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几乎在所有的软件中都会有上传文件的需求，自己动手写一个在springboot项目中的文件上传功能
具体步骤如下：
一、引入依赖（基础依赖在父工程的pom文件中）

<dependencies><!-- https://mvnrepository.com/artifact/org.apache.commons/commons-lang3 --><dependency><groupId>org.apache.commons</groupId><artifactId>commons-lang3</artifactId><version>3.8</version></dependency><!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api --><dependency><groupId>org.slf4j</groupId><artifactId>slf4j-api</artifactId><version>1.7.27</version></dependency><!-- thymeleaf模板插件 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-thymeleaf</artifactId></dependency></dependencies>

二、编写配置文件

server:port: 9999servlet:context-path: /
spring:thymeleaf:cache: falsehttp:multipart://单个文件的最大值maxFileSize: 1Mb//多个文件的最大值maxRequsetSize: 5Mb

三、文件上传的核心逻辑

@Controller
public class FileController {@RequestMapping("file")public String file(){return "file";}/*** 单文件上传* @param file* @return*/@PostMapping("/upload")@ResponseBodypublic String fileUpload(@RequestParam("filename")MultipartFile file){if(file.isEmpty()){return "上传文件为空";}//上传文件的全路径String fileName = file.getOriginalFilename();int size = (int)file.getSize();System.err.println("文件大小为："+size);//文件的上传路径String path = "D:/test";File dest = new File(path + "/" + fileName);if(!dest.getParentFile().exists()){dest.getParentFile().mkdir();}try {file.transferTo(dest);return  "上传成功";}catch (IllegalStateException  e){return "上传失败";}catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();return "false";}}/*** 多文件上传* @param request* @return*/@RequestMapping(value="multifileUpload",method=RequestMethod.POST)public @ResponseBody String multifileUpload(HttpServletRequest request) {List<MultipartFile> files = ((MultipartHttpServletRequest) request).getFiles("fileName");if (files.isEmpty()) {return "上传文件为空";}String path = "D:/test";for (MultipartFile file : files) {String fileName = file.getOriginalFilename();int size = (int) file.getSize();System.out.println(fileName + "-->" + size);if (file.isEmpty()) {return "上传文件为空";} else {File dest = new File(path + "/" + fileName);if (!dest.getParentFile().exists()) {dest.getParentFile().mkdir();}try {file.transferTo(dest);} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();return "上传失败";}}}return "上传成功";}
}

源码地址