1.JAVA基础——NIO

    //NIO文件复制测试
    public static void main(String[] args) throws Exception {
        FileInputStream fileInputStream = new FileInputStream("D:\\Baofeng5.exe");
        FileOutputStream fileOutputStream = new FileOutputStream("D:\\COPYBaofeng5.exe");
        
        FileChannel channelIn = fileInputStream.getChannel();
        FileChannel channelOut = fileOutputStream.getChannel();
        
        ByteBuffer buffer = ByteBuffer.allocate(128);

        while(true){
            buffer.clear();
            int i = channelIn.read(buffer);
            if (i == -1) {
                break;
            }
            buffer.flip();
            channelOut.write(buffer);
        }

    }

    public static void main1(String[] args) throws Exception {
        FileOutputStream stream = new FileOutputStream("D:\\a.txt");
        FileChannel inChannel = stream.getChannel();
        ByteBuffer byteBuffer = ByteBuffer.allocate(8);
        byte[] asdfg = "asdfg".getBytes();
        for (int i = 0; i < asdfg.length; i++) {
            byteBuffer.put(asdfg[i]);
        }
        byteBuffer.flip();
        System.out.println(inChannel.write(byteBuffer));
    }

    public static void main2(String[] args) throws Exception {
        FileOutputStream stream = new FileOutputStream("D:\\a.txt");
        FileChannel inChannel = stream.getChannel();
        ByteBuffer byteBuffer = ByteBuffer.allocate(8);
        byte[] asdfg = "asdfg".getBytes();
        for (int i = 0; i < asdfg.length; i++) {
            byteBuffer.put(asdfg[i]);
        }
        //byteBuffer.flip();
        System.out.println(inChannel.write(byteBuffer));
    }

    public static void main(String[] args) throws Exception{
        byte[] s = {‘h‘,‘e‘,‘l‘,‘l‘,‘o‘};
        ByteBuffer buffer = ByteBuffer.wrap(s);
        System.out.println(new String(buffer.array()));
        //对数组进行修改，同样会影响buffer的变化
        s[0] = ‘N‘;
        System.out.println(new String(buffer.array()));
        
        //对buffer进行修改，同样会影响数组的变化
        buffer.put((byte)‘K‘);
        System.out.println(new String(s));
    }

    public static void main(String[] args) throws Exception{
        byte[] s = {‘h‘,‘e‘,‘l‘,‘l‘,‘o‘};
        ByteBuffer buffer = ByteBuffer.wrap(s);

        buffer.limit(2);
        ByteBuffer slice = buffer.slice();
        //处理slice
        slice.put((byte)‘N‘);
        slice.put((byte)‘O‘);
        
        System.out.println(new String(buffer.array()));
    }

package nio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
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;

/**
 * NIO测试服务端
 * @author Leo
 *
 */
public class NIOServer {
    //通道管理器
    private Selector selector;
    
    //初始化方法，获取一个ServerSocket通道，并将该通道初始化
    public void init(int port) throws IOException{
        //获取一个ServerSocket通道
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        //设置为非阻塞
        serverSocketChannel.configureBlocking(false);
        
        //获取通道对应的serverSocket,并绑定到指定端口
        ServerSocket serverSocket = serverSocketChannel.socket();
        serverSocket.bind(new InetSocketAddress(port));
        
        this.selector = Selector.open();//获得一个通道管理器
        
        //将该通道管理器与该通道绑定，并为其注册SelectionKey.OP_ACCEPT事件
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
    }
    
    /**
     * 采用轮询的方式监听selector（通道管理器）上是否有需要处理的事件，如果有，则进行处理
     * @throws IOException
     */
    public void listen() throws IOException{
        System.out.println("服务端启动，开始监测是否有需要处理的事件");
        //轮询访问selector
        while (true) {
            //当注册的事件到达后，方法返回；否则，该方法一直阻塞
            selector.select();
            
            //获得selector中选中项（即是注册的事件）的迭代器
            Iterator<SelectionKey> iterator = this.selector.selectedKeys().iterator();
            while (iterator.hasNext()) {
                SelectionKey key = iterator.next();
                //客户端请求连接事件
                if (key.isAcceptable()) {
                    ServerSocketChannel serverSocketChannel = (ServerSocketChannel) key.channel();
                    
                    //获得与客户端连接的通道
                    SocketChannel channel = serverSocketChannel.accept();
                    //设置成非阻塞
                    channel.configureBlocking(false);
                    
                    //通过该通道往客户端输入数据
                    channel.write(ByteBuffer.wrap("服务端往客户端发送的信息".getBytes()));
                    
                    //为了让客户端可以与服务端进行传递数据，需要给通道设置读权限
                    channel.register(selector, SelectionKey.OP_READ);
                } else if(key.isReadable()){//可读事件
                    serverRead(key);
                }
                //操作完毕，删除事件的key，防止重复处理
                iterator.remove();
            }
        }
    }

    /**
     * 服务端处理客户端发来的信息
     * @param key 
     */
    private void serverRead(SelectionKey key) throws IOException{
        SocketChannel socketChannel = (SocketChannel) key.channel();
        //创建字符缓冲区
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        socketChannel.read(buffer);
        
        String msg = new String(buffer.array()).trim();
        msg = "服务端接收到的信息为：" + msg;
        System.out.println(msg);
        
        socketChannel.write(ByteBuffer.wrap(msg.getBytes()));
    }
    
    public static void main(String[] args) throws IOException{
        NIOServer nioServer = new NIOServer();
        nioServer.init(8000);
        nioServer.listen();
    }
}

package nio;

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;

/**
 * NIO测试客户端
 * @author Leo
 *
 */
public class NIOClient {

    /**
     * 通道管理器
     */
    private Selector selector;
    
    /**
     * 初始化方法，获取socket通道，并初始化该通道
     * @param ip
     * @param port
     * @throws IOException
     */
    public void initClient(String ip, int port) throws IOException{
        SocketChannel channel = SocketChannel.open();
        //设置通道为非阻塞
        channel.configureBlocking(false);
        
        //获取通道管理器
        this.selector = Selector.open();
        
        //客户端准备连接服务端，该方法并不真正连接，后续有finishConnect方法才能完成连接
        channel.connect(new InetSocketAddress(ip, port));
        //绑定通道与通道管理器，并为该通道注册SelectionKey.OP_CONNECT事件
        channel.register(selector, SelectionKey.OP_CONNECT);
    }
    
    /**
     * 轮询方式监听该selector上是否有需要处理的时间，如果有则进行处理
     * @throws IOException
     */
    private void listen() throws IOException{
        while (true) {
            selector.select();
            
            Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
            while (iterator.hasNext()) {
                SelectionKey key = iterator.next();
                
                if (key.isConnectable()) {
                    SocketChannel channel = (SocketChannel) key.channel();
                    //如果正在连接，则完成连接
                    if (channel.isConnectionPending()) {
                        channel.finishConnect();
                    }
                    //设置非阻塞
                    channel.configureBlocking(false);
                    
                    //往服务器发送消息
                    channel.write(ByteBuffer.wrap("客户端往服务端发送的信息".getBytes()));
                    
                    //在于服务端连接成功后，为了可以接收到服务端的消息，需要给通道设置读权限
                    channel.register(selector, SelectionKey.OP_READ);
                } else if(key.isReadable()){
                    clientRead(key);
//                    break loop;
                }
                
                //删除已处理的key，防止重复
                iterator.remove();
            }
        }
    }

    private void clientRead(SelectionKey key) throws IOException{
        SocketChannel socketChannel = (SocketChannel) key.channel();
        //创建字符缓冲区
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        socketChannel.read(buffer);
        
        String msg = new String(buffer.array()).trim();
        msg = "服务端接收到的信息为：" + msg;
        System.out.println(msg);
        
        //停止发送消息，否则会死循环
//        socketChannel.write(ByteBuffer.wrap("客户端接收到服务端的消息后又往服务端发送的消息".getBytes()));
    }
    
    public static void main(String[] args) throws IOException{
        NIOClient client = new NIOClient();
        client.initClient("localhost", 8000);
        client.listen();
    }
}