java nio文件传输例子，javanio文件传输,使用nio传输文件需要注

java nio文件传输例子，javanio文件传输,使用nio传输文件需要注

使用nio传输文件需要注意的是会出现粘包和服务器端缓冲区满的情况。第一种情况，客户端发送30次数据，而服务器端只接收到18次的情况，这种情况出现 主要是服务器端是以流的方式接收数据，它并不知道每次客户端传输数据的大小而造成的。第二种情况是服务器端缓冲区满，导致客户端数据传输失败，这种情况 下，需要判断传输int send = client.write(sendBuffer)的send值，如果send值为0,则服务器端的数据缓冲区可能满了。

客户端实现代码：

import java.io.FileInputStream;import java.net.InetSocketAddress;import java.nio.ByteBuffer;import java.nio.channels.FileChannel;import java.nio.channels.SelectionKey;import java.nio.channels.Selector;import java.nio.channels.SocketChannel;import java.util.Set;public class FileClient {    private int port = 8000;    /* 发送数据缓冲区 */    private static ByteBuffer sendBuffer = ByteBuffer.allocate(1024);    /* 接受数据缓冲区 */    private static ByteBuffer revBuffer = ByteBuffer.allocate(1024);    private InetSocketAddress SERVER;    private static Selector selector;    private static SocketChannel client;    public FileClient(){        try{            SERVER = new InetSocketAddress("localhost", port);            init();        }        catch(Exception e){            e.printStackTrace();        }    }    private void init(){        try {            SocketChannel socketChannel = SocketChannel.open();            socketChannel.configureBlocking(false);            selector = Selector.open();            socketChannel.register(selector, SelectionKey.OP_CONNECT);            socketChannel.connect(SERVER);            while (true) {                selector.select();                Set<SelectionKey> keySet = selector.selectedKeys();                for (final SelectionKey key : keySet) {                    if(key.isConnectable()){                        client = (SocketChannel)key.channel();                        client.finishConnect();                        client.register(selector, SelectionKey.OP_WRITE);                    }                    else if(key.isWritable()){                        sendFile(client);                    }                }                keySet.clear();            }        } catch (Exception e) {            e.printStackTrace();        }    }    private void sendFile(SocketChannel client) {        FileInputStream fis = null;        FileChannel channel = null;        try {//          fis = new FileInputStream("E:\\1.txt");//          fis = new FileInputStream("E:\\1.rar");            fis = new FileInputStream("G:\\3.rar");            channel = fis.getChannel();            int i = 1;            int count = 0;            while((count = channel.read(sendBuffer)) != -1) {                sendBuffer.flip();                 int send = client.write(sendBuffer);                System.out.println("i===========" + (i++) + "   count:" + count + " send:" + send);                // 服务器端可能因为缓存区满，而导致数据传输失败，需要重新发送                while(send == 0){                    Thread.sleep(10);                    send = client.write(sendBuffer);                    System.out.println("i重新传输====" + i + "   count:" + count + " send:" + send);                }                sendBuffer.clear();            }        } catch (Exception e) {            e.printStackTrace();        } finally {            try {                channel.close();                fis.close();                client.close();            } catch (Exception e) {                e.printStackTrace();            }        }    }    public static void main(String[] args){        new FileClient();    }}

服务器端```javaimport java.io.FileOutputStream;import java.net.InetSocketAddress;import java.net.ServerSocket;import java.nio.ByteBuffer;import java.nio.channels.FileChannel;import java.nio.channels.SelectionKey;import java.nio.channels.Selector;import java.nio.channels.ServerSocketChannel;import java.nio.channels.SocketChannel;import java.util.Set;

public class FileServer { private int port = 8000; / 发送数据缓冲区 / private static ByteBuffer revBuffer = ByteBuffer.allocate(1024); private static Selector selector; private static FileOutputStream fout; private static FileChannel ch; public FileServer(){ try{ init(); } catch(Exception e){ e.printStackTrace(); } } private void init() throws Exception{ ServerSocketChannel serverSocketChannel = ServerSocketChannel.open(); serverSocketChannel.configureBlocking(false); ServerSocket serverSocket = serverSocketChannel.socket(); serverSocket.bind(new InetSocketAddress(port)); selector = Selector.open(); serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT); System.out.println("server start on port:" + port); while (true) { try { selector.select();// 返回值为本次触发的事件数 Set<SelectionKey> selectionKeys = selector.selectedKeys();

            for (SelectionKey key : selectionKeys) {                ServerSocketChannel server = null;                SocketChannel client = null;                int count = 0;                if (key.isAcceptable()) {                    server = (ServerSocketChannel) key.channel();                    System.out.println("有客户端连接进入=============)");                    client = server.accept();                    client.configureBlocking(false);                    client.register(selector, SelectionKey.OP_READ);                    fout = new FileOutputStream("G:\\" + client.hashCode() + ".rar");                    ch = fout.getChannel();                } else if (key.isReadable()) {                    client = (SocketChannel) key.channel();                    revBuffer.clear();                    count = client.read(revBuffer);                    int k = 0;                    // 循环读取缓存区的数据，                    while(count > 0){                        System.out.println("k=" + (k++) + " 读取到数据量:" + count);                        revBuffer.flip();                        ch.write(revBuffer);                        fout.flush();                        revBuffer.clear();                        count = client.read(revBuffer);                    }                    if(count == -1){                        client.close();                        ch.close();                        fout.close();                    }                }                else if (key.isWritable()) {                    System.out.println("selectionKey.isWritable()");                }            }            System.out.println("=======selectionKeys.clear()");            selectionKeys.clear();        } catch (Exception e) {            e.printStackTrace();            break;        }    }}public static void main(String[] args){    new FileServer();}

}```