Java NIO示例

谁践踏了优雅 2022-05-22 03:21 193阅读 0赞

学习了Java的NIO框架，NIO是Java提供的非阻塞I/O，基于Channel和Buffer实现，下面给出Socket示例代码，服务端和客户端。

# 一、服务端代码 #

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.ServerSocketChannel;
    import java.nio.channels.SocketChannel;
    import java.util.Iterator;
    
    
    public class NIOServer
    {
        /**
         * 选择器
         */
        private Selector selector;
    
        /**
         * 通道
         */
        ServerSocketChannel serverSocketChannel;
    
        public void initServer(int port) throws IOException
        {
            //打开一个通道
            serverSocketChannel = ServerSocketChannel.open();
    
            //通道设置非阻塞
            serverSocketChannel.configureBlocking(false);
    
            //绑定端口号
            serverSocketChannel.socket().bind(new InetSocketAddress("localhost", port));
    
            //注册
            this.selector = Selector.open();
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        }
    
        public void listen() throws IOException
        {
            System.out.println("server started succeed!");
    
            while (true)
            {
                selector.select();
                Iterator<SelectionKey> ite = selector.selectedKeys().iterator();
                while (ite.hasNext())
                {
                    SelectionKey key = ite.next();
                    if (key.isAcceptable())
                    {
                        SocketChannel channel = serverSocketChannel.accept();
                        channel.configureBlocking(false);
                        channel.register(selector, SelectionKey.OP_READ);
                    }
                    else if (key.isReadable())
                    {
                        recvAndReply(key);
                    }
                    ite.remove();
                }
            }
        }
    
        public void recvAndReply(SelectionKey key) throws IOException
        {
            SocketChannel channel = (SocketChannel) key.channel();
            ByteBuffer buffer = ByteBuffer.allocate(256);
            int i = channel.read(buffer);
            if (i != -1)
            {
                String msg = new String(buffer.array()).trim();
                System.out.println("NIO server received message =  " + msg);
                System.out.println("NIO server reply =  " + msg);
                channel.write(ByteBuffer.wrap( msg.getBytes()));
            }
            else
            {
                channel.close();
            }
        }
    
        public static void main(String[] args) throws IOException
        {
            NIOServer server = new NIOServer();
            server.initServer(8080);
            server.listen();
        }
    }

# 二、客户端代码 #

import java.io.IOException;
    import java.net.InetSocketAddress;
    import java.nio.ByteBuffer;
    import java.nio.channels.SocketChannel;
    
    
    public class NIOClient
    {
        /**
         * 通道
         */
        SocketChannel channel;
    
        public void initClient(String host, int port) throws IOException
        {
            //构造socket连接
            InetSocketAddress servAddr = new InetSocketAddress(host, port);
    
            //打开连接
            this.channel = SocketChannel.open(servAddr);
        }
    
        public void sendAndRecv(String words) throws IOException
        {
            byte[] msg = new String(words).getBytes();
            ByteBuffer buffer = ByteBuffer.wrap(msg);
            System.out.println("Client sending: " + words);
            channel.write(buffer);
            buffer.clear();
            channel.read(buffer);
            System.out.println("Client received: " + new String(buffer.array()).trim());
    
            channel.close();
        }
    
        public static void main(String[] args) throws IOException
        {
            NIOClient client = new NIOClient();
            client.initClient("localhost", 8080);
            client.sendAndRecv("I am a client");
        }
    }

# 三、测试 #

首先启动服务端，再启动客户端，输出如下：

服务端输出

server started succeed!
    NIO server received message =  I am a client
    NIO server reply =  I am a client

客户端输出

Client sending: I am a client
    Client received: I am a client

**参考文档**

*  [深入浅出NIO之Channel、Buffer][NIO_Channel_Buffer]
 *  [Java NIO 系列教程][Java NIO]

[NIO_Channel_Buffer]: https://www.jianshu.com/p/052035037297
[Java NIO]: http://ifeve.com/java-nio-all/