NIO全解析说明

ByteBuffer header = ByteBuffer.allocate(128);
ByteBuffer body   = ByteBuffer.allocate(1024);
ByteBuffer[] bufferArray = { header, body };
channel.read(bufferArray);

public static void trainforNio() {
 RandomAccessFile fromFile=null;
 RandomAccessFile toFile=null;
 try {

  fromFile = new RandomAccessFile("src/nio.txt", "rw");
  // channel获取数据
  FileChannel fromChannel = fromFile.getChannel();
  toFile = new RandomAccessFile("src/toFile.txt", "rw");
  FileChannel toChannel = toFile.getChannel();
  System.out.println(toChannel.size());
          //position处开始向目标文件写入数据,这里是toChannel
  long position = toChannel.size();
  long count = fromChannel.size();
  toChannel.transferFrom(fromChannel, position, count);
  System.out.println(toChannel.size());
 } catch (IOException e) {
  e.printStackTrace();
 } finally {
  try {
   if (fromFile != null) {
    fromFile.close();
   }
   if (toFile != null) {
    toFile.close();
   }
  } catch (IOException e) {
   e.printStackTrace();
  }
 }
}

import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

public class Method {
 public static void nio() {
  RandomAccessFile aFile = null;
  try {

   aFile = new RandomAccessFile("src/nio.txt", "rw");
   // channel获取数据
   FileChannel fileChannel = aFile.getChannel();
   // 初始化Buffer，设定Buffer每次可以存储数据量
   // 创建的Buffer是1024byte的，如果实际数据本身就小于1024，那么limit就是实际数据大小
   ByteBuffer buf = ByteBuffer.allocate(1024);
   // channel中的数据写入Buffer
   int bytesRead = fileChannel.read(buf);
   System.out.println(bytesRead);

   while (bytesRead != -1) {
    // Buffer切换为读取模式
    buf.flip();
    // 读取数据
    while (buf.hasRemaining()) {
     System.out.print((char) buf.get());
    }
    // 清空Buffer区
    buf.compact();
    // 继续将数据写入缓存区
    bytesRead = fileChannel.read(buf);
   }
  } catch (IOException e) {
   e.printStackTrace();
  } finally {
   try {
    if (aFile != null) {
     aFile.close();
    }
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
 }
 public static void main(String[] args) {
  Method.nio();

public abstract class Selector
{
// This is a partial API listing
public static Selector open( ) throws IOException
public abstract boolean isOpen( );//判断是open
public abstract void close( ) throws IOException;//选择键设置无效
public abstract SelectionProvider provider( );
}

public abstract class SelectableChannel
extends AbstractChannel
implements Channel
{
// This is a partial API listing
public abstract SelectionKey register (Selector sel, int ops)
throws ClosedChannelException;
public abstract SelectionKey register (Selector sel, int ops,
Object att)
throws ClosedChannelException;
public abstract boolean isRegistered( );
public abstract SelectionKey keyFor (Selector sel);
public abstract int validOps( );
}

package java.nio.channels;
public abstract class SelectionKey
{
public static final int OP_READ
public static final int OP_WRITE
public static final int OP_CONNECT
public static final int OP_ACCEPT
public abstract SelectableChannel channel( );
public abstract Selector selector( );
public abstract void cancel( );
public abstract boolean isValid( );
public abstract int interestOps( );
public abstract void interestOps (int ops);
public abstract int readyOps( );
public final boolean isReadable( )
public final boolean isWritable( )
public final boolean isConnectable( )
public final boolean isAcceptable( )
public final Object attach (Object ob)
public final Object attachment( )
}

selectionKey.attach(theObject);
Object attachedObj = selectionKey.attachment();

SelectionKey key = channel.register(selector, SelectionKey.OP_READ, theObject);

public abstract class Selector
{
public abstract Set keys( );
public abstract Set selectedKeys( );
public abstract int select( ) throws IOException;
public abstract int select (long timeout) throws IOException;
public abstract int selectNow( ) throws IOException;
public abstract void wakeup( );
}

import java.net.InetSocketAddress;
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;

public class NIOServer {
 // 通道管理器
 private Selector selector;

 public void initServer(int port) throws Exception {
  // 获得一个ServerSocket通道
  ServerSocketChannel serverChannel = ServerSocketChannel.open();
  // 设置通道为 非阻塞
  serverChannel.configureBlocking(false);
  // 将该通道对于的serverSocket绑定到port端口
  serverChannel.socket().bind(new InetSocketAddress(port));
  // 获得一耳光通道管理器
  this.selector = Selector.open();

  // 将通道管理器和该通道绑定，并为该通道注册selectionKey.OP_ACCEPT事件
  // 注册该事件后，当事件到达的时候，selector.select()会返回，
  // 如果事件没有到达selector.select()会一直阻塞

  serverChannel.register(selector, SelectionKey.OP_ACCEPT);
 }

 // 采用轮训的方式监听selector上是否有需要处理的事件，如果有，进行处理
 public void listen() throws Exception {
  System.out.println("start server");
  // 轮询访问selector
  while (true) {
   // 当注册事件到达时，方法返回，否则该方法会一直阻塞
   selector.select();
   // 获得selector中选中的相的迭代器，选中的相为注册的事件
   Iterator ite = this.selector.selectedKeys().iterator();
   while (ite.hasNext()) {
    SelectionKey key = (SelectionKey) ite.next();
    // 删除已选的key 以防重负处理
    ite.remove();
    // 客户端请求连接事件
    if (key.isAcceptable()) {
     ServerSocketChannel server = (ServerSocketChannel) key.channel();
     // 获得和客户端连接的通道
     SocketChannel channel = server.accept();
     // 设置成非阻塞
     channel.configureBlocking(false);
     // 在这里可以发送消息给客户端
     channel.write(ByteBuffer.wrap(new String("hello client").getBytes()));
     // 在客户端 连接成功之后，为了可以接收到客户端的信息，需要给通道设置读的权限
     channel.register(this.selector, SelectionKey.OP_READ);
     // 获得了可读的事件

    } else if (key.isReadable()) {
     read(key);
    }

   }
  }
 }

 // 处理 读取客户端发来的信息事件
 private void read(SelectionKey key) throws Exception {
  // 服务器可读消息，得到事件发生的socket通道
  SocketChannel channel = (SocketChannel) key.channel();
  // 穿件读取的缓冲区
  ByteBuffer buffer = ByteBuffer.allocate(10);
  channel.read(buffer);
  byte[] data = buffer.array();
  String msg = new String(data).trim();
  System.out.println("server receive from client: " + msg);
  ByteBuffer outBuffer = ByteBuffer.wrap(msg.getBytes());
  channel.write(outBuffer);
 }

 public static void main(String[] args) throws Throwable {
  NIOServer server = new NIOServer();
  server.initServer(8989);
  server.listen();
 }
}

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;

public class NIOClient {

 // 通道管理器
 private Selector selector;

 /**
  * * // 获得一个Socket通道，并对该通道做一些初始化的工作 * @param ip 连接的服务器的ip // * @param port
  * 连接的服务器的端口号 * @throws IOException
  */
 public void initClient(String ip, int port) throws IOException { // 获得一个Socket通道
  SocketChannel channel = SocketChannel.open(); // 设置通道为非阻塞
  channel.configureBlocking(false); // 获得一个通道管理器
  this.selector = Selector.open(); // 客户端连接服务器,其实方法执行并没有实现连接，需要在listen()方法中调
  // 用channel.finishConnect();才能完成连接
  channel.connect(new InetSocketAddress(ip, port));
  // 将通道管理器和该通道绑定，并为该通道注册SelectionKey.OP_CONNECT事件。
  channel.register(selector, SelectionKey.OP_CONNECT);
 }

 /**
  * * // 采用轮询的方式监听selector上是否有需要处理的事件，如果有，则进行处理 * @throws // IOException
  * @throws Exception 
  */
 @SuppressWarnings("unchecked")
 public void listen() throws Exception { // 轮询访问selector
  while (true) {
   // 选择一组可以进行I/O操作的事件，放在selector中,客户端的该方法不会阻塞，
   // 这里和服务端的方法不一样，查看api注释可以知道，当至少一个通道被选中时，
   // selector的wakeup方法被调用，方法返回，而对于客户端来说，通道一直是被选中的
   selector.select(); // 获得selector中选中的项的迭代器
   Iterator ite = this.selector.selectedKeys().iterator();
   while (ite.hasNext()) {
    SelectionKey key = (SelectionKey) ite.next(); // 删除已选的key,以防重复处理
    ite.remove(); // 连接事件发生
    if (key.isConnectable()) {
     SocketChannel channel = (SocketChannel) key.channel(); // 如果正在连接，则完成连接
     if (channel.isConnectionPending()) {
      channel.finishConnect();
     } // 设置成非阻塞
     channel.configureBlocking(false);
     // 在这里可以给服务端发送信息哦
     channel.write(ByteBuffer.wrap(new String("hello server!").getBytes()));
     // 在和服务端连接成功之后，为了可以接收到服务端的信息，需要给通道设置读的权限。
     channel.register(this.selector, SelectionKey.OP_READ); // 获得了可读的事件
    } else if (key.isReadable()) {
     read(key);
    }
   }
  }
 }

 private void read(SelectionKey key) throws Exception {
  SocketChannel channel = (SocketChannel) key.channel();
  // 穿件读取的缓冲区
  ByteBuffer buffer = ByteBuffer.allocate(10);
  channel.read(buffer);
  byte[] data = buffer.array();
  String msg = new String(data).trim();
  System.out.println("client receive msg from server:" + msg);
  ByteBuffer outBuffer = ByteBuffer.wrap(msg.getBytes());
  channel.write(outBuffer);

 }

 /**
  * * // 启动客户端测试 * @throws IOException
  * @throws Exception 
  */
 public static void main(String[] args) throws Exception {
  NIOClient client = new NIOClient();
  client.initClient("localhost", 8989);
  client.listen();
 }
}