NIO的非阻塞通信

使用NIO完成网络通信的三个要点：1)通道(Channel)：负责连接   java.nio.channels.Channel 接口：|--SelectableChannel|--SocketChannel|--ServerSocketChannel|--DatagramChannel|--Pipe.SinkChannel|--Pipe.SourceChannel2)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。说明：1)非阻塞模式是针对网络IO而言的。2)FileChannel不能切换成非阻塞模式。举例：阻塞式的网络IO：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 {@Testpublic void client() throws IOException{//1. 获取通道SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9999));//2. 分配指定大小的缓冲区ByteBuffer buf = ByteBuffer.allocate(1024);//3. 读取本地文件，并发送到服务端FileChannel inChannel = FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);while(inChannel.read(buf) != -1){buf.flip();sChannel.write(buf);buf.clear();}//4. 关闭通道inChannel.close();sChannel.close();}@Testpublic void server() throws IOException{//1. 获取通道ServerSocketChannel ssChannel = ServerSocketChannel.open();//2. 绑定连接ssChannel.bind(new InetSocketAddress(9999));//3. 获取客户端连接的通道SocketChannel sChannel = ssChannel.accept(); // 阻塞式的等待远程连接//4. 分配指定大小的缓冲区ByteBuffer buf = ByteBuffer.allocate(1024);//5. 接收客户端的数据，并保存到本地FileChannel outChannel = FileChannel.open(Paths.get("2.jpg"), StandardOpenOption.WRITE, StandardOpenOption.CREATE);while(sChannel.read(buf) != -1){buf.flip();outChannel.write(buf);buf.clear();}//6. 关闭通道sChannel.close();outChannel.close();ssChannel.close();}}非阻塞式的网络IO：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;public class TestNonBlockingNIO {@Testpublic void client() throws IOException{//1. 获取通道SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9999));//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scan.close();sChannel.close();}@Testpublic 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(9999));//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<SelectionKey> 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()){//10. 获取当前选择器上“读就绪”状态的通道SocketChannel sChannel = (SocketChannel) sk.channel();//11. 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 SelectionKeyit.remove();}}}}