Java POSTing 文件导致 HTTP 422

Question

我正在尝试构建一个小型 Java 应用程序来连接到名为 CampFire 的应用程序，但在尝试将文件上传到系统时遇到了麻烦。我用来上传文件的Java代码如下:

public static String postFile(String requestUri, File f)
{
  debug("Running postFile.");
  logIn();

  debug("Sending File: " + f.getAbsolutePath() + " to " + campFireURL + requestUri);

  URL url;
  URLConnection conn;

  String linebreak = "\r\n";
  String boundary = "**********xxx**********";
  String twoHyphens = "--";


  String result = "";
  String request = twoHyphens + boundary + linebreak +
    "Content-Disposition: form-data; name=\"upload\"; filename=\"" + f.getName() + "\"" + linebreak +
    linebreak +
    "";
  debug("Request: " + request);

  try
  {
   FileInputStream in = new FileInputStream(f);

   auth.resetTries();
   Authenticator.setDefault(auth);

   // Send data
   url = new URL(campFireURL + requestUri);
   conn = url.openConnection();
   conn.setDoOutput(true);
   conn.setDoInput(true);
   conn.setUseCaches(false);

   conn.setRequestProperty("Connection", "Keep-Alive");
   conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);

   DataOutputStream wr = new DataOutputStream(conn.getOutputStream());

   wr.writeBytes(request);

   int i;
   while((i = in.read()) != -1)
   {
    wr.write(i);
   }

   wr.writeBytes(linebreak + twoHyphens + boundary + twoHyphens + linebreak);
   wr.flush();

   wr.close();
   in.close();

   result = readFromConnection(conn);
  }
  catch (Exception e)
  {
   debug(e);
   JOptionPane.showMessageDialog(null, "Error running postData: " + e.getMessage(), "HTTP POST Error", JOptionPane.ERROR_MESSAGE);
   die();
  }

  return(result);
 }

当我使用真实文件运行它时，我收到以下错误......

Running postFile.
Sending File: /home/myuser/Desktop/blah.png to https://blah.campfirenow.com/room/blah/uploads.xml
Request: --**********xxx**********
Content-Disposition: form-data; name="upload"; filename="blah.png"
Server returned HTTP response code: 422 for URL: blah blah
java.io.IOException: Server returned HTTP response code: 422 for URL: blah blah

知道我在这里做错了什么吗？我对 Java 还很陌生，想知道我是否错过了一些明显的东西？

Answer 1

HTTP error 422意思是“不可处理的实体”。快速浏览后，我发现一个错误:PNG 文件是二进制文件。您必须添加 Content-Transfer-Encoding: binary到该部分的标题。

如果仍然不起作用，那么您可以在 this answer 底部的上传文件部分找到示例。有用。