第八讲 拦截器

一、拦截器概念

二、实现拦截器

1. 实现HandlerInterceptor接口

publicclass MyInterceptor implementsHandlerInterceptor {

     

     //在请求处理的方法之前执行

     //如果返回true那么执行下一个拦截器，如果返回false那么不执行下一个拦截器

     publicbooleanpreHandle(HttpServletRequest request, HttpServletResponse response,

                Objecthandler)

                throwsException {

           

           System.out.println("--------处理前--------");

           returntrue;

     }

     

     //在请求处理的方法执行之后执行

     publicvoid postHandle(HttpServletRequest request, HttpServletResponse response,

                Objecthandler,

                ModelAndViewmodelAndView)throws Exception {

           System.out.println("--------处理后--------");

     }

     

     //在DispatcherServlet处理后执行---清理工作

     publicvoid afterCompletion(HttpServletRequest request, HttpServletResponse response,

                Objecthandler, Exceptionex)

                throwsException {

           //TODO Auto-generated method stub

           

     }

}

2. 配置拦截器

<beansxmlns="http://www.springframework.org/schema/beans"

     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

     xmlns:context="http://www.springframework.org/schema/context"

     xmlns:mvc="http://www.springframework.org/schema/mvc"

     xsi:schemaLocation="

     http://www.springframework.org/schema/beans

     http://www.springframework.org/schema/beans/spring-beans.xsd

     http://www.springframework.org/schema/context

     http://www.springframework.org/schema/context/spring-context.xsd

     http://www.springframework.org/schema/mvc

     http://www.springframework.org/schema/mvc/spring-mvc.xsd">

     <!-- 拦截器配置 -->

     <mvc:interceptors>

           <mvc:interceptor>

                <!-- /** 包括路径及其子路径 - 拦截所有的Controller

                     如果是/admin/* 拦截的是 /admin/add，/admin/list etc. /admin/user/add不被拦截

                     如果是/admin/** 拦截的是 /admin/add，/admin/list，/admin/user/add

                -->

                <mvc:mappingpath="/**"/>

                <!-- 对应的拦截器 -->

                <beanclass="com.liujie.interceptor.MyInterceptor"></bean>

           </mvc:interceptor>

     </mvc:interceptors>

---

3. 如果被拦截-能否到达指定的页面？

使用HttpServletResponse或者HttpServletRequest可以实现转发或重定向

     //在请求处理的方法之前执行

     //如果返回true那么执行下一个拦截器，如果返回false那么不执行下一个拦截器

     publicbooleanpreHandle(HttpServletRequest request, HttpServletResponse response,

                Objecthandler)

                throwsException {

           

           System.out.println("--------处理前--------");

           System.out.println(request.getContextPath());

           response.sendRedirect(request.getContextPath() + "/index.jsp");

           returnfalse;

     }

这里被拦截的情况就是：return false;

return false;
return true;

4. 拦截器应用-登录拦截器

Controller	@Controller publicclass UserController {            @RequestMapping(value ="/login")      publicString login(User user, HttpSession session) {                        if("siggy".equals(user.getName()) && "111".equals(user.getPwd())) {                 session.setAttribute("user",user);                 return"redirect:/index.jsp";            }                        return"redirect:/login.jsp";      }            @RequestMapping("/add")      publicString add() {            System.out.println("add");            return"redirect:/index.jsp";      } }
拦截器	publicclass LoginInterceptor implementsHandlerInterceptor {      //允许哪些url不被拦截，哪些需要被拦截      privateList<String> allowedPass;      publicbooleanpreHandle(HttpServletRequest request, HttpServletResponse response,                 Objecthandler)                 throwsException {                        Stringurl = request.getRequestURL().toString();            //先判断session中是否有            Objectuser = request.getSession().getAttribute("user");            if(user!= null) {                 returntrue;            }            for(Stringtemp : allowedPass) {                 if(url.endsWith(temp)) {                      returntrue;                 }            }            response.sendRedirect(request.getContextPath() + "/login.jsp");            returnfalse;      }            publicvoid postHandle(HttpServletRequest request, HttpServletResponse response,                 Objecthandler,                 ModelAndViewmodelAndView)throws Exception {      }            publicvoid afterCompletion(HttpServletRequest request, HttpServletResponse response,                 Objecthandler, Exceptionex)                 throwsException {                  }      publicvoid setAllowedPass(List<String> allowedPass) {            this.allowedPass= allowedPass;      } }
配置	<!-- 拦截器配置 -->      <mvc:interceptors>            <mvc:interceptor>                 <!-- /** 包括路径及其子路径 - 拦截所有的Controller                      如果是/admin/* 拦截的是 /admin/add，/admin/list etc. /admin/user/add不被拦截                      如果是/admin/** 拦截的是 /admin/add，/admin/list，/admin/user/add                 -->                 <!--                 <mvc:mapping path="/product/*"/>                 <mvc:mapping path="/cart/*"/>                 <mvc:mapping path="/order/*"/>                                  <mvc:exclude-mapping path="/user/*"/>                 -->                 <mvc:mappingpath="/**"/>                 <!-- 对应的拦截器 -->                 <beanclass="com.liujie.interceptor.LoginInterceptor">                      <propertyname="allowedPass">                            <list>                                 <value>login.do</value>                                 <!-- <value>add.do</value> -->                            </list>                      </property>                 </bean>            </mvc:interceptor>      </mvc:interceptors>
JSP	<body>      <formaction="login.do"method="post">            用户名：<inputname="name"type="text"/><br>            密码：<inputname="pwd"type="password"/><br>            <inputtype="submit"value="submit"/>      </form> </body>
实体类	publicclass User {            privateint id;      privateString name;      privateString pwd;          //下面省略get、set方法