372 lines
11 KiB
Markdown
372 lines
11 KiB
Markdown
# springmvc基础（基于注解）
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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.得益于servlet3.0和spring的支持，我们可以在没有web.xml的情况下完成关于servlet配置。
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新建DispatcherServletInitializer.java文件,这个类的作用相当于我们在xml方式下web.xml中配置的DispatcherServlet
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```java
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package com.heibaiying.config;
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import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
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/**
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* @author : heibaiying
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*/
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public class DispatcherServletInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
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protected Class<?>[] getRootConfigClasses() {
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return new Class[0];
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}
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protected Class<?>[] getServletConfigClasses() {
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return new Class[]{ServletConfig.class};
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}
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protected String[] getServletMappings() {
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return new String[]{"/"};
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}
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}
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```
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3.新建ServletConfig.java，文件内容如下(这个类相当于我们在xml配置方式中的springApplication.xml)
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```java
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package com.heibaiying.config;
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import com.heibaiying.exception.NoAuthExceptionResolver;
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import com.heibaiying.interceptors.MyFirstInterceptor;
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import com.heibaiying.interceptors.MySecondInterceptor;
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import org.springframework.context.annotation.Bean;
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import org.springframework.context.annotation.ComponentScan;
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import org.springframework.context.annotation.Configuration;
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import org.springframework.web.servlet.HandlerExceptionResolver;
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import org.springframework.web.servlet.ViewResolver;
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import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;
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import org.springframework.web.servlet.config.annotation.EnableWebMvc;
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import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
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import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
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import org.springframework.web.servlet.view.InternalResourceViewResolver;
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import java.util.List;
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/**
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* @author : heibaiying
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*/
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@Configuration
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@EnableWebMvc
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@ComponentScan(basePackages = {"com.heibaiying.controller"})
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public class ServletConfig implements WebMvcConfigurer {
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/**
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* 配置视图解析器
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*/
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@Bean
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public ViewResolver viewResolver() {
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InternalResourceViewResolver internalResourceViewResolver = new InternalResourceViewResolver();
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internalResourceViewResolver.setPrefix("/WEB-INF/jsp/");
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internalResourceViewResolver.setSuffix(".jsp");
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internalResourceViewResolver.setExposeContextBeansAsAttributes(true);
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return internalResourceViewResolver;
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}
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/**
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* 配置静态资源处理器
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*/
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public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
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configurer.enable();
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}
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}
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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 相关注解说明
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**1.@Configuration**
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@Configuration用于定义配置类，可替换xml配置文件，被注解的类内部包含有一个或多个被@Bean注解的方法，这些方法将会被AnnotationConfigApplicationContext或AnnotationConfigWebApplicationContext类进行扫描，并用于构建bean定义，初始化Spring容器。
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**2.@EnableWebMvc**
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简单的说就是提供了部分springmvc的功能，例如格式转换和参数绑定。
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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ServletConfig.java中注册自定义拦截器
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```java
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/**
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* 添加自定义拦截器
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*/
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public void addInterceptors(InterceptorRegistry registry) {
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registry.addInterceptor(new MyFirstInterceptor()).addPathPatterns("/mvc/**").excludePathPatterns("mvc/login");
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registry.addInterceptor(new MySecondInterceptor()).addPathPatterns("/mvc/**");
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}
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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ServletConfig.java注册自定义异常处理器
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```java
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/**
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* 添加全局异常处理器
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*/
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public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers) {
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resolvers.add(new NoAuthExceptionResolver());
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}
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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 |