SSM-SpringMVC-33：SpringMVC中攔截器Interceptor講解

 ------------吾亦無他,唯手熟爾，謙卑若愚，好學若饑-------------

攔截器Interceptor:

對處理方法進行雙向的攔截，可以對其做日志記錄等

我選擇的是實作HandlerInterceptor接口

我把執行流程放上來，單個攔截器的和多個攔截器的，然後寫個Demo案例，就可以正式結束Springmvc，過幾天寫完SSM整合，SSM就結束了，将來有機會多放幾個項目在部落格園上

圖1，單個攔截器執行流程

圖2，多個攔截器的執行流程

我會給大家定義倆個攔截器，大家跑一下，看看執行順序，另外大家可以舉一反三的擴充，定義多個攔截器或者在攔截器的方法中填實際的處理代碼

案例Demo開始

　　1.自定義第一個攔截器FirstInterceptor

package cn.dawn.day25interceptor;/**
 * Created by dawn on 2018-04-02.
 */

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

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

public class FirstInterceptor implements HandlerInterceptor{
    //在Handler執行前執行
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        System.out.println("preHandle=============");
        return true;
    }

    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle=============");
    }

    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println("afterCompletion=============");
    }
}      

　　preHandle這個方法，它的傳回值決定了下面倆個方法是否執行，如果false，則不會執行下面的那倆方法

　　2.自定義第二個攔截器SecondInterceptor

package cn.dawn.day25interceptor;/**
 * Created by dawn on 2018-04-02.
 */

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

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


public class SecondInterceptor implements HandlerInterceptor {
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        System.out.println("Second preHandle=============");
        return true;
    }

    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("Second postHandle=============");
    }

    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println("Second afterCompletion=============");
    }
}      

　　3.自定義處理器和處理方法

package cn.dawn.day25interceptor;/**
 * Created by dawn on 2018-04-02.
 */

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class FirstController {
    @RequestMapping("/first")
    public String doFirst(){
        System.out.println("Handler method");
        return "success";
    }
}      

　　4.自己的xml配置檔案中配置一道，将攔截器配置上去

<?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:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd
         http://www.springframework.org/schema/context
         http://www.springframework.org/schema/context/spring-context.xsd">

    <!--包掃描器-->
    <context:component-scan base-package="cn.dawn.day25interceptor"></context:component-scan>
    <!--視圖解析器-->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/day25/"></property>
        <property name="suffix" value=".jsp"></property>
    </bean>

    <!--攔截器配置-->
    <mvc:interceptors>  <!--配置多個攔截器，多個攔截器鍊-->

        <mvc:interceptor>
            <mvc:mapping path="/**"/>
            <bean class="cn.dawn.day25interceptor.FirstInterceptor"></bean>
        </mvc:interceptor>
        <mvc:interceptor>
            <mvc:mapping path="/**"/>
            <bean class="cn.dawn.day25interceptor.SecondInterceptor"></bean>
        </mvc:interceptor>

    </mvc:interceptors>

    <!--綁定注解驅動-->
    <mvc:annotation-driven></mvc:annotation-driven>

</beans>      

　　此處的攔截器位置的前後，決定了他們執行的先後

　　此處的/**表示任意多級目錄的任意方法，全部的意思

　　5.修改web.xml的中央排程器的上下文配置位置為上面那個xml

　　6.jsp頁面，我不是return了個success麼，是以建一個success.jsp

<%--
  Created by IntelliJ IDEA.
  User: Dawn
  Date: 2018/4/2
  Time: 14:19
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<html>
<head>
    <title>成功</title>
</head>
<body>
    <h1>SUCCESS</h1>
</body>
</html>      

　　7.啟動tomcat，通路處理器的那個處理方法/first