Netty简单使用

介绍：

Netty提供异步的、事件驱动的网络应用程序框架和工具，用以快速开发高性能、高可靠性的网络服务器和客户端程序。

使用：

hadoop、dubbo、akka等分布式功能框架

io和NIO区别：

NIO面向缓冲区，非阻塞（是通过选择器实现的）
IO面向流，是阻塞的。

1.pom文件

<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>5.0.0.Alpha1</version>
</dependency>

2.服务端

public class nettyService {

    public static void main(String[] args) throws InterruptedException {
        NioEventLoopGroup bossGroup = new NioEventLoopGroup();
        NioEventLoopGroup workerGroup = new NioEventLoopGroup();

        ServerBootstrap serverBootstrap = new ServerBootstrap();
        serverBootstrap.group(bossGroup, workerGroup);
        serverBootstrap.channel(NioServerSocketChannel.class);
        serverBootstrap.option(ChannelOption.SO_BACKLOG, 1024);//TCP的缓冲区设置
        serverBootstrap.option(ChannelOption.SO_SNDBUF, 32 * 1024);//设置发送缓冲的大小
        serverBootstrap.option(ChannelOption.SO_RCVBUF, 32 * 1024);//设置接收缓冲区大小
        serverBootstrap.option(ChannelOption.SO_KEEPALIVE, true);//保持连续
        serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel sc) throws Exception {
                ByteBuf buf = Unpooled.copiedBuffer("$_".getBytes());//拆包粘包定义结束字符串（第一种解决方案）
                sc.pipeline().addLast(new DelimiterBasedFrameDecoder(1024, buf));//在管道中加入结束字符串
                sc.pipeline().addLast(new StringDecoder());//定义接收类型为字符串把ByteBuf转成String
                sc.pipeline().addLast(new ServerHandler());//在这里配置具体数据接收方法的处理
            }
        });
        ChannelFuture future = serverBootstrap.bind(8765).sync();//绑定端口
        future.channel().closeFuture().sync();//等待关闭(程序阻塞在这里等待客户端请求)
        bossGroup.shutdownGracefully();//关闭线程
        workerGroup.shutdownGracefully();//关闭线程

    }

}

3.服务端处理类

public class ServerHandler extends ChannelHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        String body = (String) msg;
        System.out.println("" + body);//前面已经定义了接收为字符串，这里直接接收字符串就可以
        //服务端给客户端的响应
        String response = body + "我收到了 你好啊!$_";//发送的数据以定义结束的字符串结尾
        ctx.writeAndFlush(Unpooled.copiedBuffer(response.getBytes()));//发送必须还是ByteBuf类型
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }

}

4.客户端

public class Client {

    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup worker = new NioEventLoopGroup();
        Bootstrap b = new Bootstrap();
        b.group(worker)
                .channel(NioSocketChannel.class)
                .handler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel sc) throws Exception {
                        ByteBuf buf = Unpooled.copiedBuffer("$_".getBytes());//拆包粘包定义结束字符串（第一种解决方案）
                        sc.pipeline().addLast(new DelimiterBasedFrameDecoder(1024, buf));//在管道中加入结束字符串
                        sc.pipeline().addLast(new StringDecoder());//定义接收类型为字符串把ByteBuf转成String
                        sc.pipeline().addLast(new ClientHandler());//在这里配置具体数据接收方法的处理
                    }
                });
        ChannelFuture f = b.connect("127.0.0.1", 8765).sync();// 连接端口
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入发送的消息：");
        String next = scanner.next() + "$_";
        f.channel().writeAndFlush(Unpooled.copiedBuffer(next.getBytes()));// 发送信息给server
        f.channel().closeFuture().sync();
        worker.shutdownGracefully();
    }

}

5.客户端处理类

public class ClientHandler extends ChannelHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        try {
            System.out.println("1" + msg.toString());
        } finally {
            ReferenceCountUtil.release(msg);//释放缓冲区
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }

}