Java - 从套接字通道读取

Question

所以我在 java 中使用 SocketChannels 来发送和接收项目的数据。该项目与需要数据的 ByteBuffer 的第 3 方交互，但其前缀为 4 个字节，即其​​长度。

接收时我会收到一个 ByteBuffer，我需要从前面解构 4 字节长度并提取数据。我收到的消息不是固定长度的。

我目前的实现如下：

public PedResponse send(ByteBuffer message) {
        String returnString;
        try {

            message.flip();

            while (message.hasRemaining()) {
                socketChannel.write(message);
            }

            ByteBuffer readBuffer = ByteBuffer.allocate(5000);
            int bufferSize = socketChannel.read(readBuffer);
            if (bufferSize == -1) {
                socketChannel.close();
            } else {
                readBuffer.flip();
            }

            returnString = new String(deconstructMessage(readBuffer.array()), "UTF-8").trim();

            response = parser.parseResponse(returnString);

        } catch (IOException e) {
            e.printStackTrace();
        }
        return response;
    }

private ByteBuffer constructMessage(byte[] data) {

        // Construct a buffer where we'll put the data to send
        ByteBuffer sendBuffer = ByteBuffer.allocate(4 + data.length);

        // it's the default, but included for clarity
        sendBuffer.order(ByteOrder.BIG_ENDIAN);

        // Put the 4-byte length, then the data
        sendBuffer.putInt(data.length);
        sendBuffer.put(data);

        // Extract the actual bytes from our sendBuffer
        return sendBuffer;
    } 

public byte[] deconstructMessage(byte[] data) {

        byte[] filteredByteArray = Arrays.copyOfRange(data, 4, data.length - 4);

        return filteredByteArray;
    }

//Currently not being used.
private byte[] deconstructMessage(byte[] data) {

        // Construct a buffer where we'll put the data to send
        ByteBuffer receiveBuffer = ByteBuffer.allocate(data.length);

        // it's the default, but included for clarity
        receiveBuffer.order(ByteOrder.BIG_ENDIAN);

        // Get the 4-byte length, then the data
        receiveBuffer.getInt(data.length);
        receiveBuffer.get(data);

        // Extract the actual bytes from our receivedBuffer
        byte[] dataReceived = receiveBuffer.array();
        return dataReceived;
    }

如您所见，我正在创建一个大小为 5000 的新 ByteBuffer，但理想情况下我不想这样做。所以我的问题是，我怎样才能不使用这个超大的 ByteBuffer，而只是读取我收到的数据，这样我就可以使用我未使用的解构消息方法？

Answer 1

ByteBuffer 有method get()，它从当前位置返回字节。 所以，你可以先读取 4 个字节，然后得到大小。