364 lines
11 KiB
Markdown
364 lines
11 KiB
Markdown
# springmvc基础（基于xml配置）
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**开发环境：IDEA**
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**spring版本：5.1.3.RELEASE**
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**本部分内容官方文档链接：[Web Servlet](https://docs.spring.io/spring/docs/5.1.3.RELEASE/spring-framework-reference/web.html#spring-web)**
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## 一、搭建hello spring工程
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### 1.1 项目搭建
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1.新建maven web工程，并引入相应的依赖
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```xml
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<properties>
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<spring-base-version>5.1.3.RELEASE</spring-base-version>
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</properties>
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<dependencies>
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<dependency>
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<groupId>org.springframework</groupId>
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<artifactId>spring-context</artifactId>
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<version>${spring-base-version}</version>
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</dependency>
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<dependency>
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<groupId>org.springframework</groupId>
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<artifactId>spring-beans</artifactId>
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<version>${spring-base-version}</version>
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</dependency>
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<dependency>
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<groupId>org.springframework</groupId>
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<artifactId>spring-core</artifactId>
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<version>${spring-base-version}</version>
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</dependency>
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<dependency>
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<groupId>org.springframework</groupId>
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<artifactId>spring-web</artifactId>
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<version>${spring-base-version}</version>
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</dependency>
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<dependency>
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<groupId>org.springframework</groupId>
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<artifactId>spring-webmvc</artifactId>
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<version>${spring-base-version}</version>
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</dependency>
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<dependency>
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<groupId>javax.servlet</groupId>
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<artifactId>javax.servlet-api</artifactId>
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<version>4.0.1</version>
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<scope>provided</scope>
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</dependency>
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</dependencies>
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```
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2.配置web.xml
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```xml
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<?xml version="1.0" encoding="UTF-8"?>
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<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
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http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
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version="3.1">
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<!--配置spring前端控制器-->
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<servlet>
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<servlet-name>springMvc</servlet-name>
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<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
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<init-param>
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<param-name>contextConfigLocation</param-name>
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<param-value>classpath:springApplication.xml</param-value>
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</init-param>
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<load-on-startup>1</load-on-startup>
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</servlet>
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<servlet-mapping>
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<servlet-name>springMvc</servlet-name>
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<url-pattern>/</url-pattern>
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</servlet-mapping>
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</web-app>
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```
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3.在resources下新建springApplication.xml文件，文件内容如下:
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```xml
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<?xml version="1.0" encoding="UTF-8"?>
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<beans xmlns="http://www.springframework.org/schema/beans"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xmlns:context="http://www.springframework.org/schema/context"
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xmlns:mvc="http://www.springframework.org/schema/mvc"
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xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
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http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.1.xsd
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http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd">
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<!-- 开启注解包扫描-->
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<context:component-scan base-package="com.heibaiying.*"/>
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<!--使用默认的Servlet来响应静态文件 详见 1.2 -->
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<mvc:default-servlet-handler/>
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<!-- 开启注解驱动 详见 1.2 -->
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<mvc:annotation-driven/>
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<!-- 配置视图解析器 -->
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<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"
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id="internalResourceViewResolver">
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<!-- 前缀 -->
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<property name="prefix" value="/WEB-INF/jsp/"/>
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<!-- 后缀 -->
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<property name="suffix" value=".jsp"/>
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</bean>
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</beans>
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```
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4.在src 下新建controller用于测试
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```java
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package com.heibaiying.controller;
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import com.heibaiying.exception.NoAuthException;
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import org.springframework.stereotype.Controller;
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import org.springframework.web.bind.annotation.RequestMapping;
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/**
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* @author : heibaiying
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* @description : hello spring
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*/
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@Controller
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@RequestMapping("mvc")
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public class HelloController {
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@RequestMapping("hello")
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private String hello() {
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return "hello";
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}
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}
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```
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5.在WEB-INF 下新建jsp文件夹，新建hello.jsp 文件
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```jsp
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<%@ page contentType="text/html;charset=UTF-8" language="java" %>
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<html>
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<head>
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<title>Title</title>
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</head>
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<body>
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Hello Spring MVC!
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</body>
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</html>
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```
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6.启动tomcat服务，访问localhost:8080/mvc/hello
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### 1.2 相关配置讲解
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**1.\<mvc:default-servlet-handler/>**
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在web.xml配置中，我们将DispatcherServlet的拦截路径设置为“\”，则spring会捕获所有web请求，包括对静态资源的请求，为了正确处理对静态资源的请求，spring提供了两种解决方案：
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- 配置\<mvc:default-servlet-handler/> ： 配置<mvc:default-servlet-handler />后，会在Spring MVC上下文中定义一个org.springframework.web.servlet.resource.DefaultServletHttpRequestHandler，它会对进入DispatcherServlet的URL进行筛查，如果发现是静态资源的请求，就将该请求转由Web应用服务器默认的Servlet处理，如果不是静态资源的请求，才由DispatcherServlet继续处理。
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- 配置\<mvc:resources /> ：指定静态资源的位置和路径映射：
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```xml
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<mvc:resources location="/img/" mapping="/img/**"/>
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<mvc:resources location="/js/" mapping="/js/**"/>
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<mvc:resources location="/css/" mapping="/css/**"/>
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```
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**2.\<mvc:annotation-driven/>**
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<mvc:annotation-driven /> 会自动注册DefaultAnnotationHandlerMapping与AnnotationMethodHandlerAdapter
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两个bean,用以支持@Controllers分发请求。并提供了数据绑定、参数转换、json转换等功能，所以必须加上这个配置。
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## 二、配置自定义拦截器
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1.创建自定义拦截器，实现接口HandlerInterceptor（这里我们创建两个拦截器，用于测试拦截器方法的执行顺序）
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```java
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package com.heibaiying.interceptors;
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import org.springframework.web.servlet.HandlerInterceptor;
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import org.springframework.web.servlet.ModelAndView;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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/**
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* @author : heibaiying
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* @description : spring5 中 preHandle，postHandle，afterCompletion 在接口中被声明为默认方法
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*/
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public class MyFirstInterceptor implements HandlerInterceptor {
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public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
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System.out.println("进入第一个拦截器preHandle");
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return true;
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}
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// 需要注意的是，如果对应的程序报错，不一定会进入这个方法 但一定会进入afterCompletion这个方法
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public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) {
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System.out.println("进入第一个拦截器postHandle");
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}
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public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
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System.out.println("进入第一个拦截器afterCompletion");
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}
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}
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```
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```java
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package com.heibaiying.interceptors;
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import org.springframework.web.servlet.HandlerInterceptor;
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import org.springframework.web.servlet.ModelAndView;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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/**
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* @author : heibaiying
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* @description : spring5 中 preHandle，postHandle，afterCompletion 在接口中被声明为默认方法
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*/
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public class MySecondInterceptor implements HandlerInterceptor {
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public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
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System.out.println("进入第二个拦截器preHandle");
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return true;
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}
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public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) {
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System.out.println("进入第二个拦截器postHandle");
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}
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public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
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System.out.println("进入第二个拦截器afterCompletion");
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}
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}
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```
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2.在springApplication.xml中注册自定义拦截器
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```xml
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<!--配置拦截器-->
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<mvc:interceptors>
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<mvc:interceptor>
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<mvc:mapping path="/mvc/**"/>
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<mvc:exclude-mapping path="/mvc/login"/>
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<bean class="com.heibaiying.interceptors.MyFirstInterceptor"/>
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</mvc:interceptor>
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<mvc:interceptor>
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<mvc:mapping path="/mvc/**"/>
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<bean class="com.heibaiying.interceptors.MySecondInterceptor"/>
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</mvc:interceptor>
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</mvc:interceptors>
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```
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3.关于多个拦截器方法执行顺序的说明
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拦截器的执行顺序是按声明的先后顺序执行的，先声明的拦截器中的preHandle方法会先执行，然而它的postHandle方法和afterCompletion方法却会后执行。
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## 三、全局异常处理
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1.定义自定义异常
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```java
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package com.heibaiying.exception;
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/**
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* @author : heibaiying
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* @description : 自定义无权限异常
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*/
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public class NoAuthException extends RuntimeException {
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public NoAuthException() {
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super();
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}
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public NoAuthException(String message) {
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super(message);
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}
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public NoAuthException(String message, Throwable cause) {
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super(message, cause);
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}
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public NoAuthException(Throwable cause) {
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super(cause);
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}
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}
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```
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2.实现自定义异常处理器
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```java
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package com.heibaiying.exception;
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import org.springframework.web.servlet.HandlerExceptionResolver;
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import org.springframework.web.servlet.ModelAndView;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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/**
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* @author : heibaiying
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* @description : 无权限异常处理机制
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*/
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public class NoAuthExceptionResolver implements HandlerExceptionResolver {
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public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
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if (ex instanceof NoAuthException && !isAjax(request)) {
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return new ModelAndView("NoAuthPage");
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}
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return new ModelAndView();
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}
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// 判断是否是Ajax请求
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private boolean isAjax(HttpServletRequest request) {
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return "XMLHttpRequest".equalsIgnoreCase(request.getHeader("X-Requested-With"));
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}
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}
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```
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3.在springApplication.xml注册自定义异常处理器
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```xml
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<!--配置全局异常处理器-->
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<bean class="com.heibaiying.exception.NoAuthExceptionResolver"/>
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```
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4.定义测试controller，抛出自定义异常
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```java
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@Controller
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@RequestMapping("mvc")
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public class HelloController {
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@RequestMapping("hello")
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private String hello() {
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return "hello";
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}
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@RequestMapping("auth")
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private void auth() {
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throw new NoAuthException("没有对应的访问权限！");
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}
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}
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```
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注：调用这个controller时，同时也可以验证在拦截器部分提到的：如果对应的程序报错，拦截器不一定会进入postHandle这个方法 但一定会进入afterCompletion这个方法 |