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">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()。