通过 URLConnection 将音频文件从客户端传输到 Http 服务器

Question

我目前正在我的学校从事一个编程项目。我需要将音频文件（MIDI 格式）从客户端成功发送到 Http 服务器。我自己已经尝试过这样做，并在互联网和 Stackoverflow 论坛上进行了大量研究。目前可以将文件从客户端发送到服务器，但在服务器端，音频文件无法播放。

以下是客户端代码：

private static void sendPOST() throws IOException{
    final int mid = 1;
    final String POST_URL = "http://localhost:8080/musiker/hörprobe?mid="+mid;
    final File uploadFile = new File("C://Users//Felix Ulbrich//Desktop//EIS Prototype MIDIs//Pop//BabyOneMoreTime.mid");
    String boundary = Long.toHexString(System.currentTimeMillis()); 
    String CRLF = "\r\n";
    String charset = "UTF-8";
    URLConnection connection = new URL(POST_URL).openConnection();
    connection.setDoOutput(true);
    connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);
    try (
            OutputStream output = connection.getOutputStream();
            PrintWriter writer = new PrintWriter(new OutputStreamWriter(output, charset), true);
        ){
        writer.append("--" + boundary).append(CRLF);
        writer.append("Content-Disposition: form-data; name=\"binaryFile\"; filename=\"" + uploadFile.getName() + "\"").append(CRLF);
        writer.append("Content-Type: " + URLConnection.guessContentTypeFromName(uploadFile.getName())).append(CRLF);
        writer.append("Content-Transfer-Encoding: binary").append(CRLF);
        writer.append(CRLF).flush();
        Files.copy(uploadFile.toPath(), output);
        output.flush();
        writer.append(CRLF).flush();

        writer.append("--" + boundary + "--").append(CRLF).flush();

        int responseCode = ((HttpURLConnection) connection).getResponseCode();
        System.out.println(responseCode);
        }
}

以下是服务器端代码：

int FILE_SIZE = Integer.MAX_VALUE-2;
                    int bytesRead = 0;
                    int current = 0;
                    FileOutputStream fos = null;
                    BufferedOutputStream bos = null;
                    byte[] mybytearray = new byte[FILE_SIZE];
                    String FILE_TO_RECEIVED = "C://root//m"+musikerid+"hp"+(hörprobenzaehler+1)+".mid";
                    File f = new File(FILE_TO_RECEIVED);
                    if(!f.exists()){
                        f.createNewFile();
                    }
                    InputStream input = t.getRequestBody();
                    fos = new FileOutputStream(FILE_TO_RECEIVED);
                    bos = new BufferedOutputStream(fos);
                    bytesRead = input.read(mybytearray,0,mybytearray.length);
                    current = bytesRead;
                    do{
                        bytesRead = input.read(mybytearray, current, mybytearray.length-current);
                        if(bytesRead >= 0){
                            current += bytesRead;
                        }
                    }while(bytesRead>-1);

                    bos.write(mybytearray,0,current);
                    bos.flush();
                    fos.close();
                    bos.close();
                    t.sendResponseHeaders(200, 0);
                    input.close();

我现在很绝望，因为我找不到任何解决这个问题的方法。我需要使用 HTTP 服务器，但不需要使用 TCP 协议（​​现在通过流使用）。我想了一个通过 ftp 的解决方案，所以我不需要先将文件转换为字节数组。我认为问题就在那里。服务器无法从字节数组正确创建音频文件（midi 文件）。如果你们中的任何人知道解决方案。请问，我需要你的帮助：D

你好，Gizpo

Answer 1

所以我已经深入研究了这个问题。我发现了几个问题：

• 您正在混合基于二进制和字符的 I/O。虽然您在客户端侥幸逃脱，但服务器却很难处理。
• 您忘记指定要发送到服务器的文件的大小。在服务器端，您无法知道（除非有人事先告诉您）（传入文件的）大小。

我已经编辑了你的代码并想出了这个：

---

客户：

private static void sendPOST() throws IOException{
        final int mid = 1;
        final String POST_URL = "http://localhost:8080/musiker/hörprobe?mid="+mid;
        final File uploadFile = new File("C://Users//Felix Ulbrich//Desktop//EIS Prototype MIDIs//Pop//BabyOneMoreTime.mid");

        String boundary = Long.toHexString(System.currentTimeMillis()); 
        String CRLF = "\r\n";
        String charset = "UTF-8";
        URLConnection connection = new URL(POST_URL).openConnection();
        connection.setDoOutput(true);
        connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);
        
        try (
            OutputStream output = connection.getOutputStream();
            PrintWriter writer = new PrintWriter(new OutputStreamWriter(output, charset), true);
        ) {
            writer.append("--" + boundary).append(CRLF);
            writer.append("Content-Disposition: form-data; name=\"binaryFile\"; filename=\"" + uploadFile.getName() + "\"").append(CRLF);
            writer.append("Content-Length: " + uploadFile.length()).append(CRLF);
            writer.append("Content-Type: " + URLConnection.guessContentTypeFromName(uploadFile.getName())).append(CRLF);
            writer.append("Content-Transfer-Encoding: binary").append(CRLF);
            writer.append(CRLF).flush();
            Files.copy(uploadFile.toPath(), output);
            output.flush();

            int responseCode = ((HttpURLConnection) connection).getResponseCode();
            System.out.println("Response code: [" + responseCode + "]");
        }
    }

服务器：

@Override
public void handle(HttpExchange t) throws IOException {
    String CRLF = "\r\n";
    int fileSize = 0;
    
    String FILE_TO_RECEIVED = "C://root//m"+musikerid+"hp"+(hörprobenzaehler+1)+".mid";
    File f = new File(FILE_TO_RECEIVED);
    if (!f.exists()) {
        f.createNewFile();
    }
    
    InputStream input = t.getRequestBody();
    String nextLine = "";
    do {
        nextLine = readLine(input, CRLF);
        if (nextLine.startsWith("Content-Length:")) {
            fileSize = 
                Integer.parseInt(
                    nextLine.replaceAll(" ", "").substring(
                        "Content-Length:".length()
                    )
                );
        }
        System.out.println(nextLine);
    } while (!nextLine.equals(""));
    
    byte[] midFileByteArray = new byte[fileSize];
    int readOffset = 0;
    while (readOffset < fileSize) {
        int bytesRead = input.read(midFileByteArray, readOffset, fileSize);
        readOffset += bytesRead;
    }
    
    BufferedOutputStream bos = 
        new BufferedOutputStream(new FileOutputStream(FILE_TO_RECEIVED));
    
    bos.write(midFileByteArray, 0, fileSize);
    bos.flush();
    
    t.sendResponseHeaders(200, 0);
}

private static String readLine(InputStream is, String lineSeparator) 
    throws IOException {

    int off = 0, i = 0;
    byte[] separator = lineSeparator.getBytes("UTF-8");
    byte[] lineBytes = new byte[1024];
    
    while (is.available() > 0) {
        int nextByte = is.read();
        if (nextByte < -1) {
            throw new IOException(
                "Reached end of stream while reading the current line!");
        }
        
        lineBytes[i] = (byte) nextByte;
        if (lineBytes[i++] == separator[off++]) {
            if (off == separator.length) {
                return new String(
                    lineBytes, 0, i-separator.length, "UTF-8");
            }
        }
        else {
            off = 0;
        }
        
        if (i == lineBytes.length) {
            throw new IOException("Maximum line length exceeded: " + i);
        }
    }
    
    throw new IOException(
        "Reached end of stream while reading the current line!");       
}