multipart原理简介
multipart的流是服务器临时文件流
multipart的流不是HTTPRequest的流，而是服务器的临时文件流
multipart/form-data是表单上传，接口可以从Mutipartfile对象获取输入流getInputStream，表面上看没产生临时文件
org.springframework.web.multipart.support.StandardMultipartHttpServletRequest的getInputStream
@Override
public InputStream getInputStream() throws IOException {
return this.part.getInputStream();
}
这里面的流是从DiskFileItem（一眼磁盘）拿的，还告诉了你临时目录位置location
multipartfile生成临时文件到默认文件夹
从原理上看，在tomcat源码的org.apache.catalina.connector.Request类中，parseParts方法就将multipart格式的请求中文件生成到临时文件夹
File location;
String locationStr = mce.getLocation();
if (locationStr == null || locationStr.length() == 0) {
location = ((File) context.getServletContext().getAttribute(
ServletContext.TEMPDIR));
} else {
// If relative, it is relative to TEMPDIR
location = new File(locationStr);
if (!location.isAbsolute()) {
location = new File(
(File) context.getServletContext().getAttribute(ServletContext.TEMPDIR),
locationStr).getAbsoluteFile();
}
}
临时文件的目录可配
这个location就是javax.servlet.MultipartConfigElement的配置，可以通过spring.servlet.multipart系列配置的location指定临时文件目录，这个临时文件用完，也会被自动清除
private final String location;// = "";
private final long maxFileSize;// = -1;
private final long maxRequestSize;// = -1;
private final int fileSizeThreshold;// = 0;
Mutipartfile的文件默认来自临时文件
Mutipartfile的注释中说明了，文件是stored in memory or temporarily on disk，存在内存或磁盘临时文件的，所以上传大文件时，会发现前端进度条走完了，代码才走进自己写得接口代码
/**
* A representation of an uploaded file received in a multipart request.
*
* <p>The file contents are either stored in memory or temporarily on disk.
* In either case, the user is responsible for copying file contents to a
* session-level or persistent store as and if desired. The temporary storage
* will be cleared at the end of request processing.
*
* @author Juergen Hoeller
* @author Trevor D. Cook
* @since 29.09.2003
* @see org.springframework.web.multipart.MultipartHttpServletRequest
* @see org.springframework.web.multipart.MultipartResolver
*/
public interface MultipartFile extends InputStreamSource {
Mutipartfile产生临时文件的好处坏处
好处
帮开发封装了上传逻辑
可以在此基础实现切片上传到本地最后合并
坏处
对我来说
文件转储时间翻倍：我的文件存储服务器不是接收请求的服务所在服务器，我还得把文件转存到文件服务器，而服务到文件服务器还得再传一遍，时间基本double
前端进度不真实：前端显示的上传进度仅是浏览器给到服务的进度
占用资源：临时文件多少占点服务器磁盘空间文章来源：https://www.toymoban.com/news/detail-622844.html
纯流式上传application/octet-stream
一段半伪代码，application/octet-stream参数体只能有文件，参数通过放headers里给就可以解决这个问题文章来源地址https://www.toymoban.com/news/detail-622844.html
@PostMapping(value = "/upload", headers = "content-type=application/octet-stream;charset=utf-8")
public Object upload(HttpServletRequest request,
@RequestHeader("userId") String userId,
@RequestHeader("fileName") String fileName,
@RequestHeader("fileSize") String fileSize,
@RequestHeader("dirId") String dirId) {
try (InputStream in = request.getInputStream()) {
fileName = URLDecoder.decode(fileName,"utf-8");
uploadFileServer(in, fileName, fileSize, userId, dirId);
return "success";
} catch (Exception e) {
log.error("上传报错", e);
return "error";
}
}
到了这里，关于SpringBoot：使用application/octet-stream 流式上传大文件，解决Mutipartfile multipart/form-data上传产生临时文件问题的文章就介绍完了。如果您还想了解更多内容，请在右上角搜索TOY模板网以前的文章或继续浏览下面的相关文章，希望大家以后多多支持TOY模板网！
