NIO阻塞與非阻塞IO

一、使用NIO完成網絡通信的三個核心
1、通道（Channel）:負責連接
java.nio.channels.Channel 接口
|– SelectableChannel
|– SocketChannel
|–ServerChannel
|–DatagramChannel
|–Pipe.SinkChannel
|–Pipe.SourceChannel

2、緩衝區（Buffer）: 負責數據的存取
3、選擇器（Selector）: 是SelectableChannel 的多路複用器，用於監控SelectableChannel 的IO狀況

阻塞

package 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 TestBlockingNIO {
    @Test
    public void client() throws IOException{
        //1、獲取通道
        SocketChannel sChannel=SocketChannel.open(new InetSocketAddress("127.0.0.1",9898));
        FileChannel inChannel=FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);
        //2、獲取指定大小的緩衝區域
        ByteBuffer buf=ByteBuffer.allocate(1024);
        //3、讀取本地文件，併發送到服務端去
        while(inChannel.read(buf)!=-1){
            buf.flip();
            sChannel.write(buf);
            buf.clear();
        }
        //4、關閉通道
        inChannel.close();
        sChannel.close();
    }

    @Test
    public void server() throws IOException{
        //1、獲取通道
        ServerSocketChannel ssChannel=ServerSocketChannel.open();
        FileChannel outChannel=FileChannel.open(Paths.get("2.jpg"),StandardOpenOption.WRITE,StandardOpenOption.CREATE);
        //2、綁定連接
        ssChannel.bind(new InetSocketAddress(9898));
        //3、獲取客戶端連接的通道
        SocketChannel sChannel=ssChannel.accept();
        //4、分配指定大小的緩衝區
        ByteBuffer buf=ByteBuffer.allocate(1024);
        //5、接受客戶端的數據，並保存到本地
        while(sChannel.read(buf)!=-1){
            buf.flip();
            outChannel.write(buf);
            buf.clear();
        }
        //6、關閉通道
        sChannel.close();
        ssChannel.close();
        outChannel.close();
    }
}

非阻塞

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;

import org.junit.Test;

/*
 * 一、使用 NIO 完成網絡通信的三個核心：
 * 
 * 1. 通道（Channel）：負責連接
 *      
 *     java.nio.channels.Channel 接口：
 *          |--SelectableChannel
 *              |--SocketChannel
 *              |--ServerSocketChannel
 *              |--DatagramChannel
 * 
 *              |--Pipe.SinkChannel
 *              |--Pipe.SourceChannel
 * 
 * 2. 緩衝區（Buffer）：負責數據的存取
 * 
 * 3. 選擇器（Selector）：是 SelectableChannel 的多路複用器。用於監控 SelectableChannel 的 IO 狀況
 * 
 */
public class TestNonBlockingNIO {

    //客戶端
    @Test
    public void client() throws IOException{
        //1. 獲取通道
        SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9898));

        //2. 切換非阻塞模式
        sChannel.configureBlocking(false);

        //3. 分配指定大小的緩衝區
        ByteBuffer buf = ByteBuffer.allocate(1024);

        //4. 發送數據給服務端
        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. 關閉通道
        sChannel.close();
    }

    //服務端
    @Test
    public void server() throws IOException{
        //1. 獲取通道
        ServerSocketChannel ssChannel = ServerSocketChannel.open();

        //2. 切換非阻塞模式
        ssChannel.configureBlocking(false);

        //3. 綁定連接
        ssChannel.bind(new InetSocketAddress(9898));

        //4. 獲取選擇器
        Selector selector = Selector.open();

        //5. 將通道註冊到選擇器上, 並且指定“監聽接收事件”
        ssChannel.register(selector, SelectionKey.OP_ACCEPT);

        //6. 輪詢式的獲取選擇器上已經“準備就緒”的事件
        while(selector.select() > 0){

            //7. 獲取當前選擇器中所有註冊的“選擇鍵(已就緒的監聽事件)”
            Iterator<SelectionKey> it = selector.selectedKeys().iterator();

            while(it.hasNext()){
                //8. 獲取準備“就緒”的是事件
                SelectionKey sk = it.next();

                //9. 判斷具體是什麼事件準備就緒
                if(sk.isAcceptable()){
                    //10. 若“接收就緒”，獲取客戶端連接
                    SocketChannel sChannel = ssChannel.accept();

                    //11. 切換非阻塞模式
                    sChannel.configureBlocking(false);

                    //12. 將該通道註冊到選擇器上
                    sChannel.register(selector, SelectionKey.OP_READ);
                }else if(sk.isReadable()){
                    //13. 獲取當前選擇器上“讀就緒”狀態的通道
                    SocketChannel sChannel = (SocketChannel) sk.channel();

                    //14. 讀取數據
                    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. 取消選擇鍵 SelectionKey
                it.remove();
            }
        }
    }
}