Java NIO

java NIO有2种模式，一种是非阻塞，一种是阻塞式的，阻塞式的和传统的BIO类似，不过可靠性不如BIO，故一般不用

 

以下关注非阻塞的方式，

NIO是非阻塞同步IO，工作在一个线程中，由selector去轮询channel，是否有请求连接就绪/读取就绪，有就进行连接/读取到buffer

当然从另一方面也可以说是阻塞的，因为selector一直在执行select方法，尝试获取通道的事件，未获取到的话就阻塞一定的时间后返回，并继续select

// server端代码

public static void main(String[] args) throws  Exception{
    //创建ServerSocketChannel，-->> ServerSocket
    ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
    InetSocketAddress inetSocketAddress = new InetSocketAddress(5555);
    serverSocketChannel.socket().bind(inetSocketAddress);
    serverSocketChannel.configureBlocking(false); //设置成非阻塞

    //开启selector,并注册accept事件
    Selector selector = Selector.open();
    serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

    while(true) {
        selector.select(2000);  //监听所有通道
        //遍历selectionKeys
        Set<SelectionKey> selectionKeys = selector.selectedKeys();
        String s = selectionKeys.toString();
        Iterator<SelectionKey> iterator = selectionKeys.iterator();
        while (iterator.hasNext()) {
            SelectionKey key = iterator.next();
            if(key.isAcceptable()) {  //处理连接事件
                SocketChannel socketChannel = serverSocketChannel.accept();
                socketChannel.configureBlocking(false);  //设置为非阻塞
                System.out.println("client:" + socketChannel.getLocalAddress() + " is connect");
                socketChannel.register(selector, SelectionKey.OP_READ); //注册客户端读取事件到selector
            } else if (key.isReadable()) {  //处理读取事件
                ByteBuffer byteBuffer = ByteBuffer.allocate(32);
                SocketChannel channel = (SocketChannel) key.channel();
                int read = channel.read(byteBuffer);

                if (read == -1) {
                    key.cancel();
                    System.out.println("client closed");
                    continue;
                }
                byteBuffer.flip();
                String str = StandardCharsets.UTF_8.decode(byteBuffer).toString();
                System.out.println("received client:" + channel.getLocalAddress() + read+" str " + str);
            }
            iterator.remove();  //事件处理完毕，要记得清除
        }
    }

}


// client端代码

private static void sendByNIO()throws Exception{
    SocketChannel socketChannel = SocketChannel.open();
    socketChannel.configureBlocking(false);
    InetSocketAddress inetSocketAddress = new InetSocketAddress("127.0.0.1", 5555);

    if(!socketChannel.connect(inetSocketAddress)) {
        while (!socketChannel.finishConnect()) {
            System.out.println("客户端正在连接中，请耐心等待");
        }
    }
    ByteBuffer byteBuffer = ByteBuffer.wrap("test msg.qwertyuikl1234567890123456789123123456789!!!!".getBytes(StandardCharsets.UTF_8));
    socketChannel.write(byteBuffer);
    Thread.sleep(1000*60);
    socketChannel.close();
}


以上是单线程的情况，一个reactor来处理所有的事件，连接，读写，也可以复杂的使用多个reactor，主reactor负责连接，读写交给副reactor，副reactor的读写的操作还可以交给线程池中的专门线程来处理

 

 

 

 

图来自于https://blog.csdn.net/wang2963973852/article/details/74418643