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BIO与NIO

1.传统BIO

（1）特点

面向数据流
阻塞式传输
一个客户端对应一个线程
在客户机增多的情况下，线程资源随之增多，会造成cpu资源枯竭

（2）需求

客户机向服务器输出字符串，逐一在服务器器上打印显示。类似一个简陋的聊天室功能。

（3）代码示例

服务器程序TimeServer.java

package com.xm.bio;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

public class TimeServer {

	public static void main(String[] args) throws IOException {
		int port = 8080;
		if(args != null && args.length>0) {
			try {
				port = Integer.parseInt(args[0]);
				
			} catch (Exception e) {
				
			}
		}
		
		ServerSocket server = null;
		try {
			server = new ServerSocket(port);
			System.out.println("开启服务器:"+server.getLocalSocketAddress());
			Socket socket = null;
			while(true) {
				socket = server.accept();
				new Thread(new TimeServerHandle(socket)).start();
			}
		} finally {
			if(server != null) {
				System.out.println("服务器已关闭！");
				server.close();
				server = null;
			}
		}

	}

}

服务器处理客户机进程TimeServerHandle.java

package com.xm.bio;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Date;

public class TimeServerHandle implements Runnable {
	
	private Socket socket;
	
	public TimeServerHandle(Socket socket) {
		this.socket = socket;
	}

	@Override
	public void run() {
		System.out.println(socket.getInetAddress().toString()+"客户机已连接");
		BufferedReader in = null;
		PrintWriter out = null;
		BufferedReader wt = null;
		try {
			in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
			out = new PrintWriter(socket.getOutputStream(), true);
			wt = new BufferedReader(new InputStreamReader(System.in));
			while(true) {
					System.out.println(in.readLine());
			}
		} catch (Exception e) {
			
		} finally {
			if(in != null) {
				try {
					in.close();
					in = null;
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			if(out != null) {
				out.close();
				out = null;
			}
			if(socket != null) {
				try {
					socket.close();
					socket = null;
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				
			}
		}
		

	}

}

客户端程序TimeClient.java

package com.xm.bio;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;

public class TimeClient {

	public static void main(String[] args) {
		int port = 8080;
		String host = "127.0.0.1";
		Socket socket = null;
		BufferedReader in = null;
		BufferedReader wt = null;
		PrintWriter out = null;
		try {
			socket = new Socket(host, port);
			wt = new BufferedReader(new InputStreamReader(System.in));
			in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
			out = new PrintWriter(socket.getOutputStream(), true);
			String body = null;
			while(true) {
				String str = wt.readLine();
				out.println(str);
			}
		} catch (UnknownHostException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally {
			try {
				wt.close();
				in.close();
				out.close();
				socket.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			
		}

	}

}

2.NIO

（1）NIO特点

1.面向缓冲区
2.传输方式为管道传输
3.非阻塞
4.支持大并发下的io处理

（2）NIO下的本地文件传输

内存映射下的缓冲通道

package com.xm.nio;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.time.Duration;
import java.time.Instant;

import org.junit.jupiter.api.Test;

public class NIOFileDemo {
	
	/**
	 * 1.通过流获取通道
	 */
	@Test
	public void test1() {
		Instant begin = Instant.now();
		//1.定义文件流
		FileInputStream fis = null;
		FileOutputStream fos = null;
		//2.获取通道
		FileChannel inChannel = null;
		FileChannel outChannel = null;
		try {
			fis = new FileInputStream("1.jpg");
			fos = new FileOutputStream("2.jpg");
			
			inChannel = fis.getChannel();
			outChannel = fos.getChannel();
			
			//3.定义缓冲区
			ByteBuffer buffer = ByteBuffer.allocate(1024);
			
			//4.读取数据到缓冲区,再从缓冲区写入到文件
			while(inChannel.read(buffer) != -1) {
				//切换到读模式
				buffer.flip();
				//写操作到管道
				outChannel.write(buffer);
				//清空buffer
				buffer.clear();
			}
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
			//5.关闭通道和流
			if(inChannel != null) {
				try {
					inChannel.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			if(outChannel != null) {
				try {
					outChannel.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			if(fis != null) {
				
				try {
					fis.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				
			}
			if(fos != null) {
				try {
					fos.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				
			}
			
			}
		Instant end = begin.plus(Duration.ofSeconds(10));
		System.out.println("Difference in milliseconds : " + Duration.between(begin, end).toMillis());
	}
	
	/**
	 * 通过文件获取管道
	 */
	@Test
	public void test2() {
		Instant begin = Instant.now();
		FileChannel inChannel =null;
		FileChannel outChannel = null;
		try {
			inChannel =FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);
			/**
			 * StandardOpenOption.CREATE与StandardOpenOption.CREATE_NEW的区别
			 * 1.StandardOpenOption.CREATE：无则创建，有则覆盖
			 * 2.StandardOpenOption.CREATE_NEW：无则创建，有则报错
			 */
			outChannel =FileChannel.open(Paths.get("2.jpg"), StandardOpenOption.WRITE,StandardOpenOption.CREATE);
			//3.定义缓冲区
			ByteBuffer buffer = ByteBuffer.allocate(1024);
			
			//4.读取数据到缓冲区,再从缓冲区写入到文件
			while(inChannel.read(buffer) != -1) {
				//切换到读模式
				buffer.flip();
				//写操作到管道
				outChannel.write(buffer);
				//清空buffer
				buffer.clear();
			}
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
			//5.关闭通道和流
			if(inChannel != null) {
				try {
					inChannel.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			if(outChannel != null) {
				try {
					outChannel.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
		Instant end = begin.plus(Duration.ofSeconds(10));
		System.out.println("Difference in milliseconds : " + Duration.between(begin, end).toMillis());
		
	}

}

物理映射下的缓冲通道

package com.xm.nio;

import java.io.IOException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.time.Duration;
import java.time.Instant;

import org.junit.Test;

public class NIOFileDemo2 {
	
	/**
	 * 使用直接缓冲区传输
	 */
	@Test
	public void test1() {
		Instant begin = Instant.now();
		FileChannel inChannel = null;
		FileChannel outChannel = null;
		
		try {
			//1.开启通道
			inChannel = FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);
			outChannel = FileChannel.open(Paths.get("2.jpg"), StandardOpenOption.WRITE,StandardOpenOption.CREATE,StandardOpenOption.READ);
			
			//2.定义物理缓冲区
			MappedByteBuffer inBuffer = inChannel.map(MapMode.READ_ONLY, 0, inChannel.size());
			MappedByteBuffer outBuffer = outChannel.map(MapMode.READ_WRITE, 0, inChannel.size());
			
			//3.缓冲区读写操作
			byte[]  dst = new byte[inBuffer.limit()];
			inBuffer.get(dst);
			outBuffer.put(dst);
			
			
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
			//4.关闭通道
			if(null != inChannel) {
				
				try {
					inChannel.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			if(null != outChannel) {
				
				try {
					outChannel.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
		Instant end = begin.plus(Duration.ofSeconds(10));
		System.out.println("Difference in milliseconds : " + Duration.between(begin, end).toMillis());
	}
	
	/**
	 * 通道之间的传输
	 */
	@Test
	public void test2() {
		Instant begin = Instant.now();
		FileChannel inChannel = null;
		FileChannel outChannel = null;
		//获取通道
		try {
			inChannel = FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);
			outChannel = FileChannel.open(Paths.get("2.jpg"), StandardOpenOption.WRITE,StandardOpenOption.CREATE);
			
			//通道间传输
			//1.to操作
			//inChannel.transferTo(0, inChannel.size(), outChannel);
			//2.from操作
			outChannel.transferFrom(inChannel, 0, inChannel.size());
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally {
			//4.关闭通道
			if(null != inChannel) {
				
				try {
					inChannel.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			if(null != outChannel) {
				
				try {
					outChannel.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
		Instant end = begin.plus(Duration.ofSeconds(10));
		System.out.println("Difference in milliseconds : " + Duration.between(begin, end).toMillis());
	}

}

（3）NIO下的网络传输

阻塞式

服务端程序

package com.xm.nio.block;

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 java.util.Scanner;

public class NIOServer {

	public static void main(String[] args) throws IOException {
		
		int port = 8989;
			
		//1.获取通道
		ServerSocketChannel serverChannel = ServerSocketChannel.open();
		
		//2.绑定端口号
		serverChannel.bind(new InetSocketAddress(port));
		
		//3.获取客户端连接
		SocketChannel socketChannel = serverChannel.accept();
		
		//定义文件传输通道
		FileChannel outChannel = FileChannel.open(Paths.get("3.jpg"), StandardOpenOption.WRITE,StandardOpenOption.CREATE);
		ByteBuffer buffer = ByteBuffer.allocate(1024);
		while(socketChannel.read(buffer)!=-1) {
			buffer.flip();
			outChannel.write(buffer);
			buffer.clear();
		}
		
		outChannel.close();
		socketChannel.close();

	}

}

客户端程序

package com.xm.nio.block;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.SocketChannel;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;

public class NIOClient {

	public static void main(String[] args) throws IOException {
		int port = 8989;
		//1.获取通道
		SocketChannel socketChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", port));
		
		
		//2.获取文件通道
		FileChannel inChannel = FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);
		inChannel.transferTo(0, inChannel.size(), socketChannel);
		
		//3.关闭通道
		inChannel.close();
		socketChannel.close();

	}

}

非阻塞式

服务端程序

package com.xm.nio.noblock;

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.ArrayList;
import java.util.Iterator;
import java.util.List;

public class NIOServer {

	public static void main(String[] args) throws IOException {
		

		int port = 8989;
			
		//1.开启通道
		ServerSocketChannel serverChannel = ServerSocketChannel.open();
		
		//2.绑定端口号
		serverChannel.bind(new InetSocketAddress(port));
		
		//3.设置非阻塞
		serverChannel.configureBlocking(false);
		
		//4.开启选择器
		Selector selector = Selector.open();
		
		//5.注册连接监听
		serverChannel.register(selector, SelectionKey.OP_ACCEPT);
		
		List<SocketChannel> channels = new ArrayList<>();
		
		while(selector.select() > 0) {
			Iterator<SelectionKey> keys = selector.selectedKeys().iterator();
			
			while(keys.hasNext()) {
				SelectionKey key = keys.next();
				if(key.isAcceptable()) {
					SocketChannel socketChannel = serverChannel.accept();
					channels.add(socketChannel);
					System.out.println("客户端连接成功："+socketChannel.getLocalAddress()+" hashcode:"+socketChannel.hashCode());
					socketChannel.configureBlocking(false);
					socketChannel.register(selector, SelectionKey.OP_READ);
				} else if(key.isReadable()) {
					SocketChannel socketChannel = (SocketChannel) key.channel();
					ByteBuffer dst = ByteBuffer.allocate(1024);
					int len;
					while(-1 != (len=socketChannel.read(dst))) {
						dst.flip();
						System.out.println(new String(dst.array(),0,len));
						/*for(SocketChannel sChannel:channels) {
							if(sChannel != socketChannel) {
								dst.flip();
								sChannel.write(dst);
							}
						}*/
						dst.clear();
					}
				}		
			}
			
			keys.remove();
		}

	}

}

客户端

package com.xm.nio.noblock;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.Iterator;
import java.util.Scanner;

public class NIOClient{
	
	SocketChannel socketChannel;
	
	
	public NIOClient() throws IOException {
		int port = 8989;
		//1.获取通道
		socketChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", port));
		//2.设置异步非阻塞
		socketChannel.configureBlocking(false);
		
		//2.获取文件通道
		FileChannel inChannel = FileChannel.open(Paths.get("1.md"), StandardOpenOption.READ);
		inChannel.transferTo(0, inChannel.size(), socketChannel);
				
				//3.关闭通道
				inChannel.close();
				socketChannel.close();
		
	}
	

	public static void main(String[] args)  {	
		try {
			new NIOClient();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
		


}

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原文地址：https://www.cnblogs.com/TimerHotel/p/java_nio.html