Netty

Netty对NIO的API进行了良好的封装，完全可以将业务代码从网络IO中解放出来，具有高性能、 高吞吐量，低延迟等优点。经常被作为通信组件来使用,eg:Dubbo、RocketMq、Zookeeper等。

        1）依赖

io.netty netty-all 4.1.35.Final

        2）服务端：

package org.example.netty;import io.netty.buffer.ByteBuf;import io.netty.buffer.Unpooled;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelInboundHandlerAdapter;import java.nio.charset.StandardCharsets;public class NettyServerHandler extends ChannelInboundHandlerAdapter { @Override public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { ByteBuf buf = (ByteBuf) msg; System.out.println("NettyServerHandler ctx:" + ctx); System.out.println("NettyServerHandler 收到消息:" + buf.toString(StandardCharsets.UTF_8)); } @Override public void channelReadComplete(ChannelHandlerContext ctx) throws Exception { ByteBuf buf = Unpooled.copiedBuffer("Netty ...".getBytes(StandardCharsets.UTF_8)); ctx.writeAndFlush(buf); } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { System.out.println("ctx:" + ctx); System.out.println("cause:" + cause); ctx.close(); }}

package org.example.netty;import io.netty.bootstrap.ServerBootstrap;import io.netty.channel.ChannelFuture;import io.netty.channel.ChannelInitializer;import io.netty.channel.ChannelOption;import io.netty.channel.nio.NioEventLoopGroup;import io.netty.channel.socket.SocketChannel;import io.netty.channel.socket.nio.NioServerSocketChannel;public class NettyServer { public static void main(String[] args) throws InterruptedException { NioEventLoopGroup bossGroup = new NioEventLoopGroup(); NioEventLoopGroup workGroup = new NioEventLoopGroup(); try { ServerBootstrap serverBootstrap = new ServerBootstrap(); serverBootstrap.group(bossGroup, workGroup) .channel(NioServerSocketChannel.class) .option(ChannelOption.SO_BACKLOG, 1024) .childHandler(new ChannelInitializer() { @Override protected void initChannel(SocketChannel socketChannel) throws Exception { socketChannel.pipeline().addLast(new NettyServerHandler()); } }); System.out.println("netty server start....."); ChannelFuture sync = serverBootstrap.bind(35599).sync(); System.out.println("....."); sync.addListener(channelFuture -> { if (channelFuture.isSuccess()) { System.out.println("监听端口35599成功"); } else { System.out.println("监听端口35599失败"); } }); sync.channel().closeFuture().sync(); System.out.println("通道关闭"); } finally { bossGroup.shutdownGracefully(); workGroup.shutdownGracefully(); System.out.println("线程池关闭"); } }}

         3）客户端：

package org.example.netty;import io.netty.bootstrap.Bootstrap;import io.netty.channel.ChannelFuture;import io.netty.channel.ChannelInitializer;import io.netty.channel.nio.NioEventLoopGroup;import io.netty.channel.socket.SocketChannel;import io.netty.channel.socket.nio.NioSocketChannel;public class NettyClient { public static void main(String[] args) throws InterruptedException { NioEventLoopGroup nioEventLoopGroup=new NioEventLoopGroup(); try { Bootstrap bootstrap=new Bootstrap(); bootstrap.group(nioEventLoopGroup) .channel(NioSocketChannel.class) .handler(new ChannelInitializer() { @Override protected void initChannel(SocketChannel socketChannel) throws Exception { socketChannel.pipeline().addLast(new NettyClientHandler()); } }); System.out.println("netty Client start....."); ChannelFuture sync = bootstrap.connect("127.0.0.1", 35599).sync(); System.out.println("netty Client connect....."); sync.channel().closeFuture().sync(); }finally { nioEventLoopGroup.shutdownGracefully(); } }}

package org.example.netty;import io.netty.buffer.ByteBuf;import io.netty.buffer.Unpooled;import io.netty.channel.ChannelHandler;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelInboundHandlerAdapter;import io.netty.util.concurrent.EventExecutorGroup;import java.nio.charset.StandardCharsets;public class NettyClientHandler extends ChannelInboundHandlerAdapter { @Override public void channelActive(ChannelHandlerContext ctx) throws Exception { System.out.println("客户端激活: " + ctx); String msg = "Netty Client ..."; ByteBuf buf = Unpooled.copiedBuffer(msg.getBytes(StandardCharsets.UTF_8)); ctx.writeAndFlush(buf); System.out.println("客户端发送消息:" + msg); } @Override public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { ByteBuf buf = (ByteBuf) msg; System.out.println("ctx:" + ctx); System.out.println("客户端收到消息:" + buf.toString(StandardCharsets.UTF_8)); } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { System.out.println("ctx:" + ctx); System.out.println("cause:" + cause); ctx.close(); }}

        NIO多路复用非阻塞                零拷贝（使用直接内存，减少了堆内、堆外的拷贝）        主从Reactor线程模型提升并发量        单线程串行执行（减少竞争）