五、NIO 的非阻塞式网络通信

一、普通IO

传统的IO当客户端请求服务端的资源，这个时候不确定是否准备好资源。如果这个时候存在问题，当前线程则会一直等待，不能再处理其他问题。就造成了阻塞。

二、NIO

NIO新增了选择器，所有的通道都会注册到选择器上，由选择器进行监控。当选择器监控到，客户端请求的资源都准备好的时候，再调用服务端的一个或多个线程，从而提高线程的利用率。

阻塞式：

package com.stu.nio;import org.junit.Test;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;/*** 一、使用 NIO 完成王阔通信的三个核心：* 1. 通道（Channel）：负责连接*  java.nio.channels.Channel 接口：*      |-- SelectableChannel:*          |-- SocketChannel:*          |-- ServerSocketChannel*          |-- DatagramChannel**          |-- Pipe.SinkChannel*          |-- Pipo.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 TestBlockingNIO {/*** 客户端*/@Testpublic void test1 () throws IOException {// 1. 获取通道SocketChannel socketChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9998));FileChannel inChannel = FileChannel.open(Paths.get("1.jpeg"), StandardOpenOption.READ);// 2. 分配指定大小的缓冲区ByteBuffer byteBuffer = ByteBuffer.allocate(1024);// 3. 读取本地文件，并发送到服务器端while (inChannel.read(byteBuffer) != -1) {byteBuffer.flip();socketChannel.write(byteBuffer);byteBuffer.clear();}// 4. 关闭通道inChannel.close();socketChannel.close();}/*** 服务端*/@Testpublic void test2() throws IOException {// 1. 获取通道ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();FileChannel outFileChannel = FileChannel.open(Paths.get("3.jpg"), StandardOpenOption.WRITE,StandardOpenOption.CREATE, StandardOpenOption.READ);// 2. 绑定连接serverSocketChannel.bind(new InetSocketAddress(9998));// 3. 获取客户端连接的通道SocketChannel socketChannel = serverSocketChannel.accept();// 4. 分配指定大小的缓存区ByteBuffer byteBuffer = ByteBuffer.allocate(1024);// 5. 接收客户端的数据，并保存到本地while (socketChannel.read(byteBuffer) != -1) {byteBuffer.flip();outFileChannel.write(byteBuffer);byteBuffer.clear();}// 6. 关闭对应的通道socketChannel.close();outFileChannel.close();serverSocketChannel.close();}
}

package com.stu.nio;import org.junit.Test;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;public class TestBlockingNIO2 {/*** 客户端*/@Testpublic void client() throws IOException {SocketChannel socketChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1",9998));FileChannel inFileChannel = FileChannel.open(Paths.get("1.jpeg"), StandardOpenOption.READ);ByteBuffer byteBuffer = ByteBuffer.allocate(1024);while (inFileChannel.read(byteBuffer) != -1) {byteBuffer.flip();socketChannel.write(byteBuffer);byteBuffer.clear();}// 不添加这一行，表明读取停止，则线程一直处于阻塞状态socketChannel.shutdownOutput();// 接收服务器的反馈int len = 0;while ((len = socketChannel.read(byteBuffer)) != -1) {byteBuffer.flip();System.out.println("返回内容：" + new String(byteBuffer.array(),0, len));byteBuffer.clear();}inFileChannel.close();socketChannel.close();}/*** 服务端*/@Testpublic void server() throws IOException {ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();FileChannel outFileChannel = FileChannel.open(Paths.get("5.jpg"), StandardOpenOption.WRITE,StandardOpenOption.CREATE);serverSocketChannel.bind(new InetSocketAddress(9998));SocketChannel socketChannel = serverSocketChannel.accept();ByteBuffer byteBuffer = ByteBuffer.allocate(1024);while (socketChannel.read(byteBuffer) != -1) {byteBuffer.flip();outFileChannel.write(byteBuffer);byteBuffer.clear();}// 发送反馈给客户端byteBuffer.put("服务端接收客户端数据成功".getBytes());byteBuffer.flip();socketChannel.write(byteBuffer);socketChannel.close();outFileChannel.close();serverSocketChannel.close();}
}

SelectionKey:

非阻塞式：

package com.stu.nio;import org.junit.Test;import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.Date;
import java.util.Iterator;
import java.util.Scanner;public class TestNonBlockingNIO {/*** 客户端*/@Testpublic void client() throws IOException {// 1.获取通道SocketChannel socketChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9998));// 2.切换非阻塞模式socketChannel.configureBlocking(false);// 3. 分配指定大小的缓存区ByteBuffer byteBuffer = ByteBuffer.allocate(1024);// 4. 发送数据给服务端Scanner scanner = new Scanner(System.in);while (scanner.hasNext()) {String str = scanner.next();String dateStr = new Date().toString() + "\n" +str;byteBuffer.put(dateStr.getBytes());byteBuffer.flip();socketChannel.write(byteBuffer);byteBuffer.clear();}// 5. 关闭通道socketChannel.close();}/*** 服务端*/@Testpublic void server() throws IOException {// 1. 获取通道ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();// 2. 切换非阻塞模式serverSocketChannel.configureBlocking(false);// 3. b绑定连接serverSocketChannel.bind(new InetSocketAddress(9998));// 4. 获取选择器Selector selector = Selector.open();// 5.将通道注册到选择器上serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);// 6. 轮询式的获取选择器上已经“猪呢比就绪”的时间while(selector.select() > 0 ) {// 7.获取当前选择器中，所有注册的"选择件"(已就绪的舰艇)Iterator<SelectionKey> it = selector.selectedKeys().iterator();while(it .hasNext()) {// 8. 获取猪呢比就绪的事件SelectionKey selectionKey = it.next();// 9. 判断具体if (selectionKey.isAcceptable()) {// 10. 若接收就绪，获取客户端连接SocketChannel socketChannel = serverSocketChannel.accept();// 11. 切换非阻塞模式socketChannel.configureBlocking(false);// 12. 将该通道注册到socketChannel.register(selector, SelectionKey.OP_READ);} else if (selectionKey.isReadable()) {// 13. 获取当前选择器上“读就绪，”状态的通道SocketChannel  socketChannel = (SocketChannel) selectionKey.channel();// 14. 读取数据ByteBuffer byteBuffer = ByteBuffer.allocate(1024);int len = 1;while ((len = socketChannel.read(byteBuffer)) > 0) {byteBuffer.flip();System.out.println("----" + new String(byteBuffer.array(),0,len));byteBuffer.clear();}}// 15. 取消选择键it.remove();}}}
}

package com.stu.nio;import org.junit.Test;import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.util.Date;
import java.util.Iterator;
import java.util.Scanner;public class TestNonBlockingNIO2 {@Testpublic void send() throws IOException {DatagramChannel datagramChannel = DatagramChannel.open();datagramChannel.configureBlocking(false);ByteBuffer byteBuffer = ByteBuffer.allocate(1024);Scanner scanner = new Scanner(System.in);while (scanner.hasNext()){String  str = scanner.next();byteBuffer.put((new Date().toString() + "\n" +str).getBytes());byteBuffer.flip();datagramChannel.send(byteBuffer, new InetSocketAddress("127.0.0.1", 9998));byteBuffer.clear();}datagramChannel.close();}@Testpublic void receive() throws IOException {DatagramChannel datagramChannel = DatagramChannel.open();datagramChannel.configureBlocking(false);datagramChannel.bind(new InetSocketAddress(9998));Selector selector = Selector.open();datagramChannel.register(selector, SelectionKey.OP_READ);while (selector.select() >0) {Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();while (iterator.hasNext()) {SelectionKey selectionKey = iterator.next();if (selectionKey.isReadable()) {ByteBuffer byteBuffer = ByteBuffer.allocate(1024);datagramChannel.receive(byteBuffer);byteBuffer.flip();System.out.println(new String(byteBuffer.array(), 0 , byteBuffer.limit()));byteBuffer.clear();}}iterator.remove();}}}

学自，b站尚硅谷

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