引导类的层次结构包括一个抽象的父类和两个具体的引导子类，服务器致力于使用一个父 Channel 来接受来自客户端的连接，并创建子 Channel 以用于它们之间的通信；而客户端将最可能只需要一个单独的、没有父 Channel 的 Channel 来用于所有的网络交互;Cloneable便于创建相同配置的引导类的浅拷贝

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public class BootstrapSharingEventLoopGroup {
        public void bootstrap() {
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap.group(new NioEventLoopGroup(), new NioEventLoopGroup())
                .channel(NioServerSocketChannel.class)
                .childHandler(
                    new SimpleChannelInboundHandler<ByteBuf>() {
                        ChannelFuture connectFuture;
                        @Override
                        public void channelActive(ChannelHandlerContext ctx)
                            throws Exception {
                            // 作为客户端连接其他服务
                            Bootstrap bootstrap = new Bootstrap();
                            bootstrap.channel(NioSocketChannel.class).handler(
                                new SimpleChannelInboundHandler<ByteBuf>() {
                                    @Override
                                    protected void channelRead0(
                                        ChannelHandlerContext ctx, ByteBuf in)
                                        throws Exception {
                                        System.out.println("Received data");
                                    }
                                });
                            // 复用 EventLoop
                            bootstrap.group(ctx.channel().eventLoop());
                            connectFuture = bootstrap.connect(
                                new InetSocketAddress("www.manning.com", 80));
                        }
    
                        @Override
                        protected void channelRead0(
                            ChannelHandlerContext channelHandlerContext,
                                ByteBuf byteBuf) throws Exception {
                            if (connectFuture.isDone()) {
                                // do something with the data
                            }
                        }
                    });
            ChannelFuture future = bootstrap.bind(new InetSocketAddress(8080));
            future.addListener(new ChannelFutureListener() {
                @Override
                public void operationComplete(ChannelFuture channelFuture)
                    throws Exception {
                    if (channelFuture.isSuccess()) {
                        System.out.println("Server bound");
                    } else {
                        System.err.println("Bind attempt failed");
                        channelFuture.cause().printStackTrace();
                    }
                }
            });
        }
    }

public class BootstrapWithInitializer {
    public void bootstrap() throws InterruptedException {
        ServerBootstrap bootstrap = new ServerBootstrap();
        bootstrap.group(new NioEventLoopGroup(), new NioEventLoopGroup())
            .channel(NioServerSocketChannel.class)
            .childHandler(new ChannelInitializerImpl());
        ChannelFuture future = bootstrap.bind(new InetSocketAddress(8080));
        future.sync();
    }

    final class ChannelInitializerImpl extends ChannelInitializer<Channel> {
        @Override
        protected void initChannel(Channel ch) throws Exception {
            ChannelPipeline pipeline = ch.pipeline();
            pipeline.addLast(new HttpClientCodec());
            pipeline.addLast(new HttpObjectAggregator(Integer.MAX_VALUE));

        }
    }
}

public class BootstrapClientWithOptionsAndAttrs {
    public void bootstrap() {
        final AttributeKey<Integer> id = AttributeKey.newInstance("ID");
        Bootstrap bootstrap = new Bootstrap();
        bootstrap.group(new NioEventLoopGroup())
            .channel(NioSocketChannel.class)
            .handler(
                new SimpleChannelInboundHandler<ByteBuf>() {
                    @Override
                    public void channelRegistered(ChannelHandlerContext ctx)
                        throws Exception {
                        Integer idValue = ctx.channel().attr(id).get();
                        // do something with the idValue
                    }

                    @Override
                    protected void channelRead0(
                        ChannelHandlerContext channelHandlerContext,
                        ByteBuf byteBuf) throws Exception {
                        System.out.println("Received data");
                    }
                }
            );
        bootstrap.option(ChannelOption.SO_KEEPALIVE, true)
            .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 5000);
        bootstrap.attr(id, 123456);
        ChannelFuture future = bootstrap.connect(
            new InetSocketAddress("www.manning.com", 80));
        future.syncUninterruptibly();
    }
}

public class BootstrapDatagramChannel {
    public void bootstrap() {
        Bootstrap bootstrap = new Bootstrap();
        bootstrap.group(new OioEventLoopGroup()).channel(
            OioDatagramChannel.class).handler(
            new SimpleChannelInboundHandler<DatagramPacket>() {
                @Override
                public void channelRead0(ChannelHandlerContext ctx,
                    DatagramPacket msg) throws Exception {
                    // Do something with the packet
                }
            }
        );
        ChannelFuture future = bootstrap.bind(new InetSocketAddress(0));
        future.addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture channelFuture)
               throws Exception {
               if (channelFuture.isSuccess()) {
                   System.out.println("Channel bound");
               } else {
                   System.err.println("Bind attempt failed");
                   channelFuture.cause().printStackTrace();
               }
            }
        });
    }
}

public class GracefulShutdown {
    public static void main(String args[]) {
        GracefulShutdown client = new GracefulShutdown();
        client.bootstrap();
    }
    public void bootstrap() {
        EventLoopGroup group = new NioEventLoopGroup();
        Bootstrap bootstrap = new Bootstrap();
        bootstrap.group(group)
             .channel(NioSocketChannel.class)
             .handler(
                new SimpleChannelInboundHandler<ByteBuf>() {
                    @Override
                    protected void channelRead0(
                            ChannelHandlerContext channelHandlerContext,
                            ByteBuf byteBuf) throws Exception {
                        System.out.println("Received data");
                    }
                }
             );
        bootstrap.connect(new InetSocketAddress("www.manning.com", 80)).syncUninterruptibly();      
        Future<?> future = group.shutdownGracefully();
        // block until the group has shutdown
        future.syncUninterruptibly();
    }
}