如何在非阻塞模式下通过SocketChannel读取和写入序列化对象？

Question

I am currently attempting to read and write serialized Objects through a NIO SocketChannel. This SocketChannel is in non-blocking mode. I can't seem to find the right way to do it without corrupting the stream, corruping the stream header, etc...

This is my current write method

private void writeData(SelectionKey key) throws IOException {
    Packet outPacket = null;
    synchronized (pendingPacketQue) {
        for (Packet packet : pendingPacketQue) {
            if (packet.getChannel().keyFor(selector).equals(key)) {
                outPacket = packet;
                break;
            }
        }
    }
    if (outPacket == null) {
        Logger.writeException("Couldn't find out bound packet in list.", LogType.SERVER);
        return;
    }
    SocketChannel connection = (SocketChannel) outPacket.getChannel();
    ObjectOutputStream outStream = new ObjectOutputStream(connection.socket().getOutputStream());
    outStream.writeObject(outPacket);
    outStream.flush();
    outStream.close();
    connection.keyFor(selector).interestOps(SelectionKey.OP_READ);
}

This is my current read method

private void readData(SelectionKey key) throws IOException, ClassNotFoundException {
    SocketChannel connection = (SocketChannel) key.channel();
    buffer.clear();
    int byteCount;
    try {
        byteCount = connection.read(buffer);
    } catch (IOException e) {
        Logger.writeException("Connenction terminated.", LogType.SERVER);
        connection.close();
        key.cancel();
        return;
    }
    if (byteCount == -1) {
        Logger.writeException("Connection error. Terminating connection.", LogType.SERVER);
        key.channel().close();
        key.cancel();
        return;
    }
    Engine.getInstance().getPacketProcessor().processData(connection, buffer.array(), byteCount);
}

public void processData(SocketChannel connection, byte[] data, int count)
        throws IOException, ClassNotFoundException {
    ByteArrayInputStream byteStream = new ByteArrayInputStream(data);
    ObjectInputStream inStream = new ObjectInputStream(byteStream);
    addToQue(inStream.readObject());
    inStream.close();
}

If you have any questions feel free to ask. Thank you!

Answer 1

You haven't necessarily read the entire object in a single read.

You can't do your writing this way either. You can't use the streams of a socket of a SocketChannel in non-blocking mode. You should have got an IllegalBlockingModeException in the sender.

Hard to see therefore how you could possibly have got to the point of corrupted stream headers etc. when you can't possibly have written anything in the first place.

In any case I strongly recommend you don't attempt this. It's too hard. You need to send the size of the object ahead of the object so you know when you've read it all, issue multiple reads and save the results until you have it all, run etc etc etc. Use java.net.Socket and the normal object input and output streams directly.