java - 我们是否需要在服务器端添加规定，以便浏览器中的文件下载可以提供暂停和恢复的便利？

Question

我创建了一个 URL，用户可以通过该 URL 下载 zip 文件。我想知道是否需要在服务器端添加某种规定，以便下载 zip 的客户端可以提供对挂起和恢复的支持。

它是用java实现的:

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // reads input file from an absolute path

  String filePath = "path to my zip file";

  File downloadFile = new File(filePath);
  FileInputStream inStream = new FileInputStream(downloadFile);

  // if you want to use a relative path to context root:
  String relativePath = getServletContext().getRealPath("");
  System.out.println("relativePath = " + relativePath);

  // obtains ServletContext
  ServletContext context = getServletContext();

  // gets MIME type of the file
  String mimeType = context.getMimeType(filePath);
  if (mimeType == null) {        
      // set to binary type if MIME mapping not found
      mimeType = "application/octet-stream";
  }
  System.out.println("MIME type: " + mimeType);

  // modifies response
  response.setContentType(mimeType);
  response.setContentLength((int) downloadFile.length());

  // forces download
  String headerKey = "Content-Disposition";
  String headerValue = String.format("attachment; filename=\"%s\"", downloadFile.getName());
  response.setHeader(headerKey, headerValue);

  // obtains response's output stream
  OutputStream outStream = response.getOutputStream();

  byte[] buffer = new byte[4096];
  int bytesRead = -1;

  while ((bytesRead = inStream.read(buffer)) != -1) {
      outStream.write(buffer, 0, bytesRead);
  }

  inStream.close();
  outStream.close();   
}

Answer 1

如果您想支持挂起和恢复，则需要添加对部分 GET 的支持，也称为对范围或范围 header 的支持。

RFC2616(第 14.35 节)详细介绍了如何处理范围请求。 https://www.rfc-editor.org/rfc/rfc2616#section-14.35

Tomcat 的默认 servlet 有一个实现，如果您愿意，您可以将其用作起点。 http://svn.apache.org/viewvc/tomcat/trunk/java/org/apache/catalina/servlets/DefaultServlet.java?view=annotate