一、使用NIO完成网络通信的三个核心

1、通道（Channel）:负责连接 java.nio.channels.Channel 接口 |– SelectableChannel |– SocketChannel |–ServerChannel |–DatagramChannel |–Pipe.SinkChannel |–Pipe.SourceChannel

2、缓冲区（Buffer）: 负责数据的存取

3、选择器（Selector）: 是SelectableChannel 的多路复用器，用于监控SelectableChannel 的IO状况

阻塞

package nio;import java.io.IOException;import java.net.InetSocketAddress;import java.nio.ByteBuffer;import java.nio.channels.FileChannel;import java.nio.channels.ServerSocketChannel;import java.nio.channels.SocketChannel;import java.nio.file.Paths;import java.nio.file.StandardOpenOption;import org.junit.Test;public class TestBlockingNIO {    @Test    public void client() throws IOException{        //1、获取通道        SocketChannel sChannel=SocketChannel.open(new InetSocketAddress("127.0.0.1",9898));        FileChannel inChannel=FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);        //2、获取指定大小的缓冲区域        ByteBuffer buf=ByteBuffer.allocate(1024);        //3、读取本地文件，并发送到服务端去        while(inChannel.read(buf)!=-1){            buf.flip();            sChannel.write(buf);            buf.clear();        }        //4、关闭通道        inChannel.close();        sChannel.close();    }    @Test    public void server() throws IOException{        //1、获取通道        ServerSocketChannel ssChannel=ServerSocketChannel.open();        FileChannel outChannel=FileChannel.open(Paths.get("2.jpg"),StandardOpenOption.WRITE,StandardOpenOption.CREATE);        //2、绑定连接        ssChannel.bind(new InetSocketAddress(9898));        //3、获取客户端连接的通道        SocketChannel sChannel=ssChannel.accept();        //4、分配指定大小的缓冲区        ByteBuffer buf=ByteBuffer.allocate(1024);        //5、接受客户端的数据，并保存到本地        while(sChannel.read(buf)!=-1){            buf.flip();            outChannel.write(buf);            buf.clear();        }        //6、关闭通道        sChannel.close();        ssChannel.close();        outChannel.close();    }}

非阻塞

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.ServerSocketChannel;import java.nio.channels.SocketChannel;import java.util.Date;import java.util.Iterator;import java.util.Scanner;import org.junit.Test;/* * 一、使用 NIO 完成网络通信的三个核心： *  * 1. 通道（Channel）：负责连接 *       *     java.nio.channels.Channel 接口： *          |--SelectableChannel *              |--SocketChannel *              |--ServerSocketChannel *              |--DatagramChannel *  *              |--Pipe.SinkChannel *              |--Pipe.SourceChannel *  * 2. 缓冲区（Buffer）：负责数据的存取 *  * 3. 选择器（Selector）：是 SelectableChannel 的多路复用器。用于监控 SelectableChannel 的 IO 状况 *  */public class TestNonBlockingNIO {
         //客户端    @Test    public void client() throws IOException{        //1. 获取通道        SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9898));        //2. 切换非阻塞模式        sChannel.configureBlocking(false);        //3. 分配指定大小的缓冲区        ByteBuffer buf = ByteBuffer.allocate(1024);        //4. 发送数据给服务端        Scanner scan = new Scanner(System.in);        while(scan.hasNext()){            String str = scan.next();            buf.put((new Date().toString() + "\n" + str).getBytes());            buf.flip();            sChannel.write(buf);            buf.clear();        }        //5. 关闭通道        sChannel.close();    }    //服务端    @Test    public void server() throws IOException{        //1. 获取通道        ServerSocketChannel ssChannel = ServerSocketChannel.open();        //2. 切换非阻塞模式        ssChannel.configureBlocking(false);        //3. 绑定连接        ssChannel.bind(new InetSocketAddress(9898));        //4. 获取选择器        Selector selector = Selector.open();        //5. 将通道注册到选择器上, 并且指定“监听接收事件”        ssChannel.register(selector, SelectionKey.OP_ACCEPT);        //6. 轮询式的获取选择器上已经“准备就绪”的事件        while(selector.select() > 0){            //7. 获取当前选择器中所有注册的“选择键(已就绪的监听事件)”            Iterator
     
       it = selector.selectedKeys().iterator();            while(it.hasNext()){                //8. 获取准备“就绪”的是事件                SelectionKey sk = it.next();                //9. 判断具体是什么事件准备就绪                if(sk.isAcceptable()){                    //10. 若“接收就绪”，获取客户端连接                    SocketChannel sChannel = ssChannel.accept();                    //11. 切换非阻塞模式                    sChannel.configureBlocking(false);                    //12. 将该通道注册到选择器上                    sChannel.register(selector, SelectionKey.OP_READ);                }else if(sk.isReadable()){                    //13. 获取当前选择器上“读就绪”状态的通道                    SocketChannel sChannel = (SocketChannel) sk.channel();                    //14. 读取数据                    ByteBuffer buf = ByteBuffer.allocate(1024);                    int len = 0;                    while((len = sChannel.read(buf)) > 0 ){                        buf.flip();                        System.out.println(new String(buf.array(), 0, len));                        buf.clear();                    }                }                //15. 取消选择键 SelectionKey                it.remove();            }        }    }}