netty(三):NIO相关概念，Reactor模型和 channel和pipeline，handler之间的关系

1.BIO,NIO,AIO区别

2.netty的Reactor模型

主从模式的编程实现：

public class HelloServer {
    public static void main(String[] args) {

        EventLoopGroup bossGroup = new NioEventLoopGroup();// 主线程组,专门管理客户的连接
        EventLoopGroup workGrop = new NioEventLoopGroup();// 从线程组，用来管业务的完成

        try {
            // serverBootstrap就是服务器启动类
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup,workGrop)
                    .channel(NioServerSocketChannel.class)// NIO的channel类型
                    .childHandler(null); // 此处可以定从线程组的任务

            // 启动serverBootstrap，绑定8088端口，启动方式是同步的方式
            ChannelFuture channelFuture = serverBootstrap.bind(8088).sync();

            // 监听关闭的channel，设置位同步方式
            channelFuture.channel().closeFuture().sync();

        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            // 关闭线程组
            bossGroup.shutdownGracefully();
            workGrop.shutdownGracefully();
        }
    }
}

3. channel和pipeline，handler之间的关系

/**
 * 初始化器：channel注册后，会执行里面的相应的初始化方法
 */
public class HelloServerInit extends ChannelInitializer<SocketChannel> {

    protected void initChannel(SocketChannel socketChannel) throws Exception {
        // 通过socketChannel获取对应处理的管道
        ChannelPipeline pipeline = socketChannel.pipeline();

        // HttpServerCodec是netty自带的handler，是http协议的编码解码器
        pipeline.addLast("HttpServerCodec",new HttpServerCodec());
        pipeline.addLast("customHandler",new CustomHandler());
    }
}

3.自定义一个http请求的handler

/**
 * 自定义助手类
 */
public class CustomHandler extends SimpleChannelInboundHandler<HttpObject> {

    protected void channelRead0(ChannelHandlerContext channelHandlerContext, HttpObject httpObject) throws Exception {
        
        //获取channel
        Channel channel = channelHandlerContext.channel();

        //显示客户端远程地址
        if (httpObject instanceof HttpRequest){
            System.out.println(channel.localAddress());
        }

        // Unpooled是一个执行拷贝的工具类,copiedBuffer将"hello"字符串拷贝到一个buffer中
        ByteBuf context = Unpooled.copiedBuffer("hello", CharsetUtil.UTF_8);

        // 构建一个http相应
        FullHttpResponse fullHttpResponse = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, context);
        fullHttpResponse.headers().set(HttpHeaderNames.CONTENT_TYPE,"text/plain");
        fullHttpResponse.headers().set(HttpHeaderNames.CONTENT_LENGTH,context.readableBytes());

        // channel的消息写到缓存区，并且flush到客户端
        channelHandlerContext.writeAndFlush(fullHttpResponse);
    }

    @Override
    public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channel。。。注册");
        super.channelRegistered(ctx);
    }

    @Override
    public void channelUnregistered(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channel。。。移除");
        super.channelUnregistered(ctx);
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channel。。。活跃");
        super.channelActive(ctx);
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channel。。。不活跃");
        super.channelInactive(ctx);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channeld读取完毕。。。");
        super.channelReadComplete(ctx);
    }

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        System.out.println("用户事件触发。。。");
        super.userEventTriggered(ctx, evt);
    }

    @Override
    public void channelWritabilityChanged(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channel可写更改");
        super.channelWritabilityChanged(ctx);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        System.out.println("补货到异常");
        super.exceptionCaught(ctx, cause);
    }

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        System.out.println("助手类添加");
        super.handlerAdded(ctx);
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        System.out.println("助手类移除");
        super.handlerRemoved(ctx);
    }
}

启动项目

源码： https://github.com/LUK-qianliu/netty