[Java] SpringBoot 文件或图片上传与下载功能的实现

<!-- 上传下载需要设计到的jar包 -->
<dependency>
 <groupId>commons-io</groupId>
 <artifactId>commons-io</artifactId>
 <version>2.6</version>
</dependency>
<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>
<!-- 图片处理类 -->
<dependency>
 <groupId>net.coobird</groupId>
 <artifactId>thumbnailator</artifactId>
 <version>0.4.8</version>
</dependency>

# 上传文件大小
spring.servlet.multipart.max-file-size=5MB
spring.servlet.multipart.max-request-size=5MB

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {
 
 @Override
 public void addResourceHandlers(ResourceHandlerRegistry registry) {
  ApplicationHome h = new ApplicationHome(getClass());
  File jarF = h.getSource();
  String dirPath = jarF.getParentFile().toString()+"/upload/";
 
  String os = System.getProperty("os.name");
 
  if (os.toLowerCase().startsWith("win")) { //如果是Windows系统
   registry.addResourceHandler("/upload/**").addResourceLocations("file:"+dirPath);
  } else {
   registry.addResourceHandler("/upload/**").addResourceLocations("file:"+dirPath);
  }
 }
 
}

// 上传文件
 @ResponseBody
 @RequestMapping("/upload")
 public String fileUpload(@RequestParam("files") MultipartFile files) throws IOException {
//  // win系统 上传路径保存设置
//  // 获取项目路径
//  File projectPath = new File(ResourceUtils.getURL("classpath:").getPath());
//  // 绝对路径=项目路径+自定义路径
//  File pathFile = new File(projectPath.getAbsolutePath(), "static/upload/");
//  if (!pathFile.exists()) {
//   pathFile.mkdirs();
//  }
//  //上传文件地址
//  UUID uuid = UUID.randomUUID();
//  File serverFile = new File(pathFile, uuid + "_" + files.getOriginalFilename());
//  files.transferTo(serverFile);
//
//  String imgPath = ("/upload/" + uuid + "_" + files.getOriginalFilename()).replace("\", "/");
//
//  return imgPath;
 
  // Linux服务器 上传路径保存设置
  // 项目路径 /home/www/
  File pathFile = new File("/home/www/upload/");
  if (!pathFile.exists()) {
   pathFile.mkdirs();
  }
  //上传文件地址
  UUID uuid = UUID.randomUUID();
  File serverFile = new File(pathFile, uuid + "_" + files.getOriginalFilename());
  files.transferTo(serverFile);
 
  String imgPath = ("/upload/" + uuid + "_" + files.getOriginalFilename()).replace("\", "/");
 
  return imgPath;
 }

<form action="" class="layui-form" enctype="multipart/form-data" method="post">
<input type="hidden" name="blogImg" id="imgPath" value="">
<div class="form-group">
<label>图片上传</label>
<input type='file' style='margin: 5px;' name='files' required><br>
<button type="button" class="layui-btn" id="img_upload">上传图片</button>
</div>
<input type="submit">
</form>

//普通图片上传
  $('#img_upload').click(function () {
   var formData = new FormData();
   //获取选择的文件
   $.each($('input[name="files"]'),function (index,item) {
  formData.append("files",item.files[0])
   });
 
   //发送异步请求
   $.ajax({
  method:'post',
  url: '[[@{/user/upload}]]', // 文件上传接口
  data:formData,
  processData: false,
  contentType:false,
  success:function (data) {
   //成功返回触发的方法
   $('#imgPath').val(data);
   alert("上传成功");
  },
  //请求失败触发的方法
  error:function () {
   alert("上传失败");
  }
   });
  });

@RequestMapping(value="/download")
public String downloads(HttpServletResponse response ,HttpServletRequest request) throws Exception{
 //要下载的图片地址
 String path = request.getServletContext().getRealPath("/upload");
 String fileName = "基础语法.jpg";
 
 //1、设置response 响应头
 response.reset(); //设置页面不缓存,清空buffer
 response.setCharacterEncoding("UTF-8"); //字符编码
 response.setContentType("multipart/form-data"); //二进制传输数据
 //设置响应头
 response.setHeader("Content-Disposition",
   "attachment;fileName="+URLEncoder.encode(fileName, "UTF-8"));
 
 File file = new File(path,fileName);
 //2、 读取文件--输入流
 InputStream input=new FileInputStream(file);
 //3、 写出文件--输出流
 OutputStream out = response.getOutputStream();
 
 byte[] buff =new byte[1024];
 int index=0;
 //4、执行 写出操作
 while((index= input.read(buff))!= -1){
  out.write(buff, 0, index);
  out.flush();
 }
 out.close();
 input.close();
 return null;
}

<a href="/download" rel="external nofollow" >点击下载</a>