@Component

public class TestInterceptor implements HandlerInterceptor {

    //请求在进入Handler之前,该方法会被调用

    //如果返回true,则表示该请求会继续往下执行,也就是才会执行到Handler

    //如果返回false,就不会执行到Handler,并且另外两个方法也不会执行

    @Override

    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {

        //因为我们使用的是注解形式的处理器(RequestMapping)

        //所以handler对象的真正的类型是HandlerMethod

        HandlerMethod hm = (HandlerMethod) handler;

        //获取该方法的注解对象

//        hm.getMethodAnnotation();

        HttpSession session = request.getSession();

        Object user = session.getAttribute("user");

        if (user != null){

            return  true;  //放行

        }

        response.sendRedirect("/log");  //重定向

        return false;

    }

    /*

    Handler中的方法执行完毕之后,向客户端返回视图之前执行.

    方法参数中的ModelAndView对象就是给客户端渲染所用的对象.

     */

    @Override

    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {

    }

    /*

    这个请求已经给客户端完成了渲染的工作之后,该方法会执行

    这个方法中一般会做资源的清理工作.

     */

    @Override

    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {

    }

}

   <mvc:interceptors>

        <mvc:interceptor>
         <!--/**表示所有请求地址都要经过拦截器-->

            <mvc:mapping path="/**"/>
         <!--下面表示这些地址可以不走拦截器-->

            <mvc:exclude-mapping path="/log"/>

            <mvc:exclude-mapping path="/login"/>

            <mvc:exclude-mapping path="/relog"/>

            <mvc:exclude-mapping path="/home"/>
         <!--在拦截器类上加了注解@Component,所以可以直接引入拦截器id,表明上面被拦截的地址需要经过哪个拦截器-->

            <ref bean="testInterceptor"/>

        </mvc:interceptor>

    </mvc:interceptors>

/*

注解上面需要配置这个注解可以用到哪里:

例如:是给类用的,还是给属性用的,还是给方法用的

 */

@Target(ElementType.METHOD)

//这个注解是在运行时候生效的

@Retention(RetentionPolicy.RUNTIME)

public @interface CheckPermission {

    String value();

}

@Controller

public class UserController {

    @CheckPermission("one")

    @RequestMapping("/one")

    public String one(){

        return "one";

    }

    @CheckPermission("two")

    @RequestMapping("/two")

    public String two(){

        return "two";

    }

    @CheckPermission("three")

    @RequestMapping("/three")

    public String three(){

        return "three";

    }

    @CheckPermission("four")

    @RequestMapping("/four")

    public String four(){

        return "four";

    }

}

package com.lanou.demo.interceptor;

import com.lanou.demo.annotation.CheckPermission;

import org.springframework.stereotype.Component;

import org.springframework.web.method.HandlerMethod;

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;

import java.util.List;

@Component

public class TestInterceptor implements HandlerInterceptor {

    @Override

    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {

        HttpSession session = request.getSession();

        List<String> list = (List<String>) session.getAttribute("arr");

         //获取Handler信息

        HandlerMethod mv = (HandlerMethod) handler;

        //判断这个请求方法是否有这个注解

        if (mv.hasMethodAnnotation(CheckPermission.class)) {

            //通过这个注解获取到请求地址

            CheckPermission annotation = mv.getMethodAnnotation(CheckPermission.class);

            String value = annotation.value();

            if (list != null){

                  //判断这个地址是否有权限

                if (list.contains(value)) {

                    //有权限,放行

                    return true;

                }

            }

        }

        //没有权限,重定向到某个页面

        response.sendRedirect("/log");

        return false;

    }

    @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 {

    }

}