首先說一下需要注意的問題

1：傳送端的javabean 一定要有註解 @Message。這個註解要加在類上。使用@Message 可以標記被序列化的類。類中所有成員都會被序列化。 否則javabean不會被序列化，也就接收不到了。接收端的javabean可以不加這個註解。習慣性的兩個端都會加上。

2、因為有  @Message 所以javabean就不需要實現Serializable介面，當然實現了也沒有問題（已測）；

3、傳送的javabean要在Client和Server端兩個端都存在，而且名稱要完全一致，全類名一致。或者直接打成單獨的jar包放在兩個端；

4、傳送端編碼，服務解碼。也就是說，編碼和和解碼的類不一定要兩個端都有。

5、網上有許多關於messagepack拆包的問題，我發現我沒有發生粘包。。。所以，沒有處理這一塊。有需要的朋友網上找找，很多的。

netty權威指南里也有相關的介紹。

遇到的坑：（1）一開始沒有加上@Message註解（2）解碼的一段程式碼應該是msg.getBytes(msg.readerIndex(), array, 0, length);但是寫成 了msg.getBytes(msg.readableBytes(), array, 0, length); 導致解碼出的msg長度0，沒有內容；

其他的問題暫無。

下面看具體程式碼，client端和server端是兩個不同的工程。

javabean 和編碼解碼的程式碼兩個端是一樣的，這裡提供一份。

handler 寫的比較簡單，可以根據需要改改；

Client端的程式碼：

NettyClient.java

package com.aowin.netty.serial.messagepack;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;

public class 
 
NettyClient {
    public void connet(){
        EventLoopGroup bosLoup=new NioEventLoopGroup();
        Bootstrap bootstrap=new Bootstrap();
        bootstrap.group(bosLoup)
                .channel(NioSocketChannel.class)
                .handler(new NettyClientInitializer());
        try {
            ChannelFuture future= bootstrap.connect("127.0.0.1",8765).sync();
            UserInfo userInfoArray[]=new UserInfo[3];
            for(int i=0;i<3;i++){
                UserInfo userInfo=new UserInfo();
                userInfo.setName("netty");
                userInfo.setAge(i);
                userInfoArray[i]=userInfo;
            }

           // future.channel().writeAndFlush(Unpooled.copiedBuffer("hello".getBytes()));
future.channel().writeAndFlush(userInfoArray);
            future.channel().closeFuture().sync();
            bosLoup.shutdownGracefully();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        NettyClient client=new NettyClient();
        client.connet();
    }
}

NettyClientHandler.java  

package com.aowin.netty.serial.messagepack;

import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;

public class NettyClientHandler  extends ChannelHandlerAdapter{
    @Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
    }

    @Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
    }

    @Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
    }

    @Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
    }
}

NettyClientInitializer.java

package com.aowin.netty.serial.messagepack;

import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
import io.netty.handler.codec.string.StringDecoder;

public class NettyClientInitializer extends ChannelInitializer{
    @Override
protected void initChannel(Channel ch) throws Exception {
        //ch.pipeline().addLast(new StringDecoder());
ch.pipeline().addLast(new MsgPackEncode());
        ch.pipeline().addLast(new MsgPackDecode());
        ch.pipeline().addLast(new NettyClientHandler());

    }
}

Server端的程式碼：

NettyServer.java

package com.aowin.netty.serial.messagepack;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;

public class NettyServer {
    public void bind() {
        EventLoopGroup bosGroup = new NioEventLoopGroup();
        EventLoopGroup workGroup = new NioEventLoopGroup();
        ServerBootstrap bootstrap = new ServerBootstrap();
        bootstrap.group(bosGroup, workGroup)
                .channel(NioServerSocketChannel.class)
                .option(ChannelOption.SO_BACKLOG, 1024)
                .option(ChannelOption.SO_SNDBUF, 32 * 1024)
                .option(ChannelOption.SO_RCVBUF, 32 * 1024)
                .option(ChannelOption.SO_KEEPALIVE, true)
                .handler(new LoggingHandler(LogLevel.DEBUG))
                .childHandler(new NettyServerInitializer());
        try {
            ChannelFuture future = bootstrap.bind("127.0.0.1", 8765).sync();
            future.channel().closeFuture().sync();
            bosGroup.shutdownGracefully();
            workGroup.shutdownGracefully();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        NettyServer server=new NettyServer();
        server.bind();
    }
}

NettyServerHandler.java

package com.aowin.netty.serial.messagepack;

import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.util.List;
import java.util.logging.Logger;

public class NettyServerHandler extends ChannelHandlerAdapter {
    Log logger= LogFactory.getLog(NettyServerHandler.class);
    @Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
    }

    @Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
    }

    @Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        List<UserInfo> list= (List<UserInfo>) msg;

        logger.info(list);
        logger.info(list.get(0));
        logger.info(list.get(1));
    }

    @Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
    }
}

NettyServerInitializer.java

package com.aowin.netty.serial.messagepack;

import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
import io.netty.handler.codec.string.StringDecoder;

public class NettyServerInitializer extends ChannelInitializer {
    protected void initChannel(Channel ch) throws Exception {
        ch.pipeline().addLast(new MsgPackEncode());
        ch.pipeline().addLast(new MsgPackDecode());
        ch.pipeline().addLast(new NettyServerHandler());
    }
}

下面是兩個端都要有的程式碼:

    解碼：

MsgPackDecode.java 

package com.aowin.netty.serial.messagepack;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageDecoder;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.msgpack.MessagePack;

import java.util.List;

public class MsgPackDecode extends MessageToMessageDecoder<ByteBuf> {
private Log logger= LogFactory.getLog(MsgPackDecode.class);
    @Override
protected void decode(ChannelHandlerContext ctx, ByteBuf msg,
                          List<Object> out) throws Exception {
        logger.info("解碼");
        final byte[] array;
        final int length = msg.readableBytes();
        array = new byte[length];
        //msg.getBytes(msg.readableBytes(), array, 0, length);
msg.getBytes(msg.readerIndex(), array, 0, length);
        MessagePack msgPack = new MessagePack();
        out.add(msgPack.read(array));
        logger.info("解碼");
    }

}

編碼：

package com.aowin.netty.serial.messagepack;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.msgpack.MessagePack;

public class MsgPackEncode  extends MessageToByteEncoder<Object> {
    private Log logger= LogFactory.getLog(MsgPackEncode.class);
    @Override
protected void encode(ChannelHandlerContext ctx, Object msg, ByteBuf out)
            throws Exception {
        logger.info("編碼");
        MessagePack msgPack = new MessagePack();
        System.out.println(msg == null);
        byte[] raw = null;
        raw = msgPack.write(msg);
        out.writeBytes(raw);
        logger.info("編碼");
    }
}

javaBean:

package com.aowin.netty.serial.messagepack;

import org.msgpack.annotation.Message;

import java.io.Serializable;

//這個註解是加在類上的
@Messagepublic class UserInfo{
    String name;
    int age;

    public String getName() {
        
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

執行結果：

客戶端：

服務端：