通过管道进行线程间通信

　　在Java语言中提供了各种各样的输入/输出流Stream,使我们能够方便地对数据进行操作，其中管道流(pipeStream)是一种特殊的流，用于在不同线程间直接传送数据。一个发送数据到输出管道，另一个线程从输入管道中读数据。通过使用管道，实现不同线程间的通信，而无需借助于临时文件之类的动西。

　　在Java的JDK中提供了4个类来使线程间可以通信:

　　(1)PipedInputStream和PipedOutputStream

　　(2)PipedReader和PipedWriter

1. 通过字节流 Stream实现线程间通信

用 PipedInputStream和PipedOutputStream实现线程间通信:

package cn.qlq.thread.eight;

import java.io.IOException;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import sun.misc.IOUtils;

/**
 * 通过管道进行线程间通信:字节流
 * 
 * @author Administrator
 *
 */
public class Demo1 {

    private static final Logger LOGGER = LoggerFactory.getLogger(Demo1.class);

    public static void main(String[] args) throws IOException {
        final PipedInputStream inputStream = new PipedInputStream();
        final PipedOutputStream outputStream = new PipedOutputStream();

        // 使管道建立连接
        // inputStream.connect(outputStream);
        outputStream.connect(inputStream);

        // 开启线程读和写入
        new Thread(new Runnable() {
            @Override
            public void run() {
                LOGGER.info("threamName ->{} 进入run ", Thread.currentThread().getName());
                try {
                    for (int i = 0; i < 10; i++) {
                        String data = String.valueOf(i);
                        outputStream.write(data.getBytes());
                        LOGGER.info("threadName->{} write data ->{}", Thread.currentThread().getName(), data);
                        outputStream.flush();
                    }
                    outputStream.close();
                    LOGGER.info("threamName ->{} 结束run ", Thread.currentThread().getName());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }, "writeThread").start();

        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    LOGGER.info("threamName ->{} 进入run ", Thread.currentThread().getName());
                    byte[] buffer = new byte[20];
                    int readLength = inputStream.read(buffer);
                    while (readLength != -1) {
                        String data = new String(buffer, 0, readLength);
                        LOGGER.info("threadName->{} read data ->{}", Thread.currentThread().getName(), data);
                        readLength = inputStream.read(buffer);
                    }
                    inputStream.close();
                    LOGGER.info("threamName ->{} 结束run ", Thread.currentThread().getName());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }, "readThread").start();
    }
}

结果:

12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threamName ->readThread 进入run
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threamName ->writeThread 进入run
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->writeThread write data ->0
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->writeThread write data ->1
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->readThread read data ->0
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->writeThread write data ->2
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->readThread read data ->12
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->writeThread write data ->3
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->readThread read data ->3
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->writeThread write data ->4
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->readThread read data ->4
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->writeThread write data ->5
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->readThread read data ->5
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->writeThread write data ->6
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->readThread read data ->6
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->writeThread write data ->7
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->readThread read data ->7
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->writeThread write data ->8
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->readThread read data ->8
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->writeThread write data ->9
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threadName->readThread read data ->9
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threamName ->writeThread 结束run
12:11:33 [cn.qlq.thread.eight.Demo1]-[INFO] threamName ->readThread 结束run

　　使用代码outputStream.connect(inputStream); (或者inputStream.connect(outputStream);)是为了使两个管道建立通信连接，这样才可以将数据进行输入与输出。

　　readThread 启动后，由于当时没有数据被写入，所以线程阻塞在int readLength = inputStream.read(buffer);  直到有数据被写入时，才继续向下运行。

2. 通过字符流 ReaderWriter实现线程间通信

　　例子与上面一样:

package cn.qlq.thread.eight;

import java.io.IOException;
import java.io.PipedReader;
import java.io.PipedWriter;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 通过管道进行线程间通信:字符流
 * 
 * @author Administrator
 *
 */
public class Demo2 {

    private static final Logger LOGGER = LoggerFactory.getLogger(Demo2.class);

    public static void main(String[] args) throws IOException {
        final PipedWriter writer = new PipedWriter();
        final PipedReader reader = new PipedReader();

        // 使管道建立连接
        // writer.connect(reader);
        reader.connect(writer);

        // 开启线程读和写入
        new Thread(new Runnable() {
            @Override
            public void run() {
                LOGGER.info("threamName ->{} 进入run ", Thread.currentThread().getName());
                try {
                    for (int i = 0; i < 5; i++) {
                        String data = String.valueOf(i);
                        writer.write(data);
                        LOGGER.info("threadName->{} write data ->{}", Thread.currentThread().getName(), data);
                    }
                    writer.close();
                    LOGGER.info("threamName ->{} 结束run ", Thread.currentThread().getName());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }, "writerThread").start();

        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    LOGGER.info("threamName ->{} 进入run ", Thread.currentThread().getName());
                    char[] buffer = new char[20];
                    int read = reader.read(buffer);
                    while (read != -1) {
                        String data = new String(buffer, 0, read);
                        LOGGER.info("threadName->{} read data ->{}", Thread.currentThread().getName(), data);
                        read = reader.read(buffer);
                    }
                    reader.close();
                    LOGGER.info("threamName ->{} 结束run ", Thread.currentThread().getName());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }, "readThread").start();
    }
}

结果:

13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threamName ->writerThread 进入run
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threamName ->readThread 进入run
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->writerThread write data ->0
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->readThread read data ->0
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->writerThread write data ->1
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->readThread read data ->1
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->writerThread write data ->2
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->readThread read data ->2
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->writerThread write data ->3
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->readThread read data ->3
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->writerThread write data ->4
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->readThread read data ->4
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->writerThread write data ->5
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->readThread read data ->5
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->writerThread write data ->6
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->readThread read data ->6
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->writerThread write data ->7
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->readThread read data ->7
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->writerThread write data ->8
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->readThread read data ->8
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->writerThread write data ->9
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threadName->readThread read data ->9
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threamName ->writerThread 结束run
13:29:52 [cn.qlq.thread.eight.Demo2]-[INFO] threamName ->readThread 结束run

　　

　　代码    // writer.connect(reader); (或者 reader.connect(writer);) 是使两个管道建立通信连接。