706 lines
21 KiB
Markdown
706 lines
21 KiB
Markdown
# Spring MVC 基础（基于注解）
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<nav>
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<a href="#一搭建-Hello-Spring-工程">一、搭建 Hello Spring 工程</a><br/>
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<a href="#二配置自定义拦截器">二、配置自定义拦截器</a><br/>
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<a href="#三全局异常处理">三、全局异常处理 </a><br/>
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<a href="#四参数绑定">四、参数绑定</a><br/>
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<a href="#41-参数绑定">4.1 参数绑定</a><br/>
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<a href="#42-日期格式转换">4.2 日期格式转换</a><br/>
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<a href="#五数据校验">五、数据校验</a><br/>
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<a href="#六文件上传与下载">六、文件上传与下载</a><br/>
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<a href="#61-文件上传">6.1 文件上传</a><br/>
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<a href="#62-文件下载">6.2 文件下载</a><br/>
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<a href="#七RESTful-风格的请求">七、RESTful 风格的请求</a><br/>
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</nav>
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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 的共同支持，我们可以在没有 `web.xml` 的情况下完成关于 servlet 配置。新建 DispatcherServletInitializer，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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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 ，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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@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.新建 Controller 用于测试整体配置是否成功：
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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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}
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```
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5.在 WEB-INF 下新建 jsp 文件夹，并创建一个简单的 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，访问的服务地址为：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 用于配置类的定义，等价于xml 配置文件，配置类内部可以包含一个或多个被 @Bean 注解的方法，这些方法将会被 AnnotationConfigApplicationContext 或 AnnotationConfigWebApplicationContext 类进行扫描，方法返回的实体会被直接注册为容器内的 Bean。
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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，用于测试拦截器的执行顺序）：
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```java
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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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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 中注册自定义拦截器：
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```java
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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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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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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 中注册自定义异常处理器：
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```java
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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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调用这个 Controller 时，同时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。
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## 四、参数绑定
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### 4.1 参数绑定
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1.新建 Programmer.java 作为测试实体类：
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```java
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@Data
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public class Programmer {
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private String name;
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private int age;
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private float salary;
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private String birthday;
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}
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```
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2.新建 ParamBindController.java 文件，跳转到指定视图：
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```java
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@Controller
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public class ParamBindController {
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@InitBinder
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protected void initBinder(WebDataBinder binder) {
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binder.addCustomFormatter(new DateFormatter("yyyy-MM-dd HH:mm:ss"));
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}
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// 参数绑定与日期格式转换
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@RequestMapping("param")
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public String param(String name, int age, double salary, @DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss") Date birthday, Model model) {
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model.addAttribute("name", name);
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model.addAttribute("age", age);
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model.addAttribute("salary", salary);
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model.addAttribute("birthday", birthday);
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return "param";
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}
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@RequestMapping("param2")
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public String param2(String name, int age, double salary, Date birthday, Model model) {
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model.addAttribute("name", name);
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model.addAttribute("age", age);
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model.addAttribute("salary", salary);
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model.addAttribute("birthday", birthday);
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return "param";
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}
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@PostMapping("param3")
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public String param3(Programmer programmer, String extendParam, Model model) {
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System.out.println("extendParam" + extendParam);
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model.addAttribute("p", programmer);
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return "param";
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}
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}
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```
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3.新建 param.jsp 文件，用于测试数据在视图中的绑定情况：
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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>Restful</title>
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</head>
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<body>
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<ul>
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<li>姓名：${empty name ? p.name : name}</li>
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<li>年龄：${empty age ? p.age : age}</li>
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<li>薪酬：${empty salary ? p.salary : salary}</li>
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<li>生日：${empty birthday ? p.birthday : birthday}</li>
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</ul>
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</body>
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</html>
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```
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4.启动 tomcat，接着可以使用 [postman](https://www.getpostman.com/) 等接口测试软件发送测试请求。
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### 4.2 日期格式转换
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Spring 支持使用以下三种方法来对参数中的日期格式进行转换：
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**方法一**：如上面的实例代码所示，在对应的 Controller 中初始化绑定：
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```java
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@InitBinder
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protected void initBinder(WebDataBinder binder) {
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binder.addCustomFormatter(new DateFormatter("yyyy-MM-dd HH:mm:ss"));
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}
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```
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**方法二**：利用 @DateTimeFormat 注解，如果是用实体类去接收参数，则在对应的实体类的属性上用 @DateTimeFormat 和 @JsonFormat 进行声明：
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```java
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public String param(@DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss") Date birthday)
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```
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**方法三**：使用全局的日期格式绑定，新建自定义日期格式转化类，之后在 `springApplication.xml` 中进行注册，采用这种方式会对全局范围内的日期格式转换生效：
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```java
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public class CustomDateConverter implements Converter<String, Date> {
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public Date convert(String s) {
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try {
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SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
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return simpleDateFormat.parse(s);
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} catch (Exception e) {
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e.printStackTrace();
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}
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return null;
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}
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}
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```
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在 ServletConfig 中进行注册：
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```java
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public void addFormatters(FormatterRegistry registry) {
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registry.addConverter(new CustomDateConverter());
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}
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```
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## 五、数据校验
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1.Spring 支持 JSR303 标准的校验，需要引入相关的依赖：
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```xml
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<!-- 数据校验依赖包 -->
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<dependency>
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<groupId>org.hibernate.validator</groupId>
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<artifactId>hibernate-validator</artifactId>
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<version>6.0.13.Final</version>
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</dependency>
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<dependency>
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<groupId>javax.validation</groupId>
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<artifactId>validation-api</artifactId>
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<version>2.0.1.Final</version>
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</dependency>
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```
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2.新建测试类 ParamValidController.java，在需要校验的参数前加上 @Validated 注解，表明该参数需要被校验。同时在方法声明中加上 bindingResult 参数，可以从这个参数中获取最终校验的结果：
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```java
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@RestController
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public class ParamValidController {
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@PostMapping("validate")
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public void valid(@Validated Programmer programmer,BindingResult bindingResult) {
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List<ObjectError> allErrors = bindingResult.getAllErrors();
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for (ObjectError error : allErrors) {
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System.out.println(error.getDefaultMessage());
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}
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}
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}
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```
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3.在 Programmer.java 的对应属性上加上注解约束，用于声明每个参数的校验规则：
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```java
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@Data
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public class Programmer {
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@NotNull
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private String name;
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@Min(value = 0,message = "年龄不能为负数！" )
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private int age;
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@Min(value = 0,message = "薪酬不能为负数！" )
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private float salary;
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private String birthday;
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}
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```
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其他支持的注解可以到 javax.validation.constraints 包下进行查看。
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## 六、文件上传与下载
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### 6.1 文件上传
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1.在 ServletConfig 中进行配置，开启文件上传：
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```java
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@Bean
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public CommonsMultipartResolver multipartResolver(){
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CommonsMultipartResolver resolver = new CommonsMultipartResolver();
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resolver.setMaxUploadSize(1024*1000*10);
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resolver.setMaxUploadSizePerFile(1024*1000);
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resolver.setDefaultEncoding("utf-8");
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return resolver;
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}
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```
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2.新建上传测试类：
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```java
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@Controller
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public class FileController {
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@GetMapping("file")
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public String filePage() {
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return "file";
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}
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/***
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* 单文件上传
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*/
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@PostMapping("upFile")
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public String upFile(MultipartFile file, HttpSession session) {
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//保存在项目根目录下 image 文件夹下，如果文件夹不存在则创建
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FileUtil.saveFile(file, session.getServletContext().getRealPath("/image"));
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// success.jsp 就是一个简单的成功页面
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return "success";
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}
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/***
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* 多文件上传 多个文件用同一个名字
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*/
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@PostMapping("upFiles")
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public String upFiles(@RequestParam(name = "file") MultipartFile[] files, HttpSession session) {
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for (MultipartFile file : files) {
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FileUtil.saveFile(file, session.getServletContext().getRealPath("images"));
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}
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return "success";
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}
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/***
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* 多文件上传方式 2 分别为不同文件指定不同名字
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*/
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@PostMapping("upFiles2")
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public String upFile(String extendParam,
|
||
@RequestParam(name = "file1") MultipartFile file1,
|
||
@RequestParam(name = "file2") MultipartFile file2, HttpSession session) {
|
||
String realPath = session.getServletContext().getRealPath("images2");
|
||
FileUtil.saveFile(file1, realPath);
|
||
FileUtil.saveFile(file2, realPath);
|
||
System.out.println("extendParam:" + extendParam);
|
||
return "success";
|
||
}
|
||
}
|
||
```
|
||
|
||
3.其中工具类 FileUtil.java 代码如下：
|
||
|
||
```java
|
||
public class FileUtil {
|
||
|
||
public static String saveFile(MultipartFile file, String path) {
|
||
InputStream inputStream = null;
|
||
FileOutputStream outputStream = null;
|
||
String fullPath = path + File.separator + file.getOriginalFilename();
|
||
try {
|
||
File saveDir = new File(path);
|
||
if (!saveDir.exists()) {
|
||
saveDir.mkdirs();
|
||
}
|
||
outputStream = new FileOutputStream(new File(fullPath));
|
||
inputStream = file.getInputStream();
|
||
byte[] bytes = new byte[1024 * 1024];
|
||
int read;
|
||
while ((read = inputStream.read(bytes)) != -1) {
|
||
outputStream.write(bytes, 0, read);
|
||
}
|
||
} catch (IOException e) {
|
||
e.printStackTrace();
|
||
} finally {
|
||
if (inputStream != null) {
|
||
try {
|
||
inputStream.close();
|
||
} catch (IOException e) {
|
||
e.printStackTrace();
|
||
}
|
||
}
|
||
if (outputStream != null) {
|
||
try {
|
||
outputStream.close();
|
||
} catch (IOException e) {
|
||
e.printStackTrace();
|
||
}
|
||
}
|
||
}
|
||
return fullPath;
|
||
}
|
||
|
||
}
|
||
```
|
||
|
||
4.新建用于上传的 jsp 页面，上传文件时表单必须声明 `enctype="multipart/form-data"` ：
|
||
|
||
```jsp
|
||
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
|
||
<html>
|
||
<head>
|
||
<title>文件上传</title>
|
||
<link rel="stylesheet" href="${pageContext.request.contextPath}/css/file.css">
|
||
</head>
|
||
<body>
|
||
|
||
<form action="${pageContext.request.contextPath }/upFile" method="post" enctype="multipart/form-data">
|
||
请选择上传文件：<input name="file" type="file"><br>
|
||
<input type="submit" value="点击上传文件">
|
||
</form>
|
||
|
||
<form action="${pageContext.request.contextPath }/upFiles" method="post" enctype="multipart/form-data">
|
||
请选择上传文件 (多选)：<input name="file" type="file" multiple><br>
|
||
<input type="submit" value="点击上传文件">
|
||
</form>
|
||
|
||
<form action="${pageContext.request.contextPath }/upFiles2" method="post" enctype="multipart/form-data">
|
||
请选择上传文件 1：<input name="file1" type="file"><br>
|
||
请选择上传文件 2：<input name="file2" type="file"><br>
|
||
文件内容额外备注: <input name="extendParam" type="text"><br>
|
||
<input type="submit" value="点击上传文件">
|
||
</form>
|
||
|
||
</body>
|
||
</html>
|
||
```
|
||
|
||
### 6.2 文件下载
|
||
|
||
1.在 fileController.java 中增加下载方法：
|
||
|
||
```java
|
||
/***
|
||
* 上传用于下载的文件
|
||
*/
|
||
@PostMapping("upFileForDownload")
|
||
public String upFileForDownload(MultipartFile file, HttpSession session, Model model) throws UnsupportedEncodingException {
|
||
String path = FileUtil.saveFile(file, session.getServletContext().getRealPath("/image"));
|
||
model.addAttribute("filePath", URLEncoder.encode(path,"utf-8"));
|
||
model.addAttribute("fileName", file.getOriginalFilename());
|
||
return "fileDownload";
|
||
}
|
||
|
||
/***
|
||
* 下载文件
|
||
*/
|
||
@GetMapping("download")
|
||
public ResponseEntity<byte[]> downloadFile(String filePath) throws IOException {
|
||
HttpHeaders headers = new HttpHeaders();
|
||
File file = new File(filePath);
|
||
// 解决文件名中文乱码
|
||
String fileName=new String(file.getName().getBytes("UTF-8"),"iso-8859-1");
|
||
headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
|
||
headers.setContentDispositionFormData("attachment", fileName);
|
||
|
||
return new ResponseEntity<byte[]>(FileUtils.readFileToByteArray(file),
|
||
headers, HttpStatus.CREATED);
|
||
}
|
||
```
|
||
|
||
2.其中 fileDownload.jsp 如下：
|
||
|
||
```jsp
|
||
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
|
||
<html>
|
||
<head>
|
||
<title>文件下载</title>
|
||
</head>
|
||
<body>
|
||
<a href="${pageContext.request.contextPath}/download?filePath=${filePath}">${fileName}</a>
|
||
</body>
|
||
</html>
|
||
```
|
||
|
||
|
||
|
||
## 七、RESTful 风格的请求
|
||
|
||
1.新建测试实体类：
|
||
|
||
```java
|
||
@Data
|
||
public class Pet {
|
||
|
||
private String ownerId;
|
||
|
||
private String petId;
|
||
}
|
||
```
|
||
|
||
2.新建 RestfulController.java，用 @PathVariable 和 @ModelAttribute 注解进行参数绑定：
|
||
|
||
```java
|
||
@RestController
|
||
public class RestfulController {
|
||
|
||
@GetMapping("restful/owners/{ownerId}/pets/{petId}")
|
||
public void get(@PathVariable String ownerId, @PathVariable String petId) {
|
||
System.out.println("ownerId:" + ownerId);
|
||
System.out.println("petId:" + petId);
|
||
}
|
||
|
||
@GetMapping("restful2/owners/{ownerId}/pets/{petId}")
|
||
public void get(@ModelAttribute Pet pet) {
|
||
System.out.println("ownerId:" + pet.getOwnerId());
|
||
System.out.println("petId:" + pet.getPetId());
|
||
}
|
||
}
|
||
```
|
||
|
||
在 RESTful 风格的请求中，资源通过 URL 进行标识和定位，而操作行为是通过 HTTP 方法进行定义，在进行不同行为时对应 HTTP 方法和 Spring 注解分别如下：
|
||
|
||
- 创建资源时：POST（@PostMapping）
|
||
- 读取资源时：GET（ @GetMapping）
|
||
- 更新资源时：PUT 或 PATCH（@PutMapping、@PatchMapping）
|
||
- 删除资源时：DELETE（@DeleteMapping） |