<!-- 上傳下載需要設(shè)計到的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導(dǎo)入高版本的-->
  <dependency>
   <groupId>javax.servlet</groupId>
   <artifactId>javax.servlet-api</artifactId>
   <version>4.0.1</version>
  </dependency>
  <!-- 圖片處理類 -->
  <dependency>
   <groupId>net.coobird</groupId>
   <artifactId>thumbnailator</artifactId>
   <version>0.4.8</version>
  </dependency>

# 上傳文件大小
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系統(tǒng)
   registry.addResourceHandler("/upload/**").addResourceLocations("file:"+dirPath);
  } else {
   registry.addResourceHandler("/upload/**").addResourceLocations("file:"+dirPath);
  }
 }

}

// 上傳文件
 @ResponseBody
 @RequestMapping("/upload")
 public String fileUpload(@RequestParam("files") MultipartFile files) throws IOException {
//  // win系統(tǒng) 上傳路徑保存設(shè)置
//  // 獲取項目路徑
//  File projectPath = new File(ResourceUtils.getURL("classpath:").getPath());
//  // 絕對路徑=項目路徑+自定義路徑
//  File pathFile = new File(projectPath.getAbsolutePath(), "static/upload/");
//  if (!pathFile.exists()) {
//   pathFile.mkdirs();
//  }
//  //上傳文件地址
//  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服務(wù)器 上傳路徑保存設(shè)置
  // 項目路徑 /home/www/
  File pathFile = new File("/home/www/upload/");
  if (!pathFile.exists()) {
   pathFile.mkdirs();
  }
  //上傳文件地址
  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>圖片上傳</label>
　　　　<input type='file' style='margin: 5px;' name='files' required><br>
　　　　<button type="button" class="layui-btn" id="img_upload">上傳圖片</button>
　　</div>
　　<input type="submit">
</form>

//普通圖片上傳
  $('#img_upload').click(function () {
   var formData = new FormData();
   //獲取選擇的文件
   $.each($('input[name="files"]'),function (index,item) {
    formData.append("files",item.files[0])
   });

   //發(fā)送異步請求
   $.ajax({
    method:'post',
    url: '[[@{/user/upload}]]', // 文件上傳接口
    data:formData,
    processData: false,
    contentType:false,
    success:function (data) {
     //成功返回觸發(fā)的方法
     $('#imgPath').val(data);
     alert("上傳成功");
    },
    //請求失敗觸發(fā)的方法
    error:function () {
     alert("上傳失敗");
    }
   });
  });

@RequestMapping(value="/download")
public String downloads(HttpServletResponse response ,HttpServletRequest request) throws Exception{
 //要下載的圖片地址
 String path = request.getServletContext().getRealPath("/upload");
 String fileName = "基礎(chǔ)語法.jpg";

 //1、設(shè)置response 響應(yīng)頭
 response.reset(); //設(shè)置頁面不緩存,清空buffer
 response.setCharacterEncoding("UTF-8"); //字符編碼
 response.setContentType("multipart/form-data"); //二進制傳輸數(shù)據(jù)
 //設(shè)置響應(yīng)頭
 response.setHeader("Content-Disposition",
   "attachment;fileName="+URLEncoder.encode(fileName, "UTF-8"));

 File file = new File(path,fileName);
 //2、 讀取文件--輸入流
 InputStream input=new FileInputStream(file);
 //3、 寫出文件--輸出流
 OutputStream out = response.getOutputStream();

 byte[] buff =new byte[1024];
 int index=0;
 //4、執(zhí)行 寫出操作
 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" >點擊下載</a>