Netty学习 2、通道（Channel）

通道（Channel）是NIO用来传输数据的。和流类似，只不过有很大的区别

区别：

• ​ 通道用来传输的是数据块，也就是Buffer。而流用来传输字节的
• ​ 通道可以同时进行读写，而流只能读或者只能写
• ​ 通道可以实现异步读写数据
• ​ 通道可以从缓冲读数据，也可以写数据到缓冲

package com.dashu.nio;


import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.Map;
import java.util.Set;



public class NioChannel {



    public static void main(String[] args) throws CharacterCodingException {
        NioChannel nioChannel = new NioChannel();
    }

   



   


    
    public void test04() {

        //输入文件
        RandomAccessFile inRandomAccessFile = null;
        //输入文件通道
        FileChannel inFileChannel = null;

        //输出通道
        RandomAccessFile outRandomAccessFile = null;
        //输出文件通道
        FileChannel outFileChannel = null;


        try {

            //创建输入文件
            inRandomAccessFile = new RandomAccessFile("d:/a.txt", "rw");

            //创建输入通道
            inFileChannel = inRandomAccessFile.getChannel();

            //缓冲区1
            ByteBuffer byteBuffer1 = ByteBuffer.allocate(100);
            //缓冲区2
            ByteBuffer byteBuffer2 = ByteBuffer.allocate(100);

            //缓冲区数组
            ByteBuffer[] byteBuffers = {byteBuffer1, byteBuffer2};

            //将输入通道中的数据写到缓冲区数组
            inFileChannel.read(byteBuffers);

            //切换缓冲区数组中缓冲区的模式：读
            for (ByteBuffer byteBuffer : byteBuffers) {
                byteBuffer.flip();
            }

            //分别打印缓冲区中的数据
            System.out.println(new String(byteBuffers[0].array(), 0, byteBuffers[0].limit()));
            System.out.println("-----------");
            System.out.println(new String(byteBuffers[1].array(), 0, byteBuffers[1].limit()));


            //创建输出文件
            outRandomAccessFile = new RandomAccessFile("d:/a2.txt", "rw");
            //创建输出通道
            outFileChannel = outRandomAccessFile.getChannel();
            //将缓冲区数组的数据写到输出通道
            outFileChannel.write(byteBuffers);

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //通道和文件输入流关闭关闭

            if (outFileChannel != null) {
                try {
                    outFileChannel.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }


            if (outRandomAccessFile != null) {
                try {
                    outRandomAccessFile.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }


            if (inFileChannel != null) {
                try {
                    inFileChannel.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }


            if (inRandomAccessFile != null) {
                try {
                    inRandomAccessFile.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }

    }


    
    public void test03() {
        //获取当前时间毫秒
        long start = System.currentTimeMillis();

        //获取文件输入通道
        FileChannel inChannel = null;

        //获取文件输出通道
        FileChannel outChannel = null;


        try {

            //创建文件输入通道（StandardOpenOption.READ：读）
            inChannel = FileChannel.open(Paths.get(""), StandardOpenOption.READ);

            //创建文件输出通道（StandardOpenOption.WRITE：写， StandardOpenOption.READ：读, StandardOpenOption.CREATE：文件不存在创建，文件存在覆盖）
            outChannel = FileChannel.open(Paths.get(""), StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE);

            //将输入文件通道的输据转移到输出文件通道
            inChannel.transferTo(0, inChannel.size(), outChannel);

            //将输入文件通道的输据转移到输出文件通道
            outChannel.transferFrom(inChannel, 0, inChannel.size());

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //通道关闭

            if (outChannel != null) {
                try {
                    outChannel.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }


            if (inChannel != null) {
                try {
                    inChannel.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }

        //获取当前时间毫秒
        long end = System.currentTimeMillis();
        //输出
        System.out.println("耗时：" + (end - start));

    }

    
    public void test02() {
        //获取当前时间毫秒
        long start = System.currentTimeMillis();

        //文件输入通道
        FileChannel inChannel = null;

        //文件输出通道
        FileChannel outChannel = null;


        try {

            // 输入通道（StandardOpenOption.READ：读）
            inChannel = FileChannel.open(Paths.get("d:/a.txt"), StandardOpenOption.READ);

            // 输入通道（StandardOpenOption.WRITE：写， StandardOpenOption.READ：读, StandardOpenOption.CREATE：文件不存在创建，文件存在覆盖）
            outChannel = FileChannel.open(Paths.get("d:/a3.txt"), StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE);

            //通过输入通道获取输入Buffer
            MappedByteBuffer inMappedByteBuffer = inChannel.map(FileChannel.MapMode.READ_ONLY, 0, inChannel.size());

            //通过输出通道获取输出Buffer
            MappedByteBuffer outMappedByteBuffer = outChannel.map(FileChannel.MapMode.READ_WRITE, 0, inChannel.size());

            //创建byte数组
            byte[] dst = new byte[inMappedByteBuffer.limit()];

            //获取输入Buffer的数据保存到byte数组
            inMappedByteBuffer.get(dst);

            //将byte数组的数据保存到输出Buffer
            outMappedByteBuffer.put(dst);

        } catch (Exception e) {
            //异常抛出
            e.printStackTrace();
        } finally {

            //通道关闭

            if (outChannel != null) {
                try {
                    outChannel.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }


            if (inChannel != null) {
                try {
                    inChannel.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }


        //获取当前时间毫秒
        long end = System.currentTimeMillis();
        //输出
        System.out.println("耗时：" + (end - start));
    }

    
    public void test01() {
        //获取当前时间毫秒
        long start = System.currentTimeMillis();

        //文件输入流
        FileInputStream fileInputStream = null;

        //文件输出流
        FileOutputStream fileOutputStream = null;

        //文件输入通道
        FileChannel inChannel = null;

        //文件输出通道
        FileChannel outChannel = null;


        try {

            //输入文件
            fileInputStream = new FileInputStream("d:/a.txt");

            //输出文件
            fileOutputStream = new FileOutputStream("d:/a2.txt");

            //输入通道
            inChannel = fileInputStream.getChannel();

            //输出通道
            outChannel = fileOutputStream.getChannel();

            //创建缓存区
            ByteBuffer byteBuffer = ByteBuffer.allocate(1024);

            //循环将”输入通道“中的数据读取到”缓存区“，然后将”缓存区“中的数据写入到”输出通道“
            while (true) {

                //先清空缓存区
                byteBuffer.clear();

                //将”输入通道“中的数据读取（存入）到”缓存区“
                int read = inChannel.read(byteBuffer);

                //判断”输入通道“中的数据是否读取完，读取完，退出循环
                if (read == -1) {
                    break;
                }

                //切换”缓存区“模式：读
                byteBuffer.flip();

                //将”缓存区“中的数据写到（存入）”输出通道“
                outChannel.write(byteBuffer);

            }
        } catch (Exception e) {
            //异常抛出
            e.printStackTrace();
        } finally {

            //关闭通道和流

            if (outChannel != null) {
                try {
                    outChannel.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }

            }

            if (inChannel != null) {
                try {
                    inChannel.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }

            }

            if (fileOutputStream != null) {
                try {
                    fileOutputStream.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }

            }

            if (fileInputStream != null) {
                try {
                    fileInputStream.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }

            }
        }

        //获取当前时间毫秒
        long end = System.currentTimeMillis();
        //输出
        System.out.println("耗时：" + (end - start));
    }
}