个人笔记--NIO

流是单向的缓冲区是双向的

例子1：

结果：

图例：

get():读取缓冲区中的数据 
rewind():可重复读 
clear():清空缓冲区，但是缓冲区的数据依然存在，但是出于被遗忘状态(指针被 拨回)

例子2：

/*
 * 一、通道（Channel）：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。Channel 本身不存储数据，因此需要配合缓冲区进行传输。
 * 
 * 二、通道的主要实现类
 *     java.nio.channels.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
 *         DatagramSocket
 *         
 * 2. 在 JDK 1.7 中的 NIO.2 针对各个通道提供了静态方法 open()
 * 3. 在 JDK 1.7 中的 NIO.2 的 Files 工具类的 newByteChannel()
 * 
 * 四、通道之间的数据传输
 * transferFrom()
 * transferTo()
 * 
 * 五、分散(Scatter)与聚集(Gather)
 * 分散读取（Scattering Reads）：将通道中的数据分散到多个缓冲区中
 * 聚集写入（Gathering Writes）：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 {
    
    //字符集
    @Test
    public void test6() throws IOException{
        Charset cs1 = Charset.forName("GBK");
        
        //获取编码器
        CharsetEncoder ce = cs1.newEncoder();
        
        //获取解码器
        CharsetDecoder cd = cs1.newDecoder();
        
        CharBuffer cBuf = CharBuffer.allocate(1024);
        cBuf.put("威武！");
        cBuf.flip();
        
        //编码
        ByteBuffer bBuf = ce.encode(cBuf);
        
        for (int i = 0; i < 12; i++) {
            System.out.println(bBuf.get());
        }
        
        //解码
        bBuf.flip();
        CharBuffer cBuf2 = cd.decode(bBuf);
        System.out.println(cBuf2.toString());
        
        System.out.println("------------------------------------------------------");
        
        Charset cs2 = Charset.forName("GBK");
        bBuf.flip();
        CharBuffer cBuf3 = cs2.decode(bBuf);
        System.out.println(cBuf3.toString());
    }
    
    @Test
    public void test5(){
        Map<String, Charset> map = Charset.availableCharsets();
        
        Set<Entry<String, Charset>> set = map.entrySet();
        
        for (Entry<String, Charset> entry : set) {
            System.out.println(entry.getKey() + "=" + entry.getValue());
        }
    }
    
    //分散和聚集
    @Test
    public void test4() throws IOException{
        RandomAccessFile raf1 = new RandomAccessFile("1.txt", "rw");
        
        //1. 获取通道
        FileChannel channel1 = raf1.getChannel();
        
        //2. 分配指定大小的缓冲区
        ByteBuffer buf1 = ByteBuffer.allocate(100);
        ByteBuffer buf2 = ByteBuffer.allocate(1024);
        
        //3. 分散读取
        ByteBuffer[] bufs = {buf1, buf2};
        channel1.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()));
        
        //4. 聚集写入
        RandomAccessFile raf2 = new RandomAccessFile("2.txt", "rw");
        FileChannel channel2 = raf2.getChannel();
        
        channel2.write(bufs);
    }
    
    //通道之间的数据传输(直接缓冲区)
    @Test
    public void test3() throws IOException{
        FileChannel inChannel = FileChannel.open(Paths.get("d:/1.mkv"), StandardOpenOption.READ);
        FileChannel outChannel = FileChannel.open(Paths.get("d:/2.mkv"), StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE);
        
//        inChannel.transferTo(0, inChannel.size(), outChannel);
        outChannel.transferFrom(inChannel, 0, inChannel.size());
        
        inChannel.close();
        outChannel.close();
    }
    
    //使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{//2127-1902-1777
        long start = System.currentTimeMillis();
        
        FileChannel inChannel = FileChannel.open(Paths.get("d:/1.mkv"), StandardOpenOption.READ);
        FileChannel outChannel = FileChannel.open(Paths.get("d:/2.mkv"), StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE);
        
        //内存映射文件
        MappedByteBuffer inMappedBuf = inChannel.map(MapMode.READ_ONLY, 0, inChannel.size());
        MappedByteBuffer outMappedBuf = outChannel.map(MapMode.READ_WRITE, 0, inChannel.size());
        
        //直接对缓冲区进行数据的读写操作
        byte[] dst = new byte[inMappedBuf.limit()];
        inMappedBuf.get(dst);
        outMappedBuf.put(dst);
        
        inChannel.close();
        outChannel.close();
        
        long end = System.currentTimeMillis();
        System.out.println("耗费时间为：" + (end - start));
    }
    
    //利用通道完成文件的复制（非直接缓冲区）
    @Test
    public void test1(){//10874-10953
        long start = System.currentTimeMillis();
        
        FileInputStream fis = null;
        FileOutputStream fos = null;
        //①获取通道
        FileChannel inChannel = null;
        FileChannel outChannel = null;
        try {
            fis = new FileInputStream("d:/1.mkv");
            fos = new FileOutputStream("d:/2.mkv");
            
            inChannel = fis.getChannel();
            outChannel = fos.getChannel();
            
            //②分配指定大小的缓冲区
            ByteBuffer buf = ByteBuffer.allocate(1024);
            
            //③将通道中的数据存入缓冲区中
            while(inChannel.read(buf) != -1){
                buf.flip(); //切换读取数据的模式
                //④将缓冲区中的数据写入通道中
                outChannel.write(buf);
                buf.clear(); //清空缓冲区
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if(outChannel != null){
                try {
                    outChannel.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            
            if(inChannel != null){
                try {
                    inChannel.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            
            if(fos != null){
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            
            if(fis != null){
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        
        long end = System.currentTimeMillis();
        System.out.println("耗费时间为：" + (end - start));
        
    }

}

阻塞式：

选择器用来监控IO状态

阻塞式例子：

/*
 * 一、使用 NIO 完成网络通信的三个核心：
 * 
 * 1. 通道（Channel）：负责连接
 *         
 *        java.nio.channels.Channel 接口：
 *             |--SelectableChannel
 *                 |--SocketChannel
 *                 |--ServerSocketChannel
 *                 |--DatagramChannel
 * 
 *                 |--Pipe.SinkChannel
 *                 |--Pipe.SourceChannel
 * 
 * 2. 缓冲区（Buffer）：负责数据的存取
 * 
 * 3. 选择器（Selector）：是 SelectableChannel 的多路复用器。用于监控 SelectableChannel 的 IO 状况
 * 
 */
public class TestBlockingNIO {

    //客户端
    @Test
    public void client() throws IOException{
        //1. 获取通道
        SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9898));
        
        FileChannel inChannel = FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);
        
        //2. 分配指定大小的缓冲区
        ByteBuffer buf = ByteBuffer.allocate(1024);
        
        //3. 读取本地文件，并发送到服务端
        while(inChannel.read(buf) != -1){
            buf.flip();
            sChannel.write(buf);
            buf.clear();
        }
        
        //4. 关闭通道
        inChannel.close();
        sChannel.close();
    }
    
    //服务端
    @Test
    public void server() throws IOException{
        //1. 获取通道
        ServerSocketChannel ssChannel = ServerSocketChannel.open();
        
        FileChannel outChannel = FileChannel.open(Paths.get("2.jpg"), StandardOpenOption.WRITE, StandardOpenOption.CREATE);
        
        //2. 绑定连接
        ssChannel.bind(new InetSocketAddress(9898));
        
        //3. 获取客户端连接的通道
        SocketChannel sChannel = ssChannel.accept();
        
        //4. 分配指定大小的缓冲区
        ByteBuffer buf = ByteBuffer.allocate(1024);
        
        //5. 接收客户端的数据，并保存到本地
        while(sChannel.read(buf) != -1){
            buf.flip();
            outChannel.write(buf);
            buf.clear();
        }
        
        //6. 关闭通道
        sChannel.close();
        outChannel.close();
        ssChannel.close();
        
    }
    
}

例子：
public class TestBlockingNIO2 {
    
    //客户端
    @Test
    public void client() throws IOException{
        SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9898));
        
        FileChannel inChannel = FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);
        
        ByteBuffer buf = ByteBuffer.allocate(1024);
        
        while(inChannel.read(buf) != -1){
            buf.flip();
            sChannel.write(buf);
            buf.clear();
        }
        
        sChannel.shutdownOutput();
        
        //接收服务端的反馈
        int len = 0;
        while((len = sChannel.read(buf)) != -1){
            buf.flip();
            System.out.println(new String(buf.array(), 0, len));
            buf.clear();
        }
        
        inChannel.close();
        sChannel.close();
    }
    
    //服务端
    @Test
    public void server() throws IOException{
        ServerSocketChannel ssChannel = ServerSocketChannel.open();
        
        FileChannel outChannel = FileChannel.open(Paths.get("2.jpg"), StandardOpenOption.WRITE, StandardOpenOption.CREATE);
        
        ssChannel.bind(new InetSocketAddress(9898));
        
        SocketChannel sChannel = ssChannel.accept();
        
        ByteBuffer buf = ByteBuffer.allocate(1024);
        
        while(sChannel.read(buf) != -1){
            buf.flip();
            outChannel.write(buf);
            buf.clear();
        }
        
        //发送反馈给客户端
        buf.put("服务端接收数据成功".getBytes());
        buf.flip();
        sChannel.write(buf);
        
        sChannel.close();
        outChannel.close();
        ssChannel.close();
    }

}

非阻塞式：

非阻塞式例子：

 * 一、使用 NIO 完成网络通信的三个核心：
 *     
 * 1. 通道（Channel）：负责连接
 *         
 *        java.nio.channels.Channel 接口：
 *             |--SelectableChannel
 *                 |--SocketChannel
 *                 |--ServerSocketChannel
 *                 |--DatagramChannel
 * 
 *                 |--Pipe.SinkChannel
 *                 |--Pipe.SourceChannel
 * 
 * 2. 缓冲区（Buffer）：负责数据的存取
 * 
 * 3. 选择器（Selector）：是 SelectableChannel 的多路复用器。用于监控 SelectableChannel 的 IO 状况
 * 
 */
public class TestNonBlockingNIO {
    
    //客户端
    @Test
    public void client() throws IOException{
        //1. 获取通道
        SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9898));
        
        //2. 切换非阻塞模式
        sChannel.configureBlocking(false);
        
        //3. 分配指定大小的缓冲区
        ByteBuffer buf = ByteBuffer.allocate(1024);
        
        //4. 发送数据给服务端
        Scanner scan = new Scanner(System.in);
        
        while(scan.hasNext()){
            String str = scan.next();
            buf.put((new Date().toString() + "\n" + str).getBytes());
            buf.flip();
            sChannel.write(buf);
            buf.clear();
        }
        
        //5. 关闭通道
        sChannel.close();
    }

    //服务端
    @Test
    public void server() throws IOException{
        //1. 获取通道
        ServerSocketChannel ssChannel = ServerSocketChannel.open();
        
        //2. 切换非阻塞模式
        ssChannel.configureBlocking(false);
        
        //3. 绑定连接
        ssChannel.bind(new InetSocketAddress(9898));
        
        //4. 获取选择器
        Selector selector = Selector.open();
        
        //5. 将通道注册到选择器上, 并且指定“监听接收事件”
        ssChannel.register(selector, SelectionKey.OP_ACCEPT);
        
        //6. 轮询式的获取选择器上已经“准备就绪”的事件
        while(selector.select() > 0){
            
            //7. 获取当前选择器中所有注册的“选择键(已就绪的监听事件)”
            Iterator<SelectionKey> it = selector.selectedKeys().iterator();
            
            while(it.hasNext()){
                //8. 获取准备“就绪”的是事件
                SelectionKey sk = it.next();
                
                //9. 判断具体是什么事件准备就绪
                if(sk.isAcceptable()){
                    //10. 若“接收就绪”，获取客户端连接
                    SocketChannel sChannel = ssChannel.accept();
                    
                    //11. 切换非阻塞模式
                    sChannel.configureBlocking(false);
                    
                    //12. 将该通道注册到选择器上
                    sChannel.register(selector, SelectionKey.OP_READ);
                }else if(sk.isReadable()){
                    //13. 获取当前选择器上“读就绪”状态的通道
                    SocketChannel sChannel = (SocketChannel) sk.channel();
                    
                    //14. 读取数据
                    ByteBuffer buf = ByteBuffer.allocate(1024);
                    
                    int len = 0;
                    while((len = sChannel.read(buf)) > 0 ){
                        buf.flip();
                        System.out.println(new String(buf.array(), 0, len));
                        buf.clear();
                    }
                }
                
                //15. 取消选择键 SelectionKey
                it.remove();
            }
        }
    }
}

例子：
public class TestNonBlockingNIO2 {
    
    @Test
    public void send() throws IOException{
        DatagramChannel dc = DatagramChannel.open();
        
        dc.configureBlocking(false);
        
        ByteBuffer buf = ByteBuffer.allocate(1024);
        
        Scanner scan = new Scanner(System.in);
        
        while(scan.hasNext()){
            String str = scan.next();
            buf.put((new Date().toString() + ":\n" + str).getBytes());
            buf.flip();
            dc.send(buf, new InetSocketAddress("127.0.0.1", 9898));
            buf.clear();
        }
        
        dc.close();
    }
    
    @Test
    public void receive() throws IOException{
        DatagramChannel dc = DatagramChannel.open();
        
        dc.configureBlocking(false);
        
        dc.bind(new InetSocketAddress(9898));
        
        Selector selector = Selector.open();
        
        dc.register(selector, SelectionKey.OP_READ);
        
        while(selector.select() > 0){
            Iterator<SelectionKey> it = selector.selectedKeys().iterator();
            
            while(it.hasNext()){
                SelectionKey sk = it.next();
                
                if(sk.isReadable()){
                    ByteBuffer buf = ByteBuffer.allocate(1024);
                    
                    dc.receive(buf);
                    buf.flip();
                    System.out.println(new String(buf.array(), 0, buf.limit()));
                    buf.clear();
                }
            }
            
            it.remove();
        }
    }

}

管道：
public class TestPipe {

    @Test
    public void test1() throws IOException{
        //1. 获取管道
        Pipe pipe = Pipe.open();
        
        //2. 将缓冲区中的数据写入管道
        ByteBuffer buf = ByteBuffer.allocate(1024);
        
        Pipe.SinkChannel sinkChannel = pipe.sink();
        buf.put("通过单向管道发送数据".getBytes());
        buf.flip();
        sinkChannel.write(buf);
        
        //3. 读取缓冲区中的数据
        Pipe.SourceChannel sourceChannel = pipe.source();
        buf.flip();
        int len = sourceChannel.read(buf);
        System.out.println(new String(buf.array(), 0, len));
        
        sourceChannel.close();
        sinkChannel.close();
    }
    
}

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