一丁稀、什么是攔截器

攔截器是SpringMVC提供的一個HandlerInterceptor接口授账，類似于Servlet 的過濾器Filter，用于對每一個請求前后進行相關(guān)的業(yè)務(wù)處理

二乍恐、攔截執(zhí)行流程

攔截器流程圖

1）客戶端發(fā)送請求
2）前端控制器（DispatcherServlet）走到第一攔截器
3）第一個攔截器返回true后百匆，執(zhí)行第二攔截器
4）第二攔截返回true后仑荐，執(zhí)行控制層（controller）
5）控制層將業(yè)務(wù)層處理好，先走到第二攔截器洒扎，再到第一個攔截
6）最終回到前端控制器DispatcherServlet
7）前端控制器再將頁面返回值客戶端

三袍冷、HandlerInterceptor為我們提供了三個方法

1）preHandle() : 在調(diào)用控制器之前執(zhí)行
2）postHandle():在調(diào)用控制器之后頁面加載之前執(zhí)行
3）afterCompletion(): 在頁面加載之后執(zhí)行

四乃戈、代碼

補充：項目目錄結(jié)構(gòu)

目錄結(jié)構(gòu)

1）pom.xml

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
    <!-- 定義Spring版本號 -->
    <spring.version>5.0.2.RELEASE</spring.version>
  </properties>

  <dependencies>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>${spring.version}</version>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-web</artifactId>
      <version>${spring.version}</version>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>${spring.version}</version>
    </dependency>

    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>servlet-api</artifactId>
      <version>2.5</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>javax.servlet.jsp</groupId>
      <artifactId>jsp-api</artifactId>
      <version>2.0</version>
      <scope>provided</scope>
    </dependency>
  </dependencies>

2）springmvc.xml中配置攔截(存放在resources目錄下)

  <?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.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">

    <!-- 開啟注解掃描 -->
    <context:component-scan base-package="work.chenc.*"></context:component-scan>

    <!-- 開啟視圖解析器 -->
    <bean id="internalResourceViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/pages/"></property>
        <property name="suffix" value=".jsp"></property>
    </bean>

    <!-- 配置攔截器 -->
    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/test/*"/>
<!--
            那些請求不需要進行攔截
            <mvc:exclude-mapping path=""/>
            -->
<!--
            那些請求需要進行攔截
            <mvc:exclude-mapping path=""/>-->
            <!-- 配置自定義攔截器 -->
            <bean class="work.chenc.interception.FirstInterception"></bean>
        </mvc:interceptor>
        <mvc:interceptor>
            <mvc:mapping path="/test/*"/>
            <bean class="work.chenc.interception.SecondInterception"></bean>
        </mvc:interceptor>
    </mvc:interceptors>

    <!-- 開啟SpringMVC注解支持 -->
    <mvc:annotation-driven/>
</beans>

3）web.xml

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
  <display-name>Archetype Created Web Application</display-name>

  <!-- 配置前端控制器 -->
  <servlet>
    <servlet-name>dispatcherServlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <!-- 加載SpringMVC配置文件 -->
    <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>classpath:springmvc.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>dispatcherServlet</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>

  <!-- 過濾字符集編碼 -->
  <filter>
    <filter-name>characterEncodingFilter</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
      <param-name>encoding</param-name>
      <param-value>UTF-8</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>characterEncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
</web-app>

4）第一個攔截器FirstInterception

package work.chenc.interception;

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

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

/**
 * 自定義攔截器-第一個攔截器
 */
public class FirstInterception implements HandlerInterceptor {
  /**
   * 預(yù)處理攔截器
   * @param request
   * @param response
   * @param handler
   * @return
   * @throws Exception
   */
  @Override
  public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    System.out.println("FirstInterception-preHandle...執(zhí)行");
    return true;
  }

  /**
   * 后處理攔截器
   * @param request
   * @param response
   * @param handler
   * @param modelAndView
   * @throws Exception
   */
  @Override
  public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    System.out.println("FirstInterception-postHandle...執(zhí)行");
  }

  /**
   * 請求處理完畢回調(diào)
   * @param request
   * @param response
   * @param handler
   * @param ex
   * @throws Exception
   */
  @Override
  public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    System.out.println("FirstInterception-afterCompletion...執(zhí)行");
  }
}

5）第二個攔截器SecondInterception

package work.chenc.interception;

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

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

/**
 * 自定義攔截器-第二個攔截器
 */
public class SecondInterception implements HandlerInterceptor {
  @Override
  public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    System.out.println("SecondInterception-preHandle...執(zhí)行");
    return true;
  }

  @Override
  public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    System.out.println("SecondInterception-postHandle...執(zhí)行");
  }

  @Override
  public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    System.out.println("SecondInterception-afterCompletion...執(zhí)行");
  }
}

6）前端控制器controller

package work.chenc.controller;

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

@Controller
@RequestMapping(value = "/test")
public class TestController {

  @RequestMapping(value = "/testInterception")
  public String testInterception() {
    System.out.println("testInterception...執(zhí)行了");
    return "success";
  }
}

7）jsp頁面 index.jsp success.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
  <title>首頁</title>
</head>
<body>
  <h1>首頁</h1>
  <a href="test/testInterception">跳轉(zhuǎn)成功頁面</a>
</body>
</html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
  <title>success</title>
</head>
<body>
  <h1>成功頁面</h1>

  <% System.out.println("success頁面加載"); %>
</body>
</html>

8）執(zhí)行結(jié)果

index.jsp

執(zhí)行結(jié)果