Java - 使用nio的ReadObject [英] Java - ReadObject with nio

问题描述

在传统的阻塞线程服务器中，我会做这样的事情

In a traditional blocking-thread server, I would do something like this

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，对象可能会非常大。在我的nio循环中，我不能简单地等待对象通过，所有其他连接（工作量小得多）将等待我。

Now, the object can be expected to be quite large. In my nio loop, I can't simply wait for the object to come through, all my other connections (with much smaller workloads) will be waiting on me.

如何在告诉我的nio频道它已准备就绪之前，我才能收到连接已通知整个对象的通知吗？

How can I only get notified that a connection has the entire object before it tells my nio channel it's ready?

推荐答案

你可以写一下对象ByteArrayOutputStream允许您在发送对象之前给出长度。在接收方，在尝试解码之前读取所需的数据量。

You can write the object to a ByteArrayOutputStream allowing you to give the length before an object sent. On the receiving side, read the amount of data required before attempting to decode it.

但是，您可能会发现使用阻塞IO更简单，更高效（而不是NIO）与Object * Stream

However, you are likely to find it much simpler and more efficient to use blocking IO (rather than NIO) with Object*Stream

编辑类似这样的东西

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;
}

这篇关于Java - 使用nio的ReadObject的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！