使用Netty进行编解码的操作过程详解

<!-- https://mvnrepository.com/artifact/org.msgpack/msgpack -->
<dependency>
  <groupId>org.msgpack</groupId>
  <artifactId>msgpack</artifactId>
  <version>0.6.12</version>
</dependency>

List<String> nameList = new ArrayList<String>();
nameList.add("Tom");
nameList.add("Jack");
MessagePack messagePack = new MessagePack();
//开始序列化
byte[] raw = messagePack.write(nameList);
//使用MessagePack的模版，来接序列化后的字节数组转换为List
List<String> deNameList = messagePack.read(raw,Templates.tList(Templates.TString));
System.out.println(deNameList.get(0));
System.out.println(deNameList.get(1));
System.out.println(deNameList.get(2));

public class MsgpackEncoder extends MessageToByteEncoder {

  @Override
  protected void encode(ChannelHandlerContext ctx, Object msg, ByteBuf out) throws Exception {
    MessagePack msgpack = new MessagePack();
    //使用MessagePack对要发送的数据进行序列化
    byte[] raw = msgpack.write(msg);
    out.writeBytes(raw);
    
  }

}

public class MsgpackDecoder extends MessageToMessageDecoder<ByteBuf> {

  @Override
  protected void decode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out) throws Exception {
    //从msg中获取需要解码的byte数组
    final int length = msg.readableBytes();
    byte[] b = new byte[length];
    msg.getBytes(msg.readerIndex(), b,0,length);
    //使用MessagePack的read方法将其反序列化成Object对象，并加入到解码列表out中
    MessagePack msgpack = new MessagePack();
    out.add(msgpack.read(b));
  }

}

public class NettyServer {
  public void bind(int port) throws Exception {
    EventLoopGroup bossGruop = new NioEventLoopGroup();
    EventLoopGroup workGroup = new NioEventLoopGroup();
    ServerBootstrap bootstrap = new ServerBootstrap();
    bootstrap.group(bossGruop, workGroup)
        .channel(NioServerSocketChannel.class)
        .option(ChannelOption.SO_BACKLOG, 1024)
        .childHandler(new ChannelInitializer<SocketChannel>() {
          @Override
          protected void initChannel(SocketChannel socketChannel) throws Exception {
            // TODO Auto-generated method stub
            socketChannel.pipeline()
             //添加支持粘包、拆包解码器，意义：从头两个字节解析出数据的长度，并且长度不超过1024个字节
            .addLast("frameDecoder",new LengthFieldBasedFrameDecoder(1024, 0, 2,0,2))
             //反序列化解码器
            .addLast("msgpack decoder",new MsgpackDecoder())
             //添加支持粘包、拆包编码器，发送的每个数据都在头部增加两个字节表消息长度
            .addLast("frameEncoder",new LengthFieldPrepender(2))
             //序列化编码器
            .addLast("msgpack encoder",new MsgpackEncoder()
             //后续自己的业务逻辑
            .addLast(new ServerHandler());
          }
        });
    try {
      ChannelFuture future = bootstrap.bind(port).sync();
      future.channel().closeFuture().sync();
    } catch (Exception e) {
      e.printStackTrace();
    } finally {
      bossGruop.shutdownGracefully();
      workGroup.shutdownGracefully();
    }
  }
}  

public class NettyClient {
  private void bind(int port, String host) {
    EventLoopGroup group = new NioEventLoopGroup();
    Bootstrap b = new Bootstrap();
    b.group(group)
        .channel(NioSocketChannel.class)
        .option(ChannelOption.TCP_NODELAY, true)
        .handler(new ChannelInitializer<SocketChannel>(){
          @Override
          protected void initChannel(SocketChannel socketChannel) throws Exception {
            // TODO Auto-generated method stub
            socketChannel.pipeline()
            .addLast("frameDecoder", new LengthFieldBasedFrameDecoder(1024, 0, 2, 0, 2))
            .addLast("msgpack decoder", new MsgpackDecoder())
            .addLast("frameEncoder", new LengthFieldPrepender(2))
            .addLast("msgpack encoder", new MsgpackEncoder())
            .addLast(new ClientHandler());
          }
        });
    try {
      ChannelFuture f = b.connect(host, port).sync();
      f.channel().closeFuture().sync();
    } catch (Exception e) {
      e.printStackTrace();
    } finally {
      group.shutdownGracefully();
    }
  }
}