Netty 5 ?自定义协议 ?教程

网上好多连接好多demo都不是netty5的，都是以前的版本，况且还有好多运行时老报错。入门级demo就不写了，估计都是那些老套路。好多公司都会有最佳实践，今天就说说如何自定义协议，一般自定义协议都是公司内部各个部门定义的，当然了我写的比较简单。

注意：

本教程是采用netty-all-5.0.0.Alpha2.jar，netty5的版本，不是网上很多的例子都是采用以前老大版本。

自定义协议：

协议 {

协议头（header）

消息体（body）

}

header格式 {

固定头，

命令码，

版本号，

长度

}

自定义协议嘛，都是可以自己定义实现的，内部商量好就可以。

packagecom.nio.netty;importjava.io.Serializable;importjava.util.Arrays;/***Createdbysdcon2017/8/26.*/publicclassMsgHeaderimplementsSerializable{//固定头privatebytestartTag;//命令码，4位privatebyte[]cmdCode;//版本2位privatebyte[]version;privateintlength;publicbyte[]getVersion(){returnversion;}publicvoidsetVersion(byte[]version){this.version=version;}publicbyte[]getCmdCode(){returncmdCode;}publicvoidsetCmdCode(byte[]cmdCode){this.cmdCode=cmdCode;}publicbytegetStartTag(){returnstartTag;}publicvoidsetStartTag(bytestartTag){this.startTag=startTag;}publicintgetLength(){returnlength;}publicvoidsetLength(intlength){this.length=length;}@OverridepublicStringtoString(){return"MsgHeader{"+"startTag="+startTag+",cmdCode="+Arrays.toString(cmdCode)+",version="+Arrays.toString(version)+",length="+length+‘}‘;}}

packagecom.nio.netty;/***Createdbysdcon2017/8/26.*/publicclassMessage{privateMsgHeaderheader;privateObjectbody;//检验和//privatebytecrcCode;//publicbytegetCrcCode(){//returncrcCode;//}////publicvoidsetCrcCode(bytecrcCode){//this.crcCode=crcCode;//}publicMsgHeadergetHeader(){returnheader;}publicvoidsetHeader(MsgHeaderheader){this.header=header;}publicObjectgetBody(){returnbody;}publicvoidsetBody(Objectbody){this.body=body;}@OverridepublicStringtoString(){return"Message{"+"header="+header+",body="+body+//",crcCode="+crcCode+‘}‘;}}

消息格式定义完成后，需要编码和解码，这里采用ByteToMessageDecoder MessageToByteEncoder，这两个编解码。

packagecom.nio.netty;importio.netty.buffer.ByteBuf;importio.netty.channel.ChannelHandlerContext;importio.netty.handler.codec.MessageToByteEncoder;/***Createdbysdcon2017/8/26.*/publicclassMsgEncoderextendsMessageToByteEncoder{publicstaticbytegetIndexToByte(inti,intindex){if(index==0){return(byte)(i%10);}else{intnum=(int)Math.pow(10,index);return(byte)((i/num)%10);}}@Overrideprotectedvoidencode(ChannelHandlerContextchannelHandlerContext,Objecto,ByteBufout)throwsException{if(oinstanceofMessage){try{Messagemsg=(Message)o;if(msg==null||msg.getHeader()==null){thrownewException("Theencodemessageisnull");}out.writeByte(msg.getHeader().getStartTag());out.writeBytes(msg.getHeader().getCmdCode());//占位byte[]lengthBytes=newbyte[]{0,0,0,0};out.writeBytes(lengthBytes);out.writeBytes(msg.getHeader().getVersion());Stringbody=(String)msg.getBody();intlength=0;if(body!=null){byte[]bodyBytes=body.getBytes();out.writeBytes(bodyBytes);length=bodyBytes.length;//if(Constants.CRCCODE_DEFAULT!=msg.getCrcCode()){//msg.setCrcCode(CRC8.calcCrc8(bodyBytes));//}//msg.setCrcCode();}//长度从int转换为byte[4]bytel1=getIndexToByte(length,3);bytel2=getIndexToByte(length,2);bytel3=getIndexToByte(length,1);bytel4=getIndexToByte(length,0);lengthBytes=newbyte[]{l1,l2,l3,l4};out.setBytes(5,lengthBytes);System.out.println("encoder:"+msg.getBody());//out.writeByte(msg.getCrcCode());}catch(Exceptione){e.printStackTrace();throwe;}}}}

packagecom.nio.netty;importio.netty.buffer.ByteBuf;importio.netty.channel.ChannelHandlerContext;importio.netty.channel.ChannelPromise;importio.netty.handler.codec.ByteToMessageCodec;importio.netty.handler.codec.ByteToMessageDecoder;importjava.util.List;/***Createdbysdcon2017/8/26.*/publicclassMsgDecoderextendsByteToMessageDecoder{@Overrideprotectedvoiddecode(ChannelHandlerContextctx,ByteBufin,Listout)throwsException{try{//内部协议这块可以约定一下，超过多大的长度就不可以了。//if(in.readableBytes()<12){//return;//}System.out.println("开始解码消息，消息长度:"+in.readableBytes());in.markReaderIndex();//设置一些消息的属性Messagemessage=newMessage();MsgHeaderheader=newMsgHeader();header.setStartTag(in.readByte());byte[]cmdCode=newbyte[4];in.readBytes(cmdCode);header.setCmdCode(cmdCode);System.out.println(newString(cmdCode,"UTF-8"));//长度从byte[4]转intbyte[]lengthBytes=newbyte[4];in.readBytes(lengthBytes);intlength=toInt(lengthBytes);System.out.println("header:"+length);header.setLength(length);if(length<0||length>10240){//过长消息或不合法消息thrownewIllegalArgumentException("wrongmessagelength");}byte[]version=newbyte[2];in.readBytes(version);header.setVersion(version);System.out.println("version:"+newString(version,"UTF-8"));if(header.getLength()>0){System.out.println("bytebuffer可读的范围"+in.readableBytes());if(in.readableBytes()>length+1){in.resetReaderIndex();System.out.println("返回了");return;}//读取body里的内容byte[]bodyBytes=newbyte[header.getLength()];in.readBytes(bodyBytes);message.setBody(newString(bodyBytes,"UTF-8"));}//crccode暂时去掉//message.setCrcCode(in.readByte());//设置头部message.setHeader(header);System.out.println("body:"+message.getBody());out.add(message);}catch(Exceptione){e.printStackTrace();throwe;}}publicstaticinttoInt(byte[]bytes){intvalue=0;for(inti=0;i<bytes.length;i++){intnum=(int)Math.pow(10,bytes.length-1-i);value+=num*bytes[i];}returnvalue;}}

消息的类已经处理完了，下面来开始写客户端和服务端的代码。

客户端代码：

packagecom.nio.netty;importio.netty.bootstrap.Bootstrap;importio.netty.buffer.ByteBuf;importio.netty.buffer.ByteBufUtil;importio.netty.buffer.Unpooled;importio.netty.channel.*;importio.netty.channel.nio.NioEventLoopGroup;importio.netty.channel.socket.SocketChannel;importio.netty.channel.socket.nio.NioSocketChannel;/***Createdbysdcon2017/8/26.*/publicclassMsgClient{publicvoidconnect(Stringip,intport)throwsException{EventLoopGroupworkerGroup=newNioEventLoopGroup();Messagemessage=newMessage();StringmsgStr="我想发送一条消息";MsgHeaderheader=newMsgHeader();header.setStartTag(newByte("0"));header.setCmdCode("1234".getBytes());header.setLength(msgStr.length());header.setVersion("11".getBytes());message.setBody(msgStr);message.setHeader(header);try{Bootstrapbs=newBootstrap();bs.group(workerGroup).channel(NioSocketChannel.class).handler(newChildChannelHandler(message));ChannelFuturef=bs.connect(ip,port).sync();//写入消息f.channel().writeAndFlush(message).sync();f.channel().closeFuture().sync();}finally{workerGroup.shutdownGracefully();}}publicstaticclassChildChannelHandlerextendsChannelInitializer{Messagemessage;publicChildChannelHandler(Messagemessage){this.message=message;}@OverrideprotectedvoidinitChannel(Channelchannel)throwsException{channel.pipeline().addLast(newMsgDecoder()).addLast(newMsgEncoder());}}publicstaticvoidmain(String[]args){try{newMsgClient().connect("127.0.0.1",9080);}catch(Exceptione){e.printStackTrace();}}}

服务端代码

packagecom.nio.netty;importio.netty.bootstrap.ServerBootstrap;importio.netty.channel.*;importio.netty.channel.nio.NioEventLoopGroup;importio.netty.channel.socket.SocketChannel;importio.netty.channel.socket.nio.NioServerSocketChannel;/***Createdbysdcon2017/8/26.*/publicclassMsgServer{publicvoidbind(intport)throwsException{EventLoopGroupbossGroup=newNioEventLoopGroup();EventLoopGroupworkerGroup=newNioEventLoopGroup();try{ServerBootstrapsb=newServerBootstrap();sb.group(bossGroup,workerGroup).channel(NioServerSocketChannel.class).option(ChannelOption.SO_BACKLOG,1024).childHandler(newChildChannelHandler());ChannelFuturecf=sb.bind(port).sync();cf.channel().closeFuture().sync();}finally{bossGroup.shutdownGracefully();workerGroup.shutdownGracefully();}}publicstaticclassChildChannelHandlerextendsChannelInitializer{@OverrideprotectedvoidinitChannel(Channelchannel)throwsException{channel.pipeline().addLast(newMsgDecoder()).addLast(newMsgEncoder());}}publicstaticvoidmain(String[]args){try{newMsgServer().bind(9080);}catch(Exceptione){e.printStackTrace();}}}

运行的时候先运行服务端，否则胡报如下的错误，

-all-5.0.0.Alpha2.jarcom.nio.netty.MsgClientjava.net.ConnectException:Connectionrefused:nofurtherinformation:/127.0.0.1:9080atsun.nio.ch.SocketChannelImpl.checkConnect(NativeMethod)atsun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:716)atio.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:223)atio.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:276)atio.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:531)atio.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:471)atio.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:385)atio.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:351)atio.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116)atio.netty.util.internal.chmv8.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1412)atio.netty.util.internal.chmv8.ForkJoinTask.doExec(ForkJoinTask.java:280)atio.netty.util.internal.chmv8.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:877)atio.netty.util.internal.chmv8.ForkJoinPool.scan(ForkJoinPool.java:1706)atio.netty.util.internal.chmv8.ForkJoinPool.runWorker(ForkJoinPool.java:1661)atio.netty.util.internal.chmv8.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:126)Processfinishedwithexitcode0

成功会打印以下信息：

开始解码消息，消息长度:35开始解码消息，消息长度2222:341234header:24version:11可读的范围24body:我想发送一条消息Processfinishedwithexitcode1

基本流程已经走完，学框架，我还是习惯先写例子，然后再学概念性的东西，会理解的更深刻一些。

参考了这篇文章，但是这篇文章似乎看不了结果，所以还是自己改了改，写了点东西。

http://www.blogs8.cn/posts/Wx8Sd43

本文出自 “不积跬步无以至千里” 博客，请务必保留此出处http://shangdc.blog.51cto.com/10093778/1959680

Netty 5 ?自定义协议 ?教程

原文地址：http://shangdc.blog.51cto.com/10093778/1959680