Mina实现自定义协议的通信

网络的传输使用需要遵循一定的规则，这些规则我们称为协议。如在互联网请求HTML页面的时候，我们要遵循HTTP协议，HTTP头的格式就是我们要遵守的规则：

Request HeadersAccept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8Accept-Charset:GBK,utf-8;q=0.7,*;q=0.3Accept-Encoding:gzip,deflate,sdchAccept-Language:zh-CN,zh;q=0.8Cache-Control:max-age=0

比如我们在做一些第三方开发的时候，经常会按照固定的格式向服务器端发送请求，服务器验证消息后，返回相应的结果。在Mina的开发中，我们也会用到这种模式。首先我们先来描述下这种方式的使用情形：

这样的方式，目前，我所在的项目组中主要用于通信和传输。为了将文件从客户端传到云端，我们先在客户端将数据根据一定的规则切片，然后通过一种特定的格式传输到服务器端。Mina，作为这中间的桥梁，秉承了框架很好的优点，快速开发。由于我们的服务器端采用的是C写的，所以我只给出客户端的编码过程，解码过程原理和开发都一样。

 用Mina执行一定协议的传输，主要有以下几个步骤：

1.         设计通信协议；

2.         编写请求（返回）对象和业务对象；

3.         编写解码（编码）器；

4.         编写客户端、服务器端。

下面根据代码，一步步介绍这个过程，由于是前提的测试代码，所以没有考虑线程安全等问题，只是一个思路：

首先是通信的协议，根据mina的构建规则，将协议设计成抽象类，由请求对象和返回对象分别去继承，协议格式如下：

package com.a2.desktop.example5.mina.potocol;import org.apache.mina.core.buffer.IoBuffer;/** * 通信协议 * @author Chen.Hui *  */public abstract class AbsMessage {/** * 协议格式： *  * tag | header length | Filename | File length | offset | checksum | temps | data *  *//** 请求或访问类型 请求Tag：0x00 返回Tag:0x01 共 8 bit */public abstract byte getTag();/** 头文件长度 共 2^16 可表示 65535 */public abstract short getHeaderlen();/** 根据UUID生成文件唯一标识，共 8*36=288 bit */public abstract byte[] getFilename();//需要設計一個算法/** 获取文件长度 2^32=4GB 共 32 bit */public abstract int getFileLen();/** 获取文件的偏移量offset 共 32 bit */public abstract int getOffset();/** 获取文件的MD5校验码 共 32 bit */public abstract byte[] getChecksum();/** 预留字段 长度不超过 128 bit */public abstract byte[] getTmp();/**data 方式传输内容 不超过1024bit*/public abstract IoBuffer getData();}

下面是请求对象（返回）和业务对象，这里的业务对象主要功能是将文件切片：

package com.a2.desktop.example5.mina.potocol;import java.io.IOException;import java.nio.charset.Charset;import org.apache.mina.core.buffer.IoBuffer;import org.slf4j.Logger;import org.slf4j.LoggerFactory;/** * 请求对象 *  * @author Chen.Hui *  */public class InfoRequest extends AbsMessage {Logger logger = LoggerFactory.getLogger(InfoRequest.class);FilePiece piece;Charset charset;public InfoRequest(FilePiece piece) {this.piece = piece;}public InfoRequest(){//empty}@Overridepublic byte getTag() {// 0x01 请求包return (byte) 0x01;}@Overridepublic short getHeaderlen() {if (getTmp() == null) {short len = (short) (1 + 2 + 36 + 4 + 4 + 4 );return len;} else {short len = (short) (1 + 2 + 36 + 4 + 4 + 4 + (short) getTmp().length);return len;}}@Overridepublic int getFileLen() {// 文件总长度try {return (int) piece.getFc().size();} catch (IOException e) {e.printStackTrace();}return 0;}@Overridepublic int getOffset() {// 传输 偏移量return piece.getOffset();}@Overridepublic byte[] getFilename() {// 文件名称/** check the bits of name */byte[] name = new byte[36];name = piece.getFilename().getBytes();return name;}@Overridepublic byte[] getChecksum() {// checksumbyte[] checksum = new byte[4];checksum = piece.getChecksum().getBytes();return checksum;}@Overridepublic byte[] getTmp() {byte[] b=new byte[5];return b;}@Overridepublic IoBuffer getData() {return piece.getBuf();}}

业务对象代码，RandomAccessFile可用于随机读写，用于文件的切片，这里还用了管道，主要目的是为了加开读写速度：

package com.a2.desktop.example5.mina.potocol;import java.io.File;import java.io.RandomAccessFile;import java.nio.ByteBuffer;import java.nio.channels.FileChannel;import java.util.UUID;import org.apache.mina.core.buffer.IoBuffer;import org.slf4j.Logger;import org.slf4j.LoggerFactory;/** * 分片文件操作类 *  * @author Chen.Hui *  */public class FilePiece {Logger logger = LoggerFactory.getLogger(FilePiece.class);private ByteBuffer[] dsts;private IoBuffer buf;private String filename;private FileChannel fc;private RandomAccessFile raf;private int offset;private String checksum;/** 构建文件的基本信息 */public FilePiece(String path, int offset) throws Exception {raf = new RandomAccessFile(new File(path), "rw");fc = raf.getChannel();this.offset = offset;dsts = new ByteBuffer[1024];for (int i = 0; i < dsts.length; i++) {dsts[i] = ByteBuffer.allocate(1024);}fc.read(dsts, offset, 1024);buf=IoBuffer.allocate(1024);filename = UUID.randomUUID().toString();logger.info("has built:" + filename + " filename size"+ filename.length());}/**这个方法还有点儿问题，数据取的不对*/public IoBuffer getBuf(){dsts[0].flip();while(dsts[0].hasRemaining()){buf.putChar(dsts[0].getChar());}buf.flip();return buf;}public String getFilename() {return filename;}public FileChannel getFc() {return fc;}public RandomAccessFile getRaf() {return raf;}public int getOffset() {return offset;}public String getChecksum() {// TODO checksum algorithemsreturn "aaaa";}}

再接下来是编码器 ，编码器的作用就是讲数据装换成用于传输的流，在Mina中这种流就是IoBuffer：

package com.a2.desktop.example5.mina.potocol;import java.nio.charset.Charset;import org.apache.mina.core.buffer.IoBuffer;import org.apache.mina.core.session.IoSession;import org.apache.mina.filter.codec.ProtocolEncoderOutput;import org.apache.mina.filter.codec.demux.MessageEncoder;/** * 编码器 * @author Chen.Hui * */public class InfoEncoder implements MessageEncoder<AbsMessage>{private Charset charset;public InfoEncoder(Charset charset){this.charset=charset;}@Overridepublic void encode(IoSession session, AbsMessage message,ProtocolEncoderOutput out) throws Exception {IoBuffer buf=IoBuffer.allocate(1024).setAutoExpand(true);if(message instanceof InfoRequest){InfoRequest req=(InfoRequest) message;buf.put(req.getTag());buf.putShort((short)req.getHeaderlen());buf.put(req.getFilename());buf.putInt(req.getFileLen());buf.putInt(req.getOffset());buf.put(req.getChecksum());buf.put(req.getTmp());buf.put(req.getData());}else if(message instanceof InfoResponse){//TODO}buf.flip();out.write(buf);}}

解码器与之类似，解码器在这里的作用主要用户服务器端解码：

package com.a2.desktop.example5.mina.potocol;import java.nio.charset.Charset;import org.apache.mina.core.buffer.IoBuffer;import org.apache.mina.core.session.IoSession;import org.apache.mina.filter.codec.ProtocolDecoderOutput;import org.apache.mina.filter.codec.demux.MessageDecoder;import org.apache.mina.filter.codec.demux.MessageDecoderResult;/** * 解码器 * @author ChenHui * */public class InfoDecoder implements MessageDecoder {private Charset charset;public InfoDecoder(Charset charset) {this.charset = charset;}@Overridepublic MessageDecoderResult decodable(IoSession session, IoBuffer in) {//System.out.println("package size:"+in.remaining());// 报头长度<56if (in.remaining() < 56) {return MessageDecoderResult.NEED_DATA;}byte tag = in.get();short head_len=in.getShort();if (tag == (short) 0x01) {System.out.println("请求标识符："+tag+" head length:"+head_len);}else{//System.out.println("未知标识符...");return MessageDecoderResult.NOT_OK;}return MessageDecoderResult.OK;}@Overridepublic MessageDecoderResult decode(IoSession session, IoBuffer in,ProtocolDecoderOutput out) throws Exception {byte tag=in.get();if(tag==0x01){InfoReqContainer irc=new InfoReqContainer();irc.setTag(tag);irc.setHeadlen(in.getShort());irc.setFilename(in.getString(36, charset.newDecoder()));irc.setFilelen(in.getInt());irc.setOffset(in.getInt());irc.setChecksum(in.getString(4, charset.newDecoder()));irc.setTemp(in.getString(5, charset.newDecoder()));//应该用head len-53irc.setData(in);out.write(irc);}return MessageDecoderResult.OK;}@Overridepublic void finishDecode(IoSession session, ProtocolDecoderOutput out)throws Exception {// TODO Auto-generated method stub}}

为了解码方便，我这里设计了一个辅助类InfoReqContainer，主要用户辅助操作：

package com.a2.desktop.example5.mina.potocol;import org.apache.mina.core.buffer.IoBuffer;/** * 请求对象解析类 *  * @author Chen.Hui *  */public class InfoReqContainer {private byte tag;private short headlen;private String filename;private int filelen;private int offset;private String temp;private String checksum;private IoBuffer data;public byte getTag() {return tag;}public void setTag(byte tag) {this.tag = tag;}public short getHeadlen() {return headlen;}public void setHeadlen(short headlen) {this.headlen = headlen;}public String getFilename() {return filename;}public void setFilename(String filename) {this.filename = filename;}public int getFilelen() {return filelen;}public void setFilelen(int filelen) {this.filelen = filelen;}public int getOffset() {return offset;}public void setOffset(int offset) {this.offset = offset;}public String getTemp() {return temp;}public void setTemp(String temp) {this.temp = temp;}public String getChecksum() {return checksum;}public void setChecksum(String checksum) {this.checksum = checksum;}public IoBuffer getData() {return data;}public void setData(IoBuffer data) {this.data = data;}}

在mina中，要将解码器和编码器绑定到协议工厂类中，才能被过滤器使用：

package com.a2.desktop.example5.mina.potocol;import org.apache.mina.filter.codec.demux.DemuxingProtocolCodecFactory;import org.apache.mina.filter.codec.demux.MessageDecoder;import org.apache.mina.filter.codec.demux.MessageEncoder;public class InfoCodecFactory extends DemuxingProtocolCodecFactory {private MessageDecoder decoder;private MessageEncoder<AbsMessage> encoder;public InfoCodecFactory(MessageDecoder decoder,MessageEncoder<AbsMessage> encoder) {this.decoder = decoder;this.encoder = encoder;addMessageDecoder(this.decoder);addMessageEncoder(AbsMessage.class, this.encoder);}}

做完了这些，编码解码的工作都完成了，最后就是写客户端和服务器端进行测试，注意文件位置，这里没有做提示：

package com.a2.desktop.example5.mina.potocol;import java.net.InetSocketAddress;import java.nio.charset.Charset;import org.apache.mina.core.future.ConnectFuture;import org.apache.mina.core.service.IoConnector;import org.apache.mina.core.session.IoSession;import org.apache.mina.filter.codec.ProtocolCodecFilter;import org.apache.mina.transport.socket.nio.NioSocketConnector;public class TestClient {private static String HOST = "127.0.0.1";private static int PORT = 8082;public static void main(String[] args) {// 创建一个非阻塞的客户端程序IoConnector connector = new NioSocketConnector();// 设置链接超时时间connector.setConnectTimeout(30000);// 添加过滤器connector.getFilterChain().addLast("codec",new ProtocolCodecFilter(new InfoCodecFactory(new InfoDecoder(Charset.forName("utf-8")),new InfoEncoder(Charset.forName("utf-8")))));// 添加业务逻辑处理器类connector.setHandler(new ClientHandler());IoSession session = null;try {ConnectFuture future = connector.connect(new InetSocketAddress(HOST, PORT));// 创建连接future.awaitUninterruptibly();// 等待连接创建完成session = future.getSession();// 获得sessionFilePiece piece = new FilePiece("D:\\Develop Libs Tar\\apache-mina-2.0.7-bin.zip", 0);InfoRequest ir = new InfoRequest(piece);session.write(ir);// 发送消息} catch (Exception e) {e.printStackTrace();System.out.println("客户端链接异常...");}session.getCloseFuture().awaitUninterruptibly();// 等待连接断开connector.dispose();}}

客户端的Handler没有做任何处理：

package com.a2.desktop.example5.mina.potocol;import org.apache.mina.core.service.IoHandler;import org.apache.mina.core.session.IdleStatus;import org.apache.mina.core.session.IoSession;public class ClientHandler implements IoHandler {@Overridepublic void sessionCreated(IoSession session) throws Exception {// TODO Auto-generated method stub}@Overridepublic void sessionOpened(IoSession session) throws Exception {// TODO Auto-generated method stub}@Overridepublic void sessionClosed(IoSession session) throws Exception {// TODO Auto-generated method stub}@Overridepublic void sessionIdle(IoSession session, IdleStatus status)throws Exception {// TODO Auto-generated method stub}@Overridepublic void exceptionCaught(IoSession session, Throwable cause)throws Exception {// TODO Auto-generated method stub}@Overridepublic void messageReceived(IoSession session, Object message)throws Exception {//System.out.println(message.toString());}@Overridepublic void messageSent(IoSession session, Object message) throws Exception {// TODO Auto-generated method stub}}

服务器端：

package com.a2.desktop.example5.mina.potocol;import java.net.InetSocketAddress;import java.nio.charset.Charset;import org.apache.mina.core.service.IoAcceptor;import org.apache.mina.core.session.IdleStatus;import org.apache.mina.core.session.IoSessionConfig;import org.apache.mina.filter.codec.ProtocolCodecFilter;import org.apache.mina.filter.logging.LogLevel;import org.apache.mina.filter.logging.LoggingFilter;import org.apache.mina.transport.socket.nio.NioSocketAcceptor;public class TestServer{private static int PORT = 8082;public static void main(String[] args) {IoAcceptor acceptor = null;try {// 创建一个非阻塞的server端的Socketacceptor = new NioSocketAcceptor();// 设置过滤器（添加自带的编解码器）acceptor.getFilterChain().addLast("codec",new ProtocolCodecFilter(new InfoCodecFactory(new InfoDecoder(Charset.forName("utf-8")),new InfoEncoder(Charset.forName("utf-8")))));// 设置日志过滤器LoggingFilter lf = new LoggingFilter();lf.setMessageReceivedLogLevel(LogLevel.DEBUG);acceptor.getFilterChain().addLast("logger", lf);// 获得IoSessionConfig对象IoSessionConfig cfg = acceptor.getSessionConfig();// 读写通道10秒内无操作进入空闲状态cfg.setIdleTime(IdleStatus.BOTH_IDLE, 100);// 绑定逻辑处理器acceptor.setHandler(new ServerHandler());// 绑定端口acceptor.bind(new InetSocketAddress(PORT));System.out.println("成功开启服务器端...");} catch (Exception e) {e.printStackTrace();}}}        

服务器端的Handler：

package com.a2.desktop.example5.mina.potocol;import org.apache.mina.core.service.IoHandler;import org.apache.mina.core.session.IdleStatus;import org.apache.mina.core.session.IoSession;public class ServerHandler implements IoHandler {@Overridepublic void sessionCreated(IoSession session) throws Exception {// TODO Auto-generated method stub}@Overridepublic void sessionOpened(IoSession session) throws Exception {// TODO Auto-generated method stub}@Overridepublic void sessionClosed(IoSession session) throws Exception {// TODO Auto-generated method stub}@Overridepublic void sessionIdle(IoSession session, IdleStatus status)throws Exception {// TODO Auto-generated method stub}@Overridepublic void exceptionCaught(IoSession session, Throwable cause)throws Exception {// TODO Auto-generated method stub}@Overridepublic void messageReceived(IoSession session, Object message)throws Exception {if (message instanceof InfoReqContainer) {InfoReqContainer irc = (InfoReqContainer) message;System.out.println("服务器端 获取成功 Tag:" + irc.getTag() + "\r\n " + "head len:"+ irc.getHeadlen() + "\r\nfilename: " + irc.getFilename()+ "\r\nfile len:"+irc.getFilelen()+"\r\noffset:"+irc.getOffset()+"\r\nchecksum:"+irc.getChecksum()+"\r\ndata:"+irc.getData().toString());session.write("success rescive");} else {System.out.println("获取失败");}}@Overridepublic void messageSent(IoSession session, Object message) throws Exception {// TODO Auto-generated method stub}}

主要还是提供一个思路，并没用很多业务的东西，也没有做事务和并发处理，当然这在项目中一定会处理。Mina很好用，用原生的NIO也同样能实现，原理都一样。Mina的异步通信原理网上一大堆，我就不写了。

谢谢观赏。

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早上突然看到文章有那么多人浏览，看来写协议做通信确实是一个热门，有时间我让我同事把服务器端的C的代码发上来，我觉得服务端的C也是一个很好的实现方式。当初考虑到性能，才决定在服务器端用C，想彻底摆脱JVM。底层都是socket所以通信肯定没问题，难点在用C编码和解码的数据格式和java有一定差别，去除这种差别之后，操作起来都是一样的。

转自:http://my.oschina.net/ielts0909/blog/85946