2、nio的例子实践

下面的例子，说明了，nio中的三大核心类的基本使用。buffer，channel，selector

package com.shengsiyuan.nio;

import org.junit.Test;

import java.io.*;
import java.net.*;
import java.nio.ByteBuffer;
import java.nio.IntBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.*;
import java.nio.channels.spi.SelectorProvider;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.Iterator;
import java.util.Set;

public class NioTest1 {

    public static void main(String[] args) {
        IntBuffer intBuffer = IntBuffer.allocate(10);

        for (int i = 0; i < intBuffer.capacity(); i++) {
            int randomNumber = new SecureRandom().nextInt(20);
            intBuffer.put(randomNumber);
        }

        intBuffer.flip();//翻转，从写转到读状态

        while (intBuffer.hasRemaining()) {
            System.out.println(intBuffer.get());
        }

    }

    public void testBuffer() {
        IntBuffer intBuffer = IntBuffer.allocate(10);

        for (int i = 0; i < intBuffer.capacity(); i++) {
            int randomNumber = new SecureRandom().nextInt(20);
            intBuffer.put(randomNumber);
        }

        intBuffer.flip();//翻转，从写转到读状态

        while (intBuffer.hasRemaining()) {
            System.out.println(intBuffer.get());
        }
    }

    /**
      * @ClassName:      NioTest1
      * @Description:     描述  读文件
      * @Author:         
      * @CreateDate:     2019/8/27 21:26
      * @Version:        1.0
     */
    @Test
    public void testChannelRead() {
        try {
            FileInputStream fileInputStream = new FileInputStream("NioTest1.txt");

            FileChannel fileChannel = fileInputStream.getChannel();

            ByteBuffer byteBuffer = ByteBuffer.allocate(512);

            fileChannel.read(byteBuffer);

            byteBuffer.flip();

            while(byteBuffer.remaining() > 0) {

                byte b = byteBuffer.get();
                System.out.println("char is : " + (char) b);

                if((char)b == 'e') {
                    byteBuffer.mark();
                }
            }

            System.out.println(byteBuffer.position());
            System.out.println(byteBuffer.limit());
            System.out.println(byteBuffer.capacity());

            byteBuffer.reset();

//            System.out.println(byteBuffer.mark());
            System.out.println(byteBuffer.position());
            System.out.println(byteBuffer.limit());
            System.out.println(byteBuffer.capacity());


            fileChannel.close();
            fileInputStream.close();

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
      * @ClassName:      NioTest1
      * @Description:     描述  写文件
      * @Author:         
      * @CreateDate:     2019/8/27 21:25
      * @Version:        1.0
     */
    @Test
    public void testChannelWrite() {
        try{
            FileInputStream fileInputStream = new FileInputStream("NioTest1.txt");
            FileChannel fileChannel = fileInputStream.getChannel();

            FileChannel randowFileChannel = new RandomAccessFile(new File("NioTest1.txt"),"rw").getChannel();

            ByteBuffer byteBuffer = ByteBuffer.allocate(512);

            byte[] byteArr = "hello nio  nihao!".getBytes();

            byteBuffer.put(byteArr);


            byteBuffer.flip();

//            fileChannel.write(byteBuffer);

            randowFileChannel.write(byteBuffer);
        }catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
      * @ClassName:      NioTest1
      * @Description:     描述  读写文件
      * @Author:         
      * @CreateDate:     2019/8/27 21:25
      * @Version:        1.0
     */
    @Test
    public void testChannelReadAndWrite() {
        try {
            FileInputStream fileInputStream = new FileInputStream("input.txt");
            FileOutputStream fileOutputStream = new FileOutputStream("out.txt");

            FileChannel inputFileChannel = fileInputStream.getChannel();
            FileChannel outputFileChannel = fileOutputStream.getChannel();

            ByteBuffer byteBuffer = ByteBuffer.allocate(512);

            while(inputFileChannel.read(byteBuffer) != -1) {

                byteBuffer.flip();

                outputFileChannel.write(byteBuffer);

//                byteBuffer.clear();
            }

        }catch (Exception e) {
            e.printStackTrace();
        }

    }

    /**   
      * @ClassName:      NioTest1
      * @Description:     描述  切下部分的byteBuffer 作为一个快照，可以实现同步
      * @Author:         
      * @CreateDate:     2019/8/27 21:24
      * @Version:        1.0
     */
    @Test
    public void testSlice() {
        try{
            ByteBuffer byteBuffer = ByteBuffer.allocate(512);

            for (int i = 0; i < 20; i++) {
                byteBuffer.put((byte)i);
            }
//            byteBuffer.flip();

            ByteBuffer newByteBuffer = byteBuffer.slice();

            byteBuffer.put((byte)'a');
            byteBuffer.put((byte)'b');

//            newByteBuffer.flip();
            System.out.println(newByteBuffer.get(0));

//            byteBuffer.put(0, (byte)9);

            newByteBuffer.put(0, (byte)9);

            System.out.println(byteBuffer.get(20));

            System.out.println(newByteBuffer.get(0));


        }catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**   
      * @ClassName:      NioTest1
      * @Description:     描述  只读的byteBuffer
      * @Author:         
      * @CreateDate:     2019/8/27 21:24
      * @Version:        1.0
     */
    @Test
    public void testReadonlyBuffer() {

        ByteBuffer byteBuffer = ByteBuffer.allocate(512);
        for (int i = 0; i < 10; i++) {
            byteBuffer.put((byte)i);
        }

        ByteBuffer readOnlyBuffer = byteBuffer.asReadOnlyBuffer();

        readOnlyBuffer.position(0);

        readOnlyBuffer.put((byte)1);

    }

    /**   
      * @ClassName:      NioTest1
      * @Description:     描述  通过直接内存，零拷贝来处理文件
      * @Author:         
      * @CreateDate:     2019/8/27 21:23
      * @Version:        1.0
     */
    @Test
    public void testChannelReadAndWriteDirect() {
        try {
            FileInputStream fileInputStream = new FileInputStream("input.txt");
            FileOutputStream fileOutputStream = new FileOutputStream("out.txt");

            FileChannel inputFileChannel = fileInputStream.getChannel();
            FileChannel outputFileChannel = fileOutputStream.getChannel();

            ByteBuffer byteBuffer = ByteBuffer.allocateDirect(512);

            while(inputFileChannel.read(byteBuffer) != -1) {

                byteBuffer.flip();

                outputFileChannel.write(byteBuffer);

                byteBuffer.clear();
            }

        }catch (Exception e) {
            e.printStackTrace();
        }

    }

    /**   
      * @ClassName:      NioTest1  内存映射，来修改文件  而不操作buffer
      * @Description:     描述 
      * @Author:         
      * @CreateDate:     2019/8/27 21:23
      * @Version:        1.0
     */
    @Test
    public void testMapBuffer() throws Exception {
        RandomAccessFile randomAccessFile = new RandomAccessFile("NioTest1.txt", "rw");
        FileChannel fileChannel = randomAccessFile.getChannel();

        MappedByteBuffer mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_WRITE, 0, 5);

        mappedByteBuffer.put(0, (byte)'a');
        mappedByteBuffer.put(3, (byte)'b');

        fileChannel.close();
        randomAccessFile.close();
    }


    /**
      * @ClassName:      NioTest1
      * @Description:     描述  测试 filelock
      * @Author:         
      * @CreateDate:     2019/8/27 21:30
      * @Version:        1.0
     */
    @Test
    public void testFilelock() throws Exception {
        FileChannel fileChannel = new RandomAccessFile("NioTest1.txt", "rw").getChannel();

        FileLock fileLock = fileChannel.lock(3, 6, false);

        System.out.println(fileLock.isValid());
        System.out.println(fileLock.isShared());
    }


    /**
      * @ClassName:      NioTest1
      * @Description:     描述
      * @Author:         
      * @CreateDate:     2019/8/27 22:36
      * @Version:        1.0
     */
    @Test
    public void testScattering() throws Exception {
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        SocketAddress address = new InetSocketAddress(8899);
        serverSocketChannel.bind(address);

        SocketChannel socketChannel = serverSocketChannel.accept();

        int messageLength = 2 + 3 +4;
        ByteBuffer[] byteBuffers = new ByteBuffer[3];

        byteBuffers[0] = ByteBuffer.allocate(2);
        byteBuffers[1] = ByteBuffer.allocate(3);
        byteBuffers[2] = ByteBuffer.allocate(4);

        while(true) {
            long readLength = 0;

            //最大读取 messageLength 长度的字符
            while(readLength < messageLength ) {
                long r = socketChannel.read(byteBuffers);
                readLength += r;

                System.out.println("byteBuffer length r is " + r);
                System.out.println("readLength length r is " + readLength);

                Arrays.asList(byteBuffers).forEach(byteBuffer -> {
                    System.out.println("p:" + byteBuffer.position() + ", l: " +byteBuffer.limit());
                });
            }

            Arrays.asList(byteBuffers).forEach(byteBuffer -> {
                byteBuffer.flip();
            });

            long writeLength = 0;
            //写会去
            while(writeLength < messageLength) {
                long w = socketChannel.write(byteBuffers);
                writeLength += w;
                System.out.println("byteBuffer length w is " + w);
                System.out.println("writeLength length w is " + writeLength);

                Arrays.asList(byteBuffers).forEach(byteBuffer -> {
                    System.out.println("p:" + byteBuffer.position() + ", l: " +byteBuffer.limit());
                });
            }

            Arrays.asList(byteBuffers).forEach(byteBuffer -> byteBuffer.clear());

        }
    }

    @Test
    public void testSelector() throws  Exception{
        Selector selector = Selector.open();

        int[] ports = {5000, 5001, 5002, 5003, 5004};

        for (int i = 0; i < ports.length; i++) {
            ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
            serverSocketChannel.configureBlocking(false); //变成非阻塞的模式 很重要

//            serverSocketChannel.bind(new InetSocketAddress(ports[i]));

            ServerSocket serverSocket = serverSocketChannel.socket();
            //这个bind 直接绑在 serverSocketChannel 可以不  尝试了下，好像区别不大，都可以走通  但是不能重复绑
            serverSocket.bind(new InetSocketAddress(ports[i]));

            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

            System.out.println("监听：" + ports[i]);
        }

        while(true) {

            int number = selector.select();
            System.out.println("number:" + number);

            Set<SelectionKey> selectionKeys = selector.selectedKeys();

            Iterator<SelectionKey> keyIterable = selectionKeys.iterator();

            System.out.println("selectionKeys : " + selectionKeys);

            while(keyIterable.hasNext()) {
                SelectionKey selectionKey = keyIterable.next();
                if(selectionKey.isAcceptable()) {//可接受的
                    ServerSocketChannel serverSocketChannel = (ServerSocketChannel) selectionKey.channel();
                    //这里为什么还要调accept  因为上面放进去的就是 ServerSocketChannel  ，而且没有调accept  接收请求
                    SocketChannel socketChannel = serverSocketChannel.accept();
                    socketChannel.configureBlocking(false);

                    System.out.println("获得链接：" + socketChannel);

                    socketChannel.register(selector, SelectionKey.OP_READ);
//                    socketChannel.register(selector, SelectionKey.OP_READ);  重复注册好像不影响

                    keyIterable.remove();//如果不remove  selectionKeys中会一直存在事件对象
                } else if(selectionKey.isReadable()) {//可读取的
                    //这里就可以直接用SocketChannel来接收，因为在accept中，是用socketChannel来注册的
                    SocketChannel socketChannel = (SocketChannel) selectionKey.channel();

                    ByteBuffer byteBuffer = ByteBuffer.allocate(512);
                    while(socketChannel.read(byteBuffer) > 0) {
                        byteBuffer.flip();

                        System.out.println("读取到客户端的消息：" + byteBuffer);
                        System.out.println("读取到客户端：" + socketChannel);

                        socketChannel.write(byteBuffer);

                        byteBuffer.clear();
                    }

                    keyIterable.remove();

                }

            }

        }


    }
}