目录
- Netty - 入门
- 1. Netty开发环境的搭建
- 2. Time程序的开发
- 2.1. TimeServer开发
- 2.2. TimeClient开发
- 3. 总结
Netty - 入门
1. Netty开发环境的搭建
使用maven构建项目：
<dependency> ?<groupId>io.netty</groupId> ?<artifactId>netty</artifactId> ?<version>3.9.4.Final</version></dependency>2. Time程序的开发
2.1. TimeServer开发
TimeServer:
public class TimeServer { ???public static void main(String[] args) { ???????int port = 8080; ???????if (args != null && args.length > 0) { ???????????try { ???????????????port = Integer.valueOf(args[0]); ???????????} catch (NumberFormatException e) { ???????????????// ???????????} ???????} ???????new TimeServer().bind(port); ???} ???private void bind(int port) { ???????//配置服务端的NIO线程组 ???????/* ???????Reactor线程组 ???????bossGroup: 服务端接受客户端连接 ???????workerGroup: 进行SocketChannel的网络读写 ????????*/ ???????EventLoopGroup bossGroup = new NioEventLoopGroup(); ???????EventLoopGroup workerGroup = new NioEventLoopGroup(); ???????try { ???????????//ServerBootstarp: 用于启动NIO服务端的辅助启动类 ???????????ServerBootstrap b = new ServerBootstrap(); ???????????b.group(bossGroup, workerGroup); ???????????/* ???????????创建的Channel伪NioServerSocketChannel ???????????对应JDK NIO中的ServerSocketChannel ????????????*/ ???????????b.channel(NioServerSocketChannel.class); ???????????b.option(ChannelOption.SO_BACKLOG, 1024); ???????????//IO事件处理类 ???????????b.childHandler(new ChildChannelHandler()); ???????????//绑定端口，同步等待成功 ???????????ChannelFuture f = b.bind(port).sync(); ???????????//等待服务端监听端口关闭 ???????????f.channel().closeFuture().sync(); ???????} catch (InterruptedException e) { ???????????e.printStackTrace(); ???????} finally { ???????????bossGroup.shutdownGracefully(); ???????} ???} ???private class ChildChannelHandler extends ChannelInitializer<SocketChannel> { ???????@Override ???????public void initChannel(SocketChannel socketChannel) throws Exception { ???????????socketChannel.pipeline().addLast(new TimeServerHandler()); ???????} ???}}TimeServerHandler:
public class TimeServerHandler extends ChannelInboundHandlerAdapter { ???@Override ???public void channelReadComplete(ChannelHandlerContext ctx) throws Exception { ???????//将消息发送队列中的消息写入到SocketChannel中发送给对方 ???????/** ????????* 调用write()方法只是把待发送的消息放到发送缓冲数组中， ????????* 调用flush()方法，将发送缓冲区中的消息全部写到SocketChannel中 ????????*/ ???????ctx.flush(); ???} ???@Override ???public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { ???????ctx.close(); ???} ???@Override ???public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { ???????/* ???????ByteBuf类似JDK中的java.nio.ByteBuffer ???????ByteBuf.readableBytes: 获取缓冲区可读的字节数 ???????ByteBuf.readBytes: 将缓冲区的字节数组复制到新建的byte数组中 ????????*/ ???????//将msg转换为Netty的ByteBuf对象 ???????ByteBuf buf = (ByteBuf) msg; ???????//创建一个字节数组 ???????byte[] req = new byte[buf.readableBytes()]; ???????//将buf中的内容复制到字节数组 ???????buf.readBytes(req); ???????//转换为字符串，获取到请求消息 ???????String body = new String(req, "UTF-8"); ???????System.out.println("The time server receive order: " + body); ???????String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ? new Date(System.currentTimeMillis()).toString() : "BAD ORDER"; ???????//创建应答消息 ???????ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes()); ???????//异步发送应答消息给客户端 ???????ctx.write(resp); ???}}2.2. TimeClient开发
TimeClient:
public class TimeClient { ???public void connect(int port, String host) throws Exception{ ???????//配置客户端NIO线程组 ???????EventLoopGroup group = new NioEventLoopGroup(); ???????try { ???????????Bootstrap b = new Bootstrap(); ???????????b.group(group); ???????????b.channel(NioSocketChannel.class); ???????????b.option(ChannelOption.TCP_NODELAY, true); ???????????b.handler(new ChannelInitializer<SocketChannel>() { ???????????????@Override ???????????????protected void initChannel(SocketChannel ch) throws Exception { ???????????????????ch.pipeline().addLast(new TimeClientHandler()); ???????????????} ???????????}); ???????????//发起异步连接请求 ???????????ChannelFuture f = b.connect(host, port).sync(); ???????????//等待客户端链路关闭 ???????????f.channel().closeFuture().sync(); ???????} finally { ???????????group.shutdownGracefully(); ???????} ???} ???public static void main(String[] args) throws Exception { ???????int port = 8080; ???????if (args != null && args.length > 0){ ???????????try { ???????????????port = Integer.valueOf(args[0]); ???????????}catch (NumberFormatException e){ ???????????????// 采用默认值 ???????????} ???????} ???????new TimeClient().connect(port, "127.0.0.1"); ???}}TimeClientHandler:
public class TimeClientHandler extends ChannelInboundHandlerAdapter { ???private final ByteBuf firstMessage; ???public TimeClientHandler() { ???????byte[] req = "QUERY TIME ORDER".getBytes(); ???????firstMessage = Unpooled.buffer(req.length); ???????firstMessage.writeBytes(req); ???} ???@Override ???public void channelActive(ChannelHandlerContext ctx) throws Exception { ???????ctx.writeAndFlush(firstMessage); ???} ???@Override ???public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { ???????ByteBuf buf = (ByteBuf) msg; ???????byte[] req = new byte[buf.readableBytes()]; ???????buf.readBytes(req); ???????String body = new String(req, "UTF-8"); ???????System.out.println("Now is: " + body); ???} ???@Override ???public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { ???????//释放资源 ???????System.out.println("Unexpected exception from downstram: " + cause.getMessage()); ???????ctx.close(); ???}}3. 总结
Server端
创建一个Reactor线程组
EventLoopGroup bossGroup = new NioEventLoopGroup();EventLoopGroup workerGroup = new NioEventLoopGroup();创建一个用于启动NIO服务的辅助启动类
ServerBootstrap b = new ServerBootstrap();设置参数
// 设置主从“线程池”b.group(bossGroup, workerGroup);// 指定Channel通道的类型b.channel(NioServerSocketChannel.class);// 设置一些参数b.option(ChannelOption.SO_BACKLOG, 1024);// 设置子通道SocketChannel的处理类b.childHandler(new ChildChannelHandler());绑定并监听某个端口
ChannelFuture f = b.bind(port).sync();端口关闭，服务停止
f.channel().closeFuture().sync();
Client端
创建一个Reactor线程组
EventLoopGroup group = new NioEventLoopGroup();创建一个辅助启动类实例
Bootstrap b = new Bootstrap();设置参数
//初始化线程池b.group(group);//指定Channel通道的类型b.channel(NioSocketChannel.class);//设置一些参数b.option(ChannelOption.TCP_NODELAY, true);//设置SocketChannel的处理器b.handler(new ChannelInitializer<SocketChannel>() { ??@Override ??protected void initChannel(SocketChannel ch) throws Exception { ??????ch.pipeline().addLast(new TimeClientHandler()); ??}});发起一个异步连接请求，连接指定的服务地址
ChannelFuture f = b.connect(host, port).sync();端口关闭，服务停止
f.channel().closeFuture().sync();
从上面的一些分析可以看出，服务端和客户端最基础的配置都是5个步骤。先创建一个线程组EventLoopGroup和辅助启动类（服务端为ServerBootstrap，客户端为Bootstrap），接着设置一系列的参数：线程池、通道类型、通道参数、处理器等，最后启动服务，服务端为bind()监听，客户端为connect()连接。
具体的处理类需要继承ChannelHandlerAdapter，这里存在一个问题，《Netty权威指南》第2版使用的Netty版本为5.x，但现在已经废弃，所以使用的是4.x的版本。书中原来继承的是ChannelHandlerAdapter，在4.x的版本中这个接口并没有channelRead方法，所以用channelInboundHandlerAdapter代替。
在TimeClientHandler中，当客户端和服务端TCP链路建立成功后，NIO线程会调用channelActive方法，发送内容给服务端。当服务端返回应答消息时，会调用channelRead方法。
在channelRead中，用到了一个很重要的Netty中的类：ByteBuf。ByteBuf是一个很好的经过优化的数据容器。ByteBuf有两部分：一个用于读，一个用于写。我们可以按顺序读取数据，并且可以跳到开始再读一遍。具体的内容可以参考这个博文：Netty 缓存buffer介绍及使用
Netty - 入门
原文地址：https://www.cnblogs.com/yisany/p/10141956.html