NIO学习笔记(技术技能)

1.FileChannel

package io.pdd.nio.file;

import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class RdmAccFile {

    public static void main(String[] args) throws Exception {
        //读取文件
        RandomAccessFile randomAccessFile=new RandomAccessFile("E:/random.txt","rw");
        //获取Channel
        FileChannel fileChannel=randomAccessFile.getChannel();
        //创建ByteBuffer
        ByteBuffer byteBuffer=ByteBuffer.allocate(1024);
        //从通道读取数据到byteBuffer
        int read = fileChannel.read(byteBuffer);
        while(read!=-1){
            //将position回归到起始位置 limit设置为position的位置(为什么这么用请看上一篇理论知识)
            byteBuffer.flip();
            while(byteBuffer.hasRemaining()){
                System.out.print((char)byteBuffer.get());
            }
            //清空已经读取过的数据(position之前的)
            byteBuffer.compact();
            read=fileChannel.read(byteBuffer);
        }
    }
}

2.ScoketChannel、ServerSocketChannel

服务端

package io.pdd.nio.data;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.util.Iterator;

/**
 * @author:liyangpeng
 * @date:2020/5/20 13:45
 */
public class NioServer {

    /**
     *
     * @param key
     * @throws IOException
     */
    public static void handleAccept(SelectionKey key) throws IOException{
        ServerSocketChannel ssChannel = (ServerSocketChannel)key.channel();
        SocketChannel sc = ssChannel.accept();
        sc.configureBlocking(false);
        sc.register(key.selector(), SelectionKey.OP_READ, ByteBuffer.allocateDirect(1024));
    }

    /**
     * 数据读取
     * @param key
     * @throws IOException
     */
    public static void handleRead(SelectionKey key) throws IOException{
        SocketChannel sc = (SocketChannel)key.channel();
        sc.configureBlocking(false);
        ByteBuffer buf = (ByteBuffer)key.attachment();
        Charset c = Charset.forName("UTF-8");
        CharsetDecoder decoder = c.newDecoder();
        int bytesRead = sc.read(buf);
        while(bytesRead>0){
            buf.flip();
            CharBuffer cb = CharBuffer.allocate(bytesRead);
            decoder.decode(buf, cb, false);
            cb.flip();
            while(cb.hasRemaining()){
                System.out.print(cb.get());
            }
            System.out.println();
            cb.clear();
            buf.clear();
            bytesRead = sc.read(buf);
        }
        if(bytesRead == -1){
            sc.close();
        }
    }

    /**
     *
     * @param key
     * @throws IOException
     */
    public static void handleWrite(SelectionKey key) throws IOException{
        ByteBuffer buf = (ByteBuffer)key.attachment();
        buf.flip();
        SocketChannel sc = (SocketChannel) key.channel();
        while(buf.hasRemaining()){
            sc.write(buf);
        }
        buf.compact();
    }

    /**
     *
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws IOException {
        Selector selector=Selector.open();
        ServerSocketChannel serverSocketChannel=ServerSocketChannel.open();
        serverSocketChannel.bind(new InetSocketAddress(8899));
        serverSocketChannel.configureBlocking(false);
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        while(true){
            if(selector.select(3000)==0){
                System.out.println("continue...");
                continue;
            }
            Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
            while(iterator.hasNext()){
                SelectionKey next = iterator.next();
                if(next.isAcceptable()){
                    handleAccept(next);
                    System.out.println("accept...");
                }
                if(next.isReadable()){
                    handleRead(next);
                    System.out.println("read..");
                }
//                if(next.isWritable()){
//                    handleWrite(next);
//                    System.out.println("write...");
//                }
//                if(next.isConnectable()){
//                    System.out.println("connect...");
//                }
                iterator.remove();
            }
        }
    }
}

客户端

package io.pdd.nio.data;

import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;

/**
 * @author:liyangpeng
 * @date:2020/5/25 14:02
 */
public class NioClient {
    public static void main(String[] args) {
        ByteBuffer byteBuffer=ByteBuffer.allocate(1024);
        SocketChannel socketChannel=null;
        try{
            socketChannel=SocketChannel.open();
            socketChannel.connect(new InetSocketAddress(8899));
            socketChannel.configureBlocking(false);
            if(socketChannel.finishConnect()){
                String info="我是新来的client...";
                byteBuffer.put(info.getBytes("UTF-8"));
                byteBuffer.flip();
                socketChannel.write(byteBuffer);
            }
            byteBuffer.clear();
            socketChannel.close();
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

3.Pipe

package io.pdd.nio.data;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.Pipe;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * @author:liyangpeng
 * @date:2020/5/25 14:52
 */
public class PipeTest {

    private final static String CHARSET="UTF-8";

    public static void main(String[] args) throws IOException {
        //线程池
        ExecutorService executorService = Executors.newFixedThreadPool(2);
        Pipe pipe=Pipe.open();
        //线程写
        executorService.submit(()->{
           Pipe.SinkChannel sinkChannel=pipe.sink();
           ByteBuffer byteBuffer=ByteBuffer.allocate(1024);
           while(true){
               String timestamp=System.currentTimeMillis()+"";
               byteBuffer.put(timestamp.getBytes(CHARSET));
               byteBuffer.flip();
               while(byteBuffer.hasRemaining()){
                   sinkChannel.write(byteBuffer);
               }
               byteBuffer.clear();
           }
        });

        //线程读
        executorService.submit(()->{
            Pipe.SourceChannel sinkChannel=pipe.source();
            ByteBuffer byteBuffer=ByteBuffer.allocate(1024);
            while(true){
                int length=sinkChannel.read(byteBuffer);
                while(length>0){
                    byteBuffer.flip();
                    byte [] bt=new byte[length];
                    int index=0;
                    while(byteBuffer.hasRemaining()){
                        bt[index]=byteBuffer.get();
                        index++;
                    }
                    System.out.println(new String(bt,CHARSET));
                    byteBuffer.clear();
                    bt=null;
                    length=sinkChannel.read(byteBuffer);
                }
            }
        });

    }
}

4.DatagramChannel

接收端

package io.pdd.nio.udp;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;

/**
 * @author:liyangpeng
 * @date:2020/5/25 15:13
 */
public class DatagramReviceTest {
    public static void main(String[] args) throws IOException {
        DatagramChannel channel=DatagramChannel.open();
//        channel.configureBlocking(false);使用非堵塞
        channel.socket().bind(new InetSocketAddress("127.0.0.1",8901));
        ByteBuffer byteBuffer=ByteBuffer.allocate(1024);
        byteBuffer.clear();
        channel.receive(byteBuffer);
        byteBuffer.flip();
        while(byteBuffer.hasRemaining()){
            System.out.print((char)byteBuffer.get());
        }
        System.out.println();
        byteBuffer.clear();
        channel.close();
    }
}

发送端

package io.pdd.nio.udp;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;

/**
 * @author:liyangpeng
 * @date:2020/5/25 15:14
 */
public class DatagramSendChannel {
    public static void main(String[] args) throws IOException {
        DatagramChannel datagramChannel= DatagramChannel.open();
        String text="hello word!";
        ByteBuffer byteBuffer=ByteBuffer.allocate(1024);
        byteBuffer.put(text.getBytes("UTF-8"));
        byteBuffer.flip();
        int send = datagramChannel.send(byteBuffer, new InetSocketAddress("127.0.0.1",8901));
        System.out.println(send);
        byteBuffer.clear();
        datagramChannel.close();
    }
}