一、pom依赖

    <dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies>

二、yml配置文件

# Spring配置
spring:# 文件上传servlet:multipart:# 单个文件大小max-file-size: 10MB# 设置总上传的文件大小max-request-size: 20MB
server:port: 9090

三、文件下载

3.1、使用Spring框架提供的下载方式

关键代码：

    /*** 使用Spring框架自带的下载方式* @param filePath* @param fileName* @return*/public ResponseEntity<Resource> download(String filePath,String fileName) throws Exception {fileName = URLEncoder.encode(fileName,"UTF-8");File file = new File(filePath);if(!file.exists()){throw new Exception("文件不存在");}return ResponseEntity.ok().header(HttpHeaders.CONTENT_DISPOSITION,"attachment; filename=" + fileName ).body(new FileSystemResource(filePath));}

请求层：

@RestController
@RequestMapping("/file")
public class FileController {@Autowiredprivate FileUtil fileUtil;@GetMapping("/spring/download")public ResponseEntity<Resource> download() throws Exception {String filePath = "D:\\1.jpg";String fileName = "Spring框架下载.jpg";return fileUtil.download(filePath,fileName);}}

浏览器输入：http://localhost:9090/file/spring/download

下载完成。

3.2、通过IOUtils以流的形式下载

关键代码：

    /*** 通过IOUtils以流的形式下载* @param filePath* @param fileName* @param response*/public void download(String filePath , String fileName, HttpServletResponse response) throws Exception {fileName = URLEncoder.encode(fileName,"UTF-8");File file=new File(filePath);if(!file.exists()){throw new Exception("文件不存在");}response.setHeader("Content-disposition","attachment;filename="+ fileName);FileInputStream fileInputStream = new FileInputStream(file);IOUtils.copy(fileInputStream,response.getOutputStream());response.flushBuffer();fileInputStream.close();}

请求层：

@RestController
@RequestMapping("/file")
public class FileController {@Autowiredprivate FileUtil fileUtil;@GetMapping("/io/download")public void ioDownload(HttpServletResponse response) throws Exception {String filePath = "D:\\1.jpg";String fileName = "IO下载.jpg";fileUtil.download(filePath,fileName,response);}}

浏览器访问：http://localhost:9090/file/io/download

下载成功。

3.3、边读边下载

关键代码：

    /*** 原始的方法，下载一些小文件，边读边下载的* @param filePath* @param fileName* @param response* @throws Exception*/public void downloadTinyFile(String filePath,String fileName, HttpServletResponse response)throws Exception{File file = new File(filePath);fileName = URLEncoder.encode(fileName, "UTF-8");if(!file.exists()){throw new Exception("文件不存在");}FileInputStream in = new FileInputStream(file);response.setHeader("Content-Disposition", "attachment;filename="+fileName);OutputStream out = response.getOutputStream();byte[] b = new byte[1024];int len = 0;while((len = in.read(b))!=-1){out.write(b, 0, len);}out.flush();out.close();in.close();}

请求层：

@RestController
@RequestMapping("/file")
public class FileController {@Autowiredprivate FileUtil fileUtil;@GetMapping("/tiny/download")public void tinyDownload(HttpServletResponse response) throws Exception {String filePath = "D:\\1.jpg";String fileName = "tiny下载.jpg";fileUtil.downloadTinyFile(filePath,fileName,response);}}

浏览器输入：http://localhost:9090/file/tiny/download

下载成功。

四、文件上传

使用MultipartFile上传文件

    /*** 上传文件* @param multipartFile* @param storagePath* @return* @throws Exception*/public String upload(MultipartFile multipartFile, String storagePath) throws Exception{if (multipartFile.isEmpty()) {throw new Exception("文件不能为空！");}String originalFilename = multipartFile.getOriginalFilename();String newFileName = UUID.randomUUID()+"_"+originalFilename;String filePath = storagePath+newFileName;File file = new File(filePath);if (!file.getParentFile().exists()) {file.getParentFile().mkdirs();}multipartFile.transferTo(file);return filePath;}

请求层：

@RestController
@RequestMapping("/file")
public class FileController {@Autowiredprivate FileUtil fileUtil;@PostMapping("/multipart/upload")public String download(MultipartFile file) throws Exception {String storagePath = "D:\\";return fileUtil.upload(file,storagePath);}}

使用postman工具测试：

在D盘找到此文件。

五、工具类完整代码

package com.example.file.utils;import org.apache.tomcat.util.http.fileupload.IOUtils;
import org.springframework.core.io.FileSystemResource;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Component;
import org.springframework.web.multipart.MultipartFile;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.net.URLEncoder;
import java.util.UUID;/*** 文件工具类* @author HTT*/
@Component
public class FileUtil {/*** 使用Spring框架自带的下载方式* @param filePath* @param fileName* @return*/public ResponseEntity<Resource> download(String filePath,String fileName) throws Exception {fileName = URLEncoder.encode(fileName,"UTF-8");File file = new File(filePath);if(!file.exists()){throw new Exception("文件不存在");}return ResponseEntity.ok().header(HttpHeaders.CONTENT_DISPOSITION,"attachment; filename=" + fileName ).body(new FileSystemResource(filePath));}/*** 通过IOUtils以流的形式下载* @param filePath* @param fileName* @param response*/public void download(String filePath , String fileName, HttpServletResponse response) throws Exception {fileName = URLEncoder.encode(fileName,"UTF-8");File file=new File(filePath);if(!file.exists()){throw new Exception("文件不存在");}response.setHeader("Content-disposition","attachment;filename="+ fileName);FileInputStream fileInputStream = new FileInputStream(file);IOUtils.copy(fileInputStream,response.getOutputStream());response.flushBuffer();fileInputStream.close();}/*** 原始的方法，下载一些小文件，边读边下载的* @param filePath* @param fileName* @param response* @throws Exception*/public void downloadTinyFile(String filePath,String fileName, HttpServletResponse response)throws Exception{File file = new File(filePath);fileName = URLEncoder.encode(fileName, "UTF-8");if(!file.exists()){throw new Exception("文件不存在");}FileInputStream in = new FileInputStream(file);response.setHeader("Content-Disposition", "attachment;filename="+fileName);OutputStream out = response.getOutputStream();byte[] b = new byte[1024];int len = 0;while((len = in.read(b))!=-1){out.write(b, 0, len);}out.flush();out.close();in.close();}/*** 上传文件* @param multipartFile* @param storagePath* @return* @throws Exception*/public String upload(MultipartFile multipartFile, String storagePath) throws Exception{if (multipartFile.isEmpty()) {throw new Exception("文件不能为空！");}String originalFilename = multipartFile.getOriginalFilename();String newFileName = UUID.randomUUID()+"_"+originalFilename;String filePath = storagePath+newFileName;File file = new File(filePath);if (!file.getParentFile().exists()) {file.getParentFile().mkdirs();}multipartFile.transferTo(file);return filePath;}}