5.NIO-网络编程-阻塞VS非阻塞

1.4、网络编程

1.4.1 阻塞VS非阻塞

阻塞：

• ServerSocketChannel.accept() 阻塞到客户端连接
• SocketChannel.read() 阻塞到客户端发送数据

//服务端
@Slf4j
public class SocketServerTest {
    public static void main(String[] args) throws IOException {
        ServerSocketChannel ssc = ServerSocketChannel.open();

        ssc.bind(new InetSocketAddress(5888));

        ArrayList<SocketChannel> channels = new ArrayList<>();
        ByteBuffer buffer = ByteBuffer.allocate(16);
        while (true) {
            log.debug("connecting...");
            SocketChannel accept = ssc.accept();//阻塞方法，等待客户端连接。
            log.debug("connected...{}", accept);
            channels.add(accept);
            for (SocketChannel channel : channels) {
                log.debug("before read...{}", channel);
                channel.read(buffer);//阻塞方法，等待客户端发送数据
                buffer.flip();
                ByteBufferUtil.debugRead(buffer);
                buffer.clear();
                log.debug("after read...{}",channel);
            }
        }
    }
}

//客户端
public class Client {
    public static void main(String[] args) throws IOException {
        SocketChannel channel = SocketChannel.open();
        channel.connect(new InetSocketAddress("localhost", 5888));

        System.out.println("waiting...");
    }
}

非阻塞

客户端不便，服务只需要设置 configureBlocking（false）

@Slf4j
public class SocketServerNiotTest {
    public static void main(String[] args) throws IOException {
        ServerSocketChannel ssc = ServerSocketChannel.open();
        ssc.bind(new InetSocketAddress(5888));
        ssc.configureBlocking(false);//设置为非阻塞
        ArrayList<SocketChannel> channels = new ArrayList<>();
        ByteBuffer buffer = ByteBuffer.allocate(16);
        while (true) {
            SocketChannel accept = ssc.accept();//阻塞方法，等待客户端连接。
            if (accept != null) {
                log.debug("connected...{}", accept);
                accept.configureBlocking(false);//设置为非阻塞
                channels.add(accept);
            }

            for (SocketChannel channel : channels) {
                int read = channel.read(buffer);//阻塞方法，等待客户端发送数据
                if (read > 0) {
                    buffer.flip();
                    ByteBufferUtil.debugRead(buffer);
                    buffer.clear();
                    log.debug("after read...{}", channel);
                }
            }
        }
    }
}

问题：非阻塞模式，不管有没有客户端连接，不管客户端有没有发数据，服务店一直在循环，占用CPU资源