基于前面12节的一个JAVA NIO的系列翻译，本文将结合所翻译的内容，用一个综合实例来分析，让大家有一个直观的理解。首先这里贴出系列翻译的文章：
Java NIO系列翻译，唯有分享，方能进步========================================================【JAVA】【NIO】1、Java NIO Tutorial原文链接：【JAVA】【NIO】2、Java NIO Overview原文链接：【JAVA】【NIO】3、Java NIO Channel原文链接：【JAVA】【NIO】4、Java NIO Buffer原文链接：【JAVA】【NIO】5、Java NIO Scatter / Gather原文链接：【JAVA】【NIO】6、Java NIO Channel to Channel Transfers原文链接：【JAVA】【NIO】7、Java NIO Selector原文链接：【JAVA】【NIO】8、Java NIO FileChannel原文链接：【JAVA】【NIO】9、Java NIO SocketChannel原文链接：【JAVA】【NIO】10、Java NIO ServerSocketChannel原文链接：【JAVA】【NIO】11、Java NIO DatagramChannel原文链接：【JAVA】【NIO】12、Java NIO Pipe原文链接：=========================================================
首先来看一个图
Selector是一个选择器，所有通道都要在这个选择器上注册相应的事件，handle是一个处理器，参数未ServerSocketChannel和SelectionKey，根据key做不同的逻辑处理，最终通过FileChannel将从客户端读取的内容实时的按字节写到文件里。
package net;import java.io.File;import java.io.IOException;import java.io.RandomAccessFile;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.ServerSocketChannel;import java.nio.channels.SocketChannel;import java.nio.charset.Charset;import java.util.Iterator;import java.util.Set;public class ServerSocketChannelDemo {private static Selector selector = null;private static Charset charset = Charset.forName("UTF-8");//具体参照FileChannel：public static void writeFile(String fileDir,String fileName,ByteBuffer buffer) {if(fileDir==null|fileDir.length()==0) {fileDir = new File("").getAbsolutePath();}if(fileDir.endsWith("\\")||fileDir.endsWith("/")) {fileDir = fileDir.substring(0,fileDir.length()-1);}RandomAccessFile raf = null;FileChannel channel = null;try {raf = new RandomAccessFile(fileDir+File.separator+fileName, "rw");channel = raf.getChannel();//buffer.flip();while(buffer.hasRemaining()) {//将写入的位置定位在文件大小的最后面，相当于追加文件内容channel.position(channel.size());channel.write(buffer);}} catch (Exception e) {e.printStackTrace();} finally {try {channel.close();raf.close();} catch (IOException e) {e.printStackTrace();}}}public static void handle(ServerSocketChannel server,SelectionKey key) throws Exception {if(key.isAcceptable()) {//建立连接通道SocketChannel sc = server.accept();sc.configureBlocking(false);//注册，收到连接请求，建立通道，处理后续数据sc.register(selector, SelectionKey.OP_READ);//将此key对应的channel设置为准备接收其它客户端请求key.interestOps(SelectionKey.OP_ACCEPT);sc.write(charset.encode("Connected !"));}else if(key.isReadable()) {//处理对客户端数据的读取请求SocketChannel sc = (SocketChannel) key.channel();ByteBuffer buffer = ByteBuffer.allocate(1);//StringBuffer sb = new StringBuffer();while(sc.read(buffer)>0) {buffer.flip();writeFile("e:", "demo.txt", buffer);//sb.append(charset.decode(buffer));}//System.out.println(sb.toString());key.interestOps(SelectionKey.OP_READ);}}public static void main(String[] args) throws Exception {//打开服务套接字通道ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();//服务套接字通道模式设置为非阻塞serverSocketChannel.configureBlocking(false);//绑定服务端口serverSocketChannel.bind(new InetSocketAddress(8090));//打开选择器selector = Selector.open();//服务端套接字通道在该选择器上注册事件，接收请求serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);while(true) {//获取在该选择器上注册的且已经就绪的通道数量int readyChannels = selector.select();if(readyChannels==0) {continue;}Set<SelectionKey> selectedKeys = selector.selectedKeys();Iterator<SelectionKey> keyIterator = selectedKeys.iterator();while(keyIterator.hasNext()) {SelectionKey key = keyIterator.next();keyIterator.remove();handle(serverSocketChannel,key);}}}}
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