Buffer 缓冲

package com.atguigu.nio;


import org.junit.Test;

import java.nio.ByteBuffer;

/*
 * 一、缓冲区（Buffer）：在 Java NIO 中负责数据的存取。缓冲区就是数组。用于存储不同数据类型的数据
 *
 * 根据数据类型不同（boolean 除外），提供了相应类型的缓冲区：
 * ByteBuffer
 * CharBuffer
 * ShortBuffer
 * IntBuffer
 * LongBuffer
 * FloatBuffer
 * DoubleBuffer
 *
 * 上述缓冲区的管理方式几乎一致，通过 allocate() 获取缓冲区
 *
 * 二、缓冲区存取数据的两个核心方法：
 * put() : 存入数据到缓冲区中
 * get() : 获取缓冲区中的数据
 *
 * 三、缓冲区中的四个核心属性：
 * capacity : 容量，表示缓冲区中最大存储数据的容量。一旦声明不能改变。
 * limit : 界限，表示缓冲区中可以操作数据的大小。（limit 后数据不能进行读写）
 * position : 位置，表示缓冲区中正在操作数据的位置。
 *
 * mark : 标记，表示记录当前 position 的位置。可以通过 reset() 恢复到 mark 的位置
 *
 * 0 <= mark <= position <= limit <= capacity
 *
 * 四、直接缓冲区与非直接缓冲区：
 * 非直接缓冲区：通过 allocate() 方法分配缓冲区，将缓冲区建立在 JVM 的内存中
 * 直接缓冲区：通过 allocateDirect() 方法分配直接缓冲区，将缓冲区建立在物理内存中。可以提高效率
 */
public class TestBuffer {

    @Test
    public void test1() {
        String str = "abcde";

        //1. 分配一个指定大小的缓冲区
        ByteBuffer buf = ByteBuffer.allocate(1024);

        System.out.println("-----------------allocate()----------------");
        System.out.println(buf.position());
        System.out.println(buf.limit());
        System.out.println(buf.capacity());

        //2. 利用 put() 存入数据到缓冲区中
        buf.put(str.getBytes());

        System.out.println("-----------------put()----------------");
        System.out.println(buf.position());
        System.out.println(buf.limit());
        System.out.println(buf.capacity());

        //3. 切换读取数据模式
        buf.flip();

        System.out.println("-----------------flip()----------------");
        System.out.println(buf.position());
        System.out.println(buf.limit());
        System.out.println(buf.capacity());

        //4. 利用 get() 读取缓冲区中的数据
        byte[] dst = new byte[buf.limit()];
        buf.get(dst);
        System.out.println(new String(dst, 0, dst.length));

        System.out.println("-----------------get()----------------");
        System.out.println(buf.position());
        System.out.println(buf.limit());
        System.out.println(buf.capacity());

        //5. rewind() : 可重复读
        buf.rewind();

        System.out.println("-----------------rewind()----------------");
        System.out.println(buf.position());
        System.out.println(buf.limit());
        System.out.println(buf.capacity());

        //6. clear() : 清空缓冲区. 但是缓冲区中的数据依然存在，但是处于“被遗忘”状态
        buf.clear();

        System.out.println("-----------------clear()----------------");
        System.out.println(buf.position());
        System.out.println(buf.limit());
        System.out.println(buf.capacity());

        System.out.println((char) buf.get());

    }


    @Test
    public void test2() {
        String str = "abcde";

        ByteBuffer buf = ByteBuffer.allocate(1024);

        buf.put(str.getBytes());

        buf.flip();

        byte[] dst = new byte[buf.limit()];
        buf.get(dst, 0, 2);
        System.out.println(new String(dst, 0, 2));
        System.out.println(buf.position());

        //mark() : 标记
        buf.mark();

        buf.get(dst, 2, 2);
        System.out.println(new String(dst, 2, 2));
        System.out.println(buf.position());

        //reset() : 恢复到 mark 的位置
        buf.reset();
        System.out.println(buf.position());

        //判断缓冲区中是否还有剩余数据
        if (buf.hasRemaining()) {

            //获取缓冲区中可以操作的数量
            System.out.println(buf.remaining());
        }
    }

    @Test
    public void test3() {
        //分配直接缓冲区
        ByteBuffer buf = ByteBuffer.allocateDirect(1024);

        System.out.println(buf.isDirect());
    }

}

Channel通道

package com.atguigu.nio;

import org.junit.Test;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;
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.Map.Entry;
import java.util.Set;

/*
 * 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 {


    //利用通道完成文件的复制（非直接缓冲区）
    @Test
    public void test1() throws IOException {
        long start = System.currentTimeMillis();

        FileInputStream in = new FileInputStream("E:\\视频测试\\超大文件测试.zip");
        FileOutputStream out = new FileOutputStream("E:\\视频测试\\2.zip");

        //①获取通道
        FileChannel inChannel = in.getChannel();
        FileChannel outChannel = out.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
        }

        outChannel.close();
        inChannel.close();
        out.close();
        in.close();

        long end = System.currentTimeMillis();
        System.out.println("耗费时间为：" + (end - start));
        //13M大小文件 402毫秒
        //10G大小文件  329945毫秒
    }

    //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 {
        long start = System.currentTimeMillis();

        FileChannel inChannel = FileChannel.open(Paths.get("E:\\视频测试\\13M大小.mp4"), StandardOpenOption.READ);
        FileChannel outChannel = FileChannel.open(Paths.get("E:\\视频测试\\3.mp4"), 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));
        // 13M 大小文件 170毫秒
    }

    //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("E:\\视频测试\\13M大小.mp4"), StandardOpenOption.READ);
        FileChannel outChannel = FileChannel.open(Paths.get("E:\\视频测试\\3.mp4"), StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE);

//      inChannel.transferTo(0, inChannel.size(), outChannel);
        outChannel.transferFrom(inChannel, 0, inChannel.size());

        inChannel.close();
        outChannel.close();
    }

    //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);
    }

    @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());
        }
    }

    //字符集
    @org.junit.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("垃圾垃圾！");
        cBuf.flip();

        //编码
        ByteBuffer bBuf = ce.encode(cBuf);

        for (int i = 0; i < bBuf.limit(); 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());
    }

}

阻塞

package com.atguigu.nio;

import org.junit.Test;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;

/*
 * 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();

    }

}

package com.atguigu.nio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;

import org.junit.Test;

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

package com.atguigu.nio;

import org.junit.Test;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Date;
import java.util.Iterator;
import java.util.Scanner;

/*
 * 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();
            }
        }
    }
}

package com.atguigu.nio;

import org.junit.Test;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.util.Date;
import java.util.Iterator;
import java.util.Scanner;

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

package com.atguigu.nio;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.Pipe;

import org.junit.Test;

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();
    }
    
}