Java-带nio的ReadObject

Question

在传统的阻塞线程服务器中，我会做这样的事情

class ServerSideThread {

    ObjectInputStream in;
    ObjectOutputStream out;
    Engine engine;

    public ServerSideThread(Socket socket, Engine engine) {
        in = new ObjectInputStream(socket.getInputStream());
        out = new ObjectOutputStream(socket.getOutputStream());
        this.engine = engine;
    }

    public void sendMessage(Message m) {
        out.writeObject(m);
    }

    public void run() {
        while(true) {
            Message m = (Message)in.readObject();
            engine.queueMessage(m,this); // give the engine a message with this as a callback
        }
    }
}

现在，可以预期该对象会很大。在我的nio循环中，我不能简单地等待对象通过，其他所有连接（工作量要小得多）都在等待我。

在告诉Nio通道已准备就绪之前，如何仅通知连接已包含整个对象？

Answer 1

您可以将对象写入ByteArrayOutputStream，以便在发送对象之前给出长度。在接收端，请先读取所需的数据量，然后再尝试对其进行解码。

但是，您可能会发现将Object * Stream与阻塞IO（而不是NIO）一起使用会更简单，更高效

像这样编辑

public static void send(SocketChannel socket,  Serializable serializable) throws IOException {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    for(int i=0;i<4;i++) baos.write(0);
    ObjectOutputStream oos = new ObjectOutputStream(baos);
    oos.writeObject(serializable);
    oos.close();
    final ByteBuffer wrap = ByteBuffer.wrap(baos.toByteArray());
    wrap.putInt(0, baos.size()-4);
    socket.write(wrap);
}

private final ByteBuffer lengthByteBuffer = ByteBuffer.wrap(new byte[4]);
private ByteBuffer dataByteBuffer = null;
private boolean readLength = true;

public Serializable recv(SocketChannel socket) throws IOException, ClassNotFoundException {
    if (readLength) {
        socket.read(lengthByteBuffer);
        if (lengthByteBuffer.remaining() == 0) {
            readLength = false;
            dataByteBuffer = ByteBuffer.allocate(lengthByteBuffer.getInt(0));
            lengthByteBuffer.clear();
        }
    } else {
        socket.read(dataByteBuffer);
        if (dataByteBuffer.remaining() == 0) {
            ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(dataByteBuffer.array()));
            final Serializable ret = (Serializable) ois.readObject();
            // clean up
            dataByteBuffer = null;
            readLength = true;
            return ret;
        }
    }
    return null;
}