java nio

1、Java Socket Client

public class PlainEchoClient {

    public static void main(String args[]) throws Exception {
        for (int i = 0; i < 20; i++) {
            startClientThread();
        }
    }

    private static void startClientThread() throws UnknownHostException,
            IOException {
        Thread t = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    startClient();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
        t.start();
    }

    private static void startClient() throws UnknownHostException, IOException {
        long beforeTime = System.nanoTime();
        String host = "127.0.0.1";
        int port = 8086;
        Socket client = new Socket(host, port);
        // 建立连接后就可以往服务端写数据了
        Writer writer = new OutputStreamWriter(client.getOutputStream());
        writer.write("Hello Server.");
        writer.flush();
        // 写完以后进行读操作
        Reader reader = new InputStreamReader(client.getInputStream());
        char chars[] = new char[64];// 假设所接收字符不超过64位，just for demo
        int len = reader.read(chars);
        StringBuffer sb = new StringBuffer();
        sb.append(new String(chars, 0, len));
        System.out.println("From server: " + sb);
        writer.close();
        reader.close();
        client.close();
        System.out.println("Client use time: "
                + (System.nanoTime() - beforeTime) + " ns");
    }
}
2、IO Socket Server
这个Socket Server模拟的是我们经常使用的thread-per-connection模式， Tomcat，JBoss等Web Container都是这种方式。

public class PlainEchoServer {
    private static final ExecutorService executorPool = Executors.newFixedThreadPool(5);

    private static class Handler implements Runnable{
        private Socket clientSocket;
        public Handler(Socket clientSocket){
            this.clientSocket = clientSocket;
        }

        @Override
        public void run() {
            try {
                BufferedReader reader = new BufferedReader(
                        new InputStreamReader(
                                clientSocket.getInputStream()));
                PrintWriter writer = new PrintWriter(
                        clientSocket.getOutputStream(), true);
                char chars[] = new char[64];
                int len = reader.read(chars);
                StringBuffer sb = new StringBuffer();
                sb.append(new String(chars, 0, len));
                System.out.println("From client: " + sb);
                writer.write(sb.toString());
                writer.flush();
            } catch (IOException e) {
                e.printStackTrace();
                try {
                    clientSocket.close();
                } catch (IOException ex) {
                    // ignore on close
                }
            }
        }
    }       

    public void serve(int port) throws IOException {
        final ServerSocket socket = new ServerSocket(port);
        try {
            while (true) {
                long beforeTime = System.nanoTime();
                final Socket clientSocket = socket.accept();
                System.out.println("Establish connection time: "+ (System.nanoTime()-beforeTime)+" ns");
                executorPool.execute(new Handler(clientSocket));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) throws IOException{
        PlainEchoServer server = new PlainEchoServer();
        server.serve(8086);
    }
}
3、NIO Socket Server

public class PlainNioEchoServer {
    public void serve(int port) throws IOException {
        ServerSocketChannel serverChannel = ServerSocketChannel.open();
        ServerSocket ss = serverChannel.socket();
        InetSocketAddress address = new InetSocketAddress(port);
        ss.bind(address); // #1
        serverChannel.configureBlocking(false);
        Selector selector = Selector.open();
        serverChannel.register(selector, SelectionKey.OP_ACCEPT); // #2
        while (true) {
            try {
                selector.select(); // #3
            } catch (IOException ex) {
                ex.printStackTrace();
                // handle in a proper way
                break;
            }
            Set readyKeys = selector.selectedKeys(); // #4
            Iterator iterator = readyKeys.iterator();
            while (iterator.hasNext()) {
                SelectionKey key = (SelectionKey) iterator.next();
                try {
                    if (key.isAcceptable()) {
                        ServerSocketChannel server = (ServerSocketChannel) key
                                .channel();
                        long beforeTime = System.nanoTime();
                        SocketChannel client = server.accept(); // #6                       
                        System.out.println("Accept connection time: "+ (System.nanoTime()-beforeTime)+" ns");
                        if (client == null){//Check if socketChannel has been created, it could be null, because it's non-blocking
                            continue;
                        }
                        client.configureBlocking(false);
                        client.register(selector, SelectionKey.OP_WRITE
                                | SelectionKey.OP_READ,
                                ByteBuffer.allocate(100));
                    }
                    if (key.isReadable()) {
                        SocketChannel client = (SocketChannel) key.channel();
                        ByteBuffer output = (ByteBuffer) key.attachment();
                        client.read(output);
                    }
                    if (key.isWritable()) {
                        SocketChannel client = (SocketChannel) key.channel();
                        ByteBuffer output = (ByteBuffer) key.attachment();
                        output.flip();
                        client.write(output);
                        output.compact();
                    }
                } catch (IOException ex) {
                    key.cancel();
                    try {
                        key.channel().close();
                    } catch (IOException cex) {
                    }
                }
                iterator.remove(); // #5
            }
        }
    }

    public static void main(String[] args) throws IOException{
        PlainNioEchoServer server = new PlainNioEchoServer();
        server.serve(8086);
    }
}