【Java nio】Channel

package com.slp.nio;

import org.junit.Test;

import java.io.*;
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;

/**
 * Created by sanglp on 2017/3/1.
 * 一、通道：用于源节点与目标节点的连接，在Java NIO中负责缓冲区中数据的传输。通道本身是不存储任何数据的，因此需要配合缓冲区进行传输数据
 * 二、通道的一些主要实现类
 * java.nio.Channel接口
 *     |--FileChannel
 *     |--SocketChannel
 *     |--ServerSocketChannel
 *     |--DatagramChannel
 * 三、获取通道
 * 1.java针对支持通道的类提供了getChannel()方法
 *     本地IO:
 *     FileInputStream/FileOutputStream/RandomAccessFile
 *     网络IO:
 *     Socket
 *     ServerSocket
 *     DategramSocket
 * 2.在jdk1.7中的NIO2针对各个通道提供了一个静态方法open()
 * 3。jdk1.7中的NIO2的Files工具类的newByteChannel()
 * 四、通道之间的数据传输
 * transferFrom()
 * transferTo()
 * 五、分散和聚集
 * 分散度区：将通道中的数据分散到多个缓冲区中
 * 聚集写入：将多个缓冲区中的数据聚集到通道中
 *
 * 六、字符集：Charset
 * 编码：字符串->字节数组
 * 解码：字节数组->字符串
 */
public class TestChannel {
    @Test
    public void test6() throws CharacterCodingException {
        Charset cs1 =  Charset.forName("GBK");
        //获取编码器和解码器
        CharsetEncoder ce = cs1.newEncoder();
        //获取解码器
        CharsetDecoder cd = cs1.newDecoder();

        CharBuffer charBuffer = CharBuffer.allocate(1024);
        charBuffer.put("桑丽平加油!!");
        charBuffer.flip();

        //编码
        ByteBuffer byteBuffer = ce.encode(charBuffer);
        for (int i=0;i<12;i++){
            System.out.println(byteBuffer.get(i));
        }

        //解码
        byteBuffer.flip();
      CharBuffer charBuffer1 =   cd.decode(byteBuffer);
        System.out.println(charBuffer1.toString());

        System.out.println("------------------------");

        Charset cs2 = Charset.forName("UTF-8");
        byteBuffer.flip();
        CharBuffer  cBuf3 =cs2.decode(byteBuffer);
        System.out.println(cBuf3.toString());
    }

    @Test
    public void test5(){
        Map<String,Charset> map=Charset.availableCharsets();
        Set<Map.Entry<String,Charset>> set = map.entrySet();
       for (Map.Entry<String,Charset> entry :set ){
           System.out.println(entry.getKey()+"="+entry.getValue());
       }
    }
    @Test
    public void test4() throws IOException {
        RandomAccessFile randomAccessFile = new RandomAccessFile("1.txt","rw");
        //获取通道
        FileChannel channel = randomAccessFile.getChannel();
        //分配指定大小的缓冲区
        ByteBuffer buffer1 = ByteBuffer.allocate(100);
        ByteBuffer buffer2 = ByteBuffer.allocate(1024);
        //分散读取
        ByteBuffer [] bufs = {buffer1,buffer2};
        channel.read(bufs);
        for (ByteBuffer byteBuffer:bufs){
            byteBuffer.flip();
        }

        System.out.println(new String(bufs[0].array(),0,bufs[0].limit()));
        System.out.println("---------------");
        System.out.println(new String(bufs[1].array(),0,bufs[1].limit()));

        //聚集写入
        RandomAccessFile randomAccessFile1 = new RandomAccessFile("2.txt","rw");
        FileChannel channel1 = randomAccessFile1.getChannel();
        channel1.write(bufs);

    }

    //通道之间的数据传输(直接缓冲区)
    @Test
    public void test3() throws IOException {
        FileChannel fileChannel = FileChannel.open(Paths.get("pipe.bmp"), StandardOpenOption.READ);
        FileChannel outChannel =FileChannel.open(Paths.get("4.bmp"),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE_NEW);

        fileChannel.transferTo(0,fileChannel.size(),outChannel);
        //outChannel.transferFrom(fileChannel,0,fileChannel.size());或者
        fileChannel.close();
        outChannel.close();
    }

    //2、利用直接缓冲区完成文件的复制(内存映射文件)
    @Test
    public void test2() throws IOException {
        FileChannel fileChannel = FileChannel.open(Paths.get("pipe.bmp"), StandardOpenOption.READ);
        FileChannel outChannel =FileChannel.open(Paths.get("3.bmp"),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE_NEW);
        //内存映射文件
        MappedByteBuffer imMappedBuf = fileChannel.map(FileChannel.MapMode.READ_ONLY,0,fileChannel.size());
        MappedByteBuffer outMappedBuf = outChannel.map(FileChannel.MapMode.READ_WRITE,0,fileChannel.size());
        //直接对缓冲区进行数据的读写操作
        byte [] dst = new byte[imMappedBuf.limit()];
        imMappedBuf.get(dst);
        outMappedBuf.put(dst);

        fileChannel.close();
        outChannel.close();

    }

    //1、利用通道完成文件的复制(费直接缓冲区)
    @org.junit.Test
    public void test1(){
        FileInputStream fis =null;
        FileOutputStream fos =null;
        FileChannel inChanne=null;
        FileChannel outChannel=null;
        try{
       fis = new FileInputStream("pipe.bmp");
        fos = new FileOutputStream("2.jpg");
        //获取通道
        inChanne =fis.getChannel();
        outChannel = fos.getChannel();
        //分配指定大小的缓冲区
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        //将通道中的数据存入缓冲区中
        while (inChanne.read(buffer)!=-1) {
            buffer.flip();//切换为读取数据的模式
            //将缓冲区中的数据写入通道
            outChannel.write(buffer);
            buffer.clear();//清空缓冲区
        }
    }catch (IOException e){
        e.printStackTrace();
    }finally {
        if(outChannel!=null){
            try {
                outChannel.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        if(inChanne!=null){
            try {
                inChanne.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        if(fis!=null){
            try {
                fis.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        if(fos!=null){
            try {
                fos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    }
}