// 單文件上傳
@RequestMapping(value = "/upload")
@ResponseBody
public String upload(@RequestParam("file") MultipartFile file) {
 try {
 if (file.isEmpty()) {
  return "文件為空";
 }
 // 獲取文件名
 String fileName = file.getOriginalFilename();
 logger.info("上傳的文件名為：" + fileName);
 // 獲取文件的后綴名
 String suffixName = fileName.substring(fileName.lastIndexOf("."));
 logger.info("文件的后綴名為：" + suffixName);

 // 設置文件存儲路徑
 String filePath = "D://aim//";
 String path = filePath + fileName + suffixName;

 File dest = new File(path);
 // 檢測是否存在目錄
 if (!dest.getParentFile().exists()) {
  dest.getParentFile().mkdirs();// 新建文件夾
 }
 file.transferTo(dest);// 文件寫入
 return "上傳成功";
 } catch (IllegalStateException e) {
  e.printStackTrace();
 } catch (IOException e) {
  e.printStackTrace();
 }
 return "上傳失敗";
}

//多文件上傳
@RequestMapping(value = "/uploadMore", method = RequestMethod.POST)
@ResponseBody
public String handleFileUpload(HttpServletRequest request) {
 List<MultipartFile> files = ((MultipartHttpServletRequest) request).getFiles("file");
 MultipartFile file = null;
 BufferedOutputStream stream = null;
 for (int i = 0; i < files.size(); ++i) {
  file = files.get(i);
  String filePath = "D://aim//";
  if (!file.isEmpty()) {
   try {
    byte[] bytes = file.getBytes();
    stream = new BufferedOutputStream(new FileOutputStream(
      new File(filePath + file.getOriginalFilename())));//設置文件路徑及名字
    stream.write(bytes);// 寫入
    stream.close();
   } catch (Exception e) {
    stream = null;
    return "第 " + i + " 個文件上傳失敗 ==> "
      + e.getMessage();
   }
  } else {
   return "第 " + i
     + " 個文件上傳失敗因為文件為空";
  }
 }
 return "上傳成功";
}

//文件下載相關代碼
@RequestMapping("/download")
public String downloadFile(HttpServletRequest request, HttpServletResponse response) {
 String fileName = "aim_test.txt";// 設置文件名，根據業務需要替換成要下載的文件名
 if (fileName != null) {
  //設置文件路徑
  String realPath = "D://aim//"
  File file = new File(realPath , fileName);
  if (file.exists()) {
   response.setContentType("application/force-download");// 設置強制下載不打開
   response.addHeader("Content-Disposition", "attachment;fileName=" + fileName);// 設置文件名
   byte[] buffer = new byte[1024];
   FileInputStream fis = null;
   BufferedInputStream bis = null;
   try {
    fis = new FileInputStream(file);
    bis = new BufferedInputStream(fis);
    OutputStream os = response.getOutputStream();
    int i = bis.read(buffer);
    while (i != -1) {
     os.write(buffer, 0, i);
     i = bis.read(buffer);
    }
    System.out.println("success");
   } catch (Exception e) {
    e.printStackTrace();
   } finally {
    if (bis != null) {
     try {
      bis.close();
     } catch (IOException e) {
      e.printStackTrace();
     }
    }
    if (fis != null) {
     try {
      fis.close();
     } catch (IOException e) {
      e.printStackTrace();
     }
    }
   }
  }
 }
 return null;
}

@Configuration
public class MultipartConfig {

 @Bean
 public MultipartConfigElement multipartConfigElement() {
  MultipartConfigFactory factory = new MultipartConfigFactory();
  // 置文件大小限制 ,超出此大小頁面會拋出異常信息
  factory.setMaxFileSize("2MB"); //KB,MB
  // 設置總上傳數據總大小
  factory.setMaxRequestSize("20MB");
  // 設置文件臨時文件夾路徑
  // factory.setLocation("E://test//");
  // 如果文件大于這個值，將以文件的形式存儲，如果小于這個值文件將存儲在內存中，默認為0
  // factory.setMaxRequestSize(0);
  return factory.createMultipartConfig();
 }
}