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();

                 }

             }

         }

     }
 }