Java Socket实战之一 单线程通信
Java Socket实战之二 多线程通信
Java Socket实战之三 传输对象
Java Socket实战之四 传输压缩对象
Java Socket实战之五 使用加密协议传输对象
Java Socket实战之六 使用NIO包实现Socket通信
前面几篇文章介绍了使用Java的Socket编程和NIO包在Socket中的应用，这篇文章说说怎样利用Socket编程来实现简单的文件传输。
这里由于前面一片文章介绍了NIO在Socket中的应用，所以这里在读写文件的时候也继续使用NIO包，所以代码看起来会比直接使用流的方式稍微复杂一点点。
下面的示例演示了客户端向服务器端发送一个文件，服务器作为响应给客户端会发一个文件。这里准备两个文件E:/test/server_send.log和E:/test/client.send.log文件，在测试完毕后在客户端和服务器相同目录下会多出两个文件E:/test/server_receive.log和E:/test/client.receive.log文件。
下面首先来看看Server类，主要关注其中的sendFile和receiveFile方法。
package com.googlecode.garbagecan.test.socket.nio;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.net.InetSocketAddress;import java.nio.ByteBuffer;import java.nio.channels.ClosedChannelException;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.Iterator;import java.util.logging.Level;import java.util.logging.Logger;public class MyServer4 {private final static Logger logger = Logger.getLogger(MyServer4.class.getName());public static void main(String[] args) {Selector selector = null;ServerSocketChannel serverSocketChannel = null;try {// Selector for incoming time requestsselector = Selector.open();// Create a new server socket and set to non blocking modeserverSocketChannel = ServerSocketChannel.open();serverSocketChannel.configureBlocking(false);// Bind the server socket to the local host and portserverSocketChannel.socket().setReuseAddress(true);serverSocketChannel.socket().bind(new InetSocketAddress(10000));// Register accepts on the server socket with the selector. This// step tells the selector that the socket wants to be put on the// ready list when accept operations occur, so allowing multiplexed// non-blocking I/O to take place.serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);// Here's where everything happens. The select method will// return when any operations registered above have occurred, the// thread has been interrupted, etc.while (selector.select() > 0) {// Someone is ready for I/O, get the ready keysIterator<SelectionKey> it = selector.selectedKeys().iterator();// Walk through the ready keys collection and process date requests.while (it.hasNext()) {SelectionKey readyKey = it.next();it.remove();// The key indexes into the selector so you// can retrieve the socket that's ready for I/Odoit((ServerSocketChannel) readyKey.channel());}}} catch (ClosedChannelException ex) {logger.log(Level.SEVERE, null, ex);} catch (IOException ex) {logger.log(Level.SEVERE, null, ex);} finally {try {selector.close();} catch(Exception ex) {}try {serverSocketChannel.close();} catch(Exception ex) {}}}private static void doit(final ServerSocketChannel serverSocketChannel) throws IOException {SocketChannel socketChannel = null;try {socketChannel = serverSocketChannel.accept();receiveFile(socketChannel, new File("E:/test/server_receive.log"));sendFile(socketChannel, new File("E:/test/server_send.log"));} finally {try {socketChannel.close();} catch(Exception ex) {}}}private static void receiveFile(SocketChannel socketChannel, File file) throws IOException {FileOutputStream fos = null;FileChannel channel = null;try {fos = new FileOutputStream(file);channel = fos.getChannel();ByteBuffer buffer = ByteBuffer.allocateDirect(1024);int size = 0;while ((size = socketChannel.read(buffer)) != -1) {buffer.flip();if (size > 0) {buffer.limit(size);channel.write(buffer);buffer.clear();}}} finally {try {channel.close();} catch(Exception ex) {}try {fos.close();} catch(Exception ex) {}}}private static void sendFile(SocketChannel socketChannel, File file) throws IOException {FileInputStream fis = null;FileChannel channel = null;try {fis = new FileInputStream(file);channel = fis.getChannel();ByteBuffer buffer = ByteBuffer.allocateDirect(1024);int size = 0;while ((size = channel.read(buffer)) != -1) {buffer.rewind();buffer.limit(size);socketChannel.write(buffer);buffer.clear();}socketChannel.socket().shutdownOutput();} finally {try {channel.close();} catch(Exception ex) {}try {fis.close();} catch(Exception ex) {}}}}
下面是Client程序代码，也主要关注sendFile和receiveFile方法
package com.googlecode.garbagecan.test.socket.nio;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.net.InetSocketAddress;import java.net.SocketAddress;import java.nio.ByteBuffer;import java.nio.channels.FileChannel;import java.nio.channels.SocketChannel;import java.util.logging.Level;import java.util.logging.Logger;public class MyClient4 {private final static Logger logger = Logger.getLogger(MyClient4.class.getName());public static void main(String[] args) throws Exception {new Thread(new MyRunnable()).start();}private static final class MyRunnable implements Runnable {public void run() {SocketChannel socketChannel = null;try {socketChannel = SocketChannel.open();SocketAddress socketAddress = new InetSocketAddress("localhost", 10000);socketChannel.connect(socketAddress);sendFile(socketChannel, new File("E:/test/client_send.log"));receiveFile(socketChannel, new File("E:/test/client_receive.log"));} catch (Exception ex) {logger.log(Level.SEVERE, null, ex);} finally {try {socketChannel.close();} catch(Exception ex) {}}}private void sendFile(SocketChannel socketChannel, File file) throws IOException {FileInputStream fis = null;FileChannel channel = null;try {fis = new FileInputStream(file);channel = fis.getChannel();ByteBuffer buffer = ByteBuffer.allocateDirect(1024);int size = 0;while ((size = channel.read(buffer)) != -1) {buffer.rewind();buffer.limit(size);socketChannel.write(buffer);buffer.clear();}socketChannel.socket().shutdownOutput();} finally {try {channel.close();} catch(Exception ex) {}try {fis.close();} catch(Exception ex) {}}}private void receiveFile(SocketChannel socketChannel, File file) throws IOException {FileOutputStream fos = null;FileChannel channel = null;try {fos = new FileOutputStream(file);channel = fos.getChannel();ByteBuffer buffer = ByteBuffer.allocateDirect(1024);int size = 0;while ((size = socketChannel.read(buffer)) != -1) {buffer.flip();if (size > 0) {buffer.limit(size);channel.write(buffer);buffer.clear();}}} finally {try {channel.close();} catch(Exception ex) {}try {fos.close();} catch(Exception ex) {}}}}}
首先运行MyServer4类启动监听，然后运行MyClient4类来向服务器发送文件以及接受服务器响应文件。运行完后，分别检查服务器和客户端接收到的文件。
孜孜不倦的追求奋斗，加油。
