springboot实现文件上传和下载功能

spring boot 引入”约定大于配置“的概念,实现自动配置,节约了开发人员的开发成本,并且凭借其微服务架构的方式和较少的配置,一出来就占据大片开发人员的芳心。大部分的配置从开发人员可见变成了相对透明了,要想进一步熟悉还需要关注源码。

1.文件上传(前端页面):

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 
<html> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 
<title>Insert title here</title> 
</head> 
<body> 
<form action="/testUpload" method="POST" enctype="multipart/form-data"> 
 <input type="file" name="file"/> 
 <input type="submit" /> 
</form> 
<a href="/testDownload" rel="external nofollow" >下载</a> 
</body> 
</html>

 表单提交加上enctype="multipart/form-data"很重要,文件以二进制流的形式传输。

2.文件上传(后端java代码)支持多文件

Way1.使用MultipartHttpServletRequest来处理上传请求,然后将接收到的文件以流的形式写入到服务器文件中:

@RequestMapping(value="/testUpload",method=RequestMethod.POST) 
 public void testUploadFile(HttpServletRequest req,MultipartHttpServletRequest multiReq) throws IOException{ 
  FileOutputStream fos=new FileOutputStream(new File("F://test//src//file//upload.jpg")); 
  FileInputStream fs=(FileInputStream) multiReq.getFile("file").getInputStream(); 
  byte[] buffer=new byte[1024]; 
  int len=0; 
  while((len=fs.read(buffer))!=-1){ 
   fos.write(buffer, 0, len); 
  } 
  fos.close(); 
  fs.close(); 
 } 

Way2.也可以这样来取得上传的file流:

// 文件上传
 @RequestMapping("/fileUpload")
 public Map fileUpload(@RequestParam("file") MultipartFile file, HttpServletRequest req) {
  Map result = new HashMap();
  SimpleDateFormat df = new SimpleDateFormat("yyyyMMdd");// 设置日期格式
  String dateDir = df.format(new Date());// new Date()为获取当前系统时间
  String serviceName = UuidUtil.get32UUID()
    + file.getOriginalFilename().substring(file.getOriginalFilename().lastIndexOf("."));
  File tempFile = new File(fileDir + dateDir + File.separator + serviceName);
  if (!tempFile.getParentFile().exists()) {
   tempFile.getParentFile().mkdirs();
  }
  if (!file.isEmpty()) {
   try {
    BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(tempFile));
    // "d:/"+file.getOriginalFilename() 指定目录
    out.write(file.getBytes());
    out.flush();
    out.close();
   } catch (FileNotFoundException e) {
    e.printStackTrace();
    result.put("msg", "上传失败," + e.getMessage());
    result.put("state", false);
    return result;
   } catch (IOException e) {
    e.printStackTrace();
    result.put("msg", "上传失败," + e.getMessage());
    result.put("state", false);
    return result;
   }
   result.put("msg", "上传成功");
   String fileId = Get8uuid.generateShortUuid();
   String fileName = file.getOriginalFilename();
   String fileType = fileName.substring(fileName.lastIndexOf(".") + 1);
   String fileUrl = webDir + dateDir + '/' + serviceName;
   uploadMapper.saveFileInfo(fileId, serviceName, fileType, fileUrl);
   result.put("state", true);
   return result;
  } else {
   result.put("msg", "上传失败,因为文件是空的");
   result.put("state", false);
   return result;
  }

3.application.properties配置文件

#上传文件大小设置
multipart.maxFileSize=500Mb
multipart.maxRequestSize=500Mb

4.文件下载将文件写到输出流里:

@RequestMapping(value="/testDownload",method=RequestMethod.GET) 
public void testDownload(HttpServletResponse res) throws IOException{ 
 File file = new File("C:/test.txt");
  resp.setHeader("content-type", "application/octet-stream");
  resp.setContentType("application/octet-stream");
  resp.setHeader("Content-Disposition", "attachment;filename=" + fileName);
  byte[] buff = new byte[1024];
  BufferedInputStream bis = null;
  OutputStream os = null;
  try {
  os = resp.getOutputStream();
  bis = new BufferedInputStream(new FileInputStream(file));
  int i = bis.read(buff);
  while (i != -1) {
  os.write(buff, 0, buff.length);
  os.flush();
  i = bis.read(buff);
  }
  } catch (IOException e) {
  e.printStackTrace();
  } finally {
  if (bis != null) {
  try {
  bis.close();
  } catch (IOException e) {
  e.printStackTrace();
  }
  }
 }

} 

5.获取文件大小

// 文件大小转换
DecimalFormat df1 = new DecimalFormat("0.00");
String fileSizeString = "";
long fileSize = file.getSize();
if (fileSize < 1024) {
 fileSizeString = df1.format((double) fileSize) + "B";
 } else if (fileSize < 1048576) {
 fileSizeString = df1.format((double) fileSize / 1024) + "K";
 } else if (fileSize < 1073741824) {
 fileSizeString = df1.format((double) fileSize / 1048576) + "M";
 } else {
 fileSizeString = df1.format((double) fileSize / 1073741824) + "G";
 }

如果是File类则fileSize=file.length()。

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持编程小技巧。

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