【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();
             }
         }
     }

     }
 }