Java NIO 实现简单代理

通过简单代理的实现，学习Java 非阻塞IO的使用，供大家参考。本文不涉及异步IO处理。

1、首先是SocketChannel的创建，创建方式与ServerSocket相似。在有新的请求来后，启动新的线程对该Socket连接进行处理。

package jim.proxy;import java.io.IOException;import java.net.InetSocketAddress;import java.net.SocketAddress;import java.nio.channels.ServerSocketChannel;import java.nio.channels.SocketChannel;/*** * Start up the proxy. * @author Jim-Zhang * */public class ProxyBootstrap {/** * Entry. * @param args arguments */public static void main(String[] args) {// Check arguments// If the first argument is '-help',print usage.if (args == null || args.length == 0){// Start the serverstartServer(Consts.LISTEN_PORT);return;}// Check '-p'.for (int i = 0; i <args.length; i ++){String arg = args[i];if (!arg.equals(Consts.CMD_ARG_PORT)){printHelp();return;}if (i == args.length -1){printHelp();return;}// Check portString sport = args[i+1].trim();if (sport.length() == 0){ // invalidprintHelp();return;}try{int usePort = Integer.valueOf(sport);// start the serverstartServer(usePort);}catch(NumberFormatException e){printHelp();e.printStackTrace();return;}}}/** * Start up the server on specific port. * @param port Listen port */private static void startServer(int port){try {ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();SocketAddress socketAddress = new InetSocketAddress(port);// Bind serverSocketChannelserverSocketChannel.bind(socketAddress);System.out.println("Listening on port:"+port+".");while(true){// block modeSocketChannel socketChannel = serverSocketChannel.accept();ConnectionHandler.getInstance().add(socketChannel);}} catch (IOException e) {e.printStackTrace();}}/** * Print help info. */private static void printHelp(){System.out.println("Usage:");System.out.println("-p port");System.out.println("For example: -p 8200 will listen on port 8200.");}}

2、SocketChannel处理类，主要通过线程池对连接进行处理，涉及的知识较多，主要是HTTP协议、非阻塞IO的使用。

package jim.proxy;import java.io.IOException;import java.net.InetSocketAddress;import java.net.SocketAddress;import java.nio.ByteBuffer;import java.nio.channels.SelectionKey;import java.nio.channels.Selector;import java.nio.channels.SocketChannel;import java.util.Arrays;import java.util.concurrent.ArrayBlockingQueue;import java.util.concurrent.BlockingQueue;import java.util.concurrent.Executors;import java.util.concurrent.ScheduledExecutorService;/** * Connection handler. * Need to finish. * @author Jim-Zhang */public class ConnectionHandler{/** Singleton */private static final ConnectionHandler instance = new ConnectionHandler();/** Scheduled worker */private ScheduledExecutorService executorService = Executors.newScheduledThreadPool(Consts.THREAD_COUNT);/**  * Add channel. * @param socketChannel SocketChannel to handle  * */public void add(SocketChannel socketChannel){// One thread per request's SocketChannelexecutorService.execute(new HandlerThread(socketChannel));}/**  * Get {@link ConnectionHandler} object. * @return {@link ConnectionHandler} Instance * */public static ConnectionHandler getInstance(){return instance;}/** Thread for handling socket channel. */private class HandlerThread extends Thread{/** Reqeust SocketChannel */private SocketChannel socketChannel;private final BlockingQueue<String> sourceRequestData = new ArrayBlockingQueue<String>(1000);/** Target */private SocketChannel targetSocketChannel;/** Constructor */public HandlerThread(SocketChannel socketChannel){HandlerThread.this.socketChannel = socketChannel;setDaemon(true);}@Overridepublic void run() {// Use SocketChannel to read http data// final Socket socket = socketChannel.socket();String resourceUrl = null;try {// set non-blocksocketChannel.configureBlocking(false);Selector selector = Selector.open();SelectionKey sourceKey = socketChannel.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE);// for reading line StringBuilder lineBuilder = new StringBuilder();ByteBuffer buffer = ByteBuffer.allocate(1024);String line = null; // null for no data// for targetSelector targetSelector = null;SelectionKey targetSelectionKey = null;// Read request datawhile (true){ Thread.sleep(20);buffer.clear();// Read request dataselector.selectNow();if (sourceKey.isValid() && sourceKey.isReadable()){int readLen = socketChannel.read(buffer);if (readLen > 0){byte[] datas = new byte[readLen];buffer.rewind();buffer.get(datas);lineBuilder.append(new String(datas.clone()));byte[] dataEnd = new byte[]{datas[datas.length -2],datas[datas.length -1]};if (endof(dataEnd)){line = lineBuilder.toString();break;}}if (readLen == -1){line = lineBuilder.toString();break;}}}if (line == null || line.isEmpty()){return;}if (line != null){// Push request data to Queue to be handled laterString requestStr = line.replace(HttpHeader.PROXY_CONNECTION, "Connection");sourceRequestData.add(requestStr);}// Handle target channelwhile(true && socketChannel.isOpen()){String lineToHandle = sourceRequestData.poll();// GET http://xx/ss/dd HTTP/1.1 // Immediately open the SocketChannelif (targetSocketChannel == null && lineToHandle != null && lineToHandle.indexOf("HTTP/1.1") != -1){String targetHostStr = lineToHandle.split(" ")[1];targetHostStr = targetHostStr.substring(targetHostStr.indexOf("//")+2);targetHostStr = targetHostStr.substring(0,targetHostStr.indexOf("/")); // use SocketChannel to request dataString[] hostParams = targetHostStr.split(HttpHeader.SPLIT_CHAR);String host = hostParams[0].trim();int port = hostParams.length == 1 ?  80 : Integer.valueOf(hostParams[1].trim());SocketAddress targetAddress = new InetSocketAddress(host, port);targetSocketChannel =  SocketChannel.open(targetAddress);targetSocketChannel.configureBlocking(false);targetSelector = Selector.open();targetSelectionKey = targetSocketChannel.register(targetSelector,SelectionKey.OP_READ | SelectionKey.OP_WRITE);resourceUrl = lineToHandle;}if(targetSocketChannel != null){targetSelector.select();    if (targetSelectionKey.isWritable()){String toTargetData = lineToHandle;if (toTargetData != null){byte[] datas = toTargetData.getBytes();ByteBuffer buffers = ByteBuffer.wrap(datas);// buffers.flip();targetSocketChannel.write(buffers);targetSocketChannel.write(ByteBuffer.wrap(Consts.LINE_END));targetSocketChannel.write(ByteBuffer.wrap(Consts.LINE_END));// targetSocketChannel.write(ByteBuffer.wrap(Consts.LINE_END));// line end// targetSocketChannel.write(ByteBuffer.wrap(Consts.LINE_END));}else{// targetSocketChannel.write(ByteBuffer.wrap(Consts.STREAM_END));// targetSocketChannel.write(ByteBuffer.wrap(Consts.LINE_END));}}if (targetSelectionKey.isReadable()){ByteBuffer buffers = ByteBuffer.allocate(1024);int len = targetSocketChannel.read(buffers);if (len == 0){continue;}if (len == -1){break;}buffers.flip();socketChannel.write(buffers);buffers.compact();}}Thread.sleep(20);}} catch (Throwable e) {try {System.out.println(resourceUrl);socketChannel.close();targetSocketChannel.close();} catch (IOException e1) {e1.printStackTrace();}e.printStackTrace();}}/**  * End of stream or line. * @param data Data * @return true-end of line or stream * */private boolean endof(byte[] datas){return Arrays.equals(Consts.LINE_END,datas) || Arrays.equals(Consts.STREAM_END,datas);}}}

最后是常量定义类。

package jim.proxy;/** * Constants for proxy.Should not instatiate. * @author Jim-Zhang * */public class Consts {// private constructorprivate Consts(){throw new UnsupportedOperationException("Can not instatiate.");}/** The number of threads handle requests. */public static final int THREAD_COUNT = 200;/** Default listening port. */public static final int LISTEN_PORT = 4186;/** Listening port cmd argument */public static String CMD_ARG_PORT = "-p";/** Line end */public static String LINE_END_S = "\r\n";/** Line end */public static byte[] LINE_END = "\r\n".getBytes();/** Stream end */public static byte[] STREAM_END = new byte[]{0,0};}

以上是代理的简单实现，仅是一个HTTP代理的简单思路，目的是为了使用NIO。HTTP协议的头结束、数据压缩等都有涉及，本文只对头做了处理，而对数据压缩未做处理。

目前我另外一个实现为采用Apache HttpComponents，采用其中NHttpServer\NHttpClient使用比较完整的代理。有兴趣可以参考下HttpComponents对Http的封装。