笔记20 拦截器

场景描述：对特定的请求进行拦截

基于视图定位进行

1.视图控制器IndexController.java

 1 package controller;
 2 
 3 import javax.servlet.http.HttpServletRequest;
 4 import javax.servlet.http.HttpServletResponse;
 5 
 6 import org.springframework.web.servlet.ModelAndView;
 7 import org.springframework.web.servlet.mvc.Controller;
 8 
 9 public class IndexController implements Controller {
10     public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
11         ModelAndView mav = new ModelAndView("index");
12         mav.addObject("message", "Hello Spring MVC————————视图定位");
13         return mav;
14     }
15 }

2.拦截器IndexInterceptor.java

 1 package interceptor;
 2 
 3 import java.text.SimpleDateFormat;
 4 import java.util.Calendar;
 5 
 6 import javax.servlet.http.HttpServletRequest;
 7 import javax.servlet.http.HttpServletResponse;
 8 
 9 import org.springframework.web.servlet.HandlerInterceptor;
10 
11 public class IndexInterceptor implements HandlerInterceptor {
12     /**
13      * 在业务处理器处理请求之前被调用 如果返回false 从当前的拦截器往回执行所有拦截器的afterCompletion(),再退出拦截器链
14      * 如果返回true 执行下一个拦截器,直到所有的拦截器都执行完毕 再执行被拦截的Controller 然后进入拦截器链,
15      * 从最后一个拦截器往回执行所有的postHandle() 接着再从最后一个拦截器往回执行所有的afterCompletion()
16      */
17     public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
18         System.out.println("preHandle()，在访问Controller之前被调用");
19         return true;
20     }
21 
22     /**
23      * 在业务处理器处理请求执行完成后,生成视图之前执行的动作 可在modelAndView中加入数据，比如当前时间
24      */
25     @Override
26     public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2,
27             org.springframework.web.servlet.ModelAndView arg3) throws Exception {
28         // TODO Auto-generated method stub
29         Calendar calendar = Calendar.getInstance();
30         String dateString = (new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")).format(calendar.getTime());
31         System.out.println("postHandle(), 在访问Controller之后，访问视图之前被调用,这里可以注入一个时间到modelAndView中，用于后续视图显示");
32         arg3.addObject("date", "由拦截器生成的时间：" + dateString);
33     }
34 
35     /**
36      * 在DispatcherServlet完全处理完请求后被调用,可用于清理资源等
37      * 
38      * 当有拦截器抛出异常时,会从当前拦截器往回执行所有的拦截器的afterCompletion()
39      */
40     public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
41             throws Exception {
42         System.out.println("afterCompletion(), 在访问视图之后被调用");
43     }
44 
45 }

3.myspringmvc-servlet.xml

修改myspringmvc-servlet.xml以对/index路径进行拦截

如果要拦截其他路径：
/** 拦截所有
/category/** 拦截/category路径下的所有

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <beans xmlns="http://www.springframework.org/schema/beans" 
 3     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" 
 4     xmlns:mvc="http://www.springframework.org/schema/mvc" 
 5     xsi:schemaLocation="http://www.springframework.org/schema/beans 
 6      http://www.springframework.org/schema/beans/spring-beans-3.0.xsd 
 7      http://www.springframework.org/schema/context 
 8      http://www.springframework.org/schema/context/spring-context-3.0.xsd
 9      http://www.springframework.org/schema/mvc  
10      http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
11      "
12      >
13     <bean id="viewResolver"
14         class="org.springframework.web.servlet.view.InternalResourceViewResolver">
15         <property name="prefix" value="/WEB-INF/page/" />
16         <property name="suffix" value=".jsp" />
17     </bean>
18  
19     <bean id="simpleUrlHandlerMapping"
20         class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
21         <property name="mappings">
22             <props>
23                 <prop key="/index">indexController</prop>
24             </props>
25         </property>
26     </bean>
27     <bean id="indexController" class="controller.IndexController"></bean>
28     <mvc:interceptors>   
29         <mvc:interceptor>   
30             <mvc:mapping path="/index"/> 
31             <!-- 定义在mvc:interceptor下面的表示是对特定的请求才进行拦截的 --> 
32             <bean class="interceptor.IndexInterceptor"/>     
33         </mvc:interceptor> 
34         <!-- 当设置多个拦截器时，先按顺序调用preHandle方法，然后逆序调用每个拦截器的postHandle和afterCompletion方法 --> 
35     </mvc:interceptors>
36          
37 </beans>

4.web.xml

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
 3     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4     xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
 5 http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
 6     <servlet>
 7         <servlet-name>myspringmvc</servlet-name>
 8         <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
 9         <load-on-startup>1</load-on-startup>
10     </servlet>
11     <servlet-mapping>
12         <servlet-name>myspringmvc</servlet-name>
13         <url-pattern>/</url-pattern>
14     </servlet-mapping>
15 </web-app>

5.index.jsp WEB-INF/page目录下

 1 <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
 2 <%
 3 String path = request.getContextPath();
 4 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 5 %>
 6 
 7 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
 8 <html>
 9   <head>
10     <base href="<%=basePath%>">
11     
12     <title>My JSP 'index2.jsp' starting page</title>
13     
14     <meta http-equiv="pragma" content="no-cache">
15     <meta http-equiv="cache-control" content="no-cache">
16     <meta http-equiv="expires" content="0">    
17     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
18     <meta http-equiv="description" content="This is my page">
19     <!--
20     <link rel="stylesheet" type="text/css" href="styles.css">
21     -->
22 
23   </head>
24   
25   <body>
26     <h1>${message}</h1>
27     <h2>${date }</h2>
28   </body>
29 </html>

6.测试

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