Java NIO 阻塞式(block) 示例

传统IO存在阻塞，CPU资源不能有效的利用。

NIO非阻塞模式，选择器(Selector)会把每一个通道Channel都注册到该Selector上，其作用是监控这些通道Channel的IO情况，再分配到服务端的线程，此间服务端可以干自己的事情，提高CPU的利用率。

package com.expgiga.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;

/**
 * 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
 * <p>
 *    |--Pipe.SinkChannel
 *    |--Pipe.SourceChannel
 * <p>
 * 2.缓冲区Buffer：负责数据的存取
 * <p>
 * 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
    public void client() throws IOException {
        //1.获取通道

        SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("123.0.0.1", 9898));

        FileChannel inChannel = FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);
        //2.分配指定大小的缓冲区域
        ByteBuffer buf = ByteBuffer.allocate(1024);

        //3.读取本地文件，并发送到服务端去
        while (inChannel.read(buf) != -1) {
            buf.flip();
            sChannel.write(buf);
            buf.clear();
        }

        //4.关闭通道
        inChannel.close();
        sChannel.close();
    }


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

        //5.接受客户端的数据，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.expgiga.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;

/**
 * 
 */
public class TestBlockingNIO2 {

    //客户端
    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();

        //接受服务端的反馈
        int len = 0;
        while (sChannel.read(buf) != -1) {
            buf.flip();
            System.out.println(new String(buf.array(), 0, len));
            buf.clear();
        }

        inChannel.close();
        sChannel.close();
    }

    //服务端
    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("服务端接受客户端数据成功".getBytes());
        buf.flip();
        sChannel.write(buf);

        sChannel.close();
        outChannel.close();
        ssChannel.close();

    }
}