NIO阻塞与非阻塞式

NIO的非阻塞模式

NIO完成核心的东西是一个选择器,Selector,选择器主要是将每一个传输数据的通道注册到选择器上,选择器作用是监控这些IO的状态(读,写,连接状态),然后用选择器监控通道的状况,等待所有的线程准备就绪时,选择器将任务分配到服务端一个或者多个线程上再去运行

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:

​ SelectChannel接口下有,SocketChannel,ServerSocketChannel,DatagramChannel

​ pipe.SinkChannel和PipeSourceChannel

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

阻塞式IO代码

package com.nio02;

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 TestBlockingNIO {
    //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));

        FileChannel inChannel = FileChannel.open(Paths.get("a.txt"), StandardOpenOption.READ);

        //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
        while (inChannel.read(buf) != -1) {
            buf.flip();
            sChannel.write(buf);
            buf.clear();
        }

        //4. 关闭通道
        inChannel.close();
        sChannel.close();
    }

    //服务端
    @Test
    public void server() throws IOException {
        //1. 获取通道
        ServerSocketChannel ssChannel = ServerSocketChannel.open();
        FileChannel outChannel = FileChannel.open(Paths.get("a2.txt"), 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();
        outChannel.close();
        ssChannel.close();
    }
}

原本阻塞式IO需要shutdownOutput()

package com.nio02;

import org.junit.Test;
import scala.reflect.io.Path;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.Socket;
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 {
    //服务端
    @Test
    public void server() throws IOException {
        ServerSocketChannel ssChannel = ServerSocketChannel.open();

        FileChannel outChannel = FileChannel.open(Paths.get("a.txt"), StandardOpenOption.WRITE, StandardOpenOption.CREATE);

        ssChannel.bind(new InetSocketAddress(9898));

        SocketChannel sChannel = ssChannel.accept();

        ByteBuffer buf = ByteBuffer.allocate(1024);

        while (sChannel.read(buf)!= -1){
            buf.flip();
            outChannel.write(buf);
            buf.clear();
        }

        //发送反馈给客户端
        buf.put("服务端接受数据成功!".getBytes());
        buf.flip();
        sChannel.write(buf);

        sChannel.close();
        outChannel.close();
        ssChannel.close();
    }

    //客户端
    @Test
    public void client() throws IOException {
        SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9898));

        FileChannel inChannel = FileChannel.open(Paths.get("a.txt"),StandardOpenOption.READ);

        ByteBuffer buf = ByteBuffer.allocate(1024);

        while (inChannel.read(buf) != -1){
            buf.flip();
            sChannel.write(buf);
            buf.clear();
        }
        sChannel.shutdownOutput();
        //接受服务端的反馈
        int len = 0;
        while ((len = sChannel.read(buf))!= -1){
            buf.flip();
            System.out.println(new String(buf.array(),0,len));
            buf.clear();
        }
        inChannel.close();
        sChannel.close();
    }

}

非阻塞式IO操作

​

//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<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()){
				//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();
		}
	}
}