如何在java中手动调用netty编码方法？

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.string.StringEncoder;

public class NettyEncoderExample {
    public static void main(String[] args) {
        NioEventLoopGroup group = new NioEventLoopGroup();

        try {
            // 创建ServerBootstrap并配置
            ServerBootstrap b = new ServerBootstrap();
            b.group(group)
             .channel(NioServerSocketChannel.class)
             .childHandler(new ChannelInitializer<SocketChannel>() {
                 @Override
                 protected void initChannel(SocketChannel ch) throws Exception {
                     ChannelPipeline pipeline = ch.pipeline();
                     // 添加StringEncoder编码器
                     pipeline.addLast(new StringEncoder());
                     // 添加自定义的ChannelHandler
                     pipeline.addLast(new CustomHandler());
                 }
             });

            // 绑定端口并启动服务
            ChannelFuture f = b.bind(8888).sync();
            f.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }

    // 自定义的ChannelHandler，用于演示手动调用编码方法
    private static class CustomHandler extends SimpleChannelInboundHandler<String> {
        @Override
        protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
            // 创建ByteBuf，并写入待编码的数据
            ByteBuf buf = Unpooled.copiedBuffer(msg.getBytes());
            // 获取ChannelPipeline中的StringEncoder编码器
            StringEncoder encoder = ctx.pipeline().get(StringEncoder.class);
            // 手动调用编码方法对数据进行编码
            ByteBuf encodedBuf = (ByteBuf) encoder.encode(ctx, buf);
            // 处理编码后的数据...
        }
    }
}