Question

我对java nio感到很困惑，

package org.eclipse.java.nio.selector.test;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Set;

public class MySelector {
    public static void main(String[] args) throws IOException {
        // Create selector
        Selector selector = null;
        selector = Selector.open();
        ////////////////////////////////////////////////////////////////////////
        SocketChannel socketChannel = SocketChannel.open(new InetSocketAddress(
                "localhost", 4321));
        socketChannel.configureBlocking(false);
        socketChannel.register(selector, SelectionKey.OP_READ);
        /*
         * Let's begin select
         */
        while (true) {
            int readyChannels = selector.select();
            if (readyChannels == 0) continue;

            System.out.println("Hello, selector!");
            Set readyKeys = selector.selectedKeys();
            Iterator it = readyKeys.iterator();  
            while (it.hasNext()) {
                SelectionKey key = (SelectionKey )it.next();
                if (key.isReadable()) {
                    System.out.println("It's readable!");
                }
                it.remove();
            }
        }
    }
}

我希望选择器等待来自远程服务器的下一个输入事件，但它在服务器回复任何单词后陷入无限循环，为什么？我真的无法理解，'删除'不起作用？我不想取消或关闭频道，我想保持连接，让客户端等待服务器的回复......

Answer 1

必须在isReadable判断块中执行读取。如果您不执行读取从可读通道传输的数据，再次选择频道。所以while循环不会停止。

while (it.hasNext()) {
    SelectionKey key = (SelectionKey )it.next();
    if (key.isReadable()) {
        System.out.println("It's readable!");

        // Added read operation
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        Charset charset = Charset.forName("UTF-8");
        buffer.clear();
        if (socketChannel.read(buffer) < 0) {
            // Client connection refused
            socketChannel.close();
            return;
        }
        buffer.flip();
        System.out.println("Value = " + charset.decode(buffer).toString());

    }
    it.remove();
}

我认为“删除”有效。 “你好，读取选择器！”可能会重复输出。

java nio选择器＆amp;渠道使用问题

1 个答案: