在Web專案裡多少都會遇到檔案上傳到Server或從Server端下載資料的需求，今日就來看看Java EE提供什麼樣子的解決方案
Servlet3.0起新增了Part interface，讓我們可以更簡單的處理檔案上下傳
@MultipartConfig(
fileSizeThreshold = 1024 * 1024 //1MB The size threshold after which the file will be written to disk
,maxFileSize = 5* 1024 * 1024 //5MB The maximum size allowed for uploaded files.
,maxRequestSize = 5* 5* 1024 * 1024 //5MB The maximum size allowed for multipart/form-data requests
)
@WebServlet("/UploadFileServlet")
public class UploadFileServlet extends HttpServlet {
public void doPost(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException {
String filePath = getServletContext().getRealPath("file_upload") ;
System.out.println("filePath；"+filePath);
File file = new File(filePath);
if (!file.exists()) {
file.mkdirs();
}
Collection<Part> parts = req.getParts();
for (Part part : parts) {
String fileName = part.getSubmittedFileName();
System.out.println("upload filename；"+fileName);
part.write(filePath+File.separator+fileName);
}
System.out.println("file upload success!!");
}
}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Demo Fileupload and Download</title>
</head>
<body>
<h5>上傳檔案：</h5>
<form action="/UploadFileServlet" method="post" enctype="multipart/form-data">
<input type="file" name="選擇檔案">
<input type="submit" value="上傳">
</form>
</body>
</html>
訪問index.html上傳任意檔案
上傳payload
server log
@WebServlet(urlPatterns = "/DownloadServlet")
public class DownloadServlet extends HttpServlet {
protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
String file = "火影忍者.jpg";
String mimeType = getServletContext().getMimeType(file);
res.setContentType(mimeType);
//解決中文檔名問題
String fileName = URLEncoder.encode(file, "UTF8");
res.setHeader("Content-Disposition", "attachment; filename=\""+fileName+"\"");
//io stream操作 method1
String filePath = getServletContext().getRealPath("download")+ File.separator+file;
FileInputStream is = new FileInputStream(filePath);
ServletOutputStream outputStream = res.getOutputStream();
byte[] bytes = is.readAllBytes();
outputStream.write(bytes);
is.close();
//io stream操作 method2
//getServletContext().getResourceAsStream("/download/"+file).transferTo(res.getOutputStream());
}
}
index.html增加連結
<h5>下載檔案：</h5>
<a href="DownloadServlet">Download</a>
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