurer extends WebMvcConfigurerAdapter {
    @Autowired
    MyInterceptor myInterceptor;
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        // 多个拦截器组成一个拦截器链
        // addPathPatterns 用于添加拦截规则
        // excludePathPatterns 用户排除拦截
        List<String> list=new ArrayList<>();
        list.add("/myPub");
        list.add("/myRec");
        registry.addInterceptor(myInterceptor).addPathPatterns(list);
        super.addInterceptors(registry);
    }
}