1、创建拦截器

package com.example.demo.interceptor;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.web.servlet.HandlerInterceptor;import org.springframework.web.servlet.ModelAndView;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;/** * 〈一句话功能简述〉
 * 〈拦截器〉 * * @author 丶Zh1Guo * @create 2018/11/22 * @since 1.0.0 */public class LoginInterceptor implements HandlerInterceptor {    private Logger logger = LoggerFactory.getLogger(LoginInterceptor.class);    // 在请求处理之前，只有返回true才会执行请求    @Override    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {        logger.info("[拦截器]启动登录状态拦截");        // 得到session        HttpSession session = request.getSession();        logger.info("[拦截器]sessionID:" + session.getId());        // 得到用户信息        Object userInfo = session.getAttribute("userInfo");        //判断用户是否登录        if (userInfo != null) {            logger.info("[拦截器]用户已经登录,用户名，密码：" + session.getAttribute("userInfo"));            return true;        } else {            //不存在跳转至登录页            response.sendRedirect(request.getContextPath() + "/");    // 跳转到首页登录            logger.info("[拦截器]用户没有登录,已跳转到:" + request.getContextPath() + "/");            return false;        }    }    // 视图渲染后执行    @Override    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {    }    // 请求处理后，视图渲染前    @Override    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {    }}

2、.继承WebMvcConfigureAdapter类，覆盖其addInterceptors接口,注册自定义的拦截器

@Configuration 注解一定要有

package com.example.demo.interceptor;import org.springframework.context.annotation.Configuration;import org.springframework.web.servlet.config.annotation.InterceptorRegistry;import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;/** * 〈一句话功能简述〉
 * 〈自定义配置类〉 * * @author 丶Zh1Guo * @create 2018/11/22 * @since 1.0.0 */@Configurationpublic class LoginConfig implements WebMvcConfigurer {    /**     * 该方法用于注册拦截器     * 可注册多个拦截器，多个拦截器组成一个拦截器链     */    @Override    public void addInterceptors(InterceptorRegistry registry) {        // addPathPatterns 添加路径        // excludePathPatterns 排除路径        registry.addInterceptor(new LoginInterceptor())                .addPathPatterns("/sys/*"); // 拦截sys路径下的url//              .excludePathPatterns("");    }}

3、LoginController

/** * Copyright (C), 2017-2018, XXX有限公司 * FileName: LoginController * Author:   丶Zh1Guo * Date:     2018/11/22 11:10 * Description: 登录 * History: * 
               
                
                 
        
          * 作者姓名           修改时间           版本号              描述 */package com.example.demo.controller;import com.example.demo.dao.UserDAO;import com.example.demo.pojo.User;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestMethod;import org.springframework.web.bind.annotation.ResponseBody;import javax.servlet.http.HttpServletRequest;/** * 〈一句话功能简述〉
         
 * 〈登录〉 * * @author 丶Zh1Guo * @create 2018/11/22 * @since 1.0.0 */@Controllerpublic class LoginController {    // 日志    private Logger logger = LoggerFactory.getLogger(LoginController.class);    @Autowired    private UserDAO userDAO;    // 启动服务自动跳转登录//    @RequestMapping(value = {"/", "/login"})    @RequestMapping(value = "/")    public String login() {        return "login";    }    // 登录    @RequestMapping(value = "/loginCheck", method = RequestMethod.POST)    @ResponseBody    public String loginCheck(HttpServletRequest request) {        // 获取登录信息        String userName = request.getParameter("userName");        String password = request.getParameter("password");        // 封装成对象        User user = new User();        user.setUserName(userName);        user.setPassword(password);        // 校验用户信息        User info = userDAO.checkUser(user);        if (info != null) {            request.getSession().setAttribute("userInfo", userName + "-" + password);            logger.info("登录成功，用户名：" + userName + "密码：" + password);            return "success";        } else {            logger.info("登录失败，用户名：" + userName + "密码：" + password);            return "fail";        }    }}
        
       
     

4、未登录会自动跳转到登录页面