一.概述
Netty基于NIO的网络编程框架，是一个封装了NIO复杂的底层细节，可以拿来开发高并发的服务端和客户端的程序，简单直白你可以理解它就是一个好用的处理socket的东西就行啦。
二.Netty初体验
首先，创建maven工程添加Netty依赖，新建两个包，一个是客户端，一个服务端，先来看看服务端代码，这个是服务器类，主要的逻辑都在这里实现。
public class Server { ???public static void main(String[] args) throws Exception { ???????//1.创建两个线程组 ???????EventLoopGroup bossGroup = new NioEventLoopGroup(); ???????EventLoopGroup workerGroup = new NioEventLoopGroup(); ???????try{ ???????????//2.服务端启动类 ???????????ServerBootstrap serverBootstrap = new ServerBootstrap(); ???????????//3.定义好组，nio，以及初始化类 ???????????serverBootstrap.group(bossGroup,workerGroup)//加载线程组
.channel(NioServerSocketChannel.class)//选择NIO的通道
.childHandler(new TestServerInitializer());//自定义初始化类 ???????????System.out.println("服务器启动...."); ???????????//4.绑定端口 ???????????ChannelFuture channelFuture = serverBootstrap.bind(7889).sync(); ???????????//5.关闭任务 ???????????channelFuture.channel().closeFuture().sync(); ???????}finally { ???????????bossGroup.shutdownGracefully(); ???????????workerGroup.shutdownGracefully(); ???????} ???}}自定义的初始化类，里面主要是设置处理器到通道以及设置异常处理等初始化工作，可以重写的方法很多，这里就简单重写两个基本的方法
public class TestServerInitializer extends ChannelInitializer<SocketChannel>{ ???@Override ???protected void initChannel(SocketChannel socketChannel) throws Exception { ???????//获取管道，添加处理器 ???????ChannelPipeline channelPipeline = socketChannel.pipeline(); ???????//添加处理器 ???????channelPipeline.addLast("decoder", new StringDecoder());//字符解码 ???????channelPipeline.addLast("encoder", new StringEncoder());//字符编码 ???????channelPipeline.addLast("MyClientHandler",new MyHandler());//自定义的Handler，里面处理具体的业务 ???} ???@Override ???public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { ???????super.exceptionCaught(ctx, cause); ???}}自定义的Hander，里面是自己要处理的具体业务，这次就是简单的传输字符串。
public class MyHandler ?extends SimpleChannelInboundHandler<String>{
//处理通道信息的方法 ???@Override ???protected void messageReceived(ChannelHandlerContext channelHandlerContext, String str) throws Exception { ???????????System.out.println("准备接收客户端的数据..."); ?????????? //打印收到的客户端的信息 ???????????System.out.println(str); //发送信息给客户端 ???????????channelHandlerContext.writeAndFlush("this is server"); ???????????System.out.println("------发送给客户端成功"); ???} ???/* ????* 建立连接时，返回消息 ????*/ ???@Override ???public void channelActive(ChannelHandlerContext ctx) throws Exception { ???????System.out.println("连接的客户端地址:" + ctx.channel().remoteAddress()); ???????System.out.println(InetAddress.getLocalHost().getHostName()); ???????ctx.writeAndFlush("客户端"+ InetAddress.getLocalHost().getHostName() + "成功与服务端建立连接！ \n"); ???????super.channelActive(ctx); ???} ???@Override ???public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { ???????ctx.close(); ???}}客户端，首先也是客户端类的代码，其实调用的API不太一样之外差不多，具体看下面的代码：
public class client { ???public static void main(String[] args) throws Exception { ???????System.out.println("客户端启动...."); ???????//1.创建线程组 ???????EventLoopGroup clientGroup = new NioEventLoopGroup(); ???????????//2.客户端启动类 ???????????Bootstrap bootstrap = new Bootstrap(); ???????????//3.定义好组，nio，以及初始化类 ???????????bootstrap.group(clientGroup) ???????????????????.channel(NioSocketChannel.class) ???????????????????.handler(new TestClientInitializer()); ???????????//4.创建好通道 ???????????Channel channel = bootstrap.connect("127.0.0.1",7889).sync().channel(); ???????????channel.writeAndFlush("this is client-----"); ???????????System.out.println("----------------"); ???}}然后和服务端一样，自定义的初始化类搞起来
public class TestClientInitializer extends ChannelInitializer<SocketChannel>{
???@Override
???protected void initChannel(SocketChannel socketChannel) throws Exception {
???????//获取管道，添加处理器
???????ChannelPipeline channelPipeline = socketChannel.pipeline();
???????//添加处理器
???????channelPipeline.addLast("decoder", new StringDecoder());
???????channelPipeline.addLast("encoder", new StringEncoder());
???????channelPipeline.addLast("MyClientHandler",new MyClientHandler());
???}
}最后就是搞客户端的逻辑的Handler
public class MyClientHandler extends SimpleChannelInboundHandler<String>{ ???@Override ???protected void messageReceived(ChannelHandlerContext channelHandlerContext, String str) throws Exception { ???????System.out.println(str); ???????ByteBuf byteBuf = Unpooled.copiedBuffer("hello server ", CharsetUtil.UTF_8); ???????//获取并设置响应体,版本信息，状态，响应内容等 ???????//FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK,byteBuf); ???????//设置响应头信息 ???????//response.headers().set(HttpHeaderNames.CONTENT_TYPE,"text/plain"); ???????//channelHandlerContext.writeAndFlush("ssssssssssssssssssss"); ???} ???@Override ???public void channelActive(ChannelHandlerContext ctx) throws Exception { ???????System.out.println("正在连接... "); ???????super.channelActive(ctx); ???} ???@Override ???public void channelInactive(ChannelHandlerContext ctx) throws Exception { ???????System.out.println("连接关闭! "); ???????super.channelInactive(ctx); ???}}Netty初体验
原文地址：https://www.cnblogs.com/JimmyFanHome/p/9992482.html