我正在尝试使用“multipart/form-data”发出 POST 请求，我需要发布一个文件（下面的代码）和 4 个参数（名称、类别...）所有字符串。我已经可以使用下面的代码发送文件，但不能使用参数。    // open a URL connection to the Servlet    FileInputStream fileInputStream = new FileInputStream(sourceFile);    URL url = new URL(upLoadServerUri);    // Open a HTTP  connection to  the URL    conn = (HttpURLConnection) url.openConnection();    conn.setDoInput(true); // Allow Inputs    conn.setDoOutput(true); // Allow Outputs    conn.setUseCaches(false); // Don't use a Cached Copy    conn.setRequestMethod("POST");    conn.setRequestProperty("Connection", "Keep-Alive");    conn.setRequestProperty("ENCTYPE", "multipart/form-data");    conn.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);    conn.setRequestProperty("fileToUpload", fileName);    dos = new DataOutputStream(conn.getOutputStream());    dos.writeBytes(twoHyphens + boundary + lineEnd);    dos.writeBytes("Content-Disposition: form-data; name=\"fileToUpload\";filename=" + fileName + "" + lineEnd);    dos.writeBytes(lineEnd);    // create a buffer of  maximum size    bytesAvailable = fileInputStream.available();    bufferSize = Math.min(bytesAvailable, maxBufferSize);    buffer = new byte[bufferSize];    // read file and write it into form...    bytesRead = fileInputStream.read(buffer, 0, bufferSize);    while (bytesRead > 0) {        dos.write(buffer, 0, bufferSize);        bytesAvailable = fileInputStream.available();        bufferSize = Math.min(bytesAvailable, maxBufferSize);        bytesRead = fileInputStream.read(buffer, 0, bufferSize);    }但是服务器从来不注册参数，我该如何解决这个问题？