dubbo源码7－编解码

一 类层次图

编解码类图.png

二 NettyCodecAdapter

• 代理DubboCountCodec

2.1 encode

• write函数发送消息，先按照preferDirect属性分配HeapByteBuf或DirectByteBuf
• NettyBackedChannelBuffer代理ByteBuf相应接口
• NettyChannel代理netty层的通信接口
• 调用协议层配置的DubboCountCodec编码接口

  public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
      ByteBuf buf = this.allocateBuffer(ctx, msg, this.preferDirect);
      this.encode(ctx, cast, buf);
      ...
    }

  protected void encode(ChannelHandlerContext ctx, Object msg, ByteBuf out) throws Exception {
    com.alibaba.dubbo.remoting.buffer.ChannelBuffer buffer = new NettyBackedChannelBuffer(out);
    Channel ch = ctx.channel();
    NettyChannel channel = NettyChannel.getOrAddChannel(ch, url, handler);
    try {
        codec.encode(channel, buffer, msg);
    } finally {
        NettyChannel.removeChannelIfDisconnected(ch);
    }
  }

2.2 decode

• 调用协议层配置的DubboCountCodec解码接口
• NEED_MORE_INPUT表示报文拆分传输，需要继续等待通信层收包，回退读索引。
• 解码成功，输出解码的对象。

protected void decode(ChannelHandlerContext ctx, ByteBuf input, List