拦截器实现

1. SSM拦截器实现：

拦截器（Interceptor)是一种动态拦截方法调用的机制，在SpringMVC中动态拦截控制器方法的执行

作用:

• 在指定的方法调用前后执行预先设定的代码
• 阻止原始方法的执行
• 总结：拦截器就是用来做增强

拦截器与过滤器

	拦截器（interceptor）	过滤器（filter）
归属	SpringMVC技术	servlet技术
拦截内容	针对SpringMVC的访问进行增强	所有访问

步骤1：定义拦截器类(实现HandlerInterceptor接口)

HandlerInterceptor的方法：

1、preHandle 在执行controller之前 返回值为boolean

• false: 拦截，不能继续执行
• true：放行

2、 postHandle

3、 afterHandle

public class MyInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        //检查session是否为空  
        HttpSession session = request.getSession();
        Student student = (Student) session.getAttribute("student");
        Object currentUser = session.getAttribute("currentUser");
        Teacher teacher = (Teacher) session.getAttribute("teacher");
        if (student == null && currentUser == null && teacher == null) {
            //重定向到登录页面
            response.sendRedirect("/");
            return false;

        }else {
            //放行
            return true;
        }
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        HandlerInterceptor.super.afterCompletion(request, response, handler, ex);
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        HandlerInterceptor.super.postHandle(request, response, handler, modelAndView);
    }
}

步骤2：配置拦截资源

 <!--配置拦截器-->
    <mvc:interceptors>
        <mvc:interceptor>
            <!--要拦截的路径  /** ：所有请求-->
            <mvc:mapping path="/**"/>
            <!--要放行的资源-->
            <mvc:exclude-mapping path="/user/login"/>
            <mvc:exclude-mapping path="/images/**"/>
            <mvc:exclude-mapping path="/js/**"/>
            <mvc:exclude-mapping path="/css/**"/>
            <bean class="com.gm.interceptor.MyInterceptor"/>
        </mvc:interceptor>
    </mvc:interceptors>

步骤3：实现使用

以登录拦截为例实现：

 @RequestMapping(value = "/user/login")
    public String Login(String userNo, String password, Model model, HttpServletRequest request) {
        User currentUser = userService.login(userNo, password);
        if ("".equals(currentUser) || currentUser == null) {
            model.addAttribute("message", "用户名或密码错误");

            return "../../index";
        }
        if (currentUser.getPermission() == 2) {
            HttpSession session = request.getSession();
            session.setMaxInactiveInterval(3600);
            // 在t_user表的信息
            session.setAttribute("currentUser", currentUser);

            // 完整的teacher信息
            Teacher teacher = teacherService.showInfoByNo(userNo);
            int depId = teacher.getDepartmentId();
            String depName = departmentService.getNameById(depId);
            teacher.setDepartmentName(depName);

            session.setAttribute("teacher", teacher);
            //model.addAttribute("userNo", userNo);
            return "teacher/main";
        } else if (currentUser.getPermission() == 1) {
            //是学生用户
            //将查询到的学生用户存放到session ,且设置时间为24H
            Student student = studentService.findByStudentNO(currentUser.getUserNo());
            HttpSession session = request.getSession();
            session.setAttribute("currentUser",currentUser);
            session.setAttribute("student", student);
            System.out.println(student.toString());
            return "redirect:/student/toPage";

        } else {
            model.addAttribute("message", "当前用户不匹配");
            return "../../index";
        }

    }

2. springboot实现拦截功能：

步骤1：定义拦截器类实现HandlerInterceptor接口

public class LoginInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        Integer uid = (Integer) request.getSession().getAttribute("uid");
        if (uid==null){
            //用户还没有登陆过，需要登陆后继续方法
            //转发到login.html
            response.sendRedirect("/web/login.html");
            //不放行
            return false;
        }
        //放行
        return true;

    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        HandlerInterceptor.super.postHandle(request, response, handler, modelAndView);
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        HandlerInterceptor.super.afterCompletion(request, response, handler, ex);
    }
}

步骤2: 配置拦截信息

@Configuration //被springmvc识别为springmvc的配置类
public class LoginInterceptorConfig implements WebMvcConfigurer {

    @Override
    //配置拦截器
    public void addInterceptors(InterceptorRegistry registry) {
        // 1、创建自定义拦截器对象
        LoginInterceptor interceptor = new LoginInterceptor();
        //2、配置白名单存入list集合
        List<String> list = new ArrayList<>();
        list.add("/bootstrap3/**");
        list.add("/css/**");
        list.add("/js/**");
        list.add("/images/**");
        list.add("/web/login.html/**");
        list.add("/web/register/**");
        list.add("/web/index/**");
        list.add("/web/products/**");
        list.add("/users/register");
        list.add("/users/login");
//registry.addInterceptor(interceptor);完成拦截器的注册,后面的addPathPatterns表示拦截哪些url
        //这里的参数/**表示所有请求,再后面的excludePathPatterns表
        // 示有哪些是白名单,且参数是列表
        registry.addInterceptor(interceptor).addPathPatterns("/**").excludePathPatterns(list);

    }
}

以上就可实现登录功能的拦截。