释放双眼，带上耳机，听听看~！
** ————吾亦无他,唯手熟尔，谦卑若愚，好学若饥————-**
拦截器Interceptor:
对处理方法进行双向的拦截，可以对其做日志记录等
我选择的是实现HandlerInterceptor接口
我把执行流程放上来，单个拦截器的和多个拦截器的，然后写个Demo案例，就可以正式结束Springmvc，过几天写完SSM整合，SSM就结束了，将来有机会多放几个项目在博客园上
图1，单个拦截器执行流程
图2，多个拦截器的执行流程
我会给大家定义俩个拦截器，大家跑一下，看看执行顺序，另外大家可以举一反三的扩充，定义多个拦截器或者在拦截器的方法中填实际的处理代码
案例Demo开始
1.自定义第一个拦截器FirstInterceptor
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2 * Created by dawn on 2018-04-02.
3 */
4
5import org.springframework.web.servlet.HandlerInterceptor;
6import org.springframework.web.servlet.ModelAndView;
7
8import javax.servlet.http.HttpServletRequest;
9import javax.servlet.http.HttpServletResponse;
10
11public class FirstInterceptor implements HandlerInterceptor{
12 //在Handler执行前执行
13 public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
14 System.out.println("preHandle=============");
15 return true;
16 }
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18 public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
19 System.out.println("postHandle=============");
20 }
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22 public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
23 System.out.println("afterCompletion=============");
24 }
25}
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preHandle这个方法，它的返回值决定了下面俩个方法是否执行，如果false，则不会执行下面的那俩方法
2.自定义第二个拦截器SecondInterceptor
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2 * Created by dawn on 2018-04-02.
3 */
4
5import org.springframework.web.servlet.HandlerInterceptor;
6import org.springframework.web.servlet.ModelAndView;
7
8import javax.servlet.http.HttpServletRequest;
9import javax.servlet.http.HttpServletResponse;
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11
12public class SecondInterceptor implements HandlerInterceptor {
13 public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
14 System.out.println("Second preHandle=============");
15 return true;
16 }
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18 public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
19 System.out.println("Second postHandle=============");
20 }
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22 public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
23 System.out.println("Second afterCompletion=============");
24 }
25}
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3.自定义处理器和处理方法
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2 * Created by dawn on 2018-04-02.
3 */
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5import org.springframework.stereotype.Controller;
6import org.springframework.web.bind.annotation.RequestMapping;
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8@Controller
9public class FirstController {
10 @RequestMapping("/first")
11 public String doFirst(){
12 System.out.println("Handler method");
13 return "success";
14 }
15}
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4.自己的xml配置文件中配置一道，将拦截器配置上去
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2<beans xmlns="http://www.springframework.org/schema/beans"
3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4 xmlns:mvc="http://www.springframework.org/schema/mvc"
5 xmlns:context="http://www.springframework.org/schema/context"
6 xsi:schemaLocation="http://www.springframework.org/schema/beans
7 http://www.springframework.org/schema/beans/spring-beans.xsd
8 http://www.springframework.org/schema/mvc
9 http://www.springframework.org/schema/mvc/spring-mvc.xsd
10 http://www.springframework.org/schema/context
11 http://www.springframework.org/schema/context/spring-context.xsd">
12
13 <!--包扫描器-->
14 <context:component-scan base-package="cn.dawn.day25interceptor"></context:component-scan>
15 <!--视图解析器-->
16 <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
17 <property name="prefix" value="/day25/"></property>
18 <property name="suffix" value=".jsp"></property>
19 </bean>
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21 <!--拦截器配置-->
22 <mvc:interceptors> <!--配置多个拦截器，多个拦截器链-->
23
24 <mvc:interceptor>
25 <mvc:mapping path="/**"/>
26 <bean class="cn.dawn.day25interceptor.FirstInterceptor"></bean>
27 </mvc:interceptor>
28 <mvc:interceptor>
29 <mvc:mapping path="/**"/>
30 <bean class="cn.dawn.day25interceptor.SecondInterceptor"></bean>
31 </mvc:interceptor>
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33 </mvc:interceptors>
34
35 <!--绑定注解驱动-->
36 <mvc:annotation-driven></mvc:annotation-driven>
37
38</beans>
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**此处的拦截器位置的前后，决定了他们执行的先后
**
此处的/**表示任意多级目录的任意方法，全部的意思
5.修改web.xml的中央调度器的上下文配置位置为上面那个xml
6.jsp页面，我不是return了个success么，所以建一个success.jsp
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2 Created by IntelliJ IDEA.
3 User: Dawn
4 Date: 2018/4/2
5 Time: 14:19
6 To change this template use File | Settings | File Templates.
7--%>
8<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
9<html>
10<head>
11 <title>成功</title>
12</head>
13<body>
14 <h1>SUCCESS</h1>
15</body>
16</html>
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7.启动tomcat，访问处理器的那个处理方法/first
