管道（pipe）示例（带注释）

不念不忘少年蓝@ 2023-02-20 03:27 6阅读 0赞

## pipe 说明 ##

管道可以被用来仅在同一个 Java 虚拟机内部传输数据。虽然有更加有效率的方式来在线程之间传输数据，但是使用管道的好处在于封装性。1

## code ##

package com.nio.demo;
    
    import java.io.IOException;
    import java.nio.ByteBuffer;
    import java.nio.channels.Channels;
    import java.nio.channels.Pipe;
    import java.nio.channels.ReadableByteChannel;
    import java.nio.channels.WritableByteChannel;
    import java.util.Random;
    
    public class PipeTest {
    
    	public static void main(String[] args) throws Exception {
    		// 创建一个可写通道，用于向控制台输出管道中的内容
    		WritableByteChannel out = Channels.newChannel(System.out);
    		//启动一个工作线程，向管道写入数据，返回值为管道读的一端
    		ReadableByteChannel readableByteChannel = startWorker(10);
    		//创建一个缓冲区，用于接收管道中的数据
    		ByteBuffer buffer = ByteBuffer.allocate(100);
    		//如果工作线程中的管道一端不关闭，这个地方会一直阻塞在这里，即使没有数据传输
    		while(readableByteChannel.read(buffer)>=0) {
    			//将缓冲区翻转成一个准备读出元素的释放状态
    			buffer.flip();
    			//输出到控制台
    			out.write(buffer);
    			//清空缓冲区
    			buffer.clear();
    		}
    
    	}
    
    	private static ReadableByteChannel startWorker(int reps) throws Exception {
    		//打开一个管道
    		Pipe pipe = Pipe.open();
    		//创建工作线程，并打开管道写的一端(pipe.sink())
    		Worker worker=new Worker(pipe.sink(), reps);
    		worker.start();
    		//返回管道读的一端
    		return (pipe.source());
    	}
    	//工作线程类
    	private static class Worker extends Thread {
    		WritableByteChannel channel;
    		private int reps;
    
    		public Worker(WritableByteChannel channel, int reps) {
    			this.channel = channel;
    			this.reps = reps;
    		}
    
    		@Override
    		public void run() {
    			ByteBuffer buffer = ByteBuffer.allocate(100);
    			try {
    				for (int i = 0; i < reps; i++) {
    					doSomeWork(buffer);
    					while (channel.write(buffer) > 0) {
    						// empty
    					}
    				}
    			} catch (IOException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    		}
    
    		private String[] products = { "No good deed goes unpunished", "To be, or what?",
    				"No matter where you go, there you are", "Just say \"Yo\"", "My karma ran over my dogma" };
    		private Random rand = new Random();
    
    		private void doSomeWork(ByteBuffer buffer) {
    			int product = rand.nextInt(products.length);
    			buffer.clear();
    			buffer.put(products[product].getBytes());
    			buffer.put("\r\n".getBytes());
    			buffer.flip();
    		}
    
    	}
    
    }

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1.  《Java Nio》 ↩︎