Jetserver开源项目学习（八）—— 解码编码器的用法

/**
 * A simple event encoder will receive an incoming event, and convert it to a
 * {@link ChannelBuffer}. It will read the event type and put it as the
 * opcode(i.e first byte of the buffer), then it will read the event body and
 * put convert to ChannelBuffer if necessary and put it as the body of the
 * message.
 * 
 * @author Abraham Menacherry
 * 
 */
@Sharable
public class EventEncoder extends OneToOneEncoder
{
    private static final Logger LOG = LoggerFactory
            .getLogger(EventDecoder.class);

    @Override
    protected Object encode(ChannelHandlerContext ctx, Channel channel,
            Object msg) throws Exception
    {
        if (null == msg)
        {
            LOG.error("Received null message in EventEncoder");
            return msg;
        }
        Event event = (Event) msg;
        ChannelBuffer opcode = ChannelBuffers.buffer(1);
        opcode.writeByte(event.getType());
        ChannelBuffer buffer = null;
        if(null != event.getSource())
        {
            ChannelBuffer data = (ChannelBuffer) event.getSource();
            buffer = ChannelBuffers.wrappedBuffer(opcode, data);
        }
        else
        {
            buffer = opcode;
        }
        return buffer;
    }

}