HTTP文件上传原理
- 2019 年 10 月 3 日
- 笔记
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??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????HTTP?????????????????????????????????????????????????????????????????????????????????????
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HTTP????
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- ???????
post? - ???????????????
<input type="file"/>? - ????????
enctype="multipart/form-data"?
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<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> <html> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <body> <form action="<%=request.getContextPath() %>/UploadServletDemo" enctype="multipart/form-data" method="post"> ?????<input type="text" name="username"><br/> ????1?<input type="file" name="file1"><br/> ????2?<input type="file" name="file2"><br/> <input type="submit" value="??"> </form> </body> </html>??????????Servlet?
@WebServlet("/UploadServletDemo") public class UploadServletDemo extends HttpServlet{ @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); // ????(POST)?? ServletInputStream in = request.getInputStream();//???????????????????? // ??? InputStreamReader inReaser = new InputStreamReader(in); // ??? BufferedReader reader = new BufferedReader(inReaser); String str = null; while ((str=reader.readLine()) != null){ System.out.println(str); } } }?????????????Fiddler??????????????Post?????????????????
POST http://localhost:8080/javawebservlet_war/UploadServletDemo HTTP/1.1 Host: localhost:8080 Connection: keep-alive Content-Length: 446 Cache-Control: max-age=0 Origin: http://localhost:8080 Upgrade-Insecure-Requests: 1 Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryqj67FUBQUHXZj78G User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.131 Safari/537.36 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3 Referer: http://localhost:8080/javawebservlet_war/ Accept-Encoding: gzip, deflate, br Accept-Language: zh-CN,zh;q=0.9,en;q=0.8,und;q=0.7,zh-TW;q=0.6 Cookie: JSESSIONID=6BE280EF3CBE213F73430FFDF015DE97 ------WebKitFormBoundaryqj67FUBQUHXZj78G Content-Disposition: form-data; name="username" abc ------WebKitFormBoundaryqj67FUBQUHXZj78G Content-Disposition: form-data; name="file1"; filename="??1.txt" Content-Type: text/plain ABC??1 ------WebKitFormBoundaryqj67FUBQUHXZj78G Content-Disposition: form-data; name="file2"; filename="??2.txt" Content-Type: text/plain BDF??2 ------WebKitFormBoundaryqj67FUBQUHXZj78G--?????????????HTTP?????????HTTP??????????????????????????????????????
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryqj67FUBQUHXZj78G??????????boundary???????????????????boundary???????????------FormBoundary????------FormBoundary????????
------FormBoundary Content-Disposition: form-data; name="param1" value1 ------FormBoundary??boundary????????????????????????????????????????????Content-Disposition??????????????????form-data?name?????????????????????????????Content-Type??????????MIME????????????????????????
HTTP???????????????????????????????????????????????????????????????????
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boundary???????--
FileUpload??
?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????Bug?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????
??????????FileUploadDemo???????????FileUpload???
FileUpload Demo
??????????Demo?
@WebServlet("/FileUpload") public class FileUploadDemo extends HttpServlet { @Override public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { DiskFileItemFactory fac = new DiskFileItemFactory(); ServletFileUpload upload = new ServletFileUpload(fac); upload.setFileSizeMax(10 * 1024 * 1024); upload.setSizeMax(20 * 1024 * 1024); if (upload.isMultipartContent(request)) { try { List<FileItem> list = upload.parseRequest(request); for (FileItem item : list) { if (item.isFormField()) { String fileName = item.getFieldName(); String value = item.getString("UTF-8"); System.out.println(fileName + ":" + value); } else { String name = item.getName(); String id = UUID.randomUUID().toString(); name = id + name; String realPath = getServletContext().getRealPath("/upload"); File file = new File(realPath, name); item.write(file); item.delete(); } } } catch (Exception e) { e.printStackTrace(); } } else { System.out.println("????"); } } }??
???????HTTP?????????????????????????????????
2019?7?31? ?????????
