Java Netty Server的高效channelRead

Question

I'm using netty to develop a proxy server and my proxy ProxyBackendHandler class is as follows. There on channelRead method I need to get the msg data and write to client as TextWebSocketFrame. To do that I have used a StringBuilder and a while loop to iterate the ByteBuf. Can anyone suggest me a better way to do this as it seems that above code has high perfomance overhead when the high data loads.

public class ProxyBackendHandler extends ChannelInboundHandlerAdapter {

    private final Channel inboundChannel;
    StringBuilder sReplyBuffer;

    public ProxyBackendHandler(Channel inboundChannel) {
        this.inboundChannel = inboundChannel;
        sReplyBuffer = new StringBuilder(4000);
    }

    @Override
    public void channelRead(final ChannelHandlerContext ctx, Object msg) {

        // Please suggest a efficient implementation for read msg and pass it to writeAndFlush.
        ByteBuf in = (ByteBuf) msg;
        sReplyBuffer.setLength(0); 

        try {
            while (in.isReadable()) { 
                sReplyBuffer.append((char) in.readByte());
            }
        } finally {
            ((ByteBuf) msg).release(); 
        }

        inboundChannel.writeAndFlush(new TextWebSocketFrame (sReplyBuffer.toString())).addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture future) {
                if (future.isSuccess()) {
                    ctx.channel().read();
                    System.out.println("Sent To Client");
                } else {
                    future.channel().close();
                }
            }
        });
    }
}

Answer 1

Maybe something like this:

public class ProxyBackendHandler extends ChannelInboundHandlerAdapter {

    private final Channel inboundChannel;

    public ProxyBackendHandler(Channel inboundChannel) {
        this.inboundChannel = inboundChannel;
    }

    @Override
    public void channelRead(final ChannelHandlerContext ctx, Object msg) {
        inboundChannel.writeAndFlush(new TextWebSocketFrame((ByteBuf) msg)).addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture future) {
                if (future.isSuccess()) {
                    ctx.channel().read();
                    System.out.println("Sent To Client");
                } else {
                    future.channel().close();
                }
            }
        });
    }
}

Answer 2

I suggest not using a StringBuilder at all. Just use the buffer you already have. You don't state what a TextWebSocketFrame might be, or why you think you need it, but ultimately a proxy server only has to copy bytes. You don't need StringBuilders or extra classes for that. Or Netty, frankly.