15. Interceptor - HandlerInterceptor

15.1 基本介绍

1. 在 Spring Boot 项目中, 拦截器是开发中常用手段,要来做登陆验证、性能检查、日志记录等

2. 基本步骤：

   ① 编写一个拦截器实现 HandlerInterceptor 接口
   ② 拦截器注册到配置类中(实现 WebMvcConfigurer 的 addInterceptors)
   ③ 指定拦截规则
   ④ 回顾 SpringMVC ==> 文章链接

15.2 拦截器应用实例

15.2.1 需求说明

• 使用拦截器防止用户非法登录
• 如图 - 使用拦截器就不需要在每个方法验证了
• 浏览器输入 http://localhost:8080/manage.html
• 如果用户没有登录,则返回登录界面

15.2.2 代码实现

1. 创建 D:\xjs_springboot\springboot-usersys\src\main\java\com\xjs\springboot\interceptor\LoginInterceptor.java

package com.xjs.springboot.interceptor;

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;
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;

/** * @Author: 谢家升 * @Version: 1.0 */
@Slf4j
@Component
public class LoginInterceptor implements HandlerInterceptor {
    

    /** * Called before the target method is executed * * @param request * @param response * @param handler * @return * @throws Exception */
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    
        //1. 获取访问的 URI
        String uri = request.getRequestURI();
        log.info("preHandle拦截到的请求的URI={}", uri);

        //2. 进行登录校验
        HttpSession session = request.getSession();
        Object loginAdmin = session.getAttribute("loginAdmin");
        if (null != loginAdmin) {
    //Indicates that the user has successfully logged in
            return true;

        } else {
    //It means that the user has not logged in successfully

            //拦截,重新返回到登录页面
            request.setAttribute("msg", "你没有登录/请登录~~");
            request.getRequestDispatcher("/").forward(request, response);

            return false;
        }
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    
        log.info("postHandle() 执行了...");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    
        log.info("afterCompletion() 执行了...");
    }
}

2. 创建 D:\xjs_springboot\springboot-usersys\src\main\java\com\xjs\springboot\config\WebConfig.java

package com.xjs.springboot.config;

import com.xjs.springboot.interceptor.LoginInterceptor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/** * @Author: 谢家升 * @Version: 1.0 */
@Configuration
public class WebConfig implements WebMvcConfigurer {
    

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
    

        //注册自定义拦截器LoginInterceptor
        registry.addInterceptor(new LoginInterceptor())
                .addPathPatterns("/**") //这里拦截所有的请求
                .excludePathPatterns("/","/login","/images/**"); //指定要放行的,根据业务需要来添加放行的请求路径

    }
}

3. 修改 D:\xjs_springboot\springboot-usersys\src\main\java\com\xjs\springboot\controller\AdminController.java ,去掉 session Verify that the user is logged in with the code,并完成测试,Pay attention to the page and background logs

package com.xjs.springboot.controller;

import com.xjs.springboot.bean.Admin;
import com.xjs.springboot.bean.User;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;

import javax.servlet.http.HttpSession;
import java.util.ArrayList;

/** * @Author: 谢家升 * @Version: 1.0 */
@Controller
@Slf4j
public class AdminController {
    

    //Respond to a user's login request
    @PostMapping("/login")
    public String login(Admin admin, HttpSession session, Model model) {
    

        //验证用户是否合法
        if (StringUtils.hasText(admin.getName()) && "888".equals(admin.getPassword())) {
    

            //Save the logged in user tosession
            session.setAttribute("loginAdmin", admin);

            /**合法 重定向到 manage.html * 1. Not using request forwarding is to prevent refreshing the page from causing the form to be repeatedly submitted * 2. Why is it written here manage.html Because this can be more explicit which page to go to * 3. 这里的 manage.html said to find The method's mapping path is  manage.html */
            return "redirect:/manage.html";

        } else {
    
            //不合法 重新登录！
            model.addAttribute("msg", "账号/用户名错误");
            return "adminLogin";
        }
    }

    //处理用户请求 manage.html
    @GetMapping("/manage.html")
    public String mainPage(Model model, HttpSession session) {
    

        This is temporarily used in the methodsession验证,Later, we will use interceptor verification uniformly
        //Object loginAdmin = session.getAttribute("loginAdmin");
        //
        //if (loginAdmin != null) { //说明成功登录过
        // //这里集合-模拟用户数据,放入到request域中,并显示
        // ArrayList<User> users = new ArrayList<>();
        // users.add(new User(1, "关羽", "123456", 20, "[email protected]"));
        // users.add(new User(2, "张飞", "123456", 26, "[email protected]"));
        // users.add(new User(3, "赵云", "123456", 28, "[email protected]"));
        // users.add(new User(4, "马超", "123456", 22, "[email protected]"));
        // users.add(new User(5, "黄忠", "123456", 50, "[email protected]"));
        //
        // //将数据放入到request域中
        // model.addAttribute("users", users);
        //
        // return "manage"; //This is where our view resolves to /template/manage.html
        //} else {
    
        // //Return to the login page here,并给出提示
        // model.addAttribute("msg", "你没有登录/请登录");
        //
        // return "adminLogin"; //请求转发到 adminLogin.html
        //}

        log.info("进入mainPage()");

        //这里集合-模拟用户数据,放入到request域中,并显示
        ArrayList<User> users = new ArrayList<>();
        users.add(new User(1, "关羽", "123456", 20, "[email protected]"));
        users.add(new User(2, "张飞", "123456", 26, "[email protected]"));
        users.add(new User(3, "赵云", "123456", 28, "[email protected]"));
        users.add(new User(4, "马超", "123456", 22, "[email protected]"));
        users.add(new User(5, "黄忠", "123456", 50, "[email protected]"));

        //将数据放入到request域中
        model.addAttribute("users", users);

        return "manage"; //This is where our view resolves to /template/manage.html
    }

}

15.2.3 注意事项和细节

1. URI 和 URL 的区别

• URI = Universal Resource Identifier
• URL = Universal Resource Locator
• Identifier：标识符
• Locator：定位器
• 从字面上来看,URI 可以唯一标识一个资源,URL 可以提供找到该资源的路径
• 举例说明：

String requestURI = request.getRequestURI();
String requestURL = request.getRequestURL().toString();

2. 注册拦截器,依然可以使用如下方式

package com.xjs.springboot.config;

import com.xjs.springboot.interceptor.LoginInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/** * @Author: 谢家升 * @Version: 1.0 */
@Configuration
public class WebConfig /*implements WebMvcConfigurer*/ {
    

    //@Override
    //public void addInterceptors(InterceptorRegistry registry) {
    
    //
    // //注册自定义拦截器LoginInterceptor
    // registry.addInterceptor(new LoginInterceptor())
    // .addPathPatterns("/**") //这里拦截所有的请求
    // .excludePathPatterns("/","/login","/images/**"); //指定要放行的,根据业务需要来添加放行的请求路径
    //
    //}

    @Bean
    public WebMvcConfigurer webMvcConfigurer() {
    

        return new WebMvcConfigurer() {
    
            @Override
            public void addInterceptors(InterceptorRegistry registry) {
    
                //注册拦截器
                registry.addInterceptor(new LoginInterceptor())
                        .addPathPatterns("/**")
                        .excludePathPatterns("/", "/login", "/images/**");
            }
        };
    }

}