pom.xml

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<!-- 文件上传 -->
<dependency>
   <groupId>commons-fileupload</groupId>
   <artifactId>commons-fileupload</artifactId>
   <version>1.3.3</version>
</dependency>
<!--servlet-api 导入高版本的 -->
<dependency>
   <groupId>javax.servlet</groupId>
   <artifactId>javax.servlet-api</artifactId>
   <version>4.0.1</version>
</dependency>

spring.xml

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<import resource="spring-mvc.xml" />

spring-mvc.xml

  1. DispatcherServlet 从 Spring 容器获取名称为 multipartResolver 的对象，如果存在，则调用 isMultipart (request) 方法检查当前 Web 请求是否为 multipart 类型
  2. 如果是 multipart 类型，DispatcherServlet 将调用 MultipartResolver 的 resolveMultipart (request) 方法，对原始 request 进行装饰，并返回一个 MultipartHttpServletRequest 供后继处理流程使用
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<!-- bean id 名称必须为 multipartResolver 不可修改-->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
   <!-- 请求的编码格式，必须和 jSP 的 pageEncoding 属性一致，以便正确读取表单的内容，默认为 ISO-8859-1 -->
   <property name="defaultEncoding" value="utf-8"/>
   <!-- 上传文件大小上限，单位为字节（10485760=10M） -->
   <property name="maxUploadSize" value="10485760"/>
   <property name="maxInMemorySize" value="40960"/>
</bean>

前端

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<form action="/upload" enctype="multipart/form-data" method="post">
 <input type="file" name="files"/>
 <input type="submit" value="upload">
</form>

后端

方法一「推荐」，通过 MultipartFile 接收

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/*
* MultipartFile 常用方法：
* String getOriginalFilename ()：获取上传文件的原名
* InputStream getInputStream ()：获取文件流
* void transferTo (File dest)：将上传文件保存到一个目录文件中
*/
@RequestMapping ("/fileUpload")
public void fileUpload (@RequestParam("files") List<MultipartFile> files, HttpServletRequest request) throws IOException {
		for (MultipartFile file : files) {
			file.transferTo (new File (Constants.PRO_REAL_PATH +"/"+ file.getOriginalFilename ()));
		}
}

方法二

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@RequestMapping ("/fileUpload1")
public void fileUpload1(HttpServletRequest request) throws IOException {
		List<MultipartFile> multipartFiles = new ArrayList<>();

		MultipartResolver multipartResolver = new CommonsMultipartResolver(request.getSession().getServletContext());
		//判断 request 是否有文件上传,即多部分请求...
		if (multipartResolver.isMultipart(request)){
			MultipartHttpServletRequest multipartHttpServletRequest = (MultipartHttpServletRequest) request;
			Iterator<String> names = multipartHttpServletRequest.getFileNames();
			while (names.hasNext()) {
				String name = names.next();
				List<MultipartFile> files = multipartHttpServletRequest.getFiles(name);
				multipartFiles.addAll(files);
			}

			for (MultipartFile multipartFile : multipartFiles) {
				String fileName = multipartFile.getOriginalFilename();
				String fileTotalName = Constants.PRO_REAL_PATH + File.separator + fileName;
				File f = new File(fileTotalName);
				multipartFile.transferTo(f);
			}
		}
}

方法三「不要在 spring-mvc.xml 配置 multipartResolver」

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@RequestMapping ("/upload")
public void fileUpload (HttpServletRequest request, HttpServletResponse response) throws IOException {
		MultipartResolver multipartResolver = new CommonsMultipartResolver(request.getSession().getServletContext());
		//判断 request 是否有文件上传,即多部分请求...
		if (multipartResolver.isMultipart(request))
		{
			//转换成多部分request
			MultipartHttpServletRequest multipartRequest = multipartResolver.resolveMultipart(request);

			// file 是指 文件上传标签的 name=值
			// 根据 name 获取上传的文件...
			List<MultipartFile> files = multipartRequest.getFiles("files");
			for (MultipartFile file : files) {
				//上传后记录的文件...
				File imageFile = new File(Constants.PRO_REAL_PATH, file.getOriginalFilename());
				//上传...
				file.transferTo(imageFile);
			}
		}
}