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。
package com.nio.netty;
import java.io.Serializable;
import java.util.Arrays;
/**
* Created by sdc on 2017/8/26.
*/
public class MsgHeader implements Serializable{
//固定头
private byte startTag;
//命令码，4位
private byte[] cmdCode;
//版本 2位
private byte[] version;
private int length;
public byte[] getVersion() {
return version;
}
public void setVersion(byte[] version) {
this.version = version;
}
public byte[] getCmdCode() {
return cmdCode;
}
public void setCmdCode(byte[] cmdCode) {
this.cmdCode = cmdCode;
}
public byte getStartTag() {
return startTag;
}
public void setStartTag(byte startTag) {
this.startTag = startTag;
}
public int getLength() {
return length;
}
public void setLength(int length) {
this.length = length;
}
@Override
public String toString() {
return "MsgHeader{" +
"startTag=" + startTag +
", cmdCode=" + Arrays.toString(cmdCode) +
", version=" + Arrays.toString(version) +
", length=" + length +
‘}‘;
}
}package com.nio.netty;
/**
* Created by sdc on 2017/8/26.
*/
public class Message {
private MsgHeader header;
private Object body;
//检验和
// private byte crcCode;
// public byte getCrcCode() {
// return crcCode;
// }
//
// public void setCrcCode(byte crcCode) {
// this.crcCode = crcCode;
// }
public MsgHeader getHeader() {
return header;
}
public void setHeader(MsgHeader header) {
this.header = header;
}
public Object getBody() {
return body;
}
public void setBody(Object body) {
this.body = body;
}
@Override
public String toString() {
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。
package com.nio.netty;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
/**
* Created by sdc on 2017/8/26.
*/
public class MsgEncoder extends MessageToByteEncoder {
public static byte getIndexToByte(int i, int index){
if(index == 0){
return (byte)(i % 10);
}else{
int num = (int)Math.pow(10, index);
return (byte)((i / num) % 10);
}
}
@Override
protected void encode(ChannelHandlerContext channelHandlerContext, Object o, ByteBuf out) throws Exception {
if (o instanceof Message) {
try {
Message msg = (Message)o;
if (msg == null || msg.getHeader() == null) {
throw new Exception("The encode message is null");
}
out.writeByte(msg.getHeader().getStartTag());
out.writeBytes(msg.getHeader().getCmdCode());
//占位
byte[] lengthBytes = new byte[]{0, 0, 0, 0};
out.writeBytes(lengthBytes);
out.writeBytes(msg.getHeader().getVersion());
String body = (String) msg.getBody();
int length = 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]
byte l1 = getIndexToByte(length, 3);
byte l2 = getIndexToByte(length, 2);
byte l3 = getIndexToByte(length, 1);
byte l4 = getIndexToByte(length, 0);
lengthBytes = new byte[]{l1, l2, l3, l4};
out.setBytes(5, lengthBytes);
System.out.println("encoder:" + msg.getBody());
// out.writeByte(msg.getCrcCode());
}catch(Exception e){
e.printStackTrace();
throw e;
}
}
}
}package com.nio.netty;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPromise;
import io.netty.handler.codec.ByteToMessageCodec;
import io.netty.handler.codec.ByteToMessageDecoder;
import java.util.List;
/**
* Created by sdc on 2017/8/26.
*/
public class MsgDecoder extends ByteToMessageDecoder {
@Override
protected void decode(ChannelHandlerContext ctx, ByteBuf in, List out) throws Exception {
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
Message message = new Message();
MsgHeader header = new MsgHeader();
header.setStartTag(in.readByte());
byte[] cmdCode = new byte[4];
in.readBytes(cmdCode);
header.setCmdCode(cmdCode);
System.out.println(new String(cmdCode, "UTF-8"));
//长度从byte[4]转int
byte[] lengthBytes = new byte[4];
in.readBytes(lengthBytes);
int length = 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
throw new IllegalArgumentException("wrong message length");
}
byte[] version = new byte[2];
in.readBytes(version);
header.setVersion(version);
System.out.println("version:" + new String(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 = new byte[header.getLength()];
in.readBytes(bodyBytes);
message.setBody(new String(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(Exception e){
e.printStackTrace();
throw e;
}
}
public static int toInt(byte[] bytes){
int value = 0;
for(int i=0; i<bytes.length; i++){
int num = (int)Math.pow(10, bytes.length - 1 - i);
value += num * bytes[i];
}
return value;
}
}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：
package com.nio.netty;
import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufUtil;
import io.netty.buffer.Unpooled;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
/**
* Created by sdc on 2017/8/26.
*/
public class MsgClient {
public void connect(String ip, int port) throws Exception {
EventLoopGroup workerGroup = new NioEventLoopGroup();
Message message = new Message();
String msgStr = "我想发送一条消息";
MsgHeader header = new MsgHeader();
header.setStartTag(new Byte("0"));
header.setCmdCode("1234".getBytes());
header.setLength(msgStr.length());
header.setVersion("11".getBytes());
message.setBody(msgStr);
message.setHeader(header);
try {
Bootstrap bs = new Bootstrap();
bs.group(workerGroup).channel(NioSocketChannel.class).handler(new ChildChannelHandler(message));
ChannelFuture f = bs.connect(ip,port).sync();
//写入消息
f.channel().writeAndFlush(message).sync();
f.channel().closeFuture().sync();
} finally {
workerGroup.shutdownGracefully();
}
}
public static class ChildChannelHandler extends ChannelInitializer {
Message message;
public ChildChannelHandler(Message message) {
this.message = message;
}
@Override
protected void initChannel(Channel channel) throws Exception {
channel.pipeline().addLast(new MsgDecoder())
.addLast(new MsgEncoder());
}
}
public static void main(String[] args){
try {
new MsgClient().connect("127.0.0.1", 9080);
} catch (Exception e) {
e.printStackTrace();
}
}
}服务端代码
package com.nio.netty;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
/**
* Created by sdc on 2017/8/26.
*/
public class MsgServer {
public void bind(int port) throws Exception {
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap sb = new ServerBootstrap();
sb.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
.option(ChannelOption.SO_BACKLOG, 1024)
.childHandler(new ChildChannelHandler());
ChannelFuture cf = sb.bind(port).sync();
cf.channel().closeFuture().sync();
}finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
public static class ChildChannelHandler extends ChannelInitializer {
@Override
protected void initChannel(Channel channel) throws Exception {
channel.pipeline()
.addLast(new MsgDecoder())
.addLast(new MsgEncoder());
}
}
public static void main(String[] args){
try {
new MsgServer().bind(9080);
} catch (Exception e) {
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.jar com.nio.netty.MsgClient java.net.ConnectException: Connection refused: no further information: /127.0.0.1:9080 at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:716) at io.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:223) at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:276) at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:531) at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:471) at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:385) at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:351) at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116) at io.netty.util.internal.chmv8.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1412) at io.netty.util.internal.chmv8.ForkJoinTask.doExec(ForkJoinTask.java:280) at io.netty.util.internal.chmv8.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:877) at io.netty.util.internal.chmv8.ForkJoinPool.scan(ForkJoinPool.java:1706) at io.netty.util.internal.chmv8.ForkJoinPool.runWorker(ForkJoinPool.java:1661) at io.netty.util.internal.chmv8.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:126) Process finished with exit code 0
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2222:34 1234 header:24 version:11 可读的范围24 body:我想发送一条消息 Process finished with exit code 1
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
原文地址：http://shangdc.blog.51cto.com/10093778/1959680
