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

package controller;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller;

public class IndexController implements Controller {
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
        ModelAndView mav = new ModelAndView("index");
        mav.addObject("message", "Hello Spring MVC————————视图定位");
        return mav;
    }
}

2.拦截器IndexInterceptor.java

package interceptor;

import java.text.SimpleDateFormat;
import java.util.Calendar;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.HandlerInterceptor;

public class IndexInterceptor implements HandlerInterceptor {
    /**
     * 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
     * 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,
     * 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()
     */
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        System.out.println("preHandle()，在访问Controller之前被调用");
        return true;
    }

    /**
     * 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
     */
    @Override
    public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2,
            org.springframework.web.servlet.ModelAndView arg3) throws Exception {
        // TODO Auto-generated method stub
        Calendar calendar = Calendar.getInstance();
        String dateString = (new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")).format(calendar.getTime());
        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");
        arg3.addObject("date", "由拦截器生成的时间：" + dateString);
    }

    /**
     * 在DispatcherServlet完全处理完请求后被调用,可用于清理资源等
     * 
     * 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()
     */
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        System.out.println("afterCompletion(), 在访问视图之后被调用");
    }

}

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

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="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-3.0.xsd 
     http://www.springframework.org/schema/context 
     http://www.springframework.org/schema/context/spring-context-3.0.xsd
     http://www.springframework.org/schema/mvc  
     http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
     "
     >
    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/page/" />
        <property name="suffix" value=".jsp" />
    </bean>
 
    <bean id="simpleUrlHandlerMapping"
        class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
        <property name="mappings">
            <props>
                <prop key="/index">indexController</prop>
            </props>
        </property>
    </bean>
    <bean id="indexController" class="controller.IndexController"></bean>
    <mvc:interceptors>   
        <mvc:interceptor>   
            <mvc:mapping path="/index"/> 
            <!-- 定义在mvc:interceptor下面的表示是对特定的请求才进行拦截的 --> 
            <bean class="interceptor.IndexInterceptor"/>     
        </mvc:interceptor> 
        <!-- 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 --> 
    </mvc:interceptors>
         
</beans>

4.web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <servlet>
        <servlet-name>myspringmvc</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>myspringmvc</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

5.index.jsp   WEB-INF/page目录下

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'index2.jsp' starting page</title>
    
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
    <h1>${message}</h1>
    <h2>${date }</h2>
  </body>
</html>

6.测试