Java入門系列-25-NIO(實現非阻塞網絡通訊)

時間 2019-12-08

標籤 java 入門系列 nio 實現阻塞網絡通訊欄目 Java 简体版

原文原文鏈接

還記得以前介紹NIO時對比傳統IO的一大特色嗎？就是NIO是非阻塞式的，這篇文章帶你們來看一下非阻塞的網絡操做。java

補充：以數組的形式使用緩衝區

package testnio;

import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

public class TestBufferArray {

    public static void main(String[] args) throws IOException {
        RandomAccessFile raf1=new RandomAccessFile("D:/1.txt","rw");
        
        //1.獲取通道
        FileChannel channel1=raf1.getChannel();
        
        //2.建立緩衝區數組
        ByteBuffer buf1=ByteBuffer.allocate(512);
        ByteBuffer buf2=ByteBuffer.allocate(512);
        ByteBuffer[] bufs= {buf1,buf2};
        //3.將數據讀入緩衝區數組
        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()));
        
        //寫入緩衝區數組到通道中
        RandomAccessFile raf2=new RandomAccessFile("D:/2.txt","rw");
        FileChannel channel2=raf2.getChannel();
        channel2.write(bufs);
        
    }
}

使用NIO實現阻塞式網絡通訊

TCP協議的網絡通訊傳統實現方式是經過套接字編程(Socket和ServerSocket)，NIO實現TCP網絡通訊須要用到 Channel 接口的兩個實現類：SocketChannel和ServerSocketChannel編程

使用NIO實現阻塞式網絡通訊數組

客戶端服務器

package com.jikedaquan.blockingnio;

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

public class Client {

    public static void main(String[] args) {

        SocketChannel sChannel=null;

        FileChannel inChannel=null;
        try {
            //一、獲取通道
            sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 1666));
            //用於讀取文件            
            inChannel = FileChannel.open(Paths.get("F:/a.jpg"), StandardOpenOption.READ);

            //二、分配指定大小的緩衝區
            ByteBuffer buf=ByteBuffer.allocate(1024);

            //三、讀取本地文件，發送到服務器端

            while(inChannel.read(buf)!=-1) {
                buf.flip();
                sChannel.write(buf);
                buf.clear();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            //關閉通道
            if (inChannel!=null) {
                try {
                    inChannel.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            if(sChannel!=null) {
                try {
                    sChannel.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

new InetSocketAddress("127.0.0.1", 1666) 用於向客戶端套接字通道(SocketChannel)綁定要鏈接地址和端口網絡

服務端dom

package com.jikedaquan.blockingnio;

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 Server {

    public static void main(String[] args) {

        ServerSocketChannel ssChannel=null;

        FileChannel outChannel=null;

        SocketChannel sChannel=null;
        try {
            //一、獲取通道
            ssChannel = ServerSocketChannel.open();
            //用於保存文件的通道
            outChannel = FileChannel.open(Paths.get("F:/b.jpg"), StandardOpenOption.WRITE,StandardOpenOption.CREATE);

            //二、綁定要監聽的端口號
            ssChannel.bind(new InetSocketAddress(1666));
            //三、獲取客戶端鏈接的通道
            sChannel = ssChannel.accept();

            //四、分配指定大小的緩衝區
            ByteBuffer buf=ByteBuffer.allocate(1024);

            //五、接收客戶端的數據，並保存到本地
            while(sChannel.read(buf)!=-1) {
                buf.flip();
                outChannel.write(buf);
                buf.clear();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            //六、關閉通道
            if(sChannel!=null) {
                try {
                    sChannel.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(outChannel!=null) {
                try {
                    outChannel.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(ssChannel!=null) {
                try {
                    ssChannel.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }   
            }       
        }
    }   
}

服務端套接字僅綁定要監聽的端口便可 ssChannel.bind(new InetSocketAddress(1666));tcp

上面的代碼使用NIO實現的網絡通訊，可能有同窗會問，沒有看到阻塞效果啊，確實是阻塞式的看不到效果，由於客戶端發送一次數據就結束了，服務端也是接收一次數據就結束了。那若是服務端接收完成數據後，再向客戶端反饋呢？測試

可以看到阻塞效果的網絡通訊.net

客戶端code

package com.jikedaquan.blockingnio2;

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

public class Client {

    public static void main(String[] args) {
        SocketChannel sChannel=null;
        FileChannel inChannel=null;
        try {
            sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 1666));
            inChannel = FileChannel.open(Paths.get("F:/a.jpg"), StandardOpenOption.READ);

            ByteBuffer buf=ByteBuffer.allocate(1024);

            while(inChannel.read(buf)!=-1) {
                buf.flip();
                sChannel.write(buf);
                buf.clear();
            }
            
            //sChannel.shutdownOutput();//去掉註釋掉將不會阻塞

            //接收服務器端的反饋
            int len=0;
            while((len=sChannel.read(buf))!=-1) {
                buf.flip();
                System.out.println(new String(buf.array(),0,len));
                buf.clear();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(inChannel!=null) {
                try {
                    inChannel.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(sChannel!=null) {
                try {
                    sChannel.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

服務端

package com.jikedaquan.blockingnio2;

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 Server {

    public static void main(String[] args) {

        ServerSocketChannel ssChannel=null;
        FileChannel outChannel=null;
        SocketChannel sChannel=null;
        try {
            ssChannel = ServerSocketChannel.open();
            outChannel = FileChannel.open(Paths.get("F:/a.jpg"),StandardOpenOption.WRITE,StandardOpenOption.CREATE);

            ssChannel.bind(new InetSocketAddress(1666));
            sChannel = ssChannel.accept();
            ByteBuffer buf=ByteBuffer.allocate(1024);

            while(sChannel.read(buf)!=-1) {
                buf.flip();
                outChannel.write(buf);
                buf.clear();
            }

            //發送反饋給客戶端
            buf.put("服務端接收數據成功".getBytes());
            buf.flip();
            sChannel.write(buf);
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(sChannel!=null) {
                try {
                    sChannel.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(outChannel!=null) {
                try {
                    outChannel.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(ssChannel!=null) {
                try {
                    ssChannel.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

服務端將向客戶端發送兩次數據

選擇器(Selector)

想要實現非阻塞的IO，必需要先弄懂選擇器。Selector 抽象類，可經過調用此類的 open 方法建立選擇器，該方法將使用系統的默認選擇器提供者建立新的選擇器。

將通道設置爲非阻塞以後，須要將通道註冊到選擇器中，註冊的同時須要指定一個選擇鍵的類型 (SelectionKey)。

選擇鍵(SelectionKey)能夠認爲是一種標記，標記通道的類型和狀態。

SelectionKey的靜態字段：
OP_ACCEPT：用於套接字接受操做的操做集位
OP_CONNECT：用於套接字鏈接操做的操做集位
OP_READ：用於讀取操做的操做集位
OP_WRITE：用於寫入操做的操做集位

用於檢測通道狀態的方法：

方法名稱	說明
isAcceptable()	測試此鍵的通道是否已準備好接受新的套接字鏈接
isConnectable()	測試此鍵的通道是否已完成其套接字鏈接操做
isReadable()	測試此鍵的通道是否已準備好進行讀取
isWritable()	測試此鍵的通道是否已準備好進行寫入

將通道註冊到選擇器：

ssChannel.register(selector, SelectionKey.OP_ACCEPT);

IO操做準備就緒的通道大於0，輪詢選擇器

while(selector.select()>0) {
    //獲取選擇鍵，根據不一樣的狀態作不一樣的操做
}

實現非阻塞式TCP協議網絡通訊

非阻塞模式：channel.configureBlocking(false);

客戶端

package com.jikedaquan.nonblockingnio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;
import java.util.Date;
import java.util.Scanner;

public class Client {

    public static void main(String[] args) {
        SocketChannel sChannel=null;
        try {
            //一、獲取通道
            sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1",1666));
            
            //二、切換非阻塞模式
            sChannel.configureBlocking(false);
            
            //三、分配指定大小的緩衝區
            ByteBuffer buf=ByteBuffer.allocate(1024);
            //四、發送數據給服務端
            Scanner scanner=new Scanner(System.in);
            //循環從控制檯錄入數據發送給服務端
            while(scanner.hasNext()) {
                
                String str=scanner.next();
                buf.put((new Date().toString()+"\n"+str).getBytes());
                buf.flip();
                sChannel.write(buf);
                buf.clear();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            //五、關閉通道
            if(sChannel!=null) {
                try {
                    sChannel.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

服務端

package com.jikedaquan.nonblockingnio;

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.Iterator;

public class Server {

    public static void main(String[] args) throws IOException {
        
        //一、獲取通道
        ServerSocketChannel ssChannel=ServerSocketChannel.open();
        //二、切換非阻塞模式
        ssChannel.configureBlocking(false);
        //三、綁定監聽的端口號
        ssChannel.bind(new InetSocketAddress(1666));
        //四、獲取選擇器
        Selector selector=Selector.open();
        //五、將通道註冊到選擇器上，並指定「監聽接收事件」
        ssChannel.register(selector, SelectionKey.OP_ACCEPT);
        
        //六、輪詢式的獲取選擇器上已經 「準備就緒」的事件
        while(selector.select()>0) {
            //七、獲取當前選擇器中全部註冊的「選擇鍵(已就緒的監聽事件)」
            Iterator<SelectionKey> it=selector.selectedKeys().iterator();
            while(it.hasNext()) {
                //八、獲取準備就緒的事件
                SelectionKey sk=it.next();
                //九、判斷具體是什麼事件準備就緒
                if(sk.isAcceptable()) {
                    //十、若「接收就緒」，獲取客戶端鏈接
                    SocketChannel sChannel=ssChannel.accept();
                    //十一、切換非阻塞模式
                    sChannel.configureBlocking(false);
                    //十二、將該通道註冊到選擇器上
                    sChannel.register(selector, SelectionKey.OP_READ);
                }else if(sk.isReadable()) {
                    //1三、獲取當前選擇器上「讀就緒」狀態的通道
                    SocketChannel sChannel=(SocketChannel)sk.channel();
                    //1四、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();
                    }
                }
                //1五、取消選擇鍵 SelectionKey
                it.remove();
            }
            
        }
    }
}

服務端接收客戶端的操做須要在判斷 isAcceptable() 方法內將就緒的套接字通道以讀操做註冊到選擇器中

在判斷 isReadable() 內從通道中獲取數據

實現非阻塞式UDP協議網絡通訊

發送端

package com.jikedaquan.nonblockingnio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;
import java.util.Scanner;

public class TestDatagramSend {

    public static void main(String[] args) throws IOException {
        //獲取通道
        DatagramChannel dChannel=DatagramChannel.open();
        //非阻塞
        dChannel.configureBlocking(false);
        ByteBuffer buf=ByteBuffer.allocate(1024);
        Scanner scanner=new Scanner(System.in);
        while(scanner.hasNext()) {
            String str=scanner.next();
            buf.put(str.getBytes());
            buf.flip();
            //發送數據到目標地址和端口
            dChannel.send(buf,new InetSocketAddress("127.0.0.1", 1666));
            buf.clear();
        }
        dChannel.close();
    }
}

接收端

package com.jikedaquan.nonblockingnio;

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.Iterator;

public class TestDatagramReceive {
    public static void main(String[] args) throws IOException {
        //獲取通道
        DatagramChannel dChannel=DatagramChannel.open();
        dChannel.configureBlocking(false);
        //綁定監聽端口
        dChannel.bind(new InetSocketAddress(1666));
        //獲取選擇器
        Selector selector=Selector.open();
        //讀操做註冊通道
        dChannel.register(selector, SelectionKey.OP_READ);
        while(selector.select()>0) {
            Iterator<SelectionKey> it=selector.selectedKeys().iterator();
            //迭代選擇鍵
            while(it.hasNext()) {
                SelectionKey sk=it.next();
                //通道可讀
                if(sk.isReadable()) {
                    ByteBuffer buf=ByteBuffer.allocate(1024);
                    //接收數據存入緩衝區
                    dChannel.receive(buf);
                    buf.flip();
                    System.out.println(new String(buf.array(),0,buf.limit()));
                    buf.clear();
                }
            }
            
            it.remove();
        }
    }
}